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Link to web site? Brodmann's areas Neocortex size
Earwax Is MAO a neurotransmitter? Chemicals/blood vessel size
Prawn brain? Snake venom/Capoten Brain infections/BBB
GABA precursor? Nervous System Song? THC in the body
Animal taste buds Yearly smoking deaths? Brain/body ratios
Jell-O (Gelatin) brain mold? Inhalant/nail polish Polar bears and Alzheimer's
List of disorders What is Barrington's nucleus? Neo-, Paleo-, Archi- Cortex differences
Spinal nerves/Ear nerves Caffeine in white chocolate? Brain structures on both sides?

L.H.: I am making my own web site. Is it alright if I make a link on my site to Neuroscience for Kids?

Answer: Yes, feel free to create a link to Neuroscience for Kids from your new site. The best URL to use is:

Mike:What are Brodmann's Areas?

Answer: In 1909, German scientist Korbinian Brodmann published a map of the cerebral cortex. On this map, he divided the cortex into 52 different areas based on the characteristics of the tissue (e.g., the density of the neurons; the thickness of the cortex; the types of cells). The numbers associated with his map refer to the order in which he studied the different areas. [Picture of Brodmann's Areas]

T.R.:What is the ratio of neocortex to total brain size in humans and other animals?

Answer: In humans, the neocortex accounts for 76% of the total brain. For other animals:

Sperm Whale: 87%
Chimpanzee: 72%
Monkeys: 55-60%
Rodents: 40-50%
Platypus: 48%
Marsupials: 20-30%
Insectivores: 10-20%

(Reference: Nieuwenhuys, R., Ten Donkelaar, H.J. and Nicholson, C., The Central nervous System of Vertebrates, Vol. 3, Berlin: Springer, 1998)

A.S.: How does earwax get in your ears?

Answer: The scientific name for earwax is "cerumen." There are specialized wax secreting glands (called "ceruminous glands") located in the ear canal. These glands make earwax. Earwax keeps the eardrum (tympanic membrane) soft and waterproof. Earwax also prevents small objects from reaching the tympanic membrane.

M.H. Is MAO a neurotransmitter?

Answer: No. MAO (monoamine oxidase) is not a neurotransmitter. MAO is an enzyme that destroys monoamine neurotransmitters such as dopamine, norepinephrine and serotonin.

Ian D. What are the substances that cause the blood vessels in the skin to dilate and constrict? Are there different substances according to the stimulus that caused the vessel change (e.g., exercise, embarrassment, irritation, food)?

Answer from Dr. Chris B. (anesthesiologist and Neuroscientist Network member): Norepinephrine released by the sympathetic nervous system causes vasoconstriction and acetylcholine released by the parasympathetic nervous system cause vasodilation. This is independent of the cause (e.g., exercise, embarrassment, etc.) and is the primary short term control of vascular tone. There are also mechanical causes, e.g., "trauma" (for example, gently thumping on a vein will cause it to dilate, thumping on an artery will cause it to constrict) which are not mediated by neurotransmitters. A number of circulating compounds can cause constriction and dilation, e.g., histamine, bradykinin, are vasodilators while angiotensin and epinephrine are constrictors. The former two are not generally involved in vascular tone except in pathologic circumstances, e.g., bee sting, allergic reaction, anaphylaxis. In contrast, angiotensin plays an important role in the kidney's longer term control of blood pressure and epinephrine (adrenalin) is released by the adrenal gland under certain conditions, e.g., fright, (this is one of the reasons your heart beats faster when you are scared (sometimes known as the "fright or flight response."

Nicole F. Do prawns have brains?

Answer: Yes, they do, but their brains are not very big. Prawns and shrimp do have a centralized collection of nerve cells that can be considered to be a brain. Description of the brain of crustaceans (crabs, shrimps, lobsters, etc.).

More about the Invertebrate Nervous System .

Tori I was watching the Discovery Channel the other day and something caught my eye and I have been wondering about it ever since. I think they said that a venomous snake in Brazil is used to make a drug called Capoten. Can you give me some information on this?

Answer: Capoten is used to control high blood pressure. This drug comes from the venom of a Brazilian pit viper, the jararac snake (Bothrops jararaca).

J.K.: Can antibodies cross the blood-brain barrier (BBB)? How does the body fight infections in the brain?

