How do we sneeze? - Part 2

Here is the second part of my question about how we sneeze. How are the sneeze droplets propelled at such a fast speed? I have heard sneeze travels at 100 mph. How is this possible?

How TB Spreads

TB bacteria are spread through the air from one person to another. The TB bacteria are put into the air when a person with TB disease of the lungs or throat coughs, speaks, or sings. People nearby may breathe in these bacteria and become infected.

  • shaking someone&rsquos hand
  • sharing food or drink
  • touching bed linens or toilet seats
  • sharing toothbrushes
  • kissing

When a person breathes in TB bacteria, the bacteria can settle in the lungs and begin to grow. From there, they can move through the blood to other parts of the body, such as the kidney, spine, and brain.

TB disease in the lungs or throat can be infectious. This means that the bacteria can be spread to other people. TB in other parts of the body, such as the kidney or spine, is usually not infectious.

People with TB disease are most likely to spread it to people they spend time with every day. This includes family members, friends, and coworkers or schoolmates.

Snot Science: A snotty setup

Proper hygiene means covering your nose when you sneeze. But a lot of people don&rsquot. How far away do you have to be to stay safe from their germs?

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January 10, 2017 at 2:58 pm

This article is one of a series of Experiments meant to teach students about how science is done, from generating a hypothesis to designing an experiment to analyzing the results with statistics. You can repeat the steps here and compare your results — or use this as inspiration to design your own experiment.

It’s flu and cold season, when everyone is trying hard not to get sick. A flu shot may help you to avoid the worst. But no matter how much you try to protect yourself, it seems someone nearby is sneezing away through most of the winter. Those sneezes spray out tiny drops of mucus, in which cold and influenza viruses hide. Sometimes it’s a fine spray, and other times, the snot gets everywhere. It’s pretty disgusting. But it’s also a good opportunity to ask some questions: How far does each kind of snot travel? And how far away do you have to stand to stay safe from viral spread?

EXPLAINER: What is a virus?

I try to answer these questions in our first DIY Science video. And here, I will show you how to do this experiment yourself, how to analyze the data and how you can interpret the results.

The idea for this experiment came originally from an experiment on Science Friday. The website showed how to plot out sneezes using a histogram — a graph showing how data points are distributed over a range. I decided to turn this into a different experiment — one that compares thick snot to thin.

The two types of mucus differ in their viscosity — a measure of a fluid’s resistance to flow. Thick gloppy boogers have a high viscosity. They slowly ooze out of your nose. Thin, drippy snot has a low viscosity. It drips quickly.

We can use what we know about viscosity to form a hypothesis — a statement that can be tested. The statement will compare a control (something in the test that will not change) to a variable (some factor that is changing).

Hypothesis: Thin snot will fly farther and spread more than thick snot

For thin snot, I used colored water. B. Brookshire/SSP

Now we have a hypothesis. How do we test it? In the Science Friday experiment, a small plastic dropper served as a fake “nose” to spray colored water onto paper. This serves as a sneeze model — a representation of something that happens in the real world.

I decided to do something similar, using a dropper with colored ”snot.” Because the best experiments are repeated many, many times, I didn’t want to replace the paper over and over. Instead, I used plastic shower curtains, which I could wipe off in between “sneezes.” (At the bottom of this post, I’ve written down my materials list, along with the cost that I paid for each item.)

Creating snot plots

For the experiment, I wanted plenty of open space. To film the video, my team used a large conference room. I lined up white shower curtains and taped them to the floor. At one end of the shower curtains, I set up a table with my artificial nose on it. Then, using a permanent marker and a measuring tape, I drew a five-meter (16.4-foot) line on the tarp stretching out from the table. I marked the line every half meter (50 centimeters, or about 20 inches).

Then I made my “snot.” For thin snot, I used half a cup of water (about 118 grams) and a few drops of blue food dye, enough to turn it a nice dark blue. (I didn’t use red or yellow in this test. Yellow wouldn’t show up well on the tarp, and red looked a little too much like someone was sneezing with a bloody nose.)

The materials for my thick snot recipe. B. Brookshire/SSP

To simulate viscous mucus, I couldn’t use water alone. I needed to find a combination of substances that would more closely stand in for snot. Mucus is mostly water, but added sugars and proteins give it its glop. So I needed fake snot with the same or similar ingredients. I realized I could use gelatin for my proteins and corn syrup as my sugar. With water, they make a good substitute for thick, gloopy snot.

I followed the recipe I found here, but I discovered that making snot is harder than it might seem. I had to tweak the recipe. To get consistent results, follow these directions carefully:

  • Bring a half cup of water (about 118 grams) to a boil in a small pot.
  • Take the water off the heat immediately. The original recipe says to keep the water boiling, but I found that if I did that, my goo never thickened.
  • Mix three tablespoons (45 grams) of gelatin into the hot water and add food coloring (I used green). The gelatin tends to clump stir with a fork to break up the clumps.
  • Add a quarter cup (59 grams) of corn syrup. When you dip your fork in again, it will bring up long, gloppy strands of snot. Do not stir the corn syrup in vigorously as this will also stop the mucus from forming. To stir, stick in your fork and make a very slow, lazy circle or two. No more than that.

The mixture will thicken more as it cools. To keep it at the same thickness, add one tablespoon of water (15 grams) to the mixture every five minutes. Remember to stir as little as possible.

You can — if you want — eat this mixture. I wouldn’t recommend it. It smells.

In experiments, it’s important to keep everything you do as consistent as possible. The most important variable for me was thick mucus versus thin mucus. What if temperature affected the thickness of my liquid? My mucus was hot. But the water I was using was not — it had just come from the tap. I made sure that both of my snot mixtures were the same temperature. Because the recipe for the thick snot requires bringing the water to a boil, I brought my thin snot to a boil, too.

Some goopy goodness. B. Brookshire/SSP

Once I had my thick and thin mucus, I loaded each into a dropper, smacked the bulb (you can yell ACHOO! for good measure, if you want) and measured how far the snot squirted. For each “sneeze,” I measured how far the fluid managed to fly. I also looked at where the most fluid was concentrated by counting the number of droplets present for each half meter of tarp.

Sneezes vary a lot between people. And drops squirted from a dropper vary, too. So I couldn’t squirt each type of snot once. I needed to squirt each kind many times.

Running the experiment multiple times would help me to avoid two types of error. I would make a Type I error if I concluded the two kinds of mucus were different when really they weren’t. This is a false positive. I’d make a Type II error if I concluded the two kinds of mucus were the same when in fact they were different. This is a false negative. I can never totally eliminate the possibility of these errors, but running the experiment more than once lessens the likelihood that I make them.

But how many runs of my experiment would I need? To find out, I would have to do some figuring. Scientists generally agree that a five percent chance of a false positive (or 0.05) is acceptable. This is called an “alpha.” False negatives aren’t quite so bad, and an acceptable risk is 20 percent or 0.2, and called “beta.” A beta of 0.2 would give me a power of 0.8, or an 80 percent probability of finding a difference between my two kinds of snot. With a power of 0.8, I could use a chart from a 1992 paper by Jacob Cohen of New York University (a free copy is here look at table 2). This chart tells me that to compare two groups (finding the “mean difference”) with an alpha of 0.05, I would need to squirt each type of snot 26 times to detect if there is a large difference between them. (For more about power analyses, see this post here.)

So I did. I squirted, measured and carefully wiped up each type of mucus 26 times. I made sure to write down all my measurements as I went along.

What did I find? In my next post, I’ll show you my data and how I grouped together and compared all of my snot spatters. If you’re trying this yourself, please leave notes in our YouTube video comments, or send me a tweet @eureka_labs! Did you have difficulty with the thick snot recipe? Did you find a better one? Let me know!

How far does a sneeze travel? We did an experiment to find out.

