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Baby/ringing bell Hairs on head Biggest brain
Surgical awareness Brain facts Aging disease
Early curare experiment MAO-inhibitors/tyramine Muscles in human body?
Teenager sleep/school start time What is "reuptake"? Who discovered diazepam?
Seeing stars? Effect of temperature on AP? Bones in body?
Cerebrum vs Cerebral Cortex Exercise and Memory Moon and Behavior
Basic tastes Dopamine functions Ear "ringing"
Action potential direction... Neurotransmitter names Third grader sleep needs

Traci: I was wondering about the experiment with a baby and a ringing bell. When the baby got older and heard the bell he did the thing as when he was younger. Do you know the name of the baby?

Answer: You may be thinking of Baby "Albert." Albert was an 11-month-old boy who was in an experiment conducted by American psychologist John B. Watson. Watson was doing an experiment on emotional response conditioning. At first, Albert liked playing with a white rat. Later when Albert saw a rat, the experimenters made a loud noise. This frightened Albert. After a few more times of pairing the rat with the loud noise, Albert became frightened of just seeing the rat.

Later on, Albert's fear generalized to anything furry like a rabbit, a fur coat and dogs. This "experiment" was done many years ago (Watson, J.B. and Raynor. Conditioned emotion reactions. Journal of Experimental Psychology, 3:1-14, 1920) and such an experiment would be considered unethical these days.

H. and C. Approximately how many hairs are on one human head?

Answer: According to The Handy Science Answer Book (1994) compiled by the Science and Technology Department of the Carnegie Library of Pittsburgh:

An average person has about 100,000 hairs on their scalp.

Jerry H. What mammal has the largest brain?

Answer: The mammal with the largest brain is the sperm whale. The brain of the sperm whale can weigh as much as 20 pounds. Even though the blue whale has a larger body size, the blue whale brain is about 5 pounds lighter than that of the sperm whale.

Stephanie S. I heard something on the news a while ago. Here's the main plot: Patients are anesthetized and are brought into surgery. However during the surgery, the anesthesia wears off and the patients feel everything that's happening to them. BUT they can't say anything or move anything because they're paralyzed for some reason. I think the term for this is "surgical awareness." Have you heard of this?

Answer from Dr. Chris B. (anesthesiologist and Neuroscientist Network member) Awareness during surgery and anesthesia does occur but is an extremely rare event. The anesthetic does not "wear off" as the story may have suggested (as an aside, in my opinion, medical/science stories are reported poorly by the media and are frequently inaccurate because the media is selling sensation and not fact. In addition, physicians and scientists are also culpable because they are willing to make their work sound more dramatic/important/sensational than it really is).

Anesthetics are given continuously during the surgery but very rarely the amount given may not be sufficient to produce complete unconsciousness. This occurs for two reasons; 1) by far, the most common reason is that the patient does not tolerate the anesthetic (all anesthetics depress the cardiovascular system) and the anesthesiologist has to turn the anesthetic down to prevent it from depressing the blood pressure to dangerous levels. This occurs most commonly in patients who are victims of severe trauma and are rapidly losing large volumes of blood. 2) awareness can also occur in patients with a history of alcoholism, sedative/hypnotic abuse (e.g., valium, barbiturates, sleeping pills) because their brains are "resistant" to the sedative effects of the anesthetic.

It should be noted that awareness is distressing, but patients usually state that pain was not a problem for them, rather it was the distress of being aware but unable to move for some reason they do not understand. The reason they can't move is that they were given a "muscle relaxant" which temporarily paralyzes the muscles. This is done to make it easier for the surgeons to spread muscles (e.g., abdominal muscles) thus making it easier to expose the surgical site. At the end of surgery, before the patient is awakened, the muscle relaxant is reversed.

This question affords another interesting opportunity to see how the media and business are increasingly intertwined. The story you saw was most likely the result of an ADVERTISING campaign for a device made by ASPECT Medical (called the BIS) which they claim is capable of detecting awareness. To sell this product they need to create a market. Anesthesiologists have no interest in it because awareness is not a significant problem (i.e., it is extremely rare and thus there is not much reason to spend money using this device on millions of patients who are not at risk of awareness) and this device has NEVER BEEN PROVED TO DETECT AWARENESS. Thus, to make money the company is basically marketing it to patients by first telling them (through "stories" like the one you saw) that awareness is a terrible problem (and needlessly scaring them) but fortunately they have a solution. Consequently, patients come to their anesthesiologists requesting that they use this unproved, useless, expensive device during their anesthetic. Anesthesiologists are thus "compelled" to buy this instrument to make their patients content. Consequently, medical costs go up, but that is not a problem for ASPECT because they reap the financial rewards.

