Muscle

Question 1

What are the three types of muscle?

Answer 1

Skeletal, smooth and cardiac

Question 2

What muscle types are regarded as striated?

Answer 2

Skeletal and cardiac

Question 3

What structures attach bones to muscle?

Answer 3

Tendon

Question 4

What happens when skeletal muscle cells are injured?

Answer 4

Satellite cells replace injured cells

Hypertrophy of surrounding fibres

Question 5

What is meant by hypertrophy of muscle cells?

Answer 5

The packing in of more protein (actin and myosin filaments)

Question 6

What changes occur to the sarcomere during muscle contraction?

Answer 6

Actin slides over myosin filaments, moving closer to M line.

This reduces the width of the H band and the I band

Question 7

What molecules block the binding sites on actin filaments?

Answer 7

Tropomyosin partially blocks binding sites. Troponin holds the tropomyosin in the blocking position.

Question 8

What effect does calcium have on the blocking of myosin binding sites?

Answer 8

Calcium binds to troponin, altering its shape. Troponin pulls away from tropomyosin which can move away from the binding site.
The exposed binding site can now bind myosin heads.

Question 9

What is the role of the sarcolplasmic reticulum?

Answer 9

Storage of calcium ions

Question 10

What is the role of transverse tubules?

Answer 10

Conduction of signal deep into the muscle tissue.

Question 11

What are the components of a motor unit?

Answer 11

Motor neuron and muscle fibre

Question 12

What is meant by an isometric contraction?

Answer 12

Contraction with constant length

E.g. weightlifting

Question 13

What is meant by an isotonic contraction?

Answer 13

Contraction with shortening length

E.g. running

Question 14

What is meant by a lengthening contraction?

Answer 14

Contraction with increasing length

E.g. sitting down

Question 15

For what two mechanisms in muscle contraction is ATP required?

Answer 15

1. Detachment of myosin heads from actin filaments to allow a new cycle to begin and contraction to be furthered.
2. Pumping of calcium ions back into the sarcoplasmic reticulum to end contraction.

Question 16

What factors can cause fatigue in high intensity, short duration exercise?

Answer 16

1. Increased [K+] causing depolarisation
2. Increased [lactic acid] to acidify proteins
3. Increased [ADP+ Pi] to delay detachment of myosin heads from actin filaments, so inhibiting cross bridge cycle.

Question 17

What factors cause fatigue in low intensity, long-term exercise?

Answer 17

1. Decreased [blood glucose]
2. Decrease muscle glycogen
3. Dehydration

Question 18

What two factors need to be considered in the characterisation of skeletal muscle fibres?

Answer 18

1. Whether the fibre is short or fast shortening

2. Whether oxidative or glycolytic ATP forming pathways are used

Question 19

What is meant by a fast shortening muscle fibre?

Answer 19

Contains myosin with high ATPase activity

Question 20

What is meant by a slow shortening muscle fibre?

Answer 20

Contains myosin with low ATPase activity

Question 21

What are the features of skeletal muscle fibres which use oxidative ATP forming pathways?

Answer 21

1. Red in colour
2. Small diameter
3. High vascularisation
4. Blood vessels contain myoglobin
5. Many mitochondria present for oxidative phosphorylation

Question 22

What are the features of skeletal muscle fibres which use glycolytic ATP forming pathways?

Answer 22

1. White in colour
2. Larger diameter
3. Lesser blood supply
4. Contains many glycolytic enzymes and glycogen
5. Few mitochondria

Question 23

What type of skeletal muscle fibre is most resistant to fatigue?

Answer 23

Slow oxidative

Question 24

What type of skeletal muscle fibre is least resistant to fatigue?

Answer 24

Fast glycolytic

Question 25

In muscle contraction, what is meant by 'recruitment'?

Answer 25

The increased activation of motor units, as a result of increased load.

Question 26

Describe the smooth muscle cross bridge cycle.

Answer 26

Calcium binds to Calmodulin Calcium-calmodulin complex binds to myosin light chain kinase This can then phosphorylate cross bridges, which can then bind to actin, allowing contraction.

Question 27

How does smooth muscle contraction differ from skeletal muscle contraction?

Answer 27

Smooth muscle contraction can be graded. | The number of actin binding sites exposed depends on the number of Action Potentials which act on the muscle cell.

Question 28

What nervous system innervates smooth muscle?

Answer 28

Autonomic