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Chapter 7: Mechanisms of Synaptic Transmission

Which of the following best describes a basic property of synapses in the central nervous system (CNS)?

A. Synaptic vesicles constitute important features for transmission in both chemical and electrical synapses.

B. A postsynaptic neuron typically receives input from different presynaptic axons that are either excitatory or inhibitory, but it cannot receive inputs from both types.

C. Synaptic delay is approximately the same for both chemical and electrical synapses.

D. Neurotransmitter (NT) receptors can regulate the gating/opening of an ion channel either directly (ionotropic receptor) or indirectly (metabotropic receptor)

E. The mechanism of indirect gating of ions normally does not involve the activation of G proteins.

D. Electrical synapses do not involve neurotransmitter and thus do not require synaptic vesicles. A typical postsynaptic neuron receives thousands of inputs, with synaptic inputs from excitatory, inhibitory, and modulatory neurons. Because there is no neurotransmitter release or receptors, synaptic delay is much shorter at electrical synapses. Ionotropic receptors are neurotransmitter gated ion channels, whereas metabotropic receptors can regulate ion channels indirectly. Indirect gating of ion channels involves G proteins, which can interact with ion channels, or G proteins that produce second messengers, which control protein kinases that phosphorylate and regulate ions channels.

Which of the following events directly determines the release of NTs from the terminal of the presynaptic neuron?

A. Activation of voltage-gated Na+ channels and Na+ influx

B. Activation of voltage-gated Na+ channels and Na+ efflux

C. Activation of voltage-gated K+ channels and K+ influx

D. Activation of voltage-gated K+ channels and K+ efflux

E. Activation of voltage-gated Ca2+ channels and Ca2+ influx

E. Although voltage-gated Na+ and K+ channels are involved in the generation and conduction of the action potential (with Na+ influx and K+ efflux), which is necessary to depolarize the presynaptic membrane potential, it is the influx of Ca2+ through the activation of voltage-gated Ca2+ channels that directly activates the fusion of synaptic vesicles and neurotransmitter release by the presynaptic axon.

The level and duration of NT release are determined predominantly by which of the following?

A. The magnitude and duration of the presynaptic action potential

B. The inactivation of the presynaptic voltage-gated Na...

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