chapter 4.6

Question 1

Three classes of conventional small-molecule neurotransmitters:

Answer 1

amino acids, the monoamines, and acetylcholine.

Question 2

Unconventional neurotransmitters

Answer 2

small-molecule neurotransmitter; mechanism of action are unusual.

Question 3

Class of large-molecule neurotransmitters

Answer 3

neuropeptides

Question 4

Amino acid neurotransmitters

Answer 4

glutamate, aspartate, glycine, and gamma-aminobutyric (GABA). The first three are common in the protein we consume, whereas GABA is synthesized by a simple modification of the structure of glutamate.

Question 5

Glutamate

Answer 5

most prevalent excitatory neurotransmitter in the mammalian CNS.

Question 6

GABA

Answer 6

most prevalent inhibitory neurotransmitter; however, it has excitatory effects at some synapses.

Question 7

Monoamines

Answer 7

each is synthesized from a single amino acid.

Question 8

Monoamine neurotransmitters

Answer 8

slightly larger than amino acid neurotransmitters and their effects tend to be more diffuse. Present in small groups of neurons whose cell bodies are located in the brain stem. These neurons often have highly branched axons with many varicosities from which monoamine neurotransmitters are diffusely released into the extracellular fluid.

Question 9

Four types of monoamine neurotransmitters

Answer 9

dopamine, epinephrine, norepinephrine, and serotonin. Subdivided into two groups, the catecholamines (all except serotonin) and indolamines on the basis of their structures.

Question 10

Catecholamines

Answer 10

each is synthesized from the amino acid tyrosine. Tyrosine is converted to L-dopa, which in turn is converted to dopamine. Neurons that release norepinephrine have an extra enzyme (not present in dopaminergic neurons), which converts the dopamine in them to norepinephrine. Neurons that release epinephrine have all the enzymes present in neurons that release norepinephrine, along with an extra enzyme that converts norepinephrine to epinephrine.

Question 11

Serotonin

Answer 11

also called 5-HT; is synthesiszed from the amino acid tryptophan and is classed as an indolamine.

Question 12

Noradrenergic

Answer 12

neurons that release norepinephrine.

Question 13

Adrenergic

Answer 13

neurons that release epinephrine.

Question 14

Acetylcholine

Answer 14

small-molecule neurotransmitter that is created by adding an acetyl group to a choline molecule. The neurotransmitter at neuromuscular junctions, at many of the synapses in the autonomic nervous system, and at synapses in several parts of the CNS.

Question 15

Cholinergic

Answer 15

neurons that release acetylcholine.

Question 16

Soluble-gas neurotransmitters

Answer 16

unconventional neurotransmitter; includes nitric oxide and carbon monoxide. Produced in the neural cytoplasm and immediately diffuse through the cell membrane into the extracellular fluid and then into nearby cells. Easily pass through cell membranes because they are soluble in lipids. Once inside another cell, they stimulate the production of a second messenger and are deactivated by being converted to other molecules.

Question 17

Soluble-gas neurotransmitters and retrograde transmission

Answer 17

at some synapses, they transmit feedback signals from the postsynaptic neuron back to the presynaptic neuron. Function of retrograde transmission seems to be to regulate the activity of presynaptic neurons.

Question 18

Endocannabinoids

Answer 18

unconventional neurotransmitter; similar to THC, the main psychoactive constituent of marijuana. Includes anandamide. Produced immediately before they are released and are synthesized from fatty compounds in the cell membrane; they tend to be released from the dendrites and cell bod; and they tend to have most of their effects on presynaptic neurons, inhibiting subsequent synaptic transmission.

Question 19

Neuropeptide transmitters

Answer 19

five groups: pituitary peptides, hypothalamic peptides, brain-gut peptides, opioid peptides, and miscellaneous peptides.

Question 20

pituitary peptides

Answer 20

contains neuropeptides that were first identified as hormones released by the pituitary.

Question 21

hypothalamic peptides

Answer 21

contains neuropeptides that were first identified as hormones released by the hypothalamus.

Question 22

brain-gut peptides

Answer 22

contains neuropeptides that were first discovered in the gut.

Question 23

opioid peptides

Answer 23

contains neuropeptides that are similar in structure to the active ingredient of opium.

Question 24

miscellaneous peptides

Answer 24

catch-all category that contains all of the neuropeptide transmitters that do not fit into one of the other four categories.