Chapter 2.2: Chemical events at the Synapse

Question 1

acetylcholine p. 50

Answer 1

(a one-member “family”) A chemical similar to

an amino acid, except that it includes an N(CH3)3 group instead of an NH2.

Question 2

amino acids p. 50

Answer 2

Amino acids Acids containing an amine group (NH2)

Question 3

catecholamines p. 50

Answer 3

Neurons synthesize nearly all neurotransmitters
from amino acids, which the body obtains from proteins. The relationship among epinephrine, norepinephrine, and dopamine—compounds known as
catecholamines, because they contain a catechol group and an amine group.

Question 4

gases p. 50

Answer 4

Nitric oxide and possibly others.

Question 5

monoamines p. 50

Answer 5

Chemicals formed by a change in certain

amino acids.

Question 6

neuropeptides p. 50

Answer 6

Chains of amino acids. The effect of a neurotransmitter depends on its receptor on the postsynaptic cell. When the neurotransmitter attaches to its receptor, the receptor may open a channel—exerting an ionotropic
effect—or it may produce a slower but longer effect—a metabotropic effect. The neuropeptides, however, are not inactivated. They simply diffuse away. Because these large molecules are resynthesized slowly, a neuron can temporarily exhaust its supply.)

Question 7

neurotransmitters p. 50

Answer 7

At a synapse, a neuron releases chemicals that affect another neuron. Those chemicals are known as neurotransmitters.

Question 8

nitric oxide p. 50

Answer 8

One special function of nitric oxide relates to blood
flow: When a brain area becomes highly active, blood flow to. Many neurons release nitric oxide when they are stimulated. In addition to influencing other neurons, nitric oxide dilates the nearby blood vessels, thereby increasing blood flow to that brain area.

Question 9

purines p. 50

Answer 9

A category of chemicals including adenosine and its

derivatives.

Question 10

exocytosis p. 51

Answer 10

Within 1 or 2 milliseconds (ms) after calcium enters the terminal (action potential), it causes exocytosis—bursts of release of neurotransmitter from the presynaptic neuron. An action potential often fails to release any transmitter, and even when it does, the amount varies.
After its release from the presynaptic cell, the neurotransmitter diffuses across the synaptic cleft to the postsynaptic membrane, where it attaches to a receptor.

Question 11

MAO p. 51

Answer 11

Neurons that release serotonin, dopamine, or norepinephrine contain an enzyme, MAO (monoamine oxidase), that breaks down these transmitters into inactive chemicals.

Question 12

vesicles p. 51

Answer 12

The presynaptic terminal stores high concentrations of neurotransmitter molecules in vesicles, tiny nearly spherical packets. (Nitric oxide is
an exception to this rule. Neurons release nitric oxide as soon as they form it instead of storing it.) The presynaptic terminal also maintains much neurotransmitter outside the vesicles.

Question 13

ionotropic effects p. 52

Answer 13

An ionotropic receptor is like that. When the neurotransmitter binds to an ionotropic receptor,
it twists the receptor enough to open its central hannel, which is shaped to let a particular type of ion pass through. In contrast to the sodium and potassium channels along an axon, which are voltage-gated, the channels controlled by a neurotransmitter are transmitter-gated or ligand-gated channels. Neurotransmitters: glutamate, GABA, Glycine, Acetylcholine,

Question 14

ligand-gated channels p. 52

Answer 14

The channels controlled by a neurotransmitter are transmitter-gated or ligand-gated channels. (A ligand is a chemical that binds to another chemical.)

Question 15

transmitter-gated channels p. 52

Answer 15

The channels controlled by a neurotransmitter are transmitter-gated or ligand-gated channels. (A ligand is a chemical that binds to another chemical.)

Question 16

G protein p. 53

Answer 16

A protein coupled to guanosine triphosphate (GTP), an energy-storing molecule. Bending the receptor protein detaches that G protein, which is then free to take its energy elsewhere in the cell. The result of that G protein is increased concentration of a second messenger inside the cell. 2nd Messenger carries information to many areas within the cell.

Question 17

metabotropic effects p. 53

Answer 17

At other receptors, neurotransmitters exert etabotropic
effects by initiating a sequence of metabolic reactions that are slower and longer lasting than ionotropic effects. metabotropic synapses use many neurotransmitters, including dopamine, norepinephrine, and serotonin and sometimes glutamate and GABA too.When a neurotransmitter attaches to a etabotropic receptor, it bends the receptor protein that goes through the membrane of the cell. The other side of that receptor is attached to a G protein. It influences activity in much or all of the cell and over a longer time.

Question 18

neuromodulators p. 53

Answer 18

Neuropeptides or neuromodulators: it synthesizes neuropeptides in the cell body and then slowly transports them to other parts of the cell. Whereas other neurotransmitters are released at the axon terminal, the neuropeptides are released mainly by dendrites, and also by the cell body and the sides of the axon. neuropeptide release requires repeated
stimulation. However, after a few dendrites release a neuropeptide, the released chemical primes other nearby dendrites to release the same neuropeptide also, including dendrites of other cells.

Question 19

second messenger p. 53

Answer 19

G protein is increased concentration of a second messenger, such as cyclic adenosine monophosphate (cyclic AMP), inside the cell. Just as the “first messenger”neurotransmitter) carries information to the postsynaptic cell, the second messenger communicates to many areas within the cell. It may open or close ion channels in the membrane or activate a portion of a chromosome.

