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Semester 2-MSK > Session 2-Skeletal Muscle > Flashcards

Session 2-Skeletal Muscle Flashcards

1
Q

What are the functions of skeletal muscle? (4)

A

1) movement
2) posture
3) joint stability
4) heat generation

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2
Q

Define fasciculation

A

Small, local, involuntary muscle contractions and relaxations

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3
Q

What do circular muscles act as?

A

Sphincters to adjust opening

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4
Q

True or false: circular muscles are arranged in concentric fibres

A

TRUE

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5
Q

Where do circular muscles attach?

A

To skin, ligaments and fascia rather than bone

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6
Q

What is the name of the circular muscles surrounding the eyes?

A

Orbicularis occuli

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7
Q

What is the name of the circular muscle surrounding the mouth?

A

Orbicularis oris

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8
Q

Which is the most common type of skeletal muscle?

A

Parallel muscles

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9
Q

What are the three main categories of parallel muscles?

A

1) strap
2) fusiform
3) fan shaped

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10
Q

What is another name for fan shaped muscles?

A

Convergent

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11
Q

Give an example of a strap muscle

A

Sartorius (lower limb)

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12
Q

Give an example of a fusiform muscle

A

Biceps brachii

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13
Q

Give an example of fan shaped muscle

A

Pec major

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14
Q

What are pennate muscles?

A

One or more aponeuroses run through muscle body from the tendon, fascicles attach to aponeuroses at an angle

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15
Q

What are the three different types of pennate muscles?

A

1) unipennate
2) bipennate
3) multipennate

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16
Q

True or false: a muscle’s insertion is more stable than its origin

A

FALSE - other way round

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17
Q

What delineates the compartments of the limbs?

A

Fascia

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18
Q

What could trauma in one compartment cause?

A

Internal bleeding which exerts pressure on blood vessels and nerves, giving rise to compartment syndrome

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19
Q

How can compartment syndrome be treated?

A

Fasciotomy (relieves pressure)

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20
Q

What are the symptoms of compartment syndrome? (4)

A

1) pain
2) paresthesia (pins and needles)
3) swollen, shiny skin (bruising)
4) compartment may feel tense and firm

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21
Q

What does a muscle agonist do?

A

Prime mover-main muscle responsible for a particular movement

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22
Q

What does a muscle antagonist do?

A

Opposes prime movers

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23
Q

Why are muscle antagonists necessary?

A

Fine control

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24
Q

What do muscle synergists do?

A

Assist prime movers

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25
Q

What do muscle neutralisers do?

A

Prevent unwanted actions that an agonist can perform

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26
Q

What do muscle fixators do?

A

Stabilise a joint - holds a body part immobile whilst another body part is moving

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27
Q

What are the two types of skeletal muscle contraction?

A

1) Isotonic-constant tension, variable muscle length

2) Isometric-constant length, variable tension

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28
Q

What are the two types of isotonic contraction?

A

1) Concentric-muscle shortens (eg lifting a load with the arm)
2) Eccentric-muscle resists extension (eg walking downhill)

29
Q

True or false: in a first class lever, the effort is at one end and load at the other

30
Q

Which is the most efficient type of lever?

A

First class

31
Q

What is an example of a first class lever?

A

Extension/flexion of the head

32
Q

True or false: in a second class lever, the effort is between the load and fulcrum

A

FALSE - that is in the third class lever. In a second class lever, the effort is at one end and the fulcrum at the other

33
Q

Give an example a second class lever

A

Plantar flexion of the foot

34
Q

Give an example of a third class lever

A

Biceps brachii in the flexion of the elbow

35
Q

What happens in rigor mortis?

A

If ATP is depleted, myosin heads cannot detach. Approx 3 hours after death, body reaches maximum stiffness

36
Q

Complete the sentence:

Muscle fibres making up a motor unit are all of the _______ contractile type so each motor unit is fast or slow contracting

37
Q

True or false: each individual muscle fibre is innervated by one motor neuron

38
Q

How many different myosin heavy chains (MHC) are there?

A

8 different isoforms

39
Q

What are the three main types of fibre types in skeletal muscle?

A

1) Slow type I (beta cardiac)
2) Fast type IIA
3) Fast type IIX

40
Q

What are type I muscle fibres known as?

A

Slow oxidative

41
Q

What are type IIA muscle fibres known as?

A

Fast oxidative

42
Q

What are type IIX muscle fibres known as?

A

Fast glycolitic

43
Q

True or false: type IIA muscle fibres have few mitochondria and carry out anaerobic glycolysis

A

FALSE - ^ is type IIX

44
Q

Complete the sentence:

___________ muscle fibres facilitate proprioception

A

Intrafusal

45
Q

What are patients with large-fibre sensory neuropathy unable to do?

A

Perform accurate movements in the absence of vision

46
Q

What innervates intrafusal muscle fibres?

A

Two sensory and one motor axons

47
Q

What does the gamma motor neurone do?

A

Alters sensitivity of the fibres and keeps the fibres taut

48
Q

What do type Ia sensory neurones do?

A

Relay the rate of change in muscle length back to the CNS

49
Q

What do type II sensory neurones do?

A

Provide position sense

50
Q

What two factors control muscle force?

A

1) size principe-small motor neurones recruited before large

2) rate code-more action potentials=more force. Subsequent action potential produce summation up to a limit (=tetani)

51
Q

True or false: healthy muscles never fully relax

52
Q

When is the only time healthy muscles relax?

A

In REM (rapid eye movement) sleep because part of the brain controlling muscle tone stops working

53
Q

What is baseline muscle tone due to? (2)

A

1) motor neurone activity

2) muscle elasticity

54
Q

What is hypotonia?

A

Lack of skeletal muscle tone

55
Q

True or false: hypotonia is most common in babies and is called floppy baby syndrome

56
Q

What can cause hypotonia?

A

Damage to motor cortex or cerebellum or spinal cord OR degeneration of muscle (myopathy)

57
Q

Where do DHP receptors come into contact with SR?

58
Q

Which Ca2+ release channels in SR are closely associated with DHP receptors, allowing rapid signalling from action potential to Ca2+ release?

A

Ryanodine receptors

59
Q

True or false: skeletal muscle fibres only have leaky K+ channels

A

FALSE - also have high concentration of Cl- leak channels

60
Q

What is a common example of a channelopathy?

A

Cystic fibrosis

61
Q

What does myotonia mean?

A

Inability to relax muscles at will

62
Q

What are the symptoms of myotonia congenita?

A

Muscle stiffness and hypertrophy

63
Q

What causes myotonia congenita?

A

Mutations in chloride channel CLCN1

64
Q

What type of drugs can relieve symptoms of myotonia congenita?

A

Anticonvulsant drugs

65
Q

True or false: there are both recessive and dominant forms of myotonia congenita

66
Q

In skeletal muscle, what is the resting membrane potential usually equal to?

A

Cl- Nernst equilibrium potential

67
Q

What are the sources of ATP in muscle? (4)

A

1) short term stores of ATP in muscle fibre
2) creatine phosphate (short term)
3) glycolysis
4) oxidative phosphorylation

68
Q

What does anaerobic glycolysis form?

Semester 2-MSK (23 decks)

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