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skeletal muscle > Motor unit. Electromyography. Sources of energy for muscle contraction. > Flashcards

Motor unit. Electromyography. Sources of energy for muscle contraction. Flashcards

1
Q

motor unit structure 1

A

cell axon = long projection
- sends signals from motor neurone to muscle fibre

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2
Q

motor unit structure 2

A

cell axon terminal = branches of end of axon
interacts with muscle fibre at neuromuscular junction

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3
Q

motor unit structure 3

A

cell body - located in brainstem/spinal cord

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4
Q

motor unit - function 1

A

MUSCLE CONTRACTION MECHANISM

1 - resting membrane potential
2 - arrival of action potential
3 - depolarisation
4 - excitation-coupling mechanism

5 - muscle contraction
6 - muscle relaxation

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5
Q

motor unit - function 2

A

CONTOL

PRECISION
- small motor units control fine movements
- examples - eye movement/ finger dexterity

POWER
- large motor units control gross movements
- examples - jumping

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6
Q

motor units - function 3

A

COORDINATION

  • small motor units recruited first then large motor units if needed
  • motor units can be summated as a combined effect to enhance muscle strength
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7
Q

electromyography - definition

A

procedure of recording muscle activity performed by motor units

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8
Q

electromyography - phase 1

A

electrodes

  • surface electrodes are placed on the skin to detect electrical activity in a range of muscle fibres
  • intramuscular electrodes are inserted inside muscle to detect electrical activity of specific muscle fibres
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9
Q

electromyography - phase 2

A

SIGNAL

when muscle depolarises/ repolarises it produces signal
- detected by electrodes
- sent to EMG device

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10
Q

electromyography - phase 3

A

RESULT

EMG device amplifies weak signal into visual presentation

signal can be interpreted according to frequency/ amplitude/ duration

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11
Q

electromyography - result

A

normal result:

at rest should display little electrical activity
at contraction = sudden electrical activity

abnormal result
at rest could display random electrical activity
indicate fibrillation potentials

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12
Q

sources of energy for muscle contraction - type 1

A

muscles already have some ATP storage as an immediate energy source for the first few seconds of activity
ATP hydrolysed -> ADP + Pi

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13
Q

sources of energy for muscle contraction - type 2

A

creatine phosphate + ADP -> creatine + ATP

rapid + short duration + high intensity

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14
Q

sources of energy for muscle contraction - type 3

A

anaerobic glycolysis

x1 glucose -> pyruvate -> lactate

  • absence of oxygen
  • x2 ATP produced
  • rapid
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15
Q

sources of energy for muscle contraction - type 4

A

aerobic metabolism

C6H12O6 + 6O2 → 6CO2 + 6H2O

  • presence of oxygen
  • x38 ATP byproduct
  • slow
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16
Q

sources of energy for muscle contraction - type 5

A

brown adipose tissues in infants burnt to produce fatty acids
- producing ATP / heat

17
Q

muscle fibres - type 1

A

type 1 = slow twitch fibres

colour = red due to myoglobin content
capillaries = high, O2 delivery
contraction = slow + long duration

force = low

size = small
metabolism =aerobic
example = m. solei
fatigue = low, high endurance

18
Q

muscle fibres - type 2a

A

type 2a = fast muscle fibres OXIDATIVE

colour - pink, moderate myoglobin content
capillaries = moderate
contraction = moderate
force - moderate
size = moderate
mitochondria = moderate, aerobic + anaerobic
fatigue = moderate
example - swimming

19
Q

muscle fibres - type 2b

A

type 2b = fast twitch fibres GLYCOLYTIC

colour = white, low myoglobin content
capillaries = less, no O2 needed
contraction = fast
force - high

size = large
metabolism = anaerobic
fatigue = high
example - weight lifting

20
Q

work output - factor 1

A

muscle contraction

21
Q

work output - factor 2

A

types of muscle contraction
- isotonic
- isometric
- isokinetic
- auxotonic

22
Q

work output - factor 3

A

more optimal muscle length = better force generated = better work output

23
Q

work output - factor 4

A

more motor units = more AP firing = more work output

24
Q

work output - factor 5

A

METABOLISM

aerobic metabolism = prolonged activities

anaerobic metabolism = intestine activities

25
Q

muscle fatigue - definition

A

temporary decrease in muscle activity

due to less work output by motor neurones

26
Q

muscle fatigue - factor 1

A

ATP depletion

muscle contraction is an ATP dependent process
insufficient levels of ATP where supply does not meet demand will lead to ATP-debt causing lactic acid production

lactic acid causes acidosis in muscles impairing enzyme function/ contraction

27
Q

muscle fatigue - factor 2

A

ION IMBALANCE

  • damaged amount of ions inside/ outside membrane
  • damages ion concentration gradient
  • damages depolarisation/ repolarisation
28
Q

muscle fatigue - factor 3

A

motor neurone

repetitive stimulation of motor neurone causes it to not effectively secrete neurotransmitter in synaptic cleft, damaging this phase of muscle contraction

29
Q

muscle fatigue - factor 4

A

INFLAMMATION

  • too much excercise damanged mitochondria + ATP
  • more ROS are produced causing oxidative damage to proteins/ DNA
30
Q

length-tension relationship - definition

A

describes how a muscle generates tension when its length changes

31
Q

length-tension relationship - phase 1

A

ascending limb

  • length = too short
  • actin/ myosin = overlap too much
  • cross bridge formation = bad
  • force generated = too low
32
Q

length-tension relationship - phase 2

A

plateau

  • muscle length is optimal
  • actin/ myosin overlap perfect
  • best cross-bridge formation
  • force generated is maximum
33
Q

length-tension relationship - phase 3

A

descending limb
- muscle fibre is long
- actin/ myosin overlap is too short
- bad cross bridge formation
- force generated is too low

34
Q

relation of velocity of contraction to load

A

velocity decreases when load increases

skeletal muscle (5 decks)

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