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Neurotransmitters, Brain and Disease

Describe neurotransmitters, their function, and impact on behavior. Discuss one neurotransmitter in detail describing the effect it has on our bodies and connection with disease. Discuss the importance of biology for understanding behavior.

For this DB, make sure you fully describe the structure of neurotransmitters, their functions in the brain and body, and how different ones might affect behavior. For the second part, remember to describe it in detail and discuss its effect on the body, as well as diseases attributed to its function or lack thereof. Also, remember to do the third part of the assignment; more than one or two sentences.

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Describe neurotransmitters, their function, and impact on behavior. Discuss one neurotransmitter in detail describing the effect it has on our bodies and connection with disease. Discuss the importance of biology for understanding behavior.

For this DB (?), make sure you fully describe the structure of neurotransmitters, their functions in the brain and body, and how different ones might affect behavior. For the second part, remember to describe it in detail and discuss its effect on the body, as well as diseases attributed to its function or lack thereof. Also, remember to do the third part of the assignment; more than one or two sentences

Let's look closer at each question:

1. Describe neurotransmitters, their function, and impact on behavior (e.g. For this DB (?), make sure you fully describe the structure of neurotransmitters, their functions in the brain and body, and how different ones might affect behavior).

Neurons are the main cells of the nervous system and there are about 100 billion of them in the brain.
Thanks to their numerous branch-like processes, they interconnect forming a massive network of "wires" that extend throughout the entire body. By sending messages across this network, the different parts of the human body interact and communicate with each other. The neuron is made up of three areas, each with a distinct function: the dendrites, the cell body, and the axon. Messages circulate through the network of neurons in the form of electrical signals (nerve impulses) always moving from the dendrite toward the axon. Neurotransmitters enable the signal from one neuron to be relayed to other neurons across the synapse, a small gap (synaptic cleft) that separates neurons. http://www.lexicon-biology.com/biology/definition2_106.html
Thus, neurotransmitters of the brain are the chemicals released by nerve cells (neurons) at synapses that influence the activity of other cells. They are indeed specialized chemical messengers (e.g., acetylcholine, dopamine, norepinephrine, serotonin) that send a message from one nerve cell to another, because most neurotransmitters play different roles throughout the body, many of which are not yet known. Neurotransmitters may excite, inhibit, or otherwise influence the activity of cells. www.ninds.nih.gov/health_and_medical/pubs/sci_report.htm

Specifically, when a message is sent from neuron to neuron it is referred to as neural transmission. Neural transmission between neurons is when one neuron releases a neurotransmitter into the synaptic vesicles into the synaptic cleft (gap between the neurons). The transmitter is then taken up by the receptors on the postsynaptic membrane. http://www.ncat.edu/~grobinso/nt.htm.

Thus, neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a neuron and another cell. A chemical can be classified as a neurotransmitter if it respects the following conditions:
1. It is synthesized endogenously, that is, within the presynaptic neuron
2. It is available in sufficient quantity in the presynaptic neuron to exert an effect on the postsynaptic neuron
3. Externally administered, it must mimic the endogenously-released substance
4. A biochemical mechanism for inactivation must be present
However, there are other materials, such as the zinc ion, that are neither synthesized nor cataboloized (i.e., degraded. see Anabolism) and are considered neurotransmitters by some. Thus, the old definitions are being revised (http://en.wikipedia.org/wiki/Neurotransmitter).

