Multiple Choice
Neurogenesis has been observed in the __________ and in the __________.
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45. Nervous System
Neurons and Action Potentials
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Which step of nerve or muscle firing would be directly affected by a change in extracellular K\(^+\) concentration?
A
Opening of voltage-gated Na\(^+\) channels
B
Release of neurotransmitter at the synapse
C
Reuptake of Ca\(^{2+}\) into the sarcoplasmic reticulum
D
Resting membrane potential
Verified step by step guidance1
Understand that the resting membrane potential is primarily established by the distribution of ions, particularly K extsuperscript{+} (potassium), across the cell membrane. The movement of K extsuperscript{+} is governed by its concentration gradient and the membrane's permeability to K extsuperscript{+}.
Recall that the resting membrane potential is maintained by the sodium-potassium pump (Na extsuperscript{+}/K extsuperscript{+} ATPase), which actively transports 3 Na extsuperscript{+} ions out of the cell and 2 K extsuperscript{+} ions into the cell, creating a high intracellular K extsuperscript{+} concentration and a low extracellular K extsuperscript{+} concentration.
Recognize that a change in extracellular K extsuperscript{+} concentration would alter the K extsuperscript{+} concentration gradient. This would directly affect the equilibrium potential for K extsuperscript{+}, as described by the Nernst equation:
Understand that the resting membrane potential is closely tied to the equilibrium potential of K extsuperscript{+}, as the membrane is most permeable to K extsuperscript{+} at rest. A change in extracellular K extsuperscript{+} concentration would therefore directly affect the resting membrane potential, potentially making it less negative (depolarized) or more negative (hyperpolarized).
Conclude that the other steps listed (opening of voltage-gated Na extsuperscript{+} channels, release of neurotransmitter at the synapse, and reuptake of Ca extsuperscript{2+} into the sarcoplasmic reticulum) are not directly influenced by extracellular K extsuperscript{+} concentration, as they involve different ions or processes. The resting membrane potential is the correct answer.
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