14. Alteration in Skeletal Muscle Function

Question 1

What happens if muscle:

a. destruction > replacement?
b. destruction

Answer 1

a. Atrophy

b. Hypertrophy.

Question 2

How does high resistance exercise affect muscle?

Answer 2

Stimulates contractile protein synthesis, fatter muscle fibres and larger muscle. Leads to hypertrophy.

Question 3

How does endurance exercise effect muscle?

Answer 3

Stimulates synthesis of mitochondrial proteins, vascular changes allow for greater oxygen utilisation. There’s a shift to oxidative metabolism. Increased endurance but not hypertrophy.

Question 4

What are three types of atrophy?

Answer 4

Disuse atrophy - e.g. from bed rest etc, loss of protein leads to reduced fibre diameter and loss of power.
Muscle atrophy with age - 50% muscle loss by 80 years old.
Denervation atrophy - lower motor neurone lesions leads to weakness, and flaccidity.

Question 5

How is the length of muscle changed?

Answer 5

Increased with sustained stretching. Decreased with immobilisation.

Question 6

What is an example of a neuromuscular junction disorder?

Answer 6

Myasthenia Gravis - autoimmune destruction of the end plate ACh receptors. There is loss of junction all folds at the end plate and widening of the synaptic cleft.

Question 7

What are the symptoms of the neuromuscular junction disorder, myasthenia gravis?

Answer 7

Fatigability and sudden falling (form reduced ACh release), dropping upper eyelid, double vision. General state of health shows fatigue and emotion.

Question 8

How is myasthenia gravis treated?

Answer 8

Acetylcholinesterase inhibitors, immune suppressants, plasmapheresis (removal of harmful antibodies from patient’s serum) or thymectomy.

Question 9

What toxins affect the neuronal Na+ channel?

Answer 9

Tetrodotoxin and sacitoxin.

Question 10

What toxin affect the Ca2+ channel?

Answer 10

Conotoxin.

Question 11

What toxin affects the K+ channel?

Answer 11

Dendrotoxin.

Question 12

What toxin affect ACh release?

Answer 12

Tetanus toxin and botulinum toxin.

Question 13

What toxins affect actylcholinesterase?

Answer 13

Physostigmine and DFP.

Question 14

What toxins affect muscle Na+ channel?

Answer 14

Tetrodotoxin, sacitoxin and u-conotoxin.

Question 15

What toxins affect AChR channel?

Answer 15

d-tubocurarine and a-bungarotoxin negatively affect it. Acetylcholine and nicotine positively affect it.

Question 16

What are six types of muscular dystrophy?

Answer 16

Duchenne-type/ Becker-type, Emery-Dreifuss, limb girdle, faciiscaoulohumeral, distal and occulopharyngeal.

Question 17

What is Duchenne muscular dystrophy?

Answer 17

Complete absence of dystrophin.

Question 18

What is Beckers muscular dystrophy?

Answer 18

Altered truncated dystrophin.

Question 19

What is Limb-girdle muscle dystrophy?

Answer 19

Deficiency of sarcoglycans.

Question 20

What is congenital mersosin deficient muscle dystrophy?

Answer 20

50% deficiency of mersosin,

Question 21

What are the consequence of Duchenne muscle dystrophy?

Answer 21

Muscle fibres tear when they contract, the enzyme Creatine kinase is liberated into serum, calcium enters cells and cause cell deaths. There is pseudohypertrophy before fat and coin necktie tissue replace muscle fibres.

Question 22

What are the origins of skeletal muscle problems?

Answer 22

Neurological, metabolism, immunological, neuromusclar junction or muscle tissue itself.

Question 23

What are the functions of skeletal muscle?

Answer 23

Movement, posture, stability of joins and heat generation.