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NMSK > Muscle fibres > Flashcards

Muscle fibres Flashcards

1
Q

Properties of skeletal muscle fibres

A

Each muscle cell known as fibre

Striated

Syncytium (multinucleated)

Cells large

Arranged in bundles known as fascicles

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2
Q

Label the image

A
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3
Q

Label the image

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4
Q

Label the image

A
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5
Q

What is the sliding filament theory

A

Muscle shortening occurs due to movement of actin filament over myosin filament

Formation of cross bridges between actin & myosin filaments

Reduction in distance between Z lines of sarcomere

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6
Q

Explain cross bridge formation

A

Tropomyosin located along both chains of actin filaments & when calcium is low blocks binding of myosin to actin (fibre at rest)

Troponin complex is attached to each tropomyosin

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7
Q

What is the role of calcium in muscle contraction

A

Troponin captures Ca2+ & undergoes conformational change that lifts tropomyosin away from actin filament

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8
Q

What are the skeletal muscle fibre types

A

Fast fibres:

Type IIa (slowest of fast)
Fast oxidative

Type IIb (fastest of fast)
Fast glycolytic

Type IIx
Intermediate properties

Slow fibres:

Type I
Slow oxidative

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9
Q

Properties of fibre types

A
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10
Q

What are the main forelimb extensors and flexors

A

Extensors:
Triceps brachii extends elbow joint
Flexor carpi radialis & flexor carpi ulnaris extend wrist joint

Flexors:
Biceps brachii flexes elbow joint
Flexor carpi radialis & flexor carpi ulnaris flex wrist joint

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11
Q

What are the main hindlimb extensors and flexors

A

Extensors:
Quadriceps femoris extends knee joint
Gluteus maximus extends hip joint

Flexors:
Hamstrings flex knee joint
Iliopsoas flex hip joint

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12
Q

What is this

A

Tendon

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13
Q

What is this

A

Tendon sheath:
Dense irregular connective tissue surrounding tendon

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14
Q

What is this

A

Smooth muscle

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15
Q

What is this

A

Skeletal muscle

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16
Q

What is this

A

Cardiac muscle

17
Q

What is hypertrophy and what is it caused by

A

Cells increasing in size
Increase in myofibrils – sarcomeres added
Increase in myofilaments

Caused by:
Anabolic factors (building up muscle):
Mechanical load
Steroids (artificial)

Mechanical loading triggers IGF-1 (insulin like growth factor) which stimulates protein synthesis

18
Q

What is atrophy and what is it caused by

A

Reduction in muscle volume/mass
Muscles fibres start to shrink

Caused by:
Catabolic factors (breaking down muscle):
Disuse
Denervation
Disease
Malnutrition

19
Q

What can cause muscle pathology

A

Injury

Nerve damage
e.g. Stringhalt in horses

Disease

Aging

20
Q

How are muscle cells repaired

A

Satellite cells
Activated following damage
Proliferate & differentiate to form muscle cells & daughter cells

  1. Lost muscle cells
  2. Clusters of activated satellite cells
  3. Myotubes form (differentiate into muscle cells)
  4. Fibres back to normal size
21
Q

What is polymyositis

A

Generalised inflammatory myopathy
Muscle damage result of cell-mediated immunity
Treated with corticoid steroids

21
Q

What is polymyositis

A

Generalised inflammatory myopathy
Muscle damage result of cell-mediated immunity
Treated with corticoid steroids

22
Q

What is Masticatory muscle myositis (MMM)

A

Focal inflammatory myopathy affecting muscle of mastication

Clinical signs include:
Trismus (lock jaw)
Fox like contour of head
Prominence of zygomatic arch

23
Q

Give example of Congenital & inherited myopathies

A

e.g. Duchenne Muscular Dystrophy
Humans, dogs & mice
Mutation in gene coding for dystrophin
Severity can vary
Leads to failure of respiratory muscles

24
Q

Give examples of endocrine myopathies

A

Hypothyroidism:
Weakness, stiffness, reluctance to move, muscle wastage
Atrophy of type II fibres

Cushings disease (hyperadrenocorticism):
Weakness, stiffness, inability to walk, muscle wastage
Selective atrophy of type II fibres
Breakdown of muscle proteins

25
Q

Give an example of a nutritional myopathy

A

e.g. selenium/vitamin E deficiency
Still birth or weak calf
Occurs in calves, lambs & foals
Can be treated if caught on time

26
Q

Give an example of an exertional myopathy

A

Exertional rhabdomyolysis in horses
Myofiber damage due to exercise stress
Unknown etiology
Muscle pain, swelling & reluctance to move

27
Q

Give an example of a metabolic myopathy

A

Equine polysaccharide storage myopathy
Abnormal accumulation of glycogen in muscles
Painful muscle cramps

28
Q

What is sarcopenia

A

Atrophy associated with aging
Loss of motor axons & motor fibres
Increase in motor unit size
Giving IGF-1 may reduce effect

NMSK (49 decks)

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