Nerve muscle II

1. What is the threshold level for initiation of an action  potential in a nerve fibre?

-55 mV

2. What neurotransmitter is secreted at the neuromuscular junction?

Acetylcholine

3. What types of ion channels are abundant on the post synaptic membrane of the NMJ?

Ach gated ion channels / ligand gated / chemically gated ion channel

4. What is the local positive potential generated at the end-plate of the NMJ called?

Motor-end-plate potential (MEPP / EPP)

5. In myelinated axon, which region has the maximum number of sodium channels?

The nodes of Ranvier

6. What is the ionic basis for post synaptic membrane hyperpolarization?

Influx of chloride ions

7. Name the ion that is present abundantly in the sarcoplasmic reticulum of the muscle.

Calcium ions

8. What is the structural / functional unit of  a skeletal muscle known as?

Sarcomerce

9. What is a single-skeletal muscle cell known as?

Muscle fibre

10. What is the process of the increase in the number of active motor units called?

Recruitment of motor units

11. If skeletal muscle fibres are destroyed afer birth, name the cells that help to replace them by addition of new cells.

Satellite cells (undifferentiated cells adjacent to the muscle cells)

12. What links the muscles to the bones?

Tendons

13. How many subunits are present in a troponin molecule?

3-subunits (I-inhibitory, T-tropomyosin binding and C-calcium binding)

14. Name the voltage-sensitive calcium channel protein in the T-tubules.

Dihydropyridine receptors (DHP)

15. What is the main function of dihydropyridine (DHP) receptor?

Acts as a voltage sensor

( Physiology; UMS 2008 )