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KINE 2P90 - Physiological Responses to Exercise > Skeletal Muscle: Structure and Function > Flashcards

Skeletal Muscle: Structure and Function Flashcards

1
Q

What are the 3 functions of skeletal muscle?

A

Force production for motion and breathing, force production for postural support and heat production during cold stress.

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2
Q

What is the myonuclear domain?

A

region of cytoplasm surrounding an individual nucleus

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3
Q

Name the 3 separate layers of connective tissue in skeletal muscle.

A

Epimysium, Perimysium and Endomysium.

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4
Q

Which is the outer layer of skeletal muscle?

A

Epimysium

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5
Q

Inner layer of connection tissue?

A

Endomysium

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6
Q

Middle layer of skeletal muscle?

A

Perimysium

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7
Q

What is a fascicle?

A

a small bundle of muscle fibres

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8
Q

What is the sarcolemma?

A

the cell plasma membrane surrounding a muscle fibre

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9
Q

what is a satellite cell?

A

undifferentiated cell found adjacent to skeletal muscle fibres. They can fuse with existing muscle fibres and contribute to hypertrophy. They can form a new muscle fibre following muscle injury.

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10
Q

What are myofibrils?

A

the portion of muscle containing the thick and thin contractile filaments

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11
Q

What is myosin?

A

contractile protein in the thick filament of a myofibril that contains the cross-bridge that can bind actin and split ATP to cause tension development.

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12
Q

What is actin?

A

a structural protein of muscle that works with myosin in permitting muscular contraction

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13
Q

What are sarcomeres?

A

the basic contractile unit of a muscle fiber

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14
Q

What is the sarcoplasmic reticulum?

A

a membranous structure that surrounds the myofibrils of muscle cells. The Terminal cisternae that store Ca++ needed for muscle contraction is here.

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15
Q

What is the transverse tubule?

A

an extension of the muscle membrane that conducts the action potential into the muscle to depolarize the terminal cisternae

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16
Q

What is terminal cisternae?

A

portion of sarcoplasmic reticulum near the transverse tubule containing the Ca++ that is released upon depolarization of the muscle

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17
Q

What are motor neurons?

A

the somatic neutron that innervates skeletal muscle fibres

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18
Q

What is a motor unit?

A

a motor unit and all the muscle fibres innervated by that single motor neuron. Responds in an “all or none” matter to a stimulus.

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19
Q

What is the neuromuscular junction?

A

synapse between axon terminal of a motor neuron and the motor end plate of a muscle’s plasma membrane

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20
Q

What is end plate potential (EPP)?

A

depolarization of a membrane region by a sodium influx.

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21
Q

How does endurance and resistance training stimulate positive adaptations to the NMJ?

A

Training increases the size of the NMJ, expands the number of synaptic vesicles (containing acetylcholine) and increasing the number of acetylcholine receptors

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22
Q

What is the sliding filament/swinging cross-bridge model?

A

the process of muscular contraction. This process proposes that muscle shortening occurs due to movement of the actin filament OVER the myosin filament.

23
Q

What is excitation-contraction coupling?

A

sequence of events in which the nerve impulse (action potential) depolarizes the muscle fibre leading to muscle shortening by cross-bridge cycling. Trigger to initiate muscle contraction.

24
Q

How does muscle contraction occur?

A

via the binding of the myosin cross-bridge to actin and the repeated cycling of myosin pulling on the actin molecule resulting in the shortening of the muscle fibre.

25
Q

How does muscle relaxation occur?

A

occurs when the motor neuron stops exciting the muscle fibre and calcium is pumped back into the sarcoplasmic reticulum. The removal of calcium causes a position change in tropomyosin which blocks the myosin cross bridge binding site resulting in muscle relaxation.

26
Q

What is troponin?

A

a protein associated with actin and tropomyosin that binds Ca++ and initiates the movement of tropomyosin on actin to allow the myosin cross-bridge to touch actin and initiate contraction.

27
Q

What is tropomyosin?

