Nerve muscle I

1. What is the resting membrane potential of a myelinated-nerve fibre?

-70mV

2. In a nerve action potential, what causes the depolarization?

Influx of sodium ions

3. In an action potential graph, when does the phase  of hyperpolarization appear?

After repolarization

4. Name of the ion responsible for the hyperpolarization phase in an action potential in a nerve fibre.

Efflux of  K

5. Influx of which ion releases acetycholine from presynaptic vesicles at the neuromuscular junction?

Calcium ion

6. Name the enzyme that inactivates acetylcholine at the neuromuscular junction.

Acetylcholine esterase

7. Why impulse transmission is faster in a myelinated neuron?

Due to saltatory conduction

8. What is the site of generation of an action potential in an intact neuron?

Axon hillock

9. Name the cells that produce myelin in peripheral nerves.

Schwann cells

10. If an axon is cut,its distal part degenerates. What is this type of degeneration known as?

Wallerian degeneration

11. Name the instrument used to measure electrical events in an excitable tissue.

Cathode ray oscilloscope (CRO)

12. Name the two scientists who classified the nerve fibres based on the diameter and speed of conduction.

Erlanger and Gasser

13. Name the type of nerve fibres that carry fast-pain sensations.

A-delta fibres

14. Name the cels that produce myelin in the central nervous system

Oligodendrocytes / oligodendroglial cells

15. Which ion mainly contributes to the membrane potential of a nerve fibre at rest?

Potassium ion

( Physiology; UMS 2008 )