C., L. and E. Can you give us some interesting facts about the nervous system? We're doing a school project.

Answer: Here are several pages of interesting facts that should help:

  1. Facts about the brain and nervous system
  2. Treasure Trove of Brain Trivia
  3. Amazing Animal Senses

Sascha What is the sickness that makes you age faster than normal?

Answer: The disorder you are probably thinking of is called Werner's Syndrome. For more about this disorder, please see:

Werner's Syndrome

M.L. I've been searching for a couple of weeks for a story I've heard about but can't find a source for. Some researcher thought that curare was an "anesthetic" so he tried it on himself. Although paralyzed, he could still feel everything. Do you know this anecdote?

Answer Perhaps this is the paper you were looking for:

Smith, S.M., Brown, H.O., Toman, J.E.P., and Goodman, L.S., The Lack of Cerebral Effects of d-Tubocurarine, Anesthesiology, Vol. 8, No. 1, (January, 1947) pp. 1-14.

M.J. Why do people taking MAO-inhibitors have to be on a tyramine restricted diet?

Answer: MAO (monoamine oxidase) is an enzyme that breaks down the class of neurotransmitters called the catecholamines. MAO inhibitors are drugs that block the action of MAO and raise the catecholamine content within neurons. These drugs are used to treat depression.

Tyramine is an amino acid found in foods such as cheese, fish and alcoholic drinks. Tyramine activates the sympathetic nervous system. Moreover, the action of tyramine is blocked by MAO. Therefore, in the presence of MAO inhibitors the action of tyramine is intensified and prolonged. This may result in dangerous hypertension and even cerebral hemorrhages.

Carolyn. How many muscles are in the human body?

Answer: There are over 600 skeletal muscles in the human body. Anatomists disagree on the exact number of muscles. Skeletal muscle makes up about 40% of total body weight.

K.H.: Do you have any information about sleep deprivation in teenagers and school start times?

Answer: Sleep deprivation IS a huge problem not only for students, but for adults as well. I will refer you to some sources of information concerning later school start times and some schools that have made the switch to later start times. Please see:

  1. carskadon.htm
  2. wahlstrom.htm

Phil W. What is "reuptake?"

Answer: Reuptake refers to the process by which a neurotransmitter is transported back into a neuron's synaptic terminal. In other words, after a neurotransmitter is released, it floats into the synaptic cleft. One mechanism that stops the action of neurotransmitter is by transporting the neurotransmitter out of the synaptic cleft back into the terminal.

Robert A. Who discovered diazepam?

Answer: Dr. Leo H. Sternbach of Hoffmann-La Roche (or just Roche) discovered diazepam. From L.H. Sternbach's chapter titled "The Discovery of CNS Active 1,4-Benzodiazepines" in the book The Benzodiazepines: From Molecular Biology to Clinical Practice edited by E.Costa, Raven Press, New York, 1983:

Near the end of 1959, we found a product that was, in most of the tests, 3 to 10 times as potent as chlordiazepoxide. We hoped that this superior potency would be associated with other advantages in its clinical spectrum of activity and selected it for a thorough evaluation. The pharmacological and toxicological data looked very promising: the clinical results were equally encouraging and led ultimately near the end of 1963 to the introduction of diazepam, under the trade name Valium.

This information is confirmed on the Hoffmann La-Roche web page (scroll down a bit).

T. Why after sitting down for a long time and you stand up fast do you sometimes see light spots or stars?

Answer: (from Dr. Chris B., Neuroscientist Network member) The phenomenon results from hypoperfusion of the brain, particularly the occipital cortex. But I do not know why one sees "stars" as opposed to something else. Hypoperfusion results because standing up too rapidly can result in a decrease in venous return so the heart is not as full as necessary to maintain adequate cardiac output.