A

a protein covering the actin-binding sites that prevent the myosin cross-bridge from touching actin

28
Q

Define muscle fatigue.

A

reduction in muscle power output that results from decreased muscle force generation and/or decreased shortening velocity.

29
Q

What are muscle cramps?

A

spasmodic and involuntary muscle contractions

30
Q

What are the two major theories of the cause of exercise-induced muscle cramps?

A

1: Caused by dehydration and electrolyte imbalance.

2: cramps originate in the central nervous system.

31
Q

Which theory of muscle cramps is more accurate?

A

Motor neuron hyperexcitability is likely the general underlying cause of muscle cramps induced by exercises therefore they probably originate in the central nervous system.

32
Q

List the muscle fiber types. And then if applicable, break them down into their subcategories.

A

Slow, Type I fibers. Fast, type II fibers. Type II can be broken down into type IIa and type Iix fibers.

33
Q

When muscle fibres are viewed, what colour do each appear?

A

Type I are blue. Type IIa are green. Type IIx are black.

34
Q

List the 3 biochemical characteristics of muscle that are important to muscle function.

A

Oxidative capacity, type of myosin isoform, abundance of contractile protein within the fiber.

35
Q

What are the performance characteristics when companies muscle fiber types?

A

1: maximal force production; 2: speed of contraction; 3: maximal power output; 4: efficiency of contraction

36
Q

How is power calculated?

A

Power = Force x Shortening velocity

37
Q

What does Vmax represent?

A

highest speed at which a fiber can shorten.

38
Q

Describe type I fibers.

A

contain large numbers of oxidative enzymes and are highly fatigue resistant. They are more efficient than type II fibers, produce a lower specific force than fast fibers and possess a slow maximal shortening velocity compared to the later.

39
Q

Describe type IIx fibers.

A

fibers that have a relatively small number of mitochondria, a limited capacity for aerobic metabolism and less resistant to fatigue than slow fibers.

40
Q

Describe type IIa fibers.

A

fibers that contain biochemical and performance (fatigue) characteristics that are between type IIb and type I fibers. Also known as intermediate muscle fibers.

41
Q

What is the fastest muscle fiber type in humans?

A

Type IIx

42
Q

Power athletes (sprinters) generally possess a large percentage of which muscle fiber type?

A

Type II muscle fibers.

43
Q

Endurance athletes (marathon runners) typically possess a larger amount of which muscle fiber type?

A

Type I muscle fibers.

44
Q

What is a muscle action?

A

term used to describe the movement movement (shortening or lengthening)

45
Q

What is concentric contraction?

A

muscle shortens

46
Q

What is eccentric contraction?

A

muscle lengthens

47
Q

What is isometric contraction?

A

muscle contracts but does not change length

48
Q

What is a twitch?

A

the tension generating response following the application of a single stimulus to muscle

49
Q

Muscle Action-Relaxation Graph Parts.

A

Stimulus. Latent period. Contraction. Relaxation.

50
Q

Describe the difference between fast and slow muscle fibers in terms of contraction.

A

Fast muscle fibers contract in a shorter time period than do slow fibers because: the speed of shortening is greater in fast fibers than in slow fibers due to the sarcoplasmic reticulum in fast fibers releasing Ca++ at a faster rate and fast fibers possess a high ATPase activity resulting in a more rapid splitting of ATP and a quicker release of energy required for contraction.

51
Q

List the four factors that the amount of force exerted during muscular contraction are dependant on.

A

Number and types of motor units recruited. Initial length of muscle. Neural stimulation of the motor units. Contractile history of the muscle.

52
Q

What is summation?

A

repeated stimulation of a muscle that leads to an increase in tension compared to a single twitch. (addition of successive twitches)

53
Q

What is tetanus?

A

highest tension developed by a muscle in response to a high frequency of stimulation.

54
Q

What is post activation potentiation (PAP)?

A

refers to the increase in muscle force production that occurs following a series of sub maximal muscle contractions.

KINE 2P90 - Physiological Responses to Exercise (2 decks)

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