Answer: Two answers from the Neuroscientist Network:

Gamma-globulins are produced within the CNS, most likely by microglia. This would provide a source of antibodies within the CNS and negate the need for them to cross the BBB. In a number of pathologic states there is an increase in the gamma-globulin fraction of the CSF protein independent of any change in the serum concentration. This proves the CNS source. There are situations where an increase in the peripheral (blood) concentration results in a "leak" into the CNS and is reflected by an increase in CSF concentrations. This is usually associated by some disruption of normal BBB functioning. Obviously in these cases, antibodies are crossing into the CNS. Though I cannot cite the source, I think there is evidence to support some gamma-globulin (antibodies) transfer into the CNS, though it is probably fairly small.

The microglia serve as the "immune" type cells of the CNS. They appear to possesses phagocytic properties and probably globulin production capability as well. They are involved in immune-related activity of the CNS and provide the first line of defense to a CNS infection from within. Whenever the brain is faced with an infectious process, it must come from outside of the CNS, thus the rest of the body is involved and as the infectious process develops, it produces alteration in the BBB functioning. Some viral infections can gain entrance to the CNS via transport through neurons in the periphery, thus avoid the BBB. These types are usually pretty devastating and very difficult to treat. In these cases, it is up to nature, through the microglia to protect us. Unfortunately, it often doesn't work so well (e.g., viral encephalitis, herpes, HIV).

This is a good question which has not been fully answered to my knowledge. The central dogma is that no antibodies pass through the BB barrier even though some Iggs have been found in the CSF. So how then do these Iggs get there? It's possible some may get actively transported across the BB barrier (against the dogma) or they are perhaps made in CNS (I don't know if any strong evidence in support of this yet). But supposing these Iggs in the CNS (and there aren't many compared to the rest of the body) don't protect the brain fully, the microglia of the CNS are phagocytic and are known to affect damaged tissue caused by infection and even the foreign bodies themselves. How do they know what a foreign body is? That is still a mystery. It seems the CNS itself is its own little germ free world where very few infections ever occur unless there is severe trauma or certain disease states. Often when the BBB is penetrated there is a certain amount of local autoimmune destruction of CNS tissue from the invading non-CNS part of the body so that might indicate that the immunologies of these two "worlds" (CNS and body) are distinctly different and separate.

A.C.: What is the precursor of the neurotransmitter called GABA?

Answer: GABA is synthesized from glutamate by an enzyme called glutamic acid decarboxylase. To work properly, this enzyme needs a cofactor called pyridoxal phosphate.

T.E.: I have visited your web site many times in the past. I once found the song "Telegraph Line" about the nervous system on your site, but I can't find it anymore. Do you still have it? I wanted to use the song with my students.

Answer: The lyrics to "Telegraph Line" are still on the Brain Songs page, but the audio and video are not. The web site that I had linked to with the audio and video is no longer working so I removed the link and have been unable to find a new one. "Telegraph Line" is available on video. It's on "Science Rock School House Rock," produced by Scholastic Rock, Inc. You may be able to find it at your local library.

J.J.: How long does THC stay in your body after you use marijuana?

Answer: The amount of time depends on several factors such as how much a person has smoked, how long a person has smoked for, and the method used to detect THC or its metabolites. Marijuana can be detected in urine, blood and saliva using methods called thin layer chromatography, high pressure liquid chromatography, gas chromatography, enzyme immunoassay and radioimmunoassay. The most psychoactive ingredient in marijuana is delta-9-tetrahydrocannabinol (THC). THC is broken down into several other compounds that are also psychoactive. The half-life of THC is about 24 hours. However, the metabolites of THC can be detected for 45 to 60 days after the last use.

Here is some additional information that may be useful (from Maistro et al., Drug Use and Misuse, 1991):

Approximately half of the THC is excreted over several days, and the remainder by the end of about a week. However, some metabolites of the THC, a number of which may still be active in the system, can be detected in the body at least thirty days following ingestion of a single dose and, following chronic use, in the urine for several weeks.

D.R.: Do all animals have taste receptors on their tongues?

Answer: No. Some animals have taste receptors (chemosensors) on their feet (e.g., butterfly and blowfly) or even over their entire bodies (e.g.,catfish and earthworm). The tongue of the snake has no taste receptors.

C.T.: How many people die each year from smoking?

Answer: According to the CDC :

An estimated 46.5 million adults in the United States smoke cigarettes even though this single behavior will result in death or disability for half of all regular users. Cigarette smoking is responsible for more than 440,000 deaths each year, or one in every five deaths.

The World Health Organization (WHO) states:

Smoking is estimated to have caused around three million deaths a year in the early 1990s, and the death toll is steadily increasing.

E.H.: What animal has the largest brain compared to its body weight?

Answer: It might surprise you to find out that humans do not have the largest brain weight to body weight ratio. According to Dr. W.H. Calvin, in his book The River That Flows Uphill, the squirrel monkey has a larger brain to body ratio (1 to 31 or about 3.2%) compared with that of humans (1/49 or about 2.0%).

