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Science For Med A ellen > Muscle > Flashcards

Muscle Flashcards

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1
Q

What are the three types of muscle?

A

Skeletal, smooth and cardiac

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2
Q

What muscle types are regarded as striated?

A

Skeletal and cardiac

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3
Q

What structures attach bones to muscle?

A

Tendon

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4
Q

What happens when skeletal muscle cells are injured?

A

Satellite cells replace injured cells

Hypertrophy of surrounding fibres

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5
Q

What is meant by hypertrophy of muscle cells?

A

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

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6
Q

What changes occur to the sarcomere during muscle contraction?

A

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

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

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7
Q

What molecules block the binding sites on actin filaments?

A

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

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8
Q

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

A

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.

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9
Q

What is the role of the sarcolplasmic reticulum?

A

Storage of calcium ions

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10
Q

What is the role of transverse tubules?

A

Conduction of signal deep into the muscle tissue.

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11
Q

What are the components of a motor unit?

A

Motor neuron and muscle fibre

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12
Q

What is meant by an isometric contraction?

A

Contraction with constant length

E.g. weightlifting

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13
Q

What is meant by an isotonic contraction?

A

Contraction with shortening length

E.g. running

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14
Q

What is meant by a lengthening contraction?

A

Contraction with increasing length

E.g. sitting down

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15
Q

For what two mechanisms in muscle contraction is ATP required?

A
  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.
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16
Q

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

A
  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.
17
Q

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

A
  1. Decreased [blood glucose]
  2. Decrease muscle glycogen
  3. Dehydration
18
Q

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

A
  1. Whether the fibre is short or fast shortening

2. Whether oxidative or glycolytic ATP forming pathways are used

19
Q

What is meant by a fast shortening muscle fibre?

A

Contains myosin with high ATPase activity

20
Q

What is meant by a slow shortening muscle fibre?

A

Contains myosin with low ATPase activity

21
Q

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

A
  1. Red in colour
  2. Small diameter
  3. High vascularisation
  4. Blood vessels contain myoglobin
  5. Many mitochondria present for oxidative phosphorylation
22
Q

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

A
  1. White in colour
  2. Larger diameter
  3. Lesser blood supply
  4. Contains many glycolytic enzymes and glycogen
  5. Few mitochondria
23
Q

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

A

Slow oxidative

24
Q

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

A

Fast glycolytic

25
Q

In muscle contraction, what is meant by ‘recruitment’?

A

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

26
Q

Describe the smooth muscle cross bridge cycle.

A

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.

27
Q

How does smooth muscle contraction differ from skeletal muscle contraction?

A

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.

28
Q

What nervous system innervates smooth muscle?

A

Autonomic

Science For Med A ellen (20 decks)

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