Multiple Choice
Which of the following factors most directly influence the speed of nerve signal conduction along an axon?
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45. Nervous System
Neurons and Action Potentials
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Select the correct statement regarding chemical synapses:
A
The postsynaptic membrane always generates an action potential after neurotransmitter binding.
B
Chemical synapses transmit signals faster than electrical synapses.
C
Neurotransmitters are released from the presynaptic neuron into the synaptic cleft.
D
Action potentials directly pass from one neuron to another through gap junctions at chemical synapses.
Verified step by step guidance1
Step 1: Understand the concept of a chemical synapse. A chemical synapse is a junction between two neurons where the signal is transmitted via neurotransmitters, which are chemical messengers. This is different from electrical synapses, where signals are transmitted directly through gap junctions.
Step 2: Analyze the first statement: 'The postsynaptic membrane always generates an action potential after neurotransmitter binding.' This is incorrect because neurotransmitter binding can either excite or inhibit the postsynaptic neuron, depending on the type of neurotransmitter and receptor involved. An action potential is not guaranteed.
Step 3: Analyze the second statement: 'Chemical synapses transmit signals faster than electrical synapses.' This is incorrect because electrical synapses are faster due to the direct passage of ions through gap junctions, whereas chemical synapses involve a slower process of neurotransmitter release and binding.
Step 4: Analyze the third statement: 'Neurotransmitters are released from the presynaptic neuron into the synaptic cleft.' This is correct because, in chemical synapses, neurotransmitters are released from vesicles in the presynaptic neuron into the synaptic cleft, where they bind to receptors on the postsynaptic membrane.
Step 5: Analyze the fourth statement: 'Action potentials directly pass from one neuron to another through gap junctions at chemical synapses.' This is incorrect because action potentials do not directly pass in chemical synapses; this occurs in electrical synapses. In chemical synapses, the signal is transmitted via neurotransmitters.
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