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Chapter 7. Neurotransmitters & Neuromodulators

Which of the following statements about neurotransmitters is true?

A. All neurotransmitters are derived from amino acid precursors.

B. Small-molecule neurotransmitters include dopamine, glycine, acetylcholine, enkephalin, and norepinephrine.

C. Large-molecule transmitters include GABA, endocannabinoids, substance P, and vasopressin.

D. Norepinephrine can act as a neurotransmitter in the periphery and a neuromodulator in the CNS.

E. Nitrous oxide is a neurotransmitter in the CNS.

Which of the following statements correctly describes the processes involved in the synthesis, storage, release, binding to a receptor, and termination of action of a common neurotransmitter?

A. Glutamate is synthesized in glia by the enzymatic conversion from glutamine and then diffuses into the neuronal terminal where it is sequestered into vesicles until released by an influx of Ca2+ into the cytoplasm after an action potential reaches the nerve terminal, it binds exclusively to ligand-gated ion channel receptors, and is inactivated by reuptake into the nerve terminal.

B. Serotonin is synthesized from trytophan, stored in synaptic vesicles until its release into the synaptic cleft; it then acts primarily on GPCRs and its actions are terminated primarily by reuptake into the presynaptic nerve terminal.

C. Norepinephrine is the only small-molecule transmitter that is synthesized in synaptic vesicles instead of being transported into the vesicle after its synthesis from the amino acid phenylalanine. After its release in response to depolarization, it binds to ligand-gated ion channels or GPCRs and its action is terminated by reuptake into the nerve terminal.

D. Acetylcholine is synthesized from acetlyene, transported from the cytoplasm into vesicles by a vesicle-associated membrane protein, released into the synaptic cleft in response to neuronal depolarization, acts on GPCRs, and its actions are terminated primarily by enzymatic degradation.

Which of the following receptors is correctly identified as an ionotropic or a GPCR and correctly paired with the ionic changes and/or second messenger induced by the binding of an agonist?

A. 5-HT1A receptors are GPCRs whose activation increases IP3 and DAG and increases K+ conduction.

B. Nicotinic receptors are ionotropic receptors whose activation decreases Na+ and K+ conduction.

C. GABAA receptors are GPCRs whose activation increases cAMP and decreases K+ conduction.

D. NMDA receptors are ionotropic receptors whose activation increases Na+, K+, and Ca2+...

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