Function by Type of Neurotransmitter
The are three major categories of substances that act as neurotransmitters:
(1) Amino acids (primarily glutamic acid, GABA, aspartic acid & glycine),
(2) Peptides (vasopressin, somatostatin, neurotensin, etc.) and
(3) Monoamines (norepinephrine, dopamine & serotonin) plus acetylcholine.
The major "workhorse" neurotransmitters of the brain are the amino acids called glutamic acid (=glutamate) and GABA. The monoamines & acetylcholine perform specialized modulating functions, often confined to specific structures. The peptides perform specialized functions in the hypothalamus or act as co-factors elsewhere in the brain.
For a well-organized categorization of neurotransmitters, see Neurotransmitter (Wikipedia).
Although there are many neurotransmitters in the central nervous system, the peripheral nervous system has only two: acetylcholine and norepinephrine (monoamines). Some (like glutamate) are excitatory, whereas others (like GABA) are primarily inhibitory. In many cases (as with dopamine) it is the receptor, which determines whether the transmitter is excitatory or inhibitory. Receptors can also determine whether a transmitter acts rapidly by direct action on an ion channel (e.g., nicotinic acetylcholine receptors) or slowly, by a second-messenger system that allows for synaptic plasticity (e.g., muscarinic acetylcholine receptors). Speed & mechanism of transmitter inactivation after the signal has been sent is also a factor. There are probably also costs & benefits involved in synthesizing, transporting and recycling various neurotransmitters in the differing chemical mileus of the brain.
Many of these issues will become clearer in discussing the synthesis, distribution and function of the major brain neurotransmitters (see http://www.benbest.com/science/anatmind/anatmd10.html#intro for more detail).
Effects on behavior...
There is also an interaction of Dopamine and Acetylcholine, for exmaple, as both neurotransmitters impact muscle contractions. For example, Acetylcholine affects muscle contraction via the five cholinergic receptors : m1, m2, m3, m4, and m5. The receptors m1, m3 and m5 are stimulatory. The receptors m2 and m4 are inhibitory. The combined stimulatory effect of m1, m3 and m5 is more powerful in total than the combined inhibitory effect of m2 and m4. So the overall effect of acetylcholine is to stimulate muscle contraction. Dopamine also affects muscle contraction via the five dopamine receptors : D1, D2, D3, D4, and D5. The receptors D2, D3 and D4 are inhibitory. The receptors D1 and D5 are stimulatory. The combined inhibitory effect of D2, D3 and D4 is more powerful in total than the combined stimulatory effect of D1 and D5. So the overall effect of dopamine is to inhibit muscle contraction.
Parkinson's Disease consequently occurs when the effect of dopamine is less than that of acetylcholine. Dopamine deficiency rather than acetylcholine excess is normally responsible for this occurring. Symptoms usually only begin to appear after about a loss of about 75% of the activity of the dopaminergic neurons. The level of dopamine tends to continue to fall slowly over time, with an attendant worsening of symptoms. http://p4.forumforfree.com/the-biochemistry-of-parkinsons-disease-vt26-parkinsons.html

Effects on behavior, cont'd...
The following excerpt explains the various neurotransmitters and the effects on behavior. it is fairly lengthy, but detailed and an excellent resource...
More than 100,000 chemical reactions go on in your brain every second! The brain is also a radio transmitter, which sends out measurable electrical wave signals. In fact the brain continues to send out these signals for as long as 37 hours after death!
Among the brain's many jobs is to be your own chemist. The brain produces more than 50 identified active drugs. Some of these are associated with memory, others with intelligence, still others are sedatives. Endorphin is the brain's painkiller, and it is 3 times more potent than morphine.
Scientific research over the last several decades has led to the revolutionary discovery of opiate-like chemicals in the body that associate with opiate specific receptors in the brain and spinal cord, including Serotonin, a hormone manufactured by your brain.
Serotonin is a neurotransmitter, involved in the transmission of nerve impulses. It is manufactured in your body using the amino acid tryptophan. It is manufactured in your body using the amino acid tryptophan. Release of serotonin or other drugs (depending on the type of nerve) causes the other nerve to fire and continue the message along the "cable"..
The neurotransmitters are dopamine, serotonin, and norepinephrine. At the neurochemical and physiological level, neurotransmitters are extremely important, since they carry impulses between nerve cells. The substance that processes the neurotransmitter called ...

Solution Summary

Describes neurotransmitters, their function, and impact on behavior. This solution also discusses one neurotransmitter in detail describing the effect it has on our bodies and connection with disease. Further, it discusses the importance of biology for understanding behavior.

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