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MSK lectures > Skeletal Muscle Physiology 2 02/10/18 > Flashcards

Skeletal Muscle Physiology 2 02/10/18 Flashcards

1
Q

What do factors does the gradation of skeletal muscle tension depend on?

A

Number of muscle fibres contracting within the muscle

Tension developed by each contracting muscle fibre

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2
Q

What is motor unit recruitment?

A

A stronger contraction can be achieved by stimulation of more motor units

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3
Q

What helps to prevent muscle fatigue?

A

Asynchronus motor unit recruitment during submaximal contractions

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4
Q

What does the tension development of a muscle fibre depend on?

A

Frequency of stimulation
Summation of contractions
Length of muscle fibre
Thickness of muscle fibre

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5
Q

Which is longer, the duration of an action potential or the duration of the resulting twitch?

A

The muscle twitch

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6
Q

How can a stronger contraction be brought about?

A

Summating twitches through repetitive fast stimulation of skeletal muscle

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7
Q

What is tetanus and how is it brought about?

A

Maximal sustained contraction

When the muscle fibre is stimulated so rapidle that it does not have an opportunity to relax between stimuli

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8
Q

Can cardiac muscles be tetanised and why/why not?

A

No

The long refractory period prevents generation of tetanic contraction

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9
Q

What is the resulting action when a skeletal muscle is stimulated once?

A

Twitch

Tia/Tamera

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10
Q

Can a single twitch bring about meaningful muscle activity?

A

No

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11
Q

When the frequency of stimulation increases what happens to the tension?

A

Increases

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12
Q

When is skeletal muscle at its optimal length?

A

When it is resting

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13
Q

How is skeletal muscle tension transferred to bone?

A

Through tissue and tendons

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14
Q

What are the two types of skeletal muscle contraction?

A

Isotonic contraction

Isometric contraction

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15
Q

What is isotonic contraction?

A

Muscle tension remains the same as the muscle length changes

I.e. in body movements and moving objects

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16
Q

What is isometric contraction?

A

Muscle tension develops at constant muscle length

I.e. supporting objects in fixed position or maintaining body posture

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17
Q

What happens to the velocity of muscle shortening as the load increases?

A

It decreases

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18
Q

Are all skeletal muscle fibres the same?

A

No

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19
Q

What are the 3 differences in skeletal muscle fibres?

A

Enzymatic pathways for ATP synthesis
Resistance to fatigue
Activity of myosin ATPase

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20
Q

Which muscle fibres are more resistant to fatigue?

A

Muscle fibres with a greater capacity to synthesise ATP

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21
Q

What does the activity of myosin ATPase determine?

A

The speed at which energy is made available for cross bridge cycling

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22
Q

What are the three types of metabolic pathway that supplies ATP to muscle fibres?

A

Transfer of high energy phosphate from creatine phosphate to ADP
Oxidative phosphorylation (when O2 is present)
Glycolysis (When O2 is not present)

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23
Q

What are the three types of skeletal muscle fibre?

A

Slow-oxidative (Type 1)
Fast-oxidative (Type 2a)
Fast-glycolytic (Type 2x)

24
Q

What are type 1 fibres mainy used for?

A

Prolonged, low work aerobic activities

25
Q

What are Type 2a fibres used for?

A

Aerobic and anaerobic metabolism and prolonged moderate work

26
Q

What are type 2x fibres used for?

A

Anaerobic metabolism and short term high intensity activities

27
Q

What is the definition of a reflex?

A

Stereotyped response to a specific stimulus

28
Q

What are the simplest form of coordinated movement?

A

Reflex actions

29
Q

What are the neural pathways for reflexes important for localising?

A

Lesions in the motor system

30
Q

What is the simplest monosynaptic spinal reflex?

A

The stretch reflex

31
Q

Is the stretch reflex positive or negative feedback?

A

Negative

32
Q

What is the sensory receptor in the stretch reflex and what is it activated by?

A

Muscle spindle activated by muscle stretch

33
Q

What does stretching the muscle spindle do?

A

Increases firing in the afferent neurons

34
Q

Where do the afferent neurons synapse and what with?

A

In the spinal cord with the alpha motor neurons

35
Q

What does activation of the reflex result in?

A

Contraction of the stretched muscle

36
Q

What coordinates the stretch reflex?

A

Simultaneous relaxation of antagonist muscle

37
Q

How can the stretch reflex be elicited?

A

Tapping the muscle tendon with a rubber hammer

38
Q

What nerve and spinal segment are responsible for the Knee jerk?

A

L3,L4

Femoral

39
Q

What nerve and spinal segment are responsible for the Ankle jerk?

A

S1,S2

Tibial

40
Q

What nerve and spinal segment are responsible for the Biceps Jerk?

A

C5, C6

Musculocutaneos

41
Q

What nerve and spinal segment are responsible for the Brachioradialis Jerk?

A

C5,C6

Radial

42
Q

What nerve and spinal segment are responsible for the Triceps Jerk?

A

C6-C7

Radial

43
Q

What are muscle spindles?

A

Sensory receptors for stretch reflex

44
Q

What are muscle spindles a collection of?

A

Specialised muscle fibres

45
Q

What are muscle spindles known as?

A

Intrafusal fibres

46
Q

What are ordinary muscle fibres known as?

A

Extrafusal fibres

47
Q

What direction do muscle spindles and fibres run in?

A

Parallel

48
Q

What are the sensory nerve endings on muscle spindles known as?

A

Annulospiral fibres

49
Q

As the muscle is stretched, what happens to the discharge from muscle spindles?

A

It increases

50
Q

Do muscle spindles have their own efferent motor nerve supply?

A

Yes

51
Q

What are the efferent neurones that supple the muscle spindles called?

A

Gamma motor neurons

52
Q

Does the contraction of intrafusal fibres contribute to the overall strength of the muscle?

A

no

53
Q

What are 4 causes of impairment of skeletal muscle function?

A

Intrinsic muscle disease
Disease of the NMJ
Disease of lower motor neurons
Disruption of input to motor nerves

54
Q

What are some causes of intrinsic muscle disease?

A 
Genetic
-Congenital
-Muscular dystrophy
-Myotonia
Acquired
-Inflammatory
-Non-inflammatory (fibromyalgia)
-Endocrine (cushings)
-Toxic (alcohol)
55
Q

What are 4 symptoms of muscle disease?

A

Muscle weakness
Delayed relaxation
Muscle pain
Muscle stiffness

56
Q

What are some useful investigations for neuromuscular disease?

A 
Electromyography
Nerve conduction studies
Muscle enzymes
Inflammatory markers
Muscle biopsy

MSK lectures (50 decks)

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