Question

12. The calcium channels are found in the axon terminal end of the neuron (True/False): _________

13. During depolarization ___________ channels open and _______ ion rushes into the cell.

14. During repolarization _____________ channels open and ________ rushes out of the cell.

15. The resting membrane potential is restored by _________________.

A. Na channel B. Calcium channel C. Potassium channel D. Na/K voltage gated channel

16. Which of the following correctly describes a graded potential?

    a. long distance signaling b. intensity of stimulation c. voltage stimulus to initiate d. voltage regulated repolarization

17. When threshold is reached, this results in __________ potential which is the basis for nerve impulse.

18. Saltatory conduction is made possible by ________.

    a. the myelin sheath b. large nerve fibers c. diphasic impulses d. erratic transmission of nerve impulses

19. The synaptic vesicles release the neurotransmitter Ach into the synaptic cleft via

    a. Endocytosis b. Exocytosis c. Transcytosis d. Phagocytosis

Answer 1

1. The Calcium channels are found in the terminal end of axon. With help of these channels, Calcium ion enters in the axon and cause fusion of neurotransmitter vesicles with the membrane, thus releasing neurotransmitter. (TRUE)
2. Depolarization means entry of positively charged ions passively into the cell from the extracellular fluid. As extracellular fluid contains more Na, the voltage gated Na channels open and there occurs a rapid influx of Na ions..
3. Repolarization means making the potential of the membrane negative. This occurs if some positive charges ion leaves the cell. There occurs opening of K channels and there occurs efflux of K ions outside the cell.
4. The Resting membrane potential is restored- Na-K voltage gated channels. This maintains the-70mV in most of the cells.
5. Graded Potential. Electrotonic potentials produced by varying intensities of stimuli are proportional to the magnitude of stimulation. These are called graded potentials.
6. When threshold is reached, the neuron fires and there is opening of Na channels and ACTION potential is generated which is the basis of nerve transmission.
7. The myelinated nerve fibres have wrapping of myelin which acts as insulator and prevent loss of current. The nerve has specific gaps where myelin is not present. These are called nodes of Ranvier. In conduction, the impulse jumps from one node of Ranvier to other node of Ranvier. This is called saltatory conduction. Therefore, myelin is necessary.
8. It is by exocytosis (exo-outside, cytosis- eating). Endocytosis means taking in of an outside particle. Transcytosis means transport of material within a cell itself. Phagocytosis means eating of an outside particle and destroying it. Answer is exocytosis.