While Dr. Jackson is recording the activity of a squid axon, he finds that a larger depolarizing shock is necessary on occasion in order to produce a new action potential. What is the most likely explanation for Dr. Jackson's observations?
a. The squid axon is such an artificial laboratory preparation, it cannot be expected to respond like an axon in a living animal.
b. Dr. Jackson's second shock probably occurs during a relative refractory period.
c. Dr. Jackson's second shock probably occurs during an absolute refractory period.
d. The squid axon in the laboratory does not have functioning sodium-potassium pumps.
Question 2
The relative refractory period occurs because
a. the cell is hyperpolarized, requiring a larger than normal stimulus in order to form another action potential.
b. it takes time for the sodium-potassium pumps to return ion concentrations to the normal resting state.
c. only one action potential at a time can travel the length of an axon.
d. sodium channels cannot reopen until the cell regains its resting potential.
(A) The structure of a neuron, showing the dendrites, nerve cell body, and axon. (B) Photomicrograph
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