Answer: (from Dr. Ed F., Neuroscientist Network member) Orthostatic hypotension, decreased blood flow to the brain because of a gravitational pooling of the blood in the lower extremities. The baroreceptor reflex minimizes this as it senses the decreased blood pressure in the aortic arch and responds by sending a signal, through the brainstem, to increase sympathetic tone in the blood vessels of the lower legs. This results in a vasoconstriction and helps force more blood to the upper part of the body.

This reflex is reduced in the elderly and by many medications. That is why people, especially elderly and those on various heart, blood pressure medications, antidepressants and any CNS depressant should get up slowly from a lying or sitting position.

Bonnie M. What is the effect of temperature on the shape of the action potential?

Answer: The effect of temperature is mainly on ionic permeability of the neuronal membrane. Specifically, sodium channels open and close faster at higher temperature. Reductions in temperature lengthen the action potential and slow conduction velocity...these are the classic experiments of Hodgkin and Katz (1949).

Z.Z. How many bones are in the human body?

Answer: Babies are born with between 300 to 350 bones. As people get older, some of these bones fuse together. Most adults have 206 bones:

21 bones in the skull

6 bones in the ears (3 on each side)

1 jaw bone (mandible)

1 bone in the neck (hyoid)

26 bones in the vertebral column (spinal column)

25 bones in the chest (1 sternum, 12 pairs of ribs)

64 bones in the upper limbs (shoulder, arm, wrist, hand and fingers)

62 bones in the lower limbs (hip, pelvis, leg, knee, ankle, foot, toes)

Laura M. What is the difference between the cerebrum and the cerebral cortex?

Answer: The cerebrum refers to the entire cerebral hemispheres. The cerebral cortex is the outermost part of the cerebrum.

G.J. Do you think exercise is good for the brain?

Answer: Yes, physical exercise does appear to be good for the brain. There are been several studies that show that exercise is beneficial to the brain. In fact, there was a recent experiment in mice that showed that running can increase the number of nerve cells in the brain. For a summary of this research, see:

Exercise and the Brain - Society for Neuroscience

Debbie G. I have always heard a full moon will affect behaviors but your page contradicts that myth. I have been teaching elementary school for 19 years and I was wondering if there have been any case studies on how a full moon affects children's behaviors. I don't keep track of when it's time for a full moon, but I can usually tell by the way my students act.

Answer: In my review of the literature on the effects of the full moon on behavior, I found that most studies show no relationship between the phase of the moon and abnormal behavior.

In all of the background research and literature searches I conducted for the Moonstruck article I did not find any papers that examined the correlation between the phase of the moon and children's behavior. As I discussed in the article, there are some problems in the design of these studies in that they only determine that a correlation does or does not exist between two variables (i.e., phase of the moon and a change in behavior). They do not prove that the phase of the moon CAUSES a particular behavior.

Mark W. What causes "ringing in the ears?"

Answer: Ringing in the ears is called "tinnitus." All of the causes are not well understood. Some forms of tinnitus are caused by problems in the inner ear, such as damaged hair cells. However, some forms may NOT have a peripheral origin. In other words, the "ringing" may be in the brain, NOT the ear. For more about tinnitus, please see:

Fighting the Phantom Noise - from Time Magazine

American Tinnitus Association

J.M. What is the function of dopamine in the brain?

Answer: Dopamine is a neurotransmitter (a catecholamine type neurotransmitter). It is found in many places in the central nervous system and has several functions including:

1. Movement: dopamine is produced in the substantia nigra (a part of the basal ganglia). In Parkinson's disease, dopamine neurons in the substantia nigra die. This disorder is characterized by tremor, rigidity and slowness of movement. When the dopamine is restored in the brain by giving L-dopa, the movement problems in many cases are reduced.

2. Attention: there is some evidence that dopamine is altered in people with attention deficit disorders.

3. Emotional behavior: an overactive dopamine system may underlie schizophrenia. Dopamine blocking drug reduce the symptoms of schizophrenia.

4. Addictive behavior

C. Are there five basic tastes? I looked it up under ask jeeves and it only gave me 4 ( sweet, sour, salty, and bitter.) What is the other one?

