Advanced muscle physiology

Question 1

What is a motor unit?

Answer 1

A motor neurone and the muscle fibres it innervates

Question 2

What makes up a fascicle?

Answer 2

Multiple muscle fibers (cells), which are made up of multiple myofibrils

Question 3

What are skeletal action potentials mediated by?

Answer 3

K+

Cl-

Question 4

What is the structure and function of the nicotinic AchR?

Answer 4

Function= depolarise post synaptic membrane- through the influx of sodium
Structure= pentameric, (combo of 4 subunits)
there are 9 different versions of the receptor

Question 5

What is the gating process of AchR?

Answer 5

C-A1C-A2C-A2O

Question 6

What is Myasthenia Gravis?

Answer 6

An autoimmune disease which attacks the AchRs on the post synaptic membrane in NMJs
Main symptom= tiredness and weakness in skeletal muscle

Question 7

What are 6 treatments of Myasthenia Gravis?

Answer 7

1. AchE inhibitors
2. Corticosteriods
3. Other immunosuppressants
4. Plasmapheresis
5. IV immunoglobulins
6. Thymectomy

Question 8

What 2 things does an AP running down a T-Tubule cause?

Answer 8

1. L-gates Ca channels to open- small Ca influx into cytosol

2. Ryanodine receptors on S.R membrane activated- release of Ca from S.R

Question 9

What causes muscle relaxation?

Answer 9

UPTAKE OF CALCIUM

1. Ca2+/ATPase on S.R membrane
2. Na+/Ca2+ exchanger