8. A neurotransmitter may be described as “excitatory” (leads to depolarization)

Question

8. A neurotransmitter may be described as “excitatory” (leads to depolarization) or “inhibitory” (no change or hyperpolarization). Which of the following determines the action of the neurotransmitter?

a. The type of charges (or¨)on the neurotransmitter

b. The type of pores in the presynaptic membrane

c. The width of the synaptic cleft

d. The receptors on the postsynaptic membrane

e. The active zones in the postsynaptic membrane

9. A 24-year-old woman suffering from a severe allergic reaction improves markedly after a subcutaneous injection of epinephrine. Transduction of this epinephrine chemical signal involves which of the following?

a. Binding of epinephrine to membrane-bound ?beta-adrenoreceptors

b. Dissociation of the alpha subunit from the beta -heterodimer of the G-protein complex

c. Binding of the G-protein alpha subunit to adenylyl cyclase

d. Stimulation of adenylyl cyclase to increase intracellular cyclic adenosine monophosphate levels

e. All of these steps

Explanation / Answer

8. Neurotransmitters released from the presynaptic membrane binds to the specific post-synaptic membrane receptors. The type of response depends on the type of receptor on the post-synaptic membrane.

ANSWER: d. The receptors on the postsynaptic membrane

9. Steps in epinephrine signaling:

ANSWER: e. All of these steps

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