JC - Motor Systems

Question 1

Do muscles actively shorten or elongate?

Answer 1

Muscles only ever actively shorten

• One muscle shortens to create a movement, another muscle shortens to return it back to its original position

Question 2

What does one muscle cell/fibre contain? (2)

Answer 2

1. Myofibrils
2. Sarcolemma

Question 3

What are myofibrils composed of?

Answer 3

Sarcomeres

Question 4

What are the 2 main myofilaments?

Answer 4

Actin and Myosin

Question 5

What is the function of T-tubules in terms of action potentials?

Answer 5

T-tubule runs into the muscle allowing for action potentials to be generated closer to the internal site

Question 6

What are T-tubules bound to?

Answer 6

Bind to voltge gated calcium channel which binds to Sarcoplasmic Reticulum

Question 7

What are the 3 types of muscle contraction?

Answer 7

• Isometric:
  Load = Force (muscle)
• Concentric:
  Load < Force (muscle)
• Eccentric:
  Load > Force (muscle)

Question 8

What are the 7 steps involved in the neuromuscular junction?

Answer 8

1. The action potential travels along myelinated motor neurone
2. Calcium enters motor neurone
3. Vesicles of Acetylcholine fuse to the motor neurone membrane
4. Acetylcholine diffuses across the extracellular matrix
5. Ligand-gated channels activate allowing substantial sodium to enter the cell and some potassium to exit
6. Voltage-gated sodium channels open along the sarcoplasmic membrane
7. Calcium is released into the sarcoplasmic reticulum

Question 9

What is the benefit of working extracellularly?

Answer 9

Less likely to damage the cell

Question 10

When are muscles stronger?

Answer 10

• Muscles are stronger at an eccentric contraction (longer muscle)
• Muscles are stronger when they are moving slower