Materials List

  • Plain white shower curtains (two, $3.99 each)
  • Permanent marker (pack of three, $5.67)
  • Scotch tape ($1.99)
  • Food coloring ($3.66)
  • Sponge (for cleaning the shower curtains, pack of three, $2.96)
  • Plastic transfer pipettes (pack of 100, $6.99)
  • Small hot plate (Oster single burner, $24.97)
  • Small pan (one quart, $12.43)
  • Measuring cups ($7.46)
  • Measuring spoons ($5.36)
  • Gelatin (Knox brand, $2.99)
  • Corn syrup (Karo brand, $2.56)

Power Words

boil To heat a liquid to the temperature at which it turns to vapor.

control A part of an experiment where there is no change from normal conditions. The control is essential to scientific experiments. It shows that any new effect is likely due only to the part of the test that a researcher has altered. For example, if scientists were testing different types of fertilizer in a garden, they would want one section of it to remain unfertilized, as the control. Its area would show how plants in this garden grow under normal conditions. And that give scientists something against which they can compare their experimental data.

data Facts and/or statistics collected together for analysis but not necessarily organized in a way that give them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.

error (In statistics) The non-deterministic (random) part of the relationship between two or more variables.

factor Something that plays a role in a particular condition or event a contributor.

false negative In statistics, a conclusion &mdash based on the data &mdash that a difference between two or more conditions being tested does not exists, when in fact one does.

false positive In statistics, a conclusion &mdash based on the data &mdash that a difference exists between two or more conditions being tested, when in fact none exists.

flu (see influenza)

hypothesis A proposed explanation for a phenomenon. In science, a hypothesis is an idea that must be rigorously tested before it is accepted or rejected.

influenza (also known as flu) A highly contagious viral infection of the respiratory passages causing fever and severe aching. It often occurs as an epidemic.

liquid A material that flows freely but keeps a constant volume, like water or oil.

mean One of several measures of the &ldquoaverage size&rdquo of a data set. Most commonly used is the arithmetic mean, obtained by adding the data and dividing by the number of data points.

model A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes.

mucus A slimy substance produced in the lungs, nose, digestive system and other parts of the body to protect against infection. Mucus is made mainly of water but also includes salt and proteins such as mucins. Some animals use mucus for other purposes, such as to move across the ground or to defend themselves against predators.

probability A mathematical calculation or assessment (essentially the chance) of how likely something is to occur.

proteins Compounds made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues they also do the work inside of cells. The hemoglobin in blood and the antibodies that attempt to fight infections are among the better-known, stand-alone proteins. Medicines frequently work by latching onto proteins.

Type I error (in statistics) A finding that some difference exists between two or more conditions being tested, when in fact there is no difference. It&rsquos also known as a false positive.

Type II error (in statistics) A finding that that there is no difference between two or more conditions being tested, when in fact there is a difference. It&rsquos also known as a false negative.

variable (in mathematics) A letter used in a mathematical expression that may take on different values. (in experiments) A factor that can be changed, especially one allowed to change in a scientific experiment. For instance, when researchers measure how much insecticide it might take to kill a fly, they might change the dose or the age at which the insect is exposed. Both the dose and age would be variables in this experiment.

viscosity The measure of a fluid&rsquos resistance to stress. Viscosity corresponds to the idea of how &ldquothick&rdquo a liquid is. Honey is very viscous, for instance, while water has relatively low viscosity.


About Bethany Brookshire

Bethany Brookshire was a longtime staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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Why We Feel Compelled to Say ‘Bless You’ When Someone Sneezes

Attributing divine blessing to a sneeze may serve various functions when ordinary explanations are lacking.

Saying “bless you” or “God bless you” after someone sneezes seems to be a reflex response. Why do we feel compelled to say it to anyone who sneezes, even if the sneezer is a stranger or the sneeze is heard from afar?

“Saying ‘God bless you’ following a sneeze is a common refrain, so common and taught from childhood that many people don’t even think of it as a blessing, but rather as an utterance without specific meaning other than a response to a sneeze that is polite in some way,” said Dr. Gail Saltz, an associate professor of psychiatry at Weill Cornell Medicine . “For many people, this response has been conditioned into them, that this is what you do when someone sneezes, anyone.”

“If it is repeated enough times, especially with positive reinforcement — the sneezer says ‘thank you’ — it becomes increasingly reflexive, it starts to be done without conscious thought,” Dr. Saltz added. “Today, people aren’t quite sure why they are saying it, but they are afraid that if they don’t say it, people will think that they are rude or don’t care about the person who sneezed.”

Dara Avenius, a New York publicist, is one of those people who finds it rude if she sneezes and someone goes on with a conversation as if she hadn’t just sneezed. She always says “bless you” to anyone who sneezes, even her dog.

How and where did this social behavior originate?

Historically, sneezes were thought to be an omen or warning from the gods, according to W. David Myers, a professor of history at Fordham University. “For European Christians, when the first plague that weakened the now Christian Roman Empire around 590 , Pope Gregory the Great believed that a sneeze was an early warning sign of plague, so he commanded Christians to respond to a sneeze with a blessing,” he said.

In ancient times, people believed that sneezing would allow evil spirits to enter your body, and saying “God bless you” kept out those evil spirits.

“That was certainly another belief,” said Dr. Myers. “But other responses to sneezing — Gesundheit, in German Salud, in Spanish — came from the idea that a sneeze is a sign of divine beneficence.”

Of all the random things that happen that could be associated with God, why sneezing?

According to Dr. Omar Sultan Haque, a psychiatrist and social scientist at Harvard Medical School, although the onset of sneezes appears to be random, attributing divine blessing may function to explain things when ordinary explanations are lacking. “Because of the deep connection in the human psyche between religion, cleanliness and the emotion of disgust, invoking God after sneezing is more likely, as compared to invoking God after other anomalous events like a random piece of debris hitting someone on the shoulder,” he said.

Kaley Komanski, a social media manager based in Orlando, recently taught herself to say “gesundheit” rather than “bless you” when people sneeze. “It took a few weeks for it to become second nature and to feel natural,” she said. “I think it’s super uncomfortable to hear ‘God bless you’ all the time. It’s probably worth mentioning that I’m an atheist, which really drove me to edit my word choice when people sneeze.”

“I think some atheists are annoyed by the use of the word God in ‘God bless you.’ Atheists probably prefer gesundheit or some equivalent, which just means ‘good health,’ a principle the faithful and faithless alike can believe in,” Dr. Haque said.

“Saying simply ‘bless you’ also reduces religious implications or revelations about your own beliefs,” said Frank Farley, a psychology professor at Temple University. “It’s more nonsectarian.”

Sharon Schweitzer, who has written about etiquette, says that even today, many people still believe that saying “God bless you” or “bless you” is an indication of social standing, social graces and kindness, whether you are familiar with the historical origins or not. “Our parents taught us to say it, so we feel compelled to do so, even in 2019.”

Dr. Farley offers a variety of motives for why so many of us feel compelled to offer a blessing after someone sneezes.

Conditioned response. People often say “thank you” when we say “God bless you” when they sneeze. The thank you serves as a reward and reinforcement

It’s catching. We may imitate others who offer a blessing we model their behavior. This might start at a young age when we see and hear adults around us doing this. Sometimes several “bless you’s” will be heard from various people in the vicinity of a sneeze, a kind of social contagion.

Micro-affections. Saying “bless you” may engender an extremely brief and passing feel-good connection to the person sneezing, a phenomenon that Dr. Farley calls “micro-affections,” an antidote to the “micro-agressions” we hear so much about.

Conformity. Many of us conform to the norm. Saying “bless you” in response to a sneeze is part of the civility that underlies many of our social mores.

Monica Eaton-Cardone, owner and chief operating officer of a cybersecurity company who travels globally for her business, said she feels compelled to say “God bless you” when someone is sick and sneezing because it’s a fast, simple way to let someone know that you care about their well-being. “There’s something so universally democratic about our health,” she said. “For me, the phrase is another way for us to connect. And besides, no matter how blessed we are, who among us couldn’t use an extra blessing?”

Why do we sneeze? Researchers find the mechanism behind each ‘achoo’

The region of the brainstem associated with sneezing was previously identified by researchers but the specific cells responsible for the reaction were previously unknown.

The scientists at Washington University in St. Louis came up with a unique way to find the neurons. They gave mice sneeze inducing compounds like capsaicin to encourage a reaction. Capsaicin is the same stuff that makes chili peppers spicy.

The researchers were monitoring the mice when they sneezed and found the signaling molecules being released. They are called neuromedin B.

It turns out that the cells responsible for sneezing are in the part of the brain that controls exhalation. The action required to sneeze. When they injected neuromedin B into the area the mice then sneezed. The Journal Nature says that this revealed the nose to brain stem pathway behind sneezes.

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If This Is Your Only Symptom, You Might Be Safe From COVID

This worrisome symptom may not actually point to a coronavirus case.


The coronavirus pandemic has put many of us so on edge that whenever we wake up with a new symptom, we immediately wonder if we've finally contracted the virus. However, many of the signs and symptoms we worry could mean COVID are also very common of other milder, seasonal ailments, like allergies or a cold. And according to experts, one symptom in particular may not be worth worrying over if it is the only symptom you have: sneezing. Keep reading to find out why experts say this symptom alone is not likely coronavirus, and for more symptoms you may be worried about, This Is How to Tell If Your Cough Is COVID, Doctors Say.