Question 20

hallucinogenic drugs p. 54

Answer 20

A drug that chemically resembles a neurotransmitter can bind to its receptor. Many hallucinogenic drugs—that is, drugs that distort perception, such as lysergic acid diethylamide (LSD)—chemically resemble serotonin. They attach to serotonin type 2A (5-HT2A) receptors and provide stimulation at inappropriate times or for longer-thanusual durations.

Question 21

nicotine p. 54

Answer 21

Nicotine, a compound present in tobacco, stimulates
a family of acetylcholine receptors, conveniently known as nicotinic receptors. Nicotinic receptors are abundant on neurons that release dopamine, so nicotine increases dopamine release there. Because dopamine release is associated with reward, nicotine stimulation is rewarding also.

Question 22

opiate drugs p. 54

Answer 22

Like morphine, heroin, and methadone. Soon investigators found that the brain produces certain neuropeptides now known as endorphins—a contraction of endogenous morphines. Opiate drugs exert their effects by binding to the same receptors
as endorphins. This discovery was important because it indicated that opiates relieve pain by acting on receptors in the brain, not in the skin.

Question 23

acetylcholinesterase p. 55

Answer 23

After acetylcholine activates a receptor, it is broken
down by the enzyme acetylcholinesterase (a-SEE-til-kolih-NES-teh-raze) into two fragments: acetate and choline. The choline diffuses back to the presynaptic neuron, which takes it up and reconnects it with acetate already in the cell to form acetylcholine again.

Question 24

amphetamineand cocaine p. 55

Answer 24

Stimulant drugs, including amphetamine and cocaine,
inhibit the transporters for dopamine, thus decreasing reuptake and prolonging dopamine’s effects. Amphetamine also blocks the serotonin and norepinephrine transporters. Methamphetamine’s effects are like those of amphetamine, but stronger. Most antidepressant drugs also block the dopamine
transporter, but much more weakly than amphetamine
and cocaine do.

Question 25

COMT p. 55

Answer 25

When stimulant drugs increase the accumulation of
dopamine in the synaptic cleft, COMT breaks down the
excess dopamine faster than the presynaptic cell can replace it. A few hours after taking a stimulant drug, a user has a deficit of dopamine and enters a withdrawal state, marked by reduced energy, reduced motivation, and mild depression.

Question 26

methylphenidate p. 55

Answer 26

Methylphenidate (Ritalin), another stimulant drug, is often prescribed for people with attention deficit/hyperactivity disorder. Methylphenidate and cocaine block the reuptake of dopamine in the same way at the same brain receptors. The differences
between the drugs relate to dose and time course.

Question 27

reuptake p. 55

Answer 27

The presynaptic neuron takes up much or most of the released neurotransmitter molecules intact and reuses them. This process, called reuptake.

Question 28

transporters p. 55

Answer 28

Reuptake occurs through special membrane proteins

called transporters.

Question 29

anandamide p. 56

Answer 29

Second, some postsynaptic neurons respond to stimulation by releasing chemicals that travel back to the presynaptic terminal to inhibit further release of transmitter. Nitric oxide is one such transmitter. Two others are anandamide and 2-AG.

Question 30

autoreceptors p. 56

Answer 30

Many presynaptic terminals have receptors sensitive
to the same transmitter they release. These receptors are known as autoreceptors—receptors that respond to the released transmitter by inhibiting further synthesis and release.

Question 31

cannabinoids p. 56

Answer 31

Cannabinoids, the active chemicals in marijuana, bind
to anandamide or 2-AG receptors on presynaptic neurons When cannabinoids attach to these receptors, they indicate, “The cell got your message. Stop sending it.” The presynaptic cell, unaware that it hadn’t sent any message at all, stops sending. In this way, the
chemicals in marijuana decrease both excitatory and inhibitory messages from many neurons.

Question 32

endocrine glands p. 57

Answer 32

Hormone-producing (see table 2.4)

Question 33

gap junction p. 57

Answer 33

1

Question 34

hormone p. 57

Answer 34

Hormonal influences resemble synaptic transmission in many ways, including the fact that many chemicals serve both as hormones and as neurotransmitters. A hormone is a chemical secreted by cells in one part of the body and conveyed by the blood to influence other cells. Hormones function more like a radio station: They convey a message to any receiver tuned to the right station. Two types of hormones are protein hormones
and peptide hormones, composed of chains of amino acids. (Proteins are longer chains and peptides are shorter .) Protein and peptide hormones attach to membrane receptors, where they activate a second messenger within the cell—exactly like a metabotropic synapse.

Question 35

oxytocin and vasopressin p. 58

Answer 35

Hypothalamus secretes releasing hormones and inhibiting hormones that control anterior pituitary. Also synthesizes vasopressin and oxytocin, which travel to posterior pituitary.

Question 36

peptide hormones and protein hormones p. 58

Answer 36

Two types of hormones are protein hormones
and peptide hormones, composed of chains of amino acids. (Proteins are longer chains and peptides are shorter .) Protein and peptide hormones attach to membrane receptors, where they activate a second messenger within the cell—exactly like a metabotropic synapse.

Question 37

releasing hormones p. 58

Answer 37

The hypothalamus secretes releasing hormones, which flow through the blood to the anterior pituitary. There they stimulate or inhibit the release of other hormones.