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|How many cells in body?||How many kids smoke?||Neuroscience videos|
|Longest nerve?||Birds/sense of taste?||Potassium chloride and the heart|
|How does Valium work?||What is 2-deoxyglucose?||G-proteins?|
|Do fish sleep?||Hardest material in body?||Neuron types?|
|Babies/taste Buds||Gyri longus/gyri brevis?||Septum pellucidum? Uncus?|
|Brainstem or brain stem?||Inability to recognize faces?||Eye size at birth?|
|What is the tegmentum?||Brain wave names?||Future BAW?|
M.B. How many cells are in the human body?
Answer: According to "The Handy Science Answer Book" compiled by the Science and Technology Department of the Carnegie Library of Pittsburgh (1994) there are 50 to 75 trillion cells in the human body. However, others estimate the number to be as high as 100 trillion. (Note: there are about 100 billion nerve cells [neurons] in the human brain.)
E.Z.: How many kids smoke each day?
Answer: According to the Monitoring the Future survey released in December, 2003:
4.5% of 8th graders reported that they smoke daily.
8.8% of 10th graders reported that they smoke daily.
15.8% of 12th graders reported that they smoke daily.
Marilyn P.: I am looking for a video of about half an hour that explains brain function, learning, research done using MRIs or anything of a similar nature. I am hoping you can recommend a video that I can get within a couple weeks.
Answer: Here are a few ideas:
N.M.: My daughter is studying cognitive brain science in college. She asked me for a model of the brain because she felt it would help her in her studies. Could you recommend what I should be looking for and where I could purchase it?
Answer: You can spend anywhere from about $3.00 to $600.00 for a brain model. Here are some choices:
A.A.: Do you have a list of organizations or agencies that have information about different neurological disorders? I want my students to write to these places for material.
A.G. Are axons and dendrites organelles?
Answer: No. Axons and dendrites are not organelles of a neuron. Think of axons and dendrites as arms and legs. Arms and legs are part of the body, but they are not organs. Axons and dendrites are part of a neuron, but they are not organelles.
D.B. What is the longest nerve in the human body?
Answer: The sciatic nerve is the longest nerve in the human body. It is made up of nerve fibers that branch from the lower spinal cord and extends down the leg.
R.H. Do birds have a sense of taste?
Answer: Birds do have taste buds and can taste. Taste buds are found in greatest number on the caudal surface of the tongue, pharyngeal floor and in association with salivary gland openings. However, in comparison with other animals, birds have very few taste buds and therefore their sense of taste is probably not as good as other animals. Here are some numbers for comparison (from G.C. Whittow [ed.], Sturkie's Avian Physiology, Fifth Edition, San Diego: Academic Press, 2000 and A.S. King and J. McLelland [eds.], Form and Function in Birds, vol. 3, London: Academic Press):
|Animal||Total # of taste buds|
Behavioral experiments have shown that some birds (parrots, hummingbirds) prefer sweet tastes, but other birds (red-winged blackbirds) do not like sweet tastes. Some birds even like bitter tastes.
K.B. Why is an intravenous injection of potassium chloride dangerous to the heart?
Answer: Too much potassium in the extracellular fluid can cause the heart to dilate and become weak and can even cause death. Potassium can slow the heart rate and block cardiac impulses from the atria to the ventricles. The reason for this is that high extracellular concentrations of potassium reduce the resting membrane potential of cardiac muscle fibers. This causes a reduction in the intensity of the action potential and weaker heart contractions. If the extracellular concentration of potassium is great enough, the resting membrane potential will be eliminated and cardiac muscle cells will not generate impulses. Therefore, the heart will stop.
S.T. How does valium affect the central nervous system?
Answer: Valium (diazepam) belongs to a class of drugs called the benzodiazepines. These drugs have their effects by enhancing the activity of GABA receptors on neurons. More specifically, they enhance the activity of a subclass of GABA receptors called the GABA-A receptors. When activated, GABA-A receptors open chloride channels. This causes hyperpolarization of neurons and neuronal inhibition. The effects of valium are thought to act on GABA-A receptors in the limbic system of the brain, especially in an area called the amygdala.
Andrew J. What is 2-deoxyglucose and how does it work?
Answer: 2-deoxyglucose (2-DG) is a molecule with a structure very similar to that of glucose. Glucose, as you may know, is the fuel for the brain. Areas of the brain that are more active, use more glucose. The 2-DG method was pioneered by Sokoloff and associates in the late 1970s to identify areas of neuronal activity. When 2-DG is injected into an animal, it is taken up by regions that are metabolically active. However, 2-DG is NOT COMPLETELY metabolized like glucose and it remains within neurons. Therefore, when 2-DG is labeled with radioactivity, it can be localized in the tissue using a histological method called autoradiography. In this way, 2-DG gives a picture of brain areas that were active.
D.B. How do G-proteins work?
Answer: G-proteins are involved with a specific type of receptor (metabotropic receptor) that controls ion channels. These receptors are located near G-proteins on the neuron membrane. When a neurotransmitter molecule binds to a receptor, it activates the nearby G-protein. This causes the G-protein to change shape and part of it breaks off to bind to a site on an ion channel. This binding causes the ion channel to open up. Another way G-proteins work is to activate enzymes. When G-proteins activate enzymes, they cause the production of second messengers. The second messengers then bind to ion channels to open them up.
A.T. Do fish sleep?
