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Semester 2 - MSK > Week 2 - Skeletal Muscle Structure, Morphology and Function > Flashcards

Week 2 - Skeletal Muscle Structure, Morphology and Function Flashcards

1
Q

What is the most common shape of muscle? Give an example of a muscle which takes this shape.

A

Fusiform

Biceps brachii

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2
Q

List the shapes a muscle may be, and give examples of each.

A 
Fusiform - biceps brachii
Circular
Convergent - pectoralis major
Parallel - sartorius
Unipennate - extensor digitorum longus
Bipennate - rectus femoris
Multipennate - deltoid
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3
Q

Describe a convergent muscle

A

Wide at origin but narrow at its insertion

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4
Q

Describe what a parallel muscle looks like

A

Straight up and down

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5
Q

What is the difference between unipennate, bipennate and multipennate muscles?

A

Unipennate - like half a feather
Bipennate - like a feather
Multipennate - like several feathers

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6
Q

What structure is every tendon continuous with?

A

The epimysium

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7
Q

What is fasciculation? Give an example of when it may occur.

A

Muscle twitching

In the eyes when tired

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8
Q

Which type of lever is most efficient?

A

1st class lever

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9
Q

Describe a first class lever

A

Pivot in the centre, with the force underneath to one side, and the load above on the other side

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10
Q

Describe a second class lever.

A

Like a wheelbarrow - force and load both on the left of the pivot.

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11
Q

Describe a 3rd class lever.

A

Like a fishing rod -

Force and load both on the right of the pivot

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12
Q

Briefly explain what happens in compartment syndrome.

A

Bleeding occurs within a compartment, which is bound by inextensible connective tissue. This raises the pressure inside the compartment, and as it cannot expand, leads to compression of the neurovasculature within the compartment.

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13
Q

Give the 4 muscle groups in terms of function.

A

Agonists
Antagonists
Synergists
Fixators

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14
Q

What is an agonist, in terms of muscles?

A

A “prime mover” - i.e. the main muscle performing a movement

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15
Q

What is a synergist?

A

A muscle aiding an agonist

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16
Q

What is an antagonist, with regards to muscles?

A

A muscle opposing the action of an agonist

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17
Q

What do fixator muscles do?

A

Stabilise the action of prime movers (agonists)

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18
Q

What are the two types of muscle contraction, and how do they differ?

A

Isotonic - tension constant, length variable

Isometric - length constant, tension variable

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19
Q

What are the two types of isotonic muscle?

A

Concentric - gets shorter

Eccentric - gets longer

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20
Q

What are the two major muscle fibre types?

A

Type I

Fast Twitch

21
Q

What are type I muscle fibres?

A

Slow oxidative

22
Q

How are fast twitch muscle fibres subdivided?

A

Type IIa - fast oxidative

Type IIb - fast glycolytic

23
Q

Which muscle fibre type appear red, and why?

A

Slow oxidative

Due to the very high myoglobin content

24
Q

Which are the palest muscle fibres?

A

Fast glycolytic

25
Q

Which muscle fibre types are aerobic and which are anaerobic?

A

Slow and fast oxidative are aerobic

Fast glycolytic are anaerobic

26
Q

Give 3 characteristics of both fast and slow oxidative muscle types.

A

High myoglobin (but more in slow)
Many mitochondria
Many capillaries

27
Q

Which muscle fibre type(s) is/are fatigue resistant?

A

Slow and fast oxidative, although slow more so.

28
Q

What functions may slow oxidative muscle fibres perform?

A

Posture

Endurance activity

29
Q

Give an example of an activity facilitated by fast oxidative muscle fibres

A

Walking

30
Q

Fast glycolytic muscle fibres rapidly fatigue. What sorts of activity do they therefore allow?

A

Short, intense activity

31
Q

What are the major functions of skeletal muscle?

A

Movement
Posture
Stability of Joints
Heat generation (although only around 20% efficient)

32
Q

What are proprioreceptors?

A

Muscle spindles that send signals to the brain telling it how much tension is being exerted.

33
Q

What does proprioreception allow?

What might disrupt it?

A

Feedback control of movement

Alcohol

34
Q

What is a motor unit?

A

A motor neurone and the muscle fibre(s) it innervates

35
Q

What structure do motor neurones leave the brain via?

A

The ventral root

36
Q

What is “crosstalk”?

A

Communication between neurones and muscle, via signalling molecules.

37
Q

Why may atrophy of a muscle cause atrophy of the nerve that innervates it, and vice versa?

A

Lack of crosstalk due to fewer chemical signals being produced.

38
Q

What two factors mean that baseline muscle tone is always present at rest?

A

Muscle activity

Motor neurone activity

39
Q

How is muscle tone controlled?

A

Feedback via afferent fibres from the muscle to the motor control centres of the brain.

40
Q

What is hypotonia?

A

Lack of muscle tone

41
Q

What are the 3 possible causes of hypotonia?

A
  1. CNS problems
  2. PNS problems
  3. Muscle problems - myopathies (primary muscle degeneration)
42
Q

What is an EMG and what is it used for?

A

An electromyogram

Used to measure electrical activity in the muscles; helps diagnose conditions such as MND.

43
Q

How is the force of contraction of skeletal muscle controlled?

A

Spatial summation

Temporal summation

44
Q

Explain spatial summation

A

More motor neurones are activated, and hence more muscle fibres contract, giving more forceful contraction

45
Q

Explain temporal summation, including what it can lead to.

A

Increased frequency of action potentials in the muscle fibres.
In extremes, this can lead to tetany.

46
Q

What is a contracture?

A

Continuous muscle contraction without relaxation

47
Q

What are the possible sources of ATP within skeletal muscle?

A

ATP stores
Creatine phosphate
Glycolysis
Oxidative phosphorylation

48
Q

Explain the pathophysiology behind muscle cramps.

A

Increased lactate causes the pH of the muscle to fall. This acts on nerve endings, causing pain.

49
Q

If blood flow to a muscle is interrupted, how quickly are the glycogen stores depleted?

A

Within around 1 minute

Semester 2 - MSK (35 decks)

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