For this question, consider only one synapse and assume only one action potentia

Question

For this question, consider only one synapse and assume only one action potential occurs. Of the events which occur at a single chemical (or "typical") synapse after an action potential occurs in the synaptic knob, which of the following happens last? A) opening of chemically gated ion channels B) release of neurotransmitter into synaptic cleft C) opening of voltage gated Ca++ channels D) binding of neurotransmitter to receptors on subsynaptic membrane E) postsynaptic potential

Which of the following is NOT or is LEAST associated with inhibitory postsynaptic potentials (IPSPs)? A) GABA (gamma-aminobutyric acid) B) neurotransmitter that opens channels permeable only to K+C) neurotransmitter that opens channels permeable to both K+ and Na+ D) action potential in presynaptic neuron.

The trigger zone of the initial segment is the site of action potential initiation because it has less voltage-gated Na+ channelscompared to other areas of the neuron. A) True B) False

Explanation / Answer

1) Of the events which occur at a single chemical (or "typical") synapse after an action potential occurs in the synaptic knob, which of the following happens last?

Answer: E) postsynaptic potential

Reason: When an action potential arrives at the axon terminal it activates Ca+2 channels in the pre-synaptic cell membrane releasing neurotransmitter into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and binds to receptors on the post-synaptic cell membrane.When a neurotransmitter binds to its receptor it causes ion channels to open or close. This can produce a localized change in the membrane potential called postsynaptic potential

2) Which of the following is NOT or is LEAST associated with inhibitory postsynaptic potentials (IPSPs)?

Answer: C) neurotransmitter that opens channels permeable to both K+ and Na+

Reason: GABA is a common neurotransmitter used in IPSPs.The open channels are selectively permeable to chloride or potassium ions and allow these ions to pass through the membrane. IPSP is due to the action potential in presynaptic neuron. An IPSP is a kind of synaptic potential that reduces the postsynaptic neuron's ability to produce an action potential.

3) The trigger zone of the initial segment is the site of action potential initiation because it has less voltage-gated Na+ channels compared to other areas of the neuron.

Answer: False

Reason: This trigger zone is located at the axon initial segment where action potentials are initiated and it contains locally highest density of Na+ channels.

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