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Anatomy > Muscle Function > Flashcards

Muscle Function Flashcards

1
Q

What does the process of skeletal muscle contraction involve?

A
  • neural stimulation of the sarcolemma: causes excitation-contraction coupling
  • muscle fibre contraction:interaction of thick and thin filaments
  • tension (force) production
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2
Q

What do synaptic vesicles contain?

A

Acetylcholine

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3
Q

The sliding filament theory

A

Vertical lines at side are z line
Thick horizontal lines are myosin filament
Thin horizontal lines are actin filament

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4
Q

Describe the six stages of the contractile cycle (skeletal muscle)

A
  1. Contraction cycle begins
  2. Active site exposure
  3. cross-bridge formation
  4. myosin head pivoting
  5. cross-bridge detachment
  6. myosin reactivation
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5
Q

Where does the energy for contraction come from?

A
  • ATP is essential for contraction
  • The enzyme myofibrillar ATPase (mATPase) located in myosin head
  • ATP is also required to pump calcium back into the SR during relaxation
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6
Q

What are the two individual fibre types?

A

Slow fibres and fast fibres

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7
Q

What are the slow fibres?

A
  • type 1 fibres:
  • slow-twitch fibres
  • slow-oxidative fibres
  • large amounts of mitochondria
  • myoglobin
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8
Q

What are the fast fibres?

A
  • type 11b fibres:
  • fast twitch fibres
  • fast-glycolytic fibres
  • larger in diameter
  • type 11a fibres:
  • intermediate fibres
  • fast-oxidative fibres
  • hybrid of type 1 and 11b
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9
Q

Power athletes such as sprinters have what kind of fibres?

A

Possess high percentage of fast fibres

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10
Q

What type of fibres do endurance athletes such as distance runners have?

A

Have high percentage of slow fibres

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11
Q

What type of fibres do others have such as cyclists and non athletes?

A

Have about 50% slow and 50% fast fibres

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12
Q

Discuss slow oxidative type 1 muscle fibres

A 
Contraction- slow twitch
Fibre size-small
Colour-red
Myoglobin concentration-high
Mitochondrial content-high
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13
Q

Discuss fast oxidative type 11a muscle fibres

A 
Contraction- fast twitch
Fibre size-intermediate
Colour-red
Myoglobin concentration-high
Mitochondrial content-high
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14
Q

Discuss fast glycolytic (type 11b) muscle fibres

A 
Contraction- fast twitch
Fibre size-large
Colour-White
Myoglobin concentration-low
Mitochondrial content-low
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15
Q

What is used to see fibre types more clearly?

A

Histochemical staining

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16
Q

What is muscle tone?

A

The resting tension in a muscle

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17
Q

In tension production and contraction types, the contractions are classified based on the resulting patterns of tension production, what are they?

A
  • isotonic contraction

- isometric contraction

18
Q

With isotonic contraction what happens when the skeletal muscle changes length?

A

This results in motion

19
Q

With isotonic contraction what happens if the muscle tension is more than the load (resistance)?

A

Muscle shortens (concentric contraction)

20
Q

With isotonic contraction what happens if the muscle tension is less than the load (resistance)?

A

Muscle lengthens( eccentric contraction)

21
Q

Discuss isometric contraction

A

Skeletal muscle develops tension, but is prevented from changing length

Iso= same, metric=measure

22
Q

Load and speed of contraction are inversely related, what does this mean?

A

The heavier the load (resistance) on a muscle

  • the longer it takes for shortening to begin
  • the less muscle will shorten
23
Q

With regards to speed of muscle contraction/relaxation, discuss muscle twitch

A
  • contraction as the result of a single stimulus
  • latent period: lasting only 2ms
  • contraction: tension is developed-15ms
  • relaxation:25ms
24
Q

Describe the development of tension in a twitch

A

As time(ms) and tension increase from resting phase, stimulus occurs at 0 which results in a resting potential half way between 0 and 5. Between 5 and 15 ms there is the contraction phase until maximum tension development is reached and then between 15 and 40ms it falls during the relaxation phase

25
Q

The tension over time for a twitch is different in what?

A

Different skeletal muscles

26
Q

What is a motor unit?

A

A motor neuron and all of the muscle cells it stimulates

27
Q

What is the optimal resting length?

A

The normal range of sarcomere lengths in the body is 75 to 130 percent of the optimal length

28
Q

With force regulation in muscle, what is the relationship between types and numbers of motor units recruited?

A

More motor units=greater force

Fast motor units= greater force

29
Q

Initial muscle length is?

A

Optimum overlap produces greatest amount of tension

Nature of the motor unit neural stimulation

30
Q

Frequency of stimulation…

A

Simple twitch, summation and tetanus

31
Q

What is a single muscle twitch composed of?

A

Latent contraction, and relaxation periods

32
Q

What does the increase of frequency of stimulation do?

A

Increasing the frequency provides temporal summation and increased muscle tension

33
Q

With regards to the number of motor units recruited, what does the stimulation of more motor neurone produce?

A

Increased muscle tension

34
Q

What is the starting length of a muscle?

A

Optimum stretch permits maximum binding of cross bridges for maximum muscle tension

35
Q

Receptors in muscle: discuss muscle spindle

A
  • detect dynamic and static changes in muscle length
  • stretch reflex
  • stretch on muscle causes reflex contraction
36
Q

Receptors in muscle: discuss Golgi tendon organ (GTO)

A
  • monitor tension developed in muscle
  • prevents damage during excessive force generation
  • stimulation results in reflex relaxation of muscles
37
Q

Muscle fatigue: when a muscle can no longer perform at the required level of activity:

A
  • depletion of metabolic reserves
  • a decline in pH within the muscle fibre- lactic acid
  • a sense of weariness due to low blood pH
  • damage to sarcolemma or sarcoplasmic reticulum
  • pathological conditions-premature fatigue-heart problems, blood loss etc.
38
Q

Anaerobic pathway produces what?

A

Lactic acid

39
Q

What is muscle atrophy and what does it do?

A
  • results due to lack of activity or loss of neuronal innervation
  • reduction in muscle fibre size, tone and power
  • examples are sedentary lifestyle, bed rest and spinal cord injury
40
Q

What is hypertrophy and what does it result in?

A
  • results due to repeated, exhaustive stimulation
  • muscle fibre increases in diameter
  • number of muscle fibre remains the same
  • there is an increase in mitochondria, glycolytic enzymes, larger glycogen reserves

Anatomy (8 decks)

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