19. A student new to neuroscience research is practicing recording resting membr

Question

19. A student new to neuroscience research is practicing recording resting membrane potentials from giant squid axons. During one of the trials, the resting membrane potential, which is normally around –60 mV, measured –15 mV. Which statement best describes what might have occurred during the experiment?

a. The student added too much potassium to the extracellular solution.

b. The student added too much sodium to the extracellular solution.

c. The student did not add enough potassium to the extracellular solution.

d. The student did not add enough sodium to the extracellular solution.

21. Which current corresponds to a flow of Na+ in response to a depolarizing stimulus in a giant axon of a squid?

a. Inward capacitive current

b. Outward capacitive current

c. Transient inward current

d. Delayed outward current

Explanation / Answer

The resting membrane potential is closer to the potassium equilibrium value. It is due to the leaky potassium channels through which the potassium ions pass from inside of the membrane to the outside giving it a negative charge. A less negative charge means depolarization but since sodium ion channels do not open without the stimulus this must be due to a higher concentration of potassium ions in the extracellular medium. A higher concentration in the extracellular medium of potassium ions inhibits the movement of potassium ions from inside to outisde through leaky channels due to disruption .of concentration gradient ( potassium ions are high inside and low outside the cell). This is why the membrane potential of a resting membrane is more positive. The answer is a.

21. Transient capacitive current

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