Answer: PROBABLY. Sleep can be defined in several ways. One way sleep is defined is as a period of rest and inactivity. Of course, because fish do not have eyelids, they can't close their eyes during rest. If your definition of sleep is a period of rest and inactivity, then "Yes, fish sleep" at least some species. It is very difficult to record brain wave patterns from fish for long periods of time, and even if you could record an electroencephalogram (EEG) the "sleeping" brain patterns in fish would probably be different from other animals because of differences in brain structure. However, many fish have rest/activity cycles that indicate "behavioral sleep." EEG recordings from the catfish have been made. These data showed differences in the brain wave patterns during waking and behavioral sleep.
Campbell and Tobler (1984) published a paper that described sleep in many different animals including bees, cockroaches, fish, amphibians, reptiles, birds, and mammals. This paper states that some species of fish show brief periods of rest while others are continuously active. The parrot fish is one fish that shows interesting "sleep" behavior: it forms a mucous cocoon in which it rests throughout the night.
(Reference: Campbell, S.S. and Tobler, I., Animal sleep: a review of sleep duration across phylogeny. Neuroscience & Biobehavioral Reviews, 8:269-300, 1994)
Dennis M.: What is the hardest material in the body?
Answer: The enamel of the tooth is the hardest material in the body. The enamel is the outermost part of the tooth; it covers the tooth crown.
T.P. Where are uniploar, bipolar and multipolar neurons found?
Answer: Unipolar neurons are not very common in vertebrates (they are more common in invertebrates). However, invertebrates, unipolar neurons are found in the ganglia of the autonomic nervous system.
Pseudounipolar neurons are found in the dorsal root ganglia.
Bipolar neurons are found in the retina and olfactory epithelium.
Multipolar neurons are the most common of these types in vertebrates. They are found all over the brain and spinal cord. Some examples: spinal motor neurons, in the hippocampus, pyramidal neurons of the cerebral cortex, Purkinje cells of the cerebellum, granule cells.
Nora: Are babies born without taste buds?
Answer: No. Babies are born with functional taste buds. Several studies have actually looked at taste buds in the human fetus. Taste buds have a non-gustatory (not taste) function from the 8th to 14th week of gestation. After the 14th week of gestation, taste pores are present and they probably develop their taste function at this time. Taste buds are fully functional by about the 15th week of gestation.
K.R. Where are the gyri longus and gyri brevis located in the brain?
Answer: The gyri longus (long gyri) and gyri brevis (short gyri) are located on the surface of the insula. The insula is an area of cerebral cortex that is buried within the lateral sulcus.
P.F. What are the uncus and septum pellucidum?
Answer: The septum pellucidum is a double-layered structure that extends from the corpus callosum to the fornix. It is made up mostly of glial-like cells and separates the right and left lateral ventricles. The word "septum" comes from the Latin word for "wall" and "pellucidum" comes from the word meaning "translucent."
The uncus is located on the anterior part of the hippocampus gyrus (on the base of the brain). The uncus receives olfactory information. "Uncus" comes from the Latin word meaning "hook."
Tom B. Is it "brainstem" or "brain stem?" Is it one or two words?
Answer: Some authors use "brainstem," others use "brain stem." In Principles of Neural Science by Kandel, Schwartz and Jessell (McGraw Hill, 2000), it is "brain stem." Physiology of Behavior by Carlson (Allyn and Bacon, 1998), The Central Nervous System by Brodal (Oxford, 1998), Human Neuroanatomy by Carpenter and Sutin (Williams and Wilkins, 1983) and Dorland's Illustrated Medical Dictionary also use "brain stem." However, in Neuroscience by Purves et al. (Sinauer, 1997) and The American Heritage Dictionary, it is "brainstem."
Linda P. What is it called when a person cannot recognize faces?
Answer: Some people who suffer damage to the temporal lobe lose their ability to recognize and identify familiar faces. This disorder is called prosopagnosia.
Pat: I heard that the eyeball was the only part of the human body that is full size at birth. Is this true?
Answer: No, it is not true. According to the text General Ophthalmology (Vaughan, Asbury and Riordan-Eva, Appleton & Lange, Stamford, 1999), the size of the eyeball at birth averages 16.5 mm in diameter (front to back measurement). In adults, the diameter is 24.2 mm. They go on to say that maximum eye size is reached when a person is 7-8 years old.
Other facts about the developing eye:
N.C.R. What part of the brain is the tegmentum?
Answer: The tegmentum refers to the ventral part of the midbrain. Structures in the tegmentum include the red nucleus, substantia nigra and periaqueductal gray.
Anne S. Can you tell me the origins of the brain wave names (alpha, beta, theta, delta) and why they were chosen? They are confusing!
Answer: First, some definitions (according to Kandel et al., Principles of Neural Science, 2000):
Beta wave frequency = 13 to 30 Hz Alpha wave frequency = 8 to 13 Hz Theta wave frequency = 4 to 7 Hz Delta wave frequency = 0.5 to 4 Hz
These names can get confusing because they do not follow a logical order of the Greek alphabet. The brain waves were named not for their frequencies, but for WHEN they were discovered. In other words, they have historical significance, not functional significance. According to the text Electroencephalography by Niedermeyer and Lopes Da Silva (1993), the terms "alpha" and "beta" waves were introduced by Berger in 1929. So, these were the first two types of brain waves identified.
The term "gamma" wave was used for a short time for very high frequency brain waves, but this term was abandoned. In 1936, Walter introduced the term "delta" and he added "theta" for those brain waves between 4-7.5 Hz. Walter skipped the Greek letters between delta and theta (epsilon, zeta and eta) and used theta because he thought theta waves were generated in the thalamus.
L.B. Will there be more Brain Awareness Weeks in the future?
Answer: Yes, there will be BAW in the future. Here are the dates for upcoming Brain Awareness Weeks:
March 14-20, 2005
March 13-19, 2006
March 12-18, 2007
More questions and answers:
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