The graph below shows the pattern traced by placing electrodes at a point on the axon of a nerve cell as it is stimulated - VCE - SSCE Biology - Question 14 - 2009 - Paper 1
Question 14
The graph below shows the pattern traced by placing electrodes at a point on the axon of a nerve cell as it is stimulated.
The graph illustrates the electrical pote... show full transcript
Worked Solution & Example Answer:The graph below shows the pattern traced by placing electrodes at a point on the axon of a nerve cell as it is stimulated - VCE - SSCE Biology - Question 14 - 2009 - Paper 1
Step 1
A. the lowest potential, J, represents the resting potential of the nerve.
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Answer
The lowest potential, J, indeed indicates the resting potential of the nerve. It reflects the state when the nerve is not actively conducting an impulse and typically sits around -70 mV.
Step 2
B. during phase F, fewer sodium ions are leaving the cell than entering it.
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During phase F, sodium ions flow into the cell due to a concentration gradient, and fewer are leaving it. This occurs as depolarization begins, making the interior more positive.
Step 3
C. during phase K, the membrane will fail to respond to further stimulation.
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In phase K, which corresponds to the refractory period, the membrane cannot respond to further stimulation. This occurs due to inactivation of sodium channels and changes in potassium channel activity.
Step 4
D. the stimulus applied only has an effect when the membrane potential is positive.
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A stimulus can generate an action potential only when the membrane reaches a threshold potential, typically when it is depolarized. While a positive potential enhances excitability, it is the rate of change rather than mere positivity that affects response.