The Centers for Disease Control and Prevention (CDC) has generated a list of coronavirus symptoms—and while they note that it's not comprehensive, it does include most of the common symptoms, such as fever, cough, shortness of breath, loss of taste or smell, headache, and fatigue. While congestion or runny nose is included on the list, sneezing is not. And for symptoms you do need to worry about, These 4 Easy-To-Miss Symptoms Could Mean You Have COVID, Experts Say.


According to the CDC, sneezing is considered a common symptom of a cold and a flu symptom sometimes. If you have a cold, you are likely to experience a sore throat and runny nose first, followed by sneezing and coughing. The Mayo Clinic says that the flu may also have these symptoms—making it seem like a common cold at first—but the flu will develop suddenly while a cold usually develops slowly. And for more coronavirus news, discover The One Thing You Can Stop Doing to Avoid COVID, According to Doctors.


Sashini Seeni, MD, a general practitioner of medicine at DoctorOnCall, says "sneezing is more likely to be a manifestation of cold, influenza infections, and allergies." And when comparing symptoms of COVID and seasonal allergies, the CDC says sneezing is more likely a symptom of seasonal allergies than it is of the coronavirus.

Seeni says it's important to take note of the other symptoms you have alongside your sneezing. If you experience "sneezing followed by itchiness, watery eyes, inflamed or swollen body parts," you're most likely just dealing with allergies. And for more up-to-date information, sign up for our daily newsletter.


Alongside allergies, colds, and the flu, sneezing can also be brought on by your environment. Marc Goldstein, MD, a board-certified allergist and chief medical advisor at Curist, explained in an article for Curist that sneezing can be the result of colder weather. According to Goldstein, cold and dry air can irritate your nasal passages and this can cause you to sneeze. And for more on the current state of the pandemic, This Is How Bad the COVID Outbreak Is in Your State.


"It is rather unlikely to have a single symptom associated with COVID-19," Seeni says. "This is due to the fact that viral infection tends to spread across the whole respiratory system, triggering lung-related ailments, and at the same time, [eliciting] systemic body response such as fever when the virus is exposed to our immune system."

You should expect to have some of the other coronavirus symptoms listed by the CDC if your sneeze is COVID-related and you are symptomatic. However, Seeni emphasized that it's impossible to be certain, so if you want to know for sure whether or not you have the virus, you should seek out a COVID test. And if you do have coronavirus, This One Thing Could Determine If Your COVID Case Will Be Severe or Mild.

What are the symptoms?

Whether you have seasonal hay fever, longer-term perennial or vasomotor rhinitis, or a viral infection, you’re likely to have similar cold and flu-like symptoms.

You’ll have either a runny or stuffy nose. Other symptoms include sore throat sneezing cough post-nasal drip – nasal mucus going down the back of your throat and fatigue.

But there are two classic hay fever symptoms that can help you tell allergies and viruses apart. Hay fever can cause you to have an itchy nose or throat and when it’s more severe it can cause swollen, blue-coloured skin under the eyes (called allergic shiners).

What Makes Me Sneeze?

If you just sneezed, something was probably irritating or tickling the inside of your nose. Sneezing, also called sternutation, is your body's way of removing an irritation from your nose.

When the inside of your nose gets a tickle, a message is sent to a special part of your brain called the sneeze center. The sneeze center then sends a message to all the muscles that have to work together to create the amazingly complicated process that we call the sneeze.

Some of the muscles involved are the abdominal (belly) muscles, the chest muscles, the diaphragm (the large muscle beneath your lungs that makes you breathe), the muscles that control your vocal cords, and muscles in the back of your throat.

Don't forget the eyelid muscles! Did you know that you always close your eyes when you sneeze?

It is the job of the sneeze center to make all these muscles work together, in just the right order, to send that irritation flying out of your nose. And fly it does &mdash sneezing can send tiny particles speeding out of your nose at up to 100 miles per hour!

Massachusetts Institute of Technology (MIT) researcher Lydia Bourouiba and her colleagues are studying what really happens when a person sneezes. They're using high-speed imaging to film the cloud of droplets that a sneeze creates. Then, the Bourouiba Research Group uses math to analyze what's going on with all those droplets. They hope to learn more about how illnesses spread.

Most anything that can irritate the inside of your nose can start a sneeze. Common causes include dust, cold air, or pepper. When you catch a cold in your nose, a virus has made a temporary home there and is causing lots of swelling and irritation. Some people have allergies, and they sneeze when they are exposed to certain things, such as animal dander (which comes from the skin of many common pets) or pollen (which comes from some plants).

Do you know anyone who sneezes when they step outside into the sunshine? About 1 out of every 3 people sneezes when exposed to bright light. They are called photic sneezers (photic means light). If you are a photic sneezer, you got it from one of your parents because it is an inherited trait. You could say that it runs in your family. Most people have some sensitivity to light that can trigger a sneeze.

Have you ever had the feeling that you are about to sneeze, but it just gets stuck? Next time that happens, try looking toward a bright light briefly (but don't look right into the sun) &mdash see if that doesn't unstick a stuck sneeze!

ICSE Solutions for Class 10 Biology – The Nervous System and Sense Organs provides ICSE Solutions for Class 10 Biology Chapter 8 The Nervous System and Sense Organs for ICSE Board Examinations. We provide step by step Solutions for ICSE Biology Class 10 Solutions Pdf. You can download the Class 10 Biology ICSE Textbook Solutions with Free PDF download option.

Short Questions

Question 1: What are the functions of the nervous system ?
Answer: The nervous system regulates, co-ordinates and links the activities of different organs and the entire organism, making it an integrated whole. It also brings about an adjustment between the organism and its environment.

Question 2: Explain the divisions of nervous system.
Answer: The nervous system is divisible into three regions:
(i) Central nervous system: Includes brain and spinal cord.
(ii) Peripheral nervous system: Includes spinal and cranial nerves.
(iii) Autonomic nervous system: Includes the sympathetic and parasympathetic nerves.

Question 3: Name three involuntary actions controlled by medulla in the hind brain.
Answer: Salivation, vomitting, blood pressure.

Question 4: Explain the terms sensory nerve, motor nerve and mixed nerve.
Answer: (i) A sensory nerve is one which sends nerve impulses from a receptor (sense organs) to the central nervous system.
(ii) A motor nerve is one which carries the impulses from the central nervous system to an effector.
(iii) A mixed nerve is one which carries both sensory and motor fibres. For example, a spinal nerve.

Question 5: What are the functions of tears ?
Answer: The functions of tears:
(i) To lubricate the surface of eye. (ii) To wash away dust particles.
(iii) To help in killing germs. (iv) To communicate emotions.

Question 6: Give the functions of spinal cord ?
Answer: (i) It controls all the reflex actions occurring below the neck.
(ii) It conducts sensory impulses from skin to the brain and motor impulses from brain to the muscles of trunk and limbs.

Question 7: How does the arrangement of nerve cells in the spinal cord differ from that in the brain ?
Answer: In spinal cord the cytons of the nerve cells forming gray matter is located in the interior of the spinal cord while in the brain gray matter is located in the exterior.

Question 8: How does an impulse travel across a synapse ?
Answer: The impulse travels across a synapse in one direction only, always from the axons to the cells — body and dendrites of the next neuron. Acetylcholine prevents its back flow.

Question 9: Name the part of the human brain which is concerned with the following :
(1) Seat of memory
(2) Coordinates muscular activity.
Answer: (1) Cerebrum
(2) Cerebellum.

Question 10: (i) What is meant by ‘reflex action’ ?
(ii) State whether the following are simple reflexes, conditioned reflexes, or neither of the two:
1. Sneezing. 2. Blushing. 3. Constriction of pupil.
4. Lifting up a book. 5. Knitting without looking.
6. Sudden application of brakes without thinking.
7. Blinking
8. Cleaning
9. Playing on the Keyboard
10. Salivation when food is put in the mouth.
Answer: (i) The reflex action is an immediate short-lived response to a stimulus, brought about by the nervous system.
(ii) 1. Simple reflex
2. Simple reflex
3. Simple reflex
4. None
5. Conditioned reflex
6. Conditioned reflex
7. Blinking—simple reflex
8. Cleaning of table—voluntary action
9. Playing on keyboard—conditioned reflex
10. Salivation when food is put in the mouth —simple reflex

Question 11: What type of reflexes are the following ?
(i) Sweating in summer, (ii) Knitting and swimming, (iii) Solving mathematical sums.
(iv) Formation of goose-pimples in cold weather. (v) Blinking of the eye.
Answer: (i) Simple reflex.
(ii) Conditioned and modified reflex.
(iii) Conditioned reflex depending upon reasoning and past experience.
(iv) Simple reflex.
(v) Simple reflex.

Question 12: In what two whys is yellow spot different from blind spot ?
Answer: Yellow spot has more cones and less rod cells. Blind spot has no photosensitive cells.

