Skeletal muscle

Question 1

The amount of force exerted is dependent on… (3)

Answer 1

1. Initial muscle length
2. Motor units
3. Neural stimultion

Question 2

List the 4 functions of skeletal muscle

Answer 2

1. Movement
2. Postural support
3. Heat generation
4. Act as an endocrine organ

Question 3

What are satellite cells - what is their function

Answer 3

Undifferentiated cells located above the sarcolemma - contribute to growth and repair by adding nuclei to existing muscle fibres

Question 4

Describe the excitation-contraction coupling

Answer 4

1. ACh released from synaptic knob
2. Muscle fibre depolarised - travels down t-tubules
3. Calcium release and binds to troponin
4. Tropomyosin shifts, exposing actin
5. ATP hydrolysed allowing myosin to bind
6. Release of Pi and ADP causes power stroke
7. Another ATP needed to detach myosin from actin
8. ACh stops, repolarising membrane
9. Calcium up taken by SR

Question 5

Fatigue

Answer 5

Decline in muscle power output

Question 6

Explanation for high intensity fatigue

Answer 6

1. Increase Pi - modify myosin head formation
2. Increase H+ - block calcium binding
3. free radicals

Question 7

Explanations for mod intensity fatigue

Answer 7

1. Free radicals - modify myosin heads
2. Depleted glycogen stores - reduced TCA intermediates, therefore ATP production

Question 8

Cause of EAMS

Answer 8

hyperactive motor neuron activity - increased excitatory of MS and decreased inhibitory of GTO

Question 9

What determines a muscle fibre? (3)

Answer 9

1. Oxidative capacity
2. ATPase isoform expressed
3. Abundance of contractile protein

Question 10

Name 4 factors that affect force regulation

Answer 10

1. Number and type of motor units
2. Muscle length
3. Firing frequency
4. Muscle state - rested/exercised

Question 11

What is tetanus?

Answer 11

The maximal force a skeletal muscle can produce despite an increase in stimulation

Question 12

What has to be compromised for greater contraction velocity? VV

Answer 12

Contraction force