Lecture 25: Skeletal Muscle

Question 1

What is the function of cardiac muscle?

Answer 1

Pumping of blood.

Question 2

What is the function of smooth muscle?

Answer 2

Control movement of fluids.

Question 3

What are the purposes of skeletal muscle?

Answer 3

To more, maintain posture, generate heat.

Question 4

What are the divisions of skeletal muscle, from muscle myofilament?

Answer 4

Muscle, muscle bundle, muscle cell/myocyte/fibre, myofibril, sarcomere - myofilaments.

Question 5

What is the sarcolemma?

Answer 5

Plasma membrane of the muscle cell.

Question 6

What is the sarcoplasm?

Answer 6

The cytoplasm of a the muscle cell.

Question 7

What is a triad?

Answer 7

A t-tubule sandwiched between two SRs.

Question 8

Longer muscle cells have ____ sarcomeres.

Answer 8

MORE

Question 9

What are the two myofilaments?

Answer 9

Thin filament - actin (+tropomyosin, troponin)

Thick filament - myosin.

Question 10

The more muscle fibres innervated by a motor neuron, the MORE/LESS precise the movements produced will be.

Answer 10

LESS.

Question 11

Explain the 3 steps of muscle contraction.

Answer 11

1. Excitation: Neuron action potential, ACh released at NMJ, muscle cell action potential.
2. Contraction: Ca2+ release from SR (due to AP), crossbridges formed, filaments slide (actin moves), uses ATP.
3. Relaxation: Ca2+ re-uptake into internal Ca2+ store, uncoupling of crossbridges.

Question 12

What must happen for actin-myosin crossbridges to uncouple?

Answer 12

No AP, ATP must bind.