Question 13: What is a Lachrymal gland ?
Answer: Lachrymal gland is a secretary gland present in top right part of the eye. Its secretion is called tears which lubricates the eye and is antiseptic in nature.

Question 14: Name the common defects of the eye.
Answer: Common defects of the eye:
(i) Near or short sightedness (Myopia)
(ii) Far or long sightedness (Hypermetropia)
(iii) Astigmatism.
(iv) Presbyopia.
(v) Night blindness.
(vi) Colour blindness.
(vii) Squint.
(viii) Cataract.

Question 15: Mention the characteristics of the image that falls on the retina of the eye.
Answer: It is real, inverted and diminished.

Question 16: What is meant by power of accommodation of the eye ? Name the muscles of the eye responsible for the same.
Answer: The power of accommodation of the eye is the process of adjusting the focal length of the lens according to the near or distant objects. The ciliary muscles attached to the lens controls its curvature and alters its focal length.

Question 17: Name an old age eye defect. Why is it caused ?
Answer: Hypermetropia. It is caused due to flattening of eye lens (Also presbyppia in which lens looses flexibility).

Question 18: With reference to the functioning of the eye, answer the questions that follow:
(i) What is meant by power of accommodation of the eye ?
(ii) What is the shape of the lens during (1) near vision, (2) distant vision ?
(iii) Name the two structures in the eye responsible for bringing about the change in the shape of the lens.
(iv) Name the cells of the retina and their respective pigments which get activated (1) in the dark, (2) in light.
Answer: (i) It is the ability of the body to focus clearly objects, both close and distant from the eye.
(ii) 1. Almost round
2. Less convex almost flat
(iii) Ciliary muscles and suspensory ligaments.
(iv) 1. Rods, rhodopsin 2. Cones, iodopsin

Question 19: What are thermoreceptors ?
Answer: These receptors are located in the skin, help in detecting temperature changes. They are in the form of free nerve endings.

Question 20: What is stereoscopic vision ?
Answer: The capacity to perceive three-dimensional image due to simultaneous focusing of both eyes on a object is called stereoscopic (binocular) vision.

Question 21: What are the functions of proprioreceptors ?
Answer: These sense organs are present in the muscles. They detect position, movement of muscles, muscle tension, internal movement of organs etc.

Question 22: Describe the structure and location of various taste buds.
Answer: Structure of taste buds: There are four primary tastes-sweet, salty, sour and bitter. The taste receptors are called taste buds. Each taste bud opens on the tongue surface through a taste pore. Each taste buds contains 60-65 spindle-shaped cells, out of which 5-15 are taste receptor cells and others supporting cells. The taste receptor cells produce protoplasmic outgrowths called taste hair. The taste hair project through taste pore and receive the stimulus of taste.

Taste buds Location
Sweet Front of the tongue
Salt Tip and sides of the tongue
Bitter Rear
Sour Back and sides of the tongue

Give Reasons

Question 1: The spinal cord and brain are called as the central nervous system.
Answer: Because they give rise to all the nerves and control all the actions of the body.

Question 2: Why injury to medulla oblongata results in death ?
Answer: Medulla oblongata controls involuntary functions like heart beat, rate of respiration, secretion of saliva gut peristalsis, etc. Injury to the Medulla oblongata may result to the stop of heart beat and breathing leading to death.

Question 3: Why do we see clearly at the central region of retina ?
Answer: The central region of the retina has fovea centralis, with the yellow spot area surrounding it. There are only cone cells responsible for clear vision and details of the objects.

Question 4: Older people require glasses to read and write.
Answer: In old age the flexibility of the lens declines and the lens becomes less convex or opaque leading to weakness of eye sight.

Question 5: Deficiency of vitamin A causes night blindness.
Answer: Because the visual purple (Rhodopsin) of the rods is not formed in the absence of vitamin A.

Question 6: When you enter into a dark room from bright because sunlight, you can not see things for a few second.
Answer: In bright light the visual purple or rhodopsin pigment is destroyed and the diameter of pupil is reduced to allow the entry of less light.

Question 7: The hand automatically shows the direction to turn a cycle without thinking.
Answer: Because of conditioned reflex which we learn by experience and gradually respond to it unconsciously.

Question 8: A person after consuming alcohol walks clumsily.
Answer: Alcohol affects the cerebellum which is the centre of body balance and co-ordination. Due to the alcohol effect the cerebellum is unable to co-ordinate muscular movements properly.


Question 1: A Sensory neuron and a Motor neuron (function)

Sensory Neuron Motor Neuron
A sensory neuron sends nerve impulses to the central nervous system from the receptor organs. A motor neuron sends nerve impulses from the central nervous system to the effector organs.

Question 2: Cerebrum and Spinal cord (arrangement of neurons).

Cerebrum Spinal cord
The inner portion of the cerebrum consists of white matter, mainly containing the axons (nerve fibres) of the neurons. The inner portion of the spinal cord consists of gray matter containing the cell bodies, motor and associated neurons whereas the white matter forms outer layer.

Question 3: Middle ear and Inner ear.

Middle Ear Inner Ear
It has three ear ossicles and eustachian tube. It has cochlea, urticulus, sacculae and semi- circular canals.
It transmits sound vibrations. It is concerned with hearing, balance and equilibrium.

Question 4: Short-sightedness and Long-sightedness.

Short-Sightedness Long-Sightedness
(i) The inability of the eye lens to focus images of distant objects on the retina so the images fall in front of the retina. The inability of the eye lens to focus near object images on the retina so the images fall beyond the retina.
(ii) It is corrected by using glasses of concave lens. It is corrected by using glasses of convex lens.

Question 5: Vitreous humour and Aqueous humour.

Vitreous Humour Aqueous Humour
(i) It is found between the retina and the lens, posterior in the eye. It is found between the cornea and the lens, anterior in the eye.
(ii) It has high specific gravity. It has low specific gravity.

Question 6: Yellow spot and Blind spot.

Yellow Spot Blind Spot
(i) It has only cone cells. It has neither cone cells nor rod cells.
(ii) Clear images are formed here. No images are formed here.

Question 7: Cochlea and Concha.

Cochlea Concha
(i) It is a part of the inner ear. It is the ear pinna of cartilage.
(ii) It contains the organs of hearing. It collects the sound waves.

Question 8: Rods and Cones.

Rods Cones
These are neurons concerned with vision in poor light. These are neurons concerned with detailed clear vision and colour perception.
They contain rhodopsin. They have iodopsin. They don’t have rhodospin.

Question 9: Retina and Choroid.

Retina Choroid
(i) It is the innermost layer of the eye-ball. It is the middle layer of eye ball tunics.
(ii) It contains neurons. It contains blood capillaries.

Question 10: Myopia and Hypermetropia.

Myopia Hypermetropia
The lengthening of the eyeball or the lens is too curved causes this defect. The shortening of the eyeball or flattening of the eye lens causes this defect.

Question 11: Cerebrum and Cerebellum.

Cerebrum Cerebellum
It is the seat of intelligence, memory and controls of voluntary activities. It co-ordinates muscular activities and maintains body balance.

Question 12: Afferent and Efferent Nerve.

Afferent (sensory) Nerve Efferent (motor) Nerve
It conducts nerve impulse from periphery to the central nervous system. It conducts nerve impulse from central nervous system (C.N.S.) to the periphery of the body.
It is generally made up of pseudo-unipolar neurons. It is generally made up of multipolar neurons.
Its dendrites are comparatively longer than the axon. Its axon is comparatively longer than dendrites.
Its axon enters into the C.N.S. Its axon emerges out from C.N.S.

Diagram Based Questions

Question 1: The following diagram is that of a human brain. Guidelines 1 to 5 indicate different parts of the surface of the brain and these are as follows:

1. Frontal lobe of cerebrum
2. Temporal lobe of cerebrum
3. Occipital lobe of cerebrum
4. Cerebellum
5. Medulla oblongata
Study the diagram and answer the following questions:
(i) What handicaps would result from:
(a) Damage toçart numbered 3.
(b) Damage to part numbered 4.
(ii) Mention one main function of each of the parts numbered 1,2, and 5.
Answer: (i) (a) The part numbered 3 is named as occipital lobe of cerebrum, which is the area of vision. If this part is damaged, the person is unable to see.
(b) The part numbered 4 is named as cerebellum, which is responsible for coordinating the muscular activity for body balancing. If this part is damaged, the
body balancing during walking and running would be affected.
(ii) Function of part 1: It governs all mental activities (reason, will, memory, intelligence, higher feelings and emotions).
Function of part 2: It controls all voluntary action and is responsible for taste and smell.
Function of part 5: It controls several involuntary activities, such as heart beat, breathing, peristaltic motion of the alimentary canal, dilation and concentration of blood vessels, etc.

