Muscle Contraction

Question 1

What are the functions of muscle in the body?

Answer 1

• movement
• maintain posture
• breathe, eat and talk
• hold and attach structures
• source of heat
• dynamic metabolic store

Question 2

What are the percentages of components in the muscle?

Answer 2

75% water
20% protein (40% myosin, 20% actin)
5% inorganic salts

Question 3

What attaches muscle to bone?

What are muscle fibres grouped into?

Answer 3

Tendons

Fascicles

Question 4

What are the three types of mysium in muscle fibres?

Answer 4

Epimysium which surrounds the entire muscle fibre.
Endomysium which surrounds individual muscle fibres.
Perimysium which surrounds a group of muscle fibres.

Question 5

What cells can be found around the outside of muscle fibres?

Answer 5

Satellite cells

Question 6

Explain how calcium leads to a contraction of a muscle?

Answer 6

Impulse reaches the end of a neurone (synaptic transmission at neuromuscular junction occurs) and then causes the sarcolemma to be depolarised. This stimulates the sarcoplasmic reticulum to release calcium ions and these then bind to tropomyosin and causes a conformational change which exposes the actin binding site. Myosin heads bind to the actin active site and cause a contraction.

Question 7

What is a tetanum?

Answer 7

A mechanical response to multiple stimuli.

Question 8

What happens to calcium after it is released from the sarcoplasmic reticulum experimentally?

Answer 8

At 3Hz, there is time for the calcium to be pumped back into the sarcoplasmic reticulum. If there is less of a delay, calcium does not have time to be pumped back to sarcoplasmic reticulum.

Question 9

What happens if there is a high rate of impulses of calcium in the cytoplasm?

Answer 9

Permits cross-bridge cycling.

Reaches a point where the force no longer can be increased and contraction can no longer occur

Question 10

What is the difference between type 1 and type 2 muscle fibres?

Answer 10

1 = slow
2 = fast

Question 11

Slow fibres can reach tetanus at — stimulation frequencies than fast fibres. Therefore, they can reach their maximal force at — rates of stimulation

Answer 11

lower, lower

Question 12

What do we need slow fibres for in the body?

Answer 12

maintaining posture, eating and breathing

Question 13

What are the two types of muscle fibre recruitment? Explain each

Answer 13

Spatial recruitment - individual muscle fibres can be activated in isolation
Temporal recruitment - motor unit activity can br modulated by increasing or reducing rate coding

Question 14

What does a motor unit consist of?

Answer 14

1 motor neuron and muscle fibres that it innervates