Question

Dr. Green is studying the role of rods in vision. Dr. Green applies a K⁺ channel blocker, which inhibits K⁺ channels, to rods in a Petri dish. Before and after adding the K⁺ channel blocker, Dr. Green also measures the concentration of neurotransmitters in the media of the Petri dish and the membrane potential of the rods. What does Dr. Green find? (Select all options that apply)

(a) Glutamate secretion decreases after addition of the K⁺ channel blocker

(b) The membrane of rods depolarizes after addition of the K⁺ channel blocker

(c) Serotonin secretion increases after addition of the K⁺ channel blocker

(d) Action potentials are generated in rods after addition of the K⁺ channel blocker

(e) cGMP secretion increases after addition of the K⁺ channel blocker

Answer 1

Answer is Option A - Glutamate secretion decreases after addition of the K+ channel blocker

Activation of photopigments by light sends a signal by hyperpolarizing the rod cell, leading to the rod cell not sending its neurotransmitter, which leads to the bipolar cell then releasing its transmitter at the bipolar-ganglion synapse and exciting the synapse.

Depolarization of rod cells (causing release of their neurotransmitter) occurs because in the dark, cells have a relatively high concentration of cyclic guanosine 3'-5' monophosphate (cGMP), which opens ion channels (largely sodium channels, though calcium can enter through these channels as well). The positive charges of the ions that enter the cell down its electrochemical gradient change the cell's membrane potential, cause depolarization, and lead to the release of the neurotransmitter glutamate. Glutamate can depolarize some neurons and hyperpolarize others, allowing photoreceptors to interact in an antagonistic manner.

potaasium channel have a great role in the depolarization of photoreceptor. normal fuction of potassium channel is the efflux of potassium ion from the cell to outside.When this channel get blocked, the depolarization of the rod cell stops.Hence the production of glutamate neurotransmitted reduces.