Question 2: The below diagram represents longitudinal section of human brain. Label its parts 1-9 as shown with guidelines.

1. Cerebrum
2. Gray matter
3. White matter
4. Mid-brain
5. Cerebellum
6. Spinal cord
7. Medulla oblongata
8. Hypothalamus
9. Pituitary body

Question 3: The below simplified diagram shows a section through the brain.

(i) Name the parts labeled A, B and C.
(ii) Give one function of each of the parts A, B and C.
(iii) What is found in region D?
Answer: (i) A—cerebrum B—medulla oblongata C—cerebellum.
(ii) a—controls memory, learning, speech and co-ordinates sensory input and motor output, b—controls vital processes such as heart rate and breathing, c—is
responsible for muscle co-ordination and balance.
(iii) D—contains cerebrospinal fluid.

Question 4: The below diagram represents the human brain as seen in an external view. Study the same and then answer the questions that follow:

(i) Name the parts labeled 1, 2, 3 and 4.
(ii) Mention the difference in the arrangement of the nerve cells in the parts marked ‘1’ and ‘4’.
(iii) What is the main function of the parts marked ‘3’ and ‘4’?
(iv) Name the sheet of nerve fibres that connect the two halves of the part labeled ‘1’.
Answer: (i) 1. Cerebrum,
2. Cerebellum,
3. Medulla oblongata,
4. Spinal cord.
(ii) 1. Gray matter is outside and white matter inside.
4. White matter s outside and gray matter is inside.
(iii) 3. Medulla oblongata controls all involuntary movements of internal organs e.g., breathing movements of lungs, beating of heart.
4. Spinal cord performs reflex action below the neck.
(iv) Corpus callosum.

Question 5: The diagram given below shows the internal structure of the spinal cord, depicting a simple reflex. Study the same and then answer the questions that follow:

(i) Name the parts numbered 1 to 5.
(ii) Using the letters of the alphabet shown in the figure indicate the direction in which an impulse enters and leaves the spinal cord.
(iii) What is the term given to the point of contact between two nerve cells ?
(iv) What is meant by ‘simple reflex’ ? Give two examples of simple reflexes and name the stimuli too.
(v) How does the arrangement of nerve cells in the spinal cord differ from that in the brain ?
Answer: (i) 1. Sensory or Afferent fibre.
2. Cell body of sensory neuron.
3. White matter.
4. Cell body of motor neuron.
5. Spinal nerve.
(ii) BCA
(iii) Synapse.
(iv) Simple reflex: It is an involuntary automatic, quick response to a stimulus.
Examples: (a) The closing of the eyelids when a strong beam of light is flashed.
(b) The withdrawal of the hand when it is pricked.
(v) In spinal cord white matter is outside and gray matter is inside. In brain white matter is inside and gray matter is outside.

Question 6: The diagram given below represents the spinal cord of a mammal, seen in a transverse section together with the nerves. Study the diagram and then answer the questions given below:

(i) Label the parts 1—8 indicated by guidelines.
(ii) What do the arrows indicate ? What is the pathway indicated termed?
(iii) What type of nerve is shown in the diagram?
Answer: (i) 1. White matter
2. Gray matter
3. Dorsal root
4. Ventral root
5. Dorsal ganglion
6. Sensory neuron
7. Spinal nerve
8. Synapse
(ii) The arrows indicate the arrangement of white and gray matter is reversed from that in the brain. The patl4way indicated is termed as nervous pathway in a simple spinal reflex.
(iii) Sensory or Afferent nerve.

Question 7: The below diagram is the surface of tongue showing taste zone.

(i) Label the parts 1-4.
(ii) Where are the receptors for sensations of taste are located?
(iii) Why person suffering from cold often complain that they cannot taste their food?
Answer: (i) 1—Bitter Taste, 2—Sour Taste, 3—Salt Taste, 4—Sweet Taste.
(ii) The receptors for sensations are located in the taste bud covering the tongue surface.
(iii) Person suffering from cold often complain that they cannot taste their food because their gustatory sensations are not operating well.

Question 8: The diagram given below represents the cross-section of the human eye:

(i) Name the parts labeled 1—12.
(ii) What is the function of the part marked ‘10’?
(iii) What would happen if part ‘5’ is damaged or cut ?
Answer: (i) 1. Sclerotic
2. Choroid
3. Retina
4. Yellow spot or fovea
5. Optic nerve
6. Blind spot
7. Lens
8. Aqueous humour
9. Pupil
10. Iris
11. Vitreous humour
12. Cornea.
(ii) The function of the part marked ‘10’, the iris, is to regulate the amount of light that enters the eye so that too much light does not damage the delicate cells of the retina.
(iii) The person would not see because the sensations from the eye would not reach the brain.

Question 9: Given below is the diagram of a part of the human ear. Study the same and then answer the questions that follows:
Labyrinth of the inner ear.
(i) Give the biological term for Malleus, Incus and Stapes.
(ii) Name the parts labeled A, B and C in the diagram.
(iii) State the functions of the parts labeled ‘A’ and ‘B’.
(iv) Name the audio receptor region present in the part labeled. ‘A’.
Answer: (i) Ear Ossicles
(ii) A —> Cochlea, B —> Semi-circular canal, C —> Vestibule.
(iii) A is concerned with the sense of hearing. B is concerned with the sense of dynamic balance.
(iv) Organ of corti or spiral organ.

Question 10: The following diagram refers to the ear of a mammal.

(i) Label the parts 1 to 10 to which the guidelines point.
(ii) Which structure:
(a) Converts sound waves into mechanical vibrations?
(b) Converts vibrations into nerve impulses?
(c) Responds to change in position?
(d) Transmits impulses to the brain?
(e) Equalizes atmospheric pressure and pressure in the ear.
Answer: (i) 1. Cochlea.
2. Auditory nerve.
3. Semi-circular canals.
4. Ear ossicles.
5. Auditory meatus.
6. Pinna.
7. Er drum.
8. Fenestra rotunda.
9. Eustachian tube.
10. Fenestra ovalis.
(ii) (a) Ear drum or tympanum.
(b) Organ of corti.
(c) Semi-circular canals.
(d) Auditory nerve.
(e) Eustachian tube.

Question 11: Given below is the diagram of the human ear. Study the same and answer the questions that follow:

(i) Give the biological term for the part labeled ‘A’ and state its function.
(ii) Name the part labeled ‘B’ and state its function.
(iii) Name the part labeled ‘C’ and state its function.
(iv) Give the function of ear wax.
Answer: (i) Ear Ossicles (Malleus, incus and stapes)—To receive, magnify and transmit the sound vibrations to the membrane of the oval window.
(ii) Eustachian tube—It equalize the air pressure on either side of ear drum allowing it to vibrate freely.
(iii) Auditory Nerve—It transmits the impulses from cochlea to brain.
(iv) Ear wax-has insect repellent properties hence prevents the entry of insects in the auditory canal. It also checks die entry of dust particles in the ear. Thus, it lubricates and protects the ear drum.

Question 12: The diagram given below is a representation of a certain phenomenon pertaining to the nervous system. Study the diagram and answer the following questions:

(i) Name the phenomenon that is being depicted.
(ii) Give the technical term for the point of contact between the two nerve cells.
(iii) Write the functions of parts 5 and 6.
(iv) How does the arrangement of neurons in the spinal cord differ from that of the brain ?
Answer: (i) Reflex action
(ii) Synapse
(iii) (1) Sensory fibre
(2) Sensory ganglion
(3) White matter
(4) Grey matter
(iv) (5) It receives messages from sensory neuron and passes it to the motor neuron.
(6) It passes impulses from the spinal cord to the effector organ.
(v) In spinal cord the grey matter is inside and white matter is outside around it. In brain grey matter is outside and white matter is inside.

Question 13: Study the following diagram carefully and then answer the questions that follow. The diagram is depicting a defect of the human eye :

(i) Identify the defect shown in the diagram.
(ii) Give two possible reasons for the above defect.
Answer: (i) Far sightedness or hypermetropia.
(ii) (a) Lens is flattened or less convex,
(b) Eyeball is short.

Question 14: Given below is a diagram depicting a defect of the human eye. Study the same and then answer the questions that follows:

(i) Name the defect shown in the diagram.
(ii) Give two possible reasons for this defect of the eye in human beings.
(iii) Name the parts labeled 1 to 4.
(iv) Name the type of lens used to correct this eye defect.
Answer: (i) Myopia, Short-sightedness.
(ii) The possible reasons for this defect may be:
(1) The eyeball is lengtheied from front to back.
(2) The lens is too curved.
(iii) (1) Vitreous chamber.
(2) Fovea centralis (yellow spot)
(3) Lens
(4) Pupil.
(iv) This defect can be corrected by suitable concave lens.

