Multiple Choice
Which of the following embryonic germ layers gives rise to nervous tissue?
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45. Nervous System
Neurons and Action Potentials
Multiple Choice
Which of the following events will cause an excitatory postsynaptic potential (EPSP) in a neuron?
A
Opening of ligand-gated Cl\(^-\) channels, allowing Cl\(^-\) to enter the postsynaptic cell
B
Opening of ligand-gated K\(^+\) channels, allowing K\(^+\) to leave the postsynaptic cell
C
Inhibition of voltage-gated Ca\(^{2+}\) channels in the presynaptic terminal
D
Opening of ligand-gated Na\(^+\) channels, allowing Na\(^+\) to enter the postsynaptic cell
Verified step by step guidance1
Step 1: Understand the concept of an excitatory postsynaptic potential (EPSP). An EPSP is a temporary depolarization of the postsynaptic membrane caused by the flow of positively charged ions into the cell. This depolarization makes the neuron more likely to fire an action potential.
Step 2: Analyze the role of ion channels in generating EPSPs. Ligand-gated ion channels open in response to neurotransmitters, allowing specific ions to flow across the membrane. For an EPSP, positively charged ions like Na\(^+\) or Ca\(^{2+}\) typically enter the postsynaptic cell, leading to depolarization.
Step 3: Evaluate the options provided in the problem. Opening ligand-gated Cl\(^-\) channels would allow negatively charged ions to enter the cell, causing hyperpolarization (inhibitory effect). Opening ligand-gated K\(^+\) channels would allow positively charged ions to leave the cell, also causing hyperpolarization. Inhibition of voltage-gated Ca\(^{2+}\) channels in the presynaptic terminal would reduce neurotransmitter release, indirectly decreasing the likelihood of an EPSP.
Step 4: Focus on the correct answer: Opening ligand-gated Na\(^+\) channels. When these channels open, Na\(^+\) ions (positively charged) flow into the postsynaptic cell, causing depolarization and generating an EPSP.
Step 5: Summarize the reasoning. The correct event that causes an EPSP is the opening of ligand-gated Na\(^+\) channels, as this allows the influx of positively charged ions, leading to depolarization of the postsynaptic membrane.
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