Answer: The 5th basic taste is called "umami." Umami is a taste that occurs when foods with glutamate (like MSG) are eaten. More information on umami:

Monell Chemical Senses Center

Sarah N. Does an action potential go in only one direction?

Answer: In "normal" cases, yes, the action potential goes in only one direction: toward the axon terminal. However, an action potential will spread in BOTH directions IF it is started in the middle of an axon. This can be done by electrically stimulating the middle of an axon. This is not the normal way action potentials are triggered. Rather, an axon potential usually starts at the axon hillock and sequentially depolarizes the neuronal membrane away from where it started. That is why in normal situations it only travels in one direction.

A.N. How did neurotransmitters get their specific names? Such as, why is dopamine called dopamine? serotonin? norepinephrine?

Answer (By Neuroscientist Network Member Dr. P.):

a) Background
Catecholamines: This name refers to all organic compounds that contain a catechol nucleus (a benzene ring with two adjacent hydroxyl residues), a side chain of two carbon atoms (the b-carbon is closest to the ring, the a-carbon is distal), and an amine (NH2) group bound to the a-carbon. The word "catechol" is derived from "catechin," a crystalline substance extracted from the spiny Asian tree "catechu" (Acacia catechu) which is used in the preparation of tannins and other brown dyes. Catechin and catechol are synonymous. In practice, the term catecholamine refers to dopamine (DA, dihydroxyphenylethylamine) and its metabolic products, norepinephrine (NE) and epinephrine (E).

b) Neurotransmitters
i. Dopamine (DA): The easiest explanation for dopamine's name is that it is a selective compression of its chemical name, dihydroxyphenylethylamine.

To better understand the nomenclature, we can start a couple steps back in the pathway that leads to the formation of DA. The amino acids phenylalanine or tyrosine can be the starting compound for the synthetic pathway. If phenylalanine (a compound similar to the catechol structure except there are no hydroxyl groups bound to the benzene ring and there is a carboxyl group (COOH) bound to the same carbon containing the amine group), an enzyme, phenylalanine hydroxylase, adds an hydroxyl group to the benzene ring. This product is tyrosine which can also be provided in the diet directly. The next step in the pathway involves the enzyme tyrosine hydroxylase, the rate limiting step in the entire process, which adds a (second) hydroxyl group to the aromatic ring. The resultant compound is "DOPA" (dihydroxyphenylalanine), a compound with a catechol backbone as described above. The final step in the synthesis of dopamine involves the removal of the carboxyl group from the two carbon side chain of DOPA by the enzyme DOPA decarboxylase. Thus dopamine is composed of the basic catechol backbone (dihydroxyphenylethylamine) with no substitutions on the two carbon side chain.

ii. Norepinephrine (NE): Once we've learned how dopamine is formed, the related catechol compounds fall easily into place. Norepinephrine is formed from dopamine through the activity of the enzyme dopamine-b-hydroxylase. Norepinephrine is simply dopamine with an hydroxyl group added to the b-carbon of the two carbon side chain. See Epinephrine for the word derivation.

iii. Epinephrine (E): The enzyme phenylethanolamine-N-methyltransferase adds a methyl group to the amine (NH2) bound to the a-carbon of norepinephrine.

The derivation of the names epinephrine and norepinephrine are most likely related to the locale of the highest concentration theses substances: the adrenal glands. Because the adrenals sit atop the kidneys, the word epinephrine can be parsed logically: "epi-" means "upon or close to, "nephr" is the contraction of "nephro," a prefix designating the kidney, and "ine," a suffix given to many chemical compounds. The prefix "nor" designates an unaltered parent compound. This suggests that norepinephrine was isolated subsequent to epinephrine and, upon discovery of the relationship, was named appropriately. The parallel nomenclature of "adrenaline" and "noradrenaline" provide a more obvious derivation.

Serotonin was named, shortly after its discovery, for its ability to cause powerful contractions of smooth muscle. Thus it was considered a major component in the serum responsible for vasoconstriction and high blood pressure. 2) Acetylcholine is straightforward, formed as product of the enzyme choline acetyltransferase.

K.B. How much sleep does a third grader need?

Answer: According to the Sleep Well web site (Stanford University Sleep Center):

Adolescents need 9 hours and 15 minutes of sleep. Children need 10 hours and adults need 8 1/4 hours.

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