Question 15: Given below is a diagrammatic representation of a defect of the human eye:

(i) Identify the defect.
(ii) Mention two reasons for the above defect.
(iii) State how the defect can be rectified.
(iv) Name the part of the eye responsible for maintaining the shape of the eyeball.
Answer: (i) Hypermetropia (Far-sightedness) because image is behind the retina.
(ii) Reasons for hypermetropia are:
1. Shortening of eyeball from front to back.
2. Lens becomes too flat.
(iii) It can be rectified by using convex lenses of appropriate power (focal Iength).
(iv) Sclerotic (or sclera).

Question 16: With respect to human eye explain:
(i) How is the image formed on the retina?
(ii) How is the amount of light entering the eye controlled?
(iii) What type of lens is used for the correction of ‘Long sight’ defect?
(iv) With the help of a ray diagram show the defect of the eye and then its correction after use of lens.
Answer: (i) Light from the source when reach the eye, it gets converged by the lens and an inverted image is formed on the retina.
(ii) The amount of light entering the eye can be controlled by dilating or constricting the pupil.
(iii) A biconcave lens is used to correct long sightedness.

Question 17: Given below is the diagram of the human ear. Study the diagram and then answer the questions that follow :

(i) What role does the ear drum play in hearing?
(ii) What common term is given to the parts labeled A, B and E?
(iii) Would there be any difference if these three parts mentioned in (ii) above were replaced by one by one ? Why?
(iv) Give the biological term for the parts labeled C and D.
(v) Name the fluid which fills the parts mentioned in (iv) above.
(vi) State the functions of the ear.
Answer: (i) The ear drum is vibrated by sound waves and passes them to internal ear.
(ii) Ear ossicles.
(iii) One big ossicle would not be able to produce effective amplification because it would require a greater force of vibration that supplied by the ear drum normally. Moreover, three smaller ossicles with proper distance between their produces multiple amplification and effective transmission.
(iv) C is semi-circular canals and D is cochlea.
(v) Endolymph.
(vi) Hearing and balancing of the body.

Sketch and Label the Diagram

Question 1: Draw a neat labeled diagram to show how hypermetropia can be rectified.

Question 2: Draw well labeled diagram of a ‘Neuron’ and name the following parts:
(1) Node of Ranvier (2) Nissil granules (3) Cyton

Question 3: Draw a labeled diagram of a myelinated neuron.

Question 4: Draw a diagram of the human eye as seen in a vertical section and label the parts which suits the following descriptions relating to the:
(i) photosensitive layer of the eye.
(ii) structure which is responsible for holding the eye lens in its position.
(iii) structure which mamtains the shape of the eye ball and the area of no vision.
(iv) anterior chamber seen in front of the eye lens.
(v) outer most transparent layer seen in front of the eye ball.

Question 5: Draw a labeled diagram of the front view of human eye.

Question 6: Draw a labeled diagram of the inner ear. Name the part of the inner ear that is responsible for static balance in human beings.

The static balance in the ear of human being is achieved by the gravity receptors located in the utriculus and sacculus in the inner ear.

Explain the Terms

1. Nerve
2. A Mixed nerve
3. Cyton
4. Ganglion
5. Voluntary-action
6. Synapse
7. Reflex action
8. Natural reflex
9. Accommodation in the eye
10. Hypermetropia
11. Presbyopia
12. Astigmatism
13. Cataract
Answer: 1. A nerve is a thread-like structure which emerges from the brain and the spinal cord. It consists of a large number of axons or nerve fibres surrounded by a connective tissue sheath. The nerves arising from the brain are called cranial nerves while those arising from the spinal cord, are called spinal nerves.
2. A mixed nerve is one which carries both sensory and motor fibres. For example, a spinal nerve. These’are mixed nerves and they have two separate connections with the spinal cord— (i) A dorsal root which is a sensory root, and (ii) A ventral root which is a motor root.
3. Cyton is the cell body of a nerve cell (neuron), containing cytoplasm and the cell organelles.
4. Ganglion is a small, solid mass of nervous tissue containing numerous cell bodies of a neuron.
5. The stimulation from the nerve cells of the receptor organ passes into the spinal nerve (along the dorsal root) into the spinal cord and from there it goes straight to the brain. From the brain another impulse passes, to the spinal cord and travels along the ventral root of the spinal nerve to reach the effector organ (a muscle), the activity of which is a response to the nerve impulse which has come from the brain.
6. Synapse is a place or a gap where two adjoining dendrites or axons meet but never unite, as there is no continuity between the nerve cells. At the synapse, acetylcholine is secreted which prevents back flow of the impulse.
7. Reflex action is an action which is nearly instantaneous and not under the control of the will. The impulse passes from the sensory cells of the receptor organ along the dorsal root into the spinal cord. From here two messages pass simultaneously—one to the brain and the other travels out along the ventral root to reach the muscle which immediately responds.
8. A natural reflex is the one in which no previous experience or learning is required and are inborn and protective, e.g., the sucking of milk of an infant from the breast of the mother or reflex of the eyelid.
9. Accomodation in the eye is the process of adjusting the eyes so that the image can be focused on the retina and seen clearly. This is done by altering the curvature of the lens by the contraction or relaxation of the ciliary muscles.
10. With age, the elasticity of the lens decreases and the individual becomes long- sighted and is called Hypermetropia In this condition, the diameter of the eyeball from front to back is too short. The clear image falls beyond the retina and the eye sees a blurred image. Hypermetropia may be corrected by the use of a biconvex lens.
11. Presbyopia: It is a condition affecting older people who cannot see near objects clearly. Their lens loses flexibility resulting in a kind of far-signtedness. This again is corrected by a convex lens.
12. Astigmatism: It is a defect in which some parts of the object are seen in focus while others are blurred. It arises due to the uneven curvature of the cornea. This is corrected by cylindrical lenses.
13. Cataract: It is a condition in which the lens turns opaque and the vision is cut down even to total blindness. It can be corrected by surgically removing the lens and by using spectacles with highly convex lense.

Name the Following

1. Unit of nervous system is.
2. The dorsal root ganglion of the spinal cord contain cell bodies of which type of neurons. –
3. Name the bony box in which the brain is located.
4. Protective membranes around brain.
5. The seat of memory and intelligence in the human brain.
6. The pigmented circular area seen in the eye.
7. The most sensitive region of the retina.
8. The innermost layer of the eye.
9. The focal length of the lens is altered by the contraction of which type of muscles.
10. The area where the image is formed but not seen by our eye is termed as.
11. The region in the eye where the rods and cones are located.
12. Yellow spot and ciliary muscles are found in.
13. The part of the eye responsible for change in the size of the pupil.
14. Fluid present in the posterior chamber of the eye.
15. The defect of the human eye caused due to the uneven surface of the cornea.
16. The type of lens used for correcting myopia.
17. Name the photoreceptors found in the retina of the eye.
18. The ear ossicle in contact with the oval window of the inner ear.
19. Name the three ear ossicles of the ear. How do they contribute in the mechanism of hearing ?
20. Name the three small bones present in the middle ear. What is the biological term for them collectively ?
21. Name the part of the ear associated with (1) static balance, (2) hearing, (3) dynamic balance.
22. Name the nerve, which transmits messages from the ear to the brain.
23. Give the technical term for the structure found in the inner ear.
1. Neuron
2. Sensory
3. Cranium
4. Meninges
5. Cerebrum
6. Iris
7. Yellow spot
8. Retina
9. Ciliary muscles
10. Retina
11. Retina
12. Eye
13. Iris
14. Vitreous humour
15. Astigmatism
16. Biconcave
17. Rod cells and cones
18. Stapes
19. Three ear ossicles are : (i)Malleus (hammer), (ii)Incus (anvil), (iii)Stapes (Stirrup)
20. Malleus, incus, stapes. Collectively called ear ossicles.
21. (i) Vestibule, (ii) Cochlea, (iii) Semi circular canals
22. Auditory nerve
23. Membranous labyrinth

