This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
The rod receptor potential differs from other surface receptors in that it shows ______? 
Select and explain. 
A. Depolarization, B. Decreased negativity, C. Increased conductance of Sodium, D. Hyperpolarization
D: Hyperpolarization
Answer: D: Hyperpolarization 
Explanation: The rod receptor potential differs from the outer surface receptors in that it shows Hyperpolarization. In most sensory receptors: Arrival of stimulus - Ion channels are opened up allowing current to flow - depolarisation of the receptor. In photoreceptors: When the light strikes the outer segment, a cascade of reactions are initiated, that close some of the Na+ channels in the outer segment and results in hyperpolarisation. Ref: Guyton and Hall 13th edition Pgno: 650-651