Muscle II- Skeletal muscle: Contraction, Tension, and Fibre types

Question 1

Do fast or slow fibres have a higher fatigue resistance

Answer 1

slow

Question 2

Why does too much overlap of actin and myosin fibres result in sub-optimal muscle strength?

Answer 2

There is no room left for many power strokes so the muscle cant contract much further

Question 3

Do fast or slow fibres have more of a capillary supply?

Answer 3

slow

Question 4

What colours to fast/slow fibres appear

Answer 4

fast- white

slow- red

Question 5

What causes a sustained period of contraction?

Answer 5

Many action potentials fired in rapid sequence causing a sustained released of calcium ions from SR, and a sustained period of actin/myosin interaction

Question 6

When do actin and myosin bind together and form cross bridges?

Answer 6

When calcium in present

Question 7

Do fast or slow fibres have a larger diameter?

Answer 7

fast

Question 8

Do fast of slow fibres have more mitochondria?

Answer 8

slow

Question 9

What is the number of activated fibres dependant on?

Answer 9

The number of neurons active at one time

Question 10

What is the role of myosin in contraction?

Answer 10

Myosin acts as a motor molecule, attaching to actin and generating force to pull

Question 11

Explain the cross bridge cycling occurring during contraction

Answer 11

• A cross bridge forms and the myosin head binds to a position on actin
• One P from ATP is released forming ADP which results in the power stroke from the myosin heads
• ADP is released
• new ATP binds to myosin head, causing dissociation of the actin-myosin complex
• ATP is hydrolysed which causes the return of the myosin heads to the resting state ( cocked state)
• a new cross bridge forms and the myosin head binds to a new position on actin

Question 12

Why does too little overlap between actin and myosin result in sub-optimal muscle contraction?

Answer 12

Lack of overlap causes lack of cross bridges that can be formed and therfore less strength

Question 13

What two things does muscle tension depend on?

Answer 13

• the number or recruited muscle fibres

- the rate at which the muscle is stimulated

Question 14

What is tetanus?

Answer 14

The plateau caused by reaching maximal signalling and contraction capable of muscle

Question 15

What is the process of activating more muscle fibres to generate more force called?

Answer 15

recruitment

Question 16

What is the role of actin in contraction?

Answer 16

Actin’s role is to be a structural element, it forms a structure to be pulled on during contraction

Question 17

What is a physical difference between fast and slow muscle fibres?

Answer 17

Slow fibres have more blood vessels