Give Technical Terms

1. The find cytoplasmic processes of the cell body of a neuron.
2. The neuron which conducts impulse from the central nervous system to the organs.
3. The brain and spinal cord together constitute the system known as.
4. The seat of intelligence and memory in the brain.
5. The part of human brain that controls body temperature.
6.. The structure which joins the two cerebral hemispheres in man.
7. The scientist, who conducted experiment on a dog to show conditioned reflex.
8. Response to a stimulus without the intervention of the will of an animal.
9. The chemical messenger by which the nerve impulse travels from one neuron to the other.
10. The number of cranial and spinal nerves in man.
11. The fluid that provides protection and nourishment to the cells of the brain.
12. Nerve that transfers impulses from ear to brain.
13. The part of the central nervous system in which the gray matter is located on the outer side and
the white matter on the inner side.
14. The junction between two nerve cells.
15. The fluid which fills the central canal of the spinal cord.
16. The path which responsible for protectingthe eye from sweat.
17. The type of lens used to correct myopia is
18. The part of the eye responsible for its shape.
19. What type of lens is used to correct ?
(a) Astigmatism (b) Myopia (c) Hypermetropia.
20. The most sensitive region of the retina.
21. What is the nature of the image that forms on the retina ?
22. The cells of the retina that are sensitive to colour.
23. Name the part of the retina on which an object is focused for the clearest vision.
24. The adjustment of the eye in order to obtain a clear vision of objects at different distances.
25. The receptors which help in the sensation of taste.
26. The fluid which conveys the vibrations of sound in the cochlea and semicircular canals.
27. The nutritive layer of the eye which also presents reflection of light.
1. Dendrites
2. Motor neurons
3. Central nervous system
4. Cerebrum
5. Hypothalamus
6. Corpus callosum
7. Ivan Pavlov
8. Reflex action
9. Acetylcholine
10. Cranial nerves: 12 pairs, Spinal nerves :31 pairs
11. Cerebrospinal fluid
12. Auditory nerve
13. Brain
14. Synapse
15. Cerebrospinal fluid
16. Eye brows
17. Concave
18. Vitreous humour
19. (a) Cylindrical lens (b) Concave lens (c) Convex lens .
20. Fovea centralis or macula
21. Real, inverted and small in size
22. Cones
23. Yellow spot
24. Accommodation of eye
25. Sensory papillae
26. Endolymph
27. Choroid

Fill in the Blanks

Complete the following sentences with appropriate words :
1. There are Billion neurons in our body.
2. A bundle of axons enclosed in a tubular sheath is called Nerve .
3. Cerebrum is the largest part of the brain.
4. Cerebrum is the site of Memory/thinking .
5. The part of brain where the respiratory centre is located is Medulla oblongata .
6. The medulla oblongata is also known as the Spinal bulb .
7. A nerve chain between a receptor and an effector organ is called Reflex arc .
8. Optic nerve is a type Sensory nerve, whereas spinal nerves are mixed nerves.
9. An inability to focus on nearby objects due to loss of elasticity of the lens with age is called Iris .
10. The part of the central nervous system which responds to the reflex action is Spinal cord .
11. Ear is the organ of balance and hearing in the body.
12. Tympanic chamber is filled with Perilymph .

True & False

1. A nerve impulse passes from one neuron to another across a synapse. (True)
2. Spinal nerves and cranial nerves constitute the central nervous system. (False, Spinal nerves and cranial nerves constitute the peripheral nervous system.)
3. Cranium is & pdrtion of the brain. (False, It is a bony box, enclosed brain.)
4. Spinal nerves are twelve pair. (False, Spinal nerves are 31 pair.)
5. The nerve impulse in the eye develops due to the chemical changes brought about in the sensitive cells (rods and cones) by the light energy of the image. (True)
6. Reflex action involves brain. (False, Reflex action involves spinal cord.)
7. A reflex action is a spontaneous response to a stimulus. (False, A reflex action is a spontaneous involuntary response to a stimulus.)
8. Reflex action is a unit of nervous action. (True)
9. Cones are the receptor cells in the retina of the eye sensitive to dim light. (False, Cones are the receptor cells in the retina of the eye sensitive to bright light.)
10. Rods are responsible for vision in the dark. (True)
11. The least distance of distinct vision for the human eye is 25 cm. (True)
12. Hypermetropia is a defect of the eye caused due to the eyeball elongation. (False, Myopia is a defect of the eye caused due to the eyeball elongation.)
13. The part of ear associated with balance is the cochlea. (False, The part of ear associated with balance is the semicircular canal.)
14. Cochlea of the ear is concerned with the sense of balance. (False, Cochlea of the ear is concerned with the sense of hearing.)
15. Deafness is caused due to the rupturing of the pinna. (False, Deafness is caused due to the rupturing of the eardrum.)

State the Location

Name Location
Yellow spot On the horizontal median axis of eye ball in retina.
Corpus callosum Thick band of nerve fibres joining two cerebral hemisphere of cerebrum.
Incus In middle ear inside tympanic activity.
Organ of Corti In the cochlea of ear.
Pinnae Side of the head, face.
Meninges Covering of brain and spinal cord.
Lacrimal gland At the upper side-ward portion of each eyelid.
Made of Ranvier On the medullated neurons.
Ganglia On each side of the spinal cord.
Cerebellum In the hind brain.
Iris In the eye behind the cornea.
Eustachian tube Between the middle ear and pharynx.
Semicircular canals In the internal ear.

State the Function

Write the functional activity of the following structures:

Name Function
Cerebrum Cerebrum is concerned with a number of senses like sight, hearing, taste, etc. The motor areas in the cortex give rise to voluntary movements such as speech, locomotion, etc. Other areas of the cerebrum are responsible for memory, intelligence, learning, emotions etc.
Hypothalamus The hypothalamus of the mid-brain regulates the body temperature, smooth muscles activity, water balance, appetite, blood pressure and the metabolism of fats and carbohydrates.
Cerebellum Cerebellum of the brain regulates and co-ordinates muscular contractions and skeletal movements. It is also concerned with balance.
Medulla oblongata Medulla oblongata is concerned with certain vital activities such as respiratory movements, heart beat and the dilation of blood vessels.
Cornea It covers and protects the iris and allows light rays into the eye.
Iris It is a muscular screen made up of radial and circular muscles that control the diameter of the central opening—the pupil, according to the intensity of illumination.
Aqueous humour It allows light rays to pass into the eye and prevents their refraction and dispersion.
Choroid coat in the eye Choroid layer with many capillaries forms the nutritive layer of the eye. The extended choroid layer forms the pigmented muscular curtain called the iris. The aperture in the centre through which light enters the aperture is called the pupil.
Ear drum It vibrates according to the sound waves and transmits them across the middle ear.
Ear ossicles The vibrations of the ear drum are amplified and transmitted to the delicate membrane sketched along the oval window.
Myelin sheath The myelin sheath covers the axon of a nerve cell, provides insulation and prevents indiscriminate distribution and leakage of nerve impulse.
Cerebrospinal fluid Cerebrospinal fluid offers some protection to the brain and spinal cord by acting as a cushion to absorb shocks. It also supplies nourishment to the brain tissue.
Acetylcholine When enough acetylcholine is secreted at the synaptic region of two nerve cells, it helps in the transmission of the nervous impulse to the next neuron under enzymatic reactions.
Cochlea It contains the organ of corti—for receiving sound reception and transmits to the brain across the auditory nerve. It is the organ of hearing.
Semi-circular canals They are concerned with maintaining equilibrium and posture of the body.
Endolymph It transmits vibrations to the hair cells of the inner ear to produce acoustic perception.
Eustachian tube It equalizes air pressure on the ear drum from inside.
Visual purple It has vitamin A derivative that helps the eyes to see in dim light.
Conjunctiva It binds the eye ball to the bony orbit of the skull and supplies nourishment.
Vitreous humour It maintains the shape of eyeball.

Choose the Odd One Out

1. Cyton, Photon, Axon, Dendrori. (Photon )
2. Cyton, Axon, Dendron, Cerebrum. (Cerebrum)
3. Coughing, Sneezing, Eating, Blinking. (Eating)
4. Corpus luteum, corpus calloswn, pens, cerebellum. (Corpus luteum)
5. Sneezing, coughing, blinking, typing. (Typing)
6. Cerebrum, Cranium, Cerebellum, Pons. (Cranium)
7. Sodium pump, Polared membrane, Threshold stimulus. (Sodium pump)
8 Pons, Cerebellum, Medulla Oblongata, Cerebrum. (Pons)
9. Choroid, Cilîary part, Iridial part, Cornea. (Cornea)
10. Rods, Cones, Night blindness, Rhodopsin. (Cones)
11. Myopia, Hypermetropia, Xerophthalnua.. Astigmatism. (Xerophthalmia)
12. Myopia, cataract, Hypermetropia, Squint, cretinism. (Cretinism)
13. Ciliar3’ muscle, Chords, Fovea, Gustatory cells. (Gustatory cells)
14. Incus, Pinna, Malleus, Stapes. (Pinna)
15. Semicircular canals, cochlea, Tympanum, Utriculus. (Tympanum)
16. Eustachian tube, Basilar membrane, Taste buds, Auditory ossicles. (Taste buds)

Multiple Choice Questions

1. The function of nervous system is to:
(a) Receive stimuli (b) Irritability.
(c) Conduction of enzymes (d) To prepare the body against reactions during emergency

2. A point of contact between wo neurons is termed:
(a) synapse (b) Sensory neuron
(c) neuro motor junction (d) Association neuron.

