Muscles Bio Science part two

Question 1

What are the four events which happen at the neuromuscular junction?

Answer 1

1. action potential arrives @ terminal of motor neuron
2. Voltage-gated calcium channels open and calcium enters the axon terminal
3. Calcium entry causes some synaptic vesicles to release their contents, by exocytosis
4. A neurotransmitter diffuses across the synaptic cleft and binds to the receptors in the sarcolemma

Question 2

What is excitation-contraction coupling? (paragraph answer)

Answer 2

the process of the muscle fibre is stimulated, and an action potential being regenerated and conducted along the sarcolemma and down the T-tubules, transferring to the Sarcoplasmic reticulum in order to reach the myofibrils and cause calcium to ‘flood’ out of the Sarcoplasmic Reticulum. Calcium is the trigger for cross bridge formation.

Question 3

What is the sliding filament theory? (sentence)

Answer 3

when myosin heads bind to the actin and pull the actin towards the centre of each sarcomere

Question 4

What is the thick filament?

Answer 4

Myosin

Question 5

What is the thin filament?

Answer 5

Actin, Troponin and tropomyosin

Question 6

At rest why can a cross bridge not be formed?

Answer 6

due to the tropomyosin blocking the actin binding sites due to being locked in place by troponin

Question 7

What are the 4 stages of the sliding filament theory?

Answer 7

1. cross bridge formation
2. the power (working) stroke
3. Crossbridge detachment
4. Cocking of myosin head

Question 8

What happens at the first stage (cross bridge formation) during the sliding filament theory?

Answer 8

the energised myosin head attaches to an actin myofilament, forming a cross bridge

Question 9

what happens during stage two ( the power stroke) in the sliding filament theory?

Answer 9

ADP and P are released and the myosin head pivots and bends, changes to its bent low energy state and as a result, pulls the actin filament towards the M line

Question 10

What happens during stage three ( cross bridge detachment) in the sliding filament theory

Answer 10

After ATP attaches to myosin, the link between myosin and actin weakens and the myosin head detaches (cross-bridge breaks)

Question 11

what happens during stage fpour ( cocking of the myosin head) in the sliding filament theory?

Answer 11

AsATP is hydrolyzed to ADP and P, the myosin head returns to its prestroke high energy or “cocked” posistion and then the cycle continues

Question 12

ATP is regenerated by three mechanisms, what are these?

Answer 12

1. direct phosporylation by creatine phosphate (CP)
2. Anaerobic respiration
3. Aerobic respiration