What is the approximate membrane potential range for a rod during hyperpolarization?

What is the approximate membrane potential range for a rod during hyperpolarization?

• A. -50 to -70 mV
• B. -30 to -50 mV
• C. -90 to -110 mV
• D. -0 to -20 mV

Answer: (A)

When photoreceptors hyperpolarize, the membrane potential becomes more negative because light closes the cGMP-gated channels, reducing the inward Na+ and Ca2+ current. In darkness, rods are relatively depolarized around -40 mV due to this ongoing influx; light shuts the channels and the potential shifts toward the reversal potential of the ions, roughly around -60 to -70 mV. So the hyperpolarized state is a more negative value, near -60 to -70 mV. Among the given options, -50 to -70 mV best captures that negative shift. The other ranges either show depolarization (less negative values) or an unrealistically large hyperpolarization for rods.

When photoreceptors hyperpolarize, the membrane potential becomes more negative because light closes the cGMP-gated channels, reducing the inward Na+ and Ca2+ current. In darkness, rods are relatively depolarized around -40 mV due to this ongoing influx; light shuts the channels and the potential shifts toward the reversal potential of the ions, roughly around -60 to -70 mV. So the hyperpolarized state is a more negative value, near -60 to -70 mV. Among the given options, -50 to -70 mV best captures that negative shift. The other ranges either show depolarization (less negative values) or an unrealistically large hyperpolarization for rods.