Question

In crayfish muscle fiber as the temperature increases synaptic EPSP amplitude increases

with a larger driving gradient for excitatory junction potentials (EJP or EPSP) at 20C what would be some responsible reasons (list 3) of why the amplitude of the EJP still increases when going from 20 C to 10 C in crayfish muscle as compared to going from 10C to 20 C?

EXPERIMENTAL RESULTS SHOWED: For the crayfish acclimated to 10°C, seven out of eight preparations presented an increase in the 30th EPSP amplitude. This is quite different from the acute change from 20°C to 10°C; the change from 10°C to 20°C resulted in only two of the seven preparations increasing the 30th/10th facilitation index, with mixed results for the facilitation of the earlier EPSPs within the train (20th/10th)

List 3 reasons:

Answer 1

The following might be the reasons for this phenomenon:

1. Negative equilibrium potential of K+ (EK), this is because the membrane is more permeable to K+ ions and the resting potential is driven primarily by the EK.
2. With a more negative EK, a larger EPSP would be produced in the muscle due to a larger driving gradient for ECa and ENa for glutamate receptor-induced depolarisation of the crustacean muscle.
3. Crayfish skeletal muscle primarily uses voltage-gated Ca2+ channels in the plasma membrane, which leads to this increase in EPSP amplitude.