Question

Order these steps: When light reaches the rods of vertebrates there is a change in the membrane potential from – 40 mV to – 70 mV. As a result of this hyperpolarization of the photoreceptor, the associated bipolar and ganglion cells fire action potentials. Place these events in order of their occurrence by placing a 1. next to the first event, 2. next ……and, finally a 5. next to the last event.

____Retinal changes from cis to trans configuration

____Bipolar cell no longer inhibited

____Activation of G protein called transducin which decreases amount of cGMP

____Sodium channels close

____Decreased glutamate release

Answer 1

in the order 1---->2-->3--->4--->5

1) Retinal changes from cis to trans configuration

2) Activation of G protein called transducin which decreases amount of cGMP

3) Sodium channels close

4) Decreased glutamate release

5) Bipolar cell no longer inhibited

In the dark, cyclic GMP is plentiful and these channels live open. Sodium cations enter freely into the rod cellular, because the mobile typically has a lower capability (is greater negative) than the outside environment, accordingly attracting the positively-charged ions. However,cyclic GMP is hydrolyzed with the aid of the now-activated phosphodiesterase, it is not available to keep the Na+ channels open. Sodium cations can now not input the cellular freely, and so the cell's ability suddenly turns into even lower relative to the external environment. A huge rate difference across the membrane is built up; this is referred to as hyperpolarization. The massive potential differences moves as an electrical impulse down the rod cellular to the synaptic terminal, and is then transferred to an adjoining nerve cellular. The nerve mobile carries this impulse all the manner to the brain. The mind then determines where the nerve impulse originated, and interprets the image