This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
When light strikes the eye there is an increase in which of the following? 
Select and explain. 
A. The activity of the transducin, B. The amount transmitter released from the photoreceptors, C. The concentration of all-trans retinal within the photoreceptors, D. The concentration of calcium within the photoreceptors
A: The activity of the transducin
Answer: A: The activity of the transducin 
Explanation: Transducin is the G protein activated. by rhodopsin when light strikes the eye. Transducin activates a phosphodiesterase that hydrolyzes cGMP When cGMP concentrations within the rods or cones decrease, sodium channels close, sodium conductance decreases, and the cell membrane potential increases (hyperpolarizes). Hyperpolarization of the cell causes a decrease in the release of neurotransmitter. Eventually the all- trans retinal dissociates from opsin and reduces the concentration of rhodopsin in the cell.