Question

8. Indicate whether the following lead to Depolarization OR Hyperpolarization (1) Opening of K+ channels on the post-synaptic membrane. (2) Opening of Cl- channels on the post-synaptic membrane. (3) Opening of Na+ channels on the post-synaptic membrane. 9. Indicate whether the following are Graded OR All-or-None responses. (1) Local potential (2) Action potential (3) EPSP (4) IPSP (5) End Plate Potential 10. True or False: Temporal summation of IPSPs increases the chance of having an action potential.

Answer 1

8)

1) It causes hyperpolarization as when there is opening of the K+ ion channel when there is presence of excess of K+ ions. This happens because it allows time for resetting the opening of the Na+ channels and there is increase in the efflux of the K+ ions through the K+ channel. The hyperpolarization tends to change the membrane potential of the cell and hence makes it more negative.

2) Hyperpolarization – This is caused by the influx of the Cl ion through opening of the Cl channels and hence makes the membrane potential of the cell more negative. It is known to inhibit action potential. As the Cl ion channel opens, it leads to keeping it open for a longer time and hence creates hyperpolarization by making the inside of the cell more negative.

3) Depolarization -This is a change in the cell where there is change in the electrical potential and hence the inside of the cell becomes more negative. This is caused by change in the permeability of the Na+ ions as it keeps the Na+ ion channel open for a longer time. As an action potential is initiated, it causes a rapid change in the membrane potential and hence changes the inside of the cell from negative to more positive.