Neurotransmitters

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Answer 27

The amino acid tyrosine is the precursor of dopamine, norepinephrine, and epinephrine. Tryptophan is the precursor of serotonin (5-hydroxytryptamine), and histamine derives from the amino acid histidine. Choline, an amino alcohol, is the precursor of acetylcholine, and the common amino acid glutamic acid is the precursor of the GABA. Note that DOPA decarboxylase is also known as aromatic L-amino acid decarboxylase, AADC.

Question 28

Glycine is primarily found in inhibitory interneurons in the spinal cord, where it blocks impulses traveling down the cord in motor neurons to stimulate skeletal muscle. The glycine receptor on motor neurons is ionotropic and is blocked by strychnine; motor impulses can then be passed without negative control, which accounts for the rigidity and convulsions caused by this toxin.

Answer 28

Glycine

Question 29

Norepinephrine, epinephrine, and dopamine (bio genic amines), known as catecholamines, are all derived from the amino acid ______

Answer 29

Tyrosine

Question 30

Norepinephrine (also known as noradrenaline) is a major transmitter in the _______ nervous system

Answer 30

Sympathetic

Question 31

Norepinephrine is the transmitter for these_________ nerves, whereas the transmitter at the intermediate ganglia is ACh.

Answer 31

Postganglionic

Question 32

The stimulatory effects of ____________are caused by their close chemical similarity to catecholamines or biogenic amines

Answer 32

Amphetamines

Question 33

The effects of neurotransmitters can be altered by changing their effective concentrations or the number of receptors. Concentrations can be altered by

Answer 33

■ changing the rate of synthesis,
■ altering the rate of release at the synapse,
■ blocking reuptake, or
■ blocking degradation.

Question 34

__________ is the most important excitatory transmitter in the CNS

Answer 34

Glutamate

Question 35

Epinephrine (also known as adrenaline) is produced by the __________ under the influence of ACh-containing nerves, analogous to the sympathetic preganglionic nerves

Answer 35

Adrenal medulla

Question 36

The receptors for norepinephrine and epinephrine are called _______ They are divided into α- and β-receptor classes and subclasses on the basis of their pharmacology

Answer 36

adrenoceptors

Question 37

Epinephrine acts on all classes of the receptors, but norepinephrine is more specific for _________

Answer 37

α-receptors

Question 38

__________ is taken up into cells by a high-affinity transporter and catabolized by the enzyme monoamine oxidase (MAO). Further oxidation and methylation by catecholamine- O -methyltransferase (COMT) convert the products to metanephrines and vanillylmandelic acid

Answer 38

Norepinephrine

Question 39

β-Blockers , such as atenolol, are used to treat hypertension and chest pain (angina) in ischemic heart disease because they antagonize the stimulatory effects of catecholamines on the heart

Answer 39

Nonspecific α-blockers have limited use

Question 40

There are five known dopamine receptors, falling into two main groups ( D 1 -like : D 1 and D 5 ; and D 2 -like : D 2 , D 3 , and D 4 ) that differ in their signaling pathways. D 1 receptors increase the production of cAMP, whereas D 2 receptors inhibit it.

Question 41

Antipsychotic drugs such as phenothiazines and haloperidol tend to inhibit D 2 -like receptors, suggesting that excessive dopamine activity may be important in causing the symptoms of schizophrenia.

Question 42

The D 2 receptor is a major receptor in the nerves that interconnect the basal ganglia. Because it is known that destruction of these nerves causes Parkinson’s disease , it is not surprising that antipsychotic drugs that inhibit the D 2 receptor tend to have the side effect of causing abnormal movements.

Question 43

The central role of serertoin 5-HT in

Answer 43

Controlling brain function

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