An article published in Natural History (December 1999-January 2000 issue) states:

Pound for pound, the record for brain size is probably held by fruit-eating squirrel monkeys (genus Saimiri) of South America, whose brain account for 5 percent of their body weight, on average.

The hummingbird also has a larger brain/body ratio compared with that of humans. An article published in Brain Behavior and Evolution (37:85-91, 1991)states that the hummingbird has a brain mass of 228.85 mg and a body mass of 5,970.38 mg. This means that the brain-to-body ratio of a hummingbird is about 3.8%.

So, there is difference in opinion. One source says that the squirrel monkey has a brain/body ratio of 3.2% and another says 5%. Another source says that hummingbirds have a brain/body ratio of 3.8% which falls in the middle of the two values given for the squirrel monkey.

Liza A.: Where can I buy a Jell-O (gelatin) brain mold?

Answer: I have two different Jell-O brain molds: one shows the top half of the brain and the other shows a lateral view of the brain. There are several places where you can buy these molds:

  1. Archie McPhee
  3. NeuroMart
  4. BrainMart

M.R.: I know that nail polish should not be sniffed. What are the dangerous chemicals in nail polish?

Answer: Some of the chemicals in nail polish that can harm you are formaldehyde, toluene, ethyl acetate, butyl acetate and isopropyl alcohol.

E.K.: Is this true? Some researchers searching for a cure for Alzheimer's disease find the study of polar bear brains useful because their brains are similar to human brains. I heard that when geriatric polar bears die in zoos that their brains are studied for lesions related to the aging process.

Answer: Yes, there are several studies that have examined the brains of old polar bears for signs of Alzheimer's disease. Several zoos, including those in Toledo, Denver, Knoxville, Royal Oak, Tacoma and Baltimore, have participated in these studies. For summaries of this research, please see:

  1. Carboxy terminal of beta-amyloid deposits in aged human, canine, and polar bear brains.
  2. N-terminal heterogeneity of parenchymal and cerebrovascular Abeta deposits.
  3. Conservation of the sequence of the Alzheimer's disease amyloid peptide in dog, polar bear and five other mammals by cross-species polymerase chain reaction analysis.
  4. Conservation of brain amyloid proteins in aged mammals and humans with Alzheimer's disease.

M.G.: Where can I find a list and description of disorders that affect the nervous system?

Answer: The National Institute of Neurological Disorders has a large list and the Dana Alliance has a collection of neurological disorder support groups in a publication called Brain Connections.

Peter C.: What is Barrington's nucleus?

Answer: Barrington's nucleus is a group of neurons located in the brain stem near the pons. Neurons in this area project to spinal cord neurons that then connect to the bladder.

L.T.: What is the difference between neocortex, paleocortex and archicortex?

Answer: The terms neocortex, paleocortex and archicortex refer to their phylogentic nature. Archicortex is the oldest, paleocortex is more recent and neocortex is the most recent. You may also run into the term "allocortex." Allocortex is divided into the paleocortex and archicortex.

Another difference is the number of cortical layers found in these areas: neocortex has 6 layers; paleocortex and archicortex have only 3 layers.

Most of the cerebral cortex in humans is neocortex. Paleocortex is found on the inferior and medial aspects of the temporal lobe (rostral insular cortex, piriform cortex, primary olfactory cortex); archicortex is found in the hippocampus.

Cyrus: Does the ear have more nerves than the spinal cord?

Answer: No. The spinal cord contains approximately 1 billion neurons (from Kalat, J.W., Biological Psychology, 6th Edition, 1998, page 24) and the auditory nerve contains 28,000 to 30,000 nerve fibers.

S.P. Does white chocolate have caffeine?

Answer: According to "The Joy of Cooking" cookbook:

"So-called white chocolate contains no chocolate at all but is prepared from vegetable fats, coloring and flavors."

White chocolate products are made with cocoa butter, the oil that is pressed out of cocoa. Some resources that I found state that cocoa butter has no caffeine. However, According to "The World of Caffeine" by B.A. Weinberg and B.K Bealer (2001) and International Cocoa Association, cocoa butter DOES contain caffeine.

M.L.: Do all structures of the brain have a right and left side?

Answer: No...there is only one pineal body, one pituitary gland, one third ventricle and one fourth ventricle. Some midline nuclei of the thalamus and the more obscure interpeduncular nucleus (in the midbrain) span the midline and do not actually have a left and right side. "Broca's area" and "Wernicke's area," two cortical areas important for language, are found only on one side (on the left for most people). Most structures are found on both sides.

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