3. Neurilemma is:
(a) The cell membrane around the nerve cell
(b) A layer of fatty substance around axon.
(c) A layer of specialized neuroglia around myelin sheath of nerve fibres.
(d) The connective tissue around a nerve tract.

4. Cerebellum is the part of the brain which is responsible for:
(a) Interpreting sensations.
(b) Conducting reflexes in the body
(c) Maintaining posture and equilibrium.
(d) Controlling thinking, memory and reasoning.

5. If the cerebellum is injured:
(a) Movement’becómes shaky and speech become defective
(b) Movement becomes unbalanced, walk uncontrolled and speech defective
(c) Movement becomes jerky, walk controlled
(d) There is no effect as the actions are under the control of will.

6. The control of reflex action is through:
(a) Central nervous system
(b) Peripheral nervous system.
(c) Autonomic nervous system. (d) None of the above.

7. The ventral root ganglion of the spinal cord contains cell bodies of the:
(a) Motor neuron
(c) Intermediate neuron
(b) synapsis
(d) sensory

8. A reflex arc in man is bst described as movement of stimuli from:
(a) Receptor cell, sensory neuron, relaying neuron, effector muscles
(b) Receptor cell, efferent nervi, relaying neuron, muscles of the body
(c) Receptor cell, spinal cord, motor neuron, relaying neuron
(d) Receptor cell, synapse, motor neuron, relaying neuron

9. Which of the following is not a natural reflex action?
(a) Knee-jerk
(b) Blinking of eyes due to strong light
(c) Salivation at the sight of food
(d) Sneezing when any irritant enters the nose

10. The part of the human eye where rod cells and cone cells are located is the:
(a) Retina (b) Cornea
(c) Choroid (d) Sciera

11. The photo receptor cells of the retina sensitive to colour are:
(a) Cones (b) Pupil
(c) Rods (d) Organ of corti

12. The aperture in the eye through which light enters is the:
(a) Pupil (b) Conjunctiva
(c) Ciliary muscles (d) Choroid

13. The sequence of ear ossicles of vertebrates starting from the tympanum is:
(a) Incus, Malleus, Stapes (b) Stapes, Malleus, Incus
(c) Malleus, Incus, Stapes (d) Stapes, Incus, Malleus

14. The parts of the human ear concerned with hearing are :
(a) Cochlea,, ear ossicles and tympanum
(b) Semicircular canals, utriculus and sacculus
(c) Eustachian tube, tympanum and utriculus
(d) Perilymph, ear ossicles and semicircular canals

Match the Column

Column ‘II’ is a list of items related to ideas in Column ‘I’. Match the term in Column ‘II’ with the suitable idea given in Column ‘I’.

Column I Column II
(i) Auditory canal (a) Channels pressure waves of air into the middle ear.
(ii) Auditory (Eustachian tube) (b) Collects pressure waves of air.
(iii) Auditory nerve (c) Converts pressure waves of air into vibrations of bone.
(iv) Incus (d) Dissipates sound waves.
(v) Malleus (e) Equalizes pressure between the middle ear and the atmosphere.
(vi) Oval window (f) Provide information about the spatial orientation of the head.
(vii) Pinna (g) Transfers vibrations from a bone to a fluid.
(viii) Round window (h) Transfers vibrations from a bone to a membrane.
(ix) Semi-circular canal (i) Transfers vibrations from a bone to a bone.
(x) Stapes (j) Transfers vibrations from a membrane to a bone.
(xi) Tympanic membrane (k) Transmits action potential to the auditory cortex.

Answer: (i) (a) (ii) (e) (iii) (k) (iv) (i) (v) (j) (vi) (g) (vii) (b) (viii) (d) (ix) (f) (x) (h) (xi) (c)

11 Things in Your House That Are Making You Sneeze

Dust isn't the culprit &mdash though it's definitely a problem.

Dust isn't the culprit &mdash though it's definitely a problem.

Sure, we'd all love our home to smell like lilacs, the seashore, or even a pumpkin pie at all times.But a 2011 study found that home fragrances &mdash like room sprays, diffusers, or candles &mdash are a common cause of respiratory allergies. In fact, any strong perfume can be irritating, which can trigger a sneeze, explains Andrew S. Kim MD, medical director of the Alllergy & Asthma Center in Fairfax, Virginia, and a fellow of the American Academy of Allergy, Asthma & Immunology.

Crack a window instead, and consider swapping out scented stuff (even laundry detergents and body lotions can be culprits) for unscented versions if you suspect they're the reason you get a tickle in your nose.

You probably use a vacuum with the intention of getting rid of allergens like dust and pet dander. But an ill-treated machine will do just the opposite, dredging up sneeze-inducing debris and spreading them through the air. Carolyn Forte, director of the Cleaning Lab at the Good Housekeeping Institute, encourages us to remember the "six or six" rule: Swap your vac's HEPA filter every six months or every sixth bag change.You'll also want to empty the bag when it's three-quarters full &mdash too stuffed, and it will inhibit suction, and all that dust you're trying to pick up will have nowhere to go.

The simple act of breathing in cold air can make you sneeze. Why? Your sneeze reflex gets set off when something irritates your nasal passages or when you stimulate the nerve that runs through your nose (the trigeminal nerve, to be exact). Cold air is known to do both.

No, don't give up your weekly fresh flower fix (it's such a nice treat!). It's really plants like ragweed that produce tiny wind-borne pollens that tend to cause allergies &mdash not plants that depend on insect pollination (like most flowers), explains Dr. Kim.

Still, he says, the strong scents of some flowers "may be irritating and cause sneezing." If that sounds like you, steer clear of heavily fragranced blooms like freesia and stargazer lilies, and opt for more neutral-smelling blossoms such as dahlias and irises.

Soft toys are notorious for harboring dust mites &mdash and there's nothing fun about microscopic skin-eating buggers all up in teddy's fur. Roughly 20 million Americans are allergic to these little critters, so if you wash your sheets regularly, but still have the sniffles, you might check your kid's toy chest.

If the stuffed animals are washable (check the care tag!), you can toss them in your machine every few months. Just place them in a pillowcase first to protect them. For non-washable fabrics, spritz with Febreze Fabric Refresher Allergen Reducer, a Good Housekeeping Seal holder, allow to dry and then vacuum.

Like cold air, bright sunlight is a common &mdash though surprising &mdash trigger for sneezing. This phenomenon is known as a photic sneeze.

Yup, it turns out exercise can trigger a big "a-choo!" The condition is called exercise-induced rhinitis (EIR), and it can also cause itchiness, a runny nose, or congestion. According to a 2006 study, EIR is common, and it's more likely to affect people who have existing nasal allergies. Fortunately, it's usually more of a nuisance than anything, but if you find it especially aggravating, ask your doctor if a remedy like a nasal spray can help.

Sorry, guys &mdash fabric strikes again! Upholstered headboards can collect allergens (read: dust) and are harder to clean than a solid surface like wood. Regular vacuuming will help remove some of the yucky stuff, but won't reach the mites living deep inside the stuffing. You can try the Febreze Fabric Refresher Allergen Reducer, if you love those tufts above your bed, but Michaelle Exhume, product analyst Cleaning Lab in the Good Housekeeping Institute, keeps it real: "If you have allergies, it's probably best to get rid of an upholstered headboard," she says.

Mold loves to grow here, and as spores travel through the air, they can cause you to sneeze. In fact, more than 80 species of the stuff are known to cause respiratory allergies.

"Wash your bathmat once a week &mdash if there's mold, use 1/2 cup of bleach and cold water," says Exhume. Rubber-backed mats can be put in the washer (check the care label for the appropriate temperature), but don't put them in the dryer.

After months of inactivity, your forced air system's can get clogged with dust, mold, and other allergens. And once you flip the on switch, all that stuff will blow right into your air. Fight this by changing your filter regularly when you do use your system. Change your filters once a month (or clean them, if they're washable).

OK, this one's a tricky because it's all about balance, but stay with us: The ideal humidity level in your home is about 40%. If the air is considerably drier than that, it can irritate your mucous membranes (and &mdash you guessed it &mdash bring on sneezing). But, overly humid air can promote the growth of mold and "studies also show that humid air promotes dust mite growth," says Dr. Kim. To get the balance right, test your home's moisture levels (you can buy affordable kits at drugstores or home improvement stores), and try a humidifier or dehumidifier as needed.

Watch the video: KPOP IDOLS Sneeze Compilation Part 2 (December 2021).