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Physiology > Week 4- skeletal muscle structure and function > Flashcards

Week 4- skeletal muscle structure and function Flashcards

1
Q

What are the functions of skeletal muscle?

A

-Force production of locomotion, breathing, postural support
-heat production during cold stress
-acts as an endocrine organ

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2
Q

Where is connective tissue found?

A

Surrounding the entire muscle

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3
Q

Where is the epimysium found?

A

Surrounding the entire muscle

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4
Q

Where is the Perimysium found?

A

surrounds fascicles

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5
Q

Where is the endomysium found?

A

surrounds muscle fibres

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6
Q

Where is the Basement found?

A

just below the endomysium

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7
Q

Where is the sarcolemma found?

A

muscle cell membrane

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8
Q

What does myofibrils contain?

A

contractile proteins actin and myosin

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9
Q

What is the use of the sarcoplasmic reticulum?

A

Storage sites of Ca, terminal cisternae

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10
Q

Where do the transverse tubules extend from?

A

sacrolemma to the sarcoplasmic reticulum

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11
Q

What is the key role of satellite cells?

A

stems cells for growth and repair

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12
Q

What happens to satellite cells during exercise?

A

increase in number of nuclei in mature muscle fibres

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13
Q

What does more myonuclear allow for?

A

greater protein synthesis

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14
Q

What does acetylcholine cause when it is release in the neuromuscular junction?

A

-end-plate potential
-depolarisation of the muscle fibre
-signal for muscle contraction

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15
Q

What forms a cross bridge to create a power stroke?

A

Actin and myosin

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16
Q

What breaks down ATP as fibres contract?

A

Myosin ATPase

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17
Q

What is fatigue?

A

a decline in muscle power output

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18
Q

What can cause a decline in muscle power output?

A

-decrease in muscle force production at cross-bridge level
-decrease in muscle shortening velocity

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19
Q

What are the possible causes of fatigue?

A
  • decreased calcium release from the sarcoplasmic reticulum
    -accumulation of metabolites that inhibit myofilament sensitivity to calcium
    -glycogen depletion
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20
Q

What are the key metabolites contributing to fatigue?

A

-Pi and free radicals- modify cross-bridge head and reduce number of cross bridge bound to actin
-H ions bind to Ca binding sites on troponin, preventing Ca binding and contraction

21
Q

What are exercise-associated muscle cramps (EAMC)?

A

spasmodic, involuntary muscle contractions during exercise

22
Q

What is an isotonic muscle contraction?

A

muscle tension remains unchanged where muscle length decreases

23
Q

What is an isokinetic muscle contraction?

A

Muscle length decreases with constant velocity

24
Q

What is a concentric muscle contraction?

A

muscle shortens, greater force

25
Q

What is an eccentric muscle contraction?

A

muscle lengthens, lesser force

26
Q

what is an isometric muscle contraction?

A

muscle contracts but does not change in length

27
Q

What is a dynamic exercise?

A

concentric, eccentric action leading to muscle length increase and decrease

28
Q

What is a static exercise?

A

isometric action, no change in muscle length

29
Q

what is oxidative capacity?

A

quantity of mitochondrial, capillaries and myoglobin in and around the fibre

30
Q

What is speed of contraction regulated by?

A

myosin ATPase activity

31
Q

What is the maximal power equation?

A

maximal power output = force X shortening velocity

32
Q

What is muscle fibre efficiency?

A

lower amount of ATP used to generate force

33
Q

what does muscle contraction speed depend on?

A

the rate of cross bridge cycling which depends on the myosin ATPase isoform

34
Q

What happens after stimulation?

A

short latent period to correspond with the depolarisation of muscle fibre

35
Q

What occurs during muscle contraction?

A

calcium release from SR and tension is developed due to cross bridge binding

36
Q

what occurs at relaxation of the muscle?

A

reuptake of calcium to SR- cross bridge detachement

37
Q

What does it mean when more motor units are recruited?

A

greater force

38
Q

What does it mean when faster motor units are recruited?

A

greater and faster force

39
Q

What occurs when muscle length changes?

A

increased cross bridge formation

40
Q

What causes the firing rate of motor neurons to increase?

A

frequency of stimulation- simple twitch, summation, tetanus

41
Q

How many axons innervate a mature muscle fibre?

A

one

42
Q

How many motor neurons supply a motor unit?

A

one

43
Q

How many fibre types does a motor unit contain?

A

one

44
Q

What is the structure of a motor neuron supplying larger faster motor units like compared to motor neurons supplying small motor units?

A

-larger cell bodies
-larger diameter
-greater number of axonal branches
-sparse afferent innervation
-more complex and extensive motor end plate of neuromuscular junction

45
Q

What motor units are harder to excite?

A

fast motor units

46
Q

How much muscle is lost at the age of 50-80%

A

50%

47
Q

What is cachexia?

A

rapid loss of muscle mass

48
Q
A

Physiology (24 decks)

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