Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physiology > Muscle mechanics > Flashcards

Muscle mechanics Flashcards

1
Q

What are the 4 key determinants of single fibre tension?

A
  • Stimulation frequency,
  • Fibre length,
  • Energy generation and fatigue,
  • Fibre thickness
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does a single stimulus (muscle contraction) cause?

A

A single twitch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What type of contraction does a single stimulus cause and what would is be used for?

A

Short and weak - brief fine motor movement eg blinking

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the two factors in whole muscle that can be called on to produce effective and graded tension appropriate to the task in hand

A
  1. Motor unit recruitment

2. Development of tension by each fibre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Defn of motor unit

A

Motor neuron and all muscle fibres it innervates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does switching on more motor units cause?

A

More cross bridging

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does more cross bridging cause?

A

More tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How many motor units are activated when weak contractions occur?

A

A few

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What determines a muscles contribution to contraction

A

Motor unit size - number of muscle fibres/unit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What occurs to prevent muscle fatigue?

A

Alternate activation of motor units

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Example of alternate activation of motor units

A

Asynchronous recruitment of motor units (submaximal contractions)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Defn fatigue

A

Inability to maintain muscle tension at a given level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the net effect of large powerful muscles (e.g. biceps brachii)

A

Large increase in tension with each additional motor unit recruited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the net effect of small precise muscles muscles (e.g. extraocular muscles)

A

Fine, small incremental increases in tension with each additional motor unit recruited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens when number of motor units recruited is increase?

A

Relative strength of whole-muscle contraction increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens when the proportion of motor units excited increase?

A

Strength of muscle contraction increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The release of what is required for contraction to occur?

A

Release of Ca2+ into the cytosol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

When does contraction end?

A

When all of Ca2+ has been removed from the cytosol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

The fact that contraction time does not end until all of Ca2+ has been removed from the cytosol allows for what?

A

Allows time for muscle tension to develop via repeated myosin-actin interaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the four factors affecting tension developed by muscle fibres

A
  1. Frequency of stimulation – cross-bridge cycling and effect on series elastic component
  2. Length of the fibre at onset of contraction
  3. Thickness of the fibre
  4. Extent of fatigue
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the three stages of frequency of muscle stimulation?

A
  1. No summation
  2. Twitch summation
  3. Tetanus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What happens if a muscle fibre is restimulated after it has completely relaxed?

A

The second twitch is the same magnitude as the first twitch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What happens if a muscle fibre is stimulated so rapidly that it does not have an opportunity to relax at all between stimuli?

A

A maximal sustained contraction known as tetanus occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Defn summation

A

The occurrence of additional twitch contractions before the previous twitch has completely relaxed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Mechanisms of twitch summation

A

x

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Are tendons contractive?

A

No but have passive elasticity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What does the shortening of sarcomeres do to tendon?

A

Stretches tendon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the effect of twitch summation on tendons? (series elastic component)

A

Greater tension produced in tendon since muscle has not completely relaxed before a new wave of contraction occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How can muscle size be increased?

A

By short bursts of high intensity training

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What does muscle size increase act as a stimulus for?

A

For hypertrophy of mainly fast-glycolytic fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What causes hypertrophy?

A

Increased actin and myosin synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Does an increase in muscle size have an effect on endurance?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Defn fatigue

A

Inability to maintain muscle tension at a given level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Muscle fatigue purpose

A

Purpose is to prevent muscle from reaching a point where it can no longer produce ATP; rigor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Defn central fatigue

A

Inadequate activation of motor neurons?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What does increased levels of phosphate cause? (muscle fatigue)

A
  1. Interfere with power stroke of myosin heads
  2. Decreased sensitivity of regulatory proteins to Ca2+?
  3. Decreased amount of Ca2+ released from lateral sacs?
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What occurs in muscle fatigue?

A
  • Increased levels of phosphate
  • Leakage of Ca2+ out of cell so it cannot be re-sequestered into sarcoplasmic reticulum
  • Depletion of glycogen energy reserves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What are three types of muscle fibres?

A
  • Slow-oxidative (type I) fibres
  • Fast-oxidative (type IIa) fibres
  • Fast-glycolytic (type IIx) fibres
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What makes a muscle fibre fast/slow?

A

The rate of myosin ATPase activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is the speed of contraction and enzymatic machinery used for?

A

ATP formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

ATP in oxidative versus Glycolytic fibres

A

Net ATP is greater in oxidative fibres, less fatiguable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

NBBB!!! Give the steps in ATP formation

A
  1. During muscle contraction, ATP is split by myosin ATPase to power cross-bridge stroking. Also, a fresh ATP must bind to myosin to let the cross bridge detach from actin at the end of a power stroke before another cycle can begin.
  2. During relaxation, ATP is needed to run the Ca2+ pump that transports Ca2+ back into the lateral sacs of the sarcoplasmic reticulum. ATP is also used by the Na+ - K+ pump to return Na+ and K+ moved during contraction-inducing action potentials.
  3. The metabolic pathways that supply the ATP needed to accomplish contraction and relaxation are
    - Transfer of a high-energy phosphate from creatine phosphate to ADP (immediate source)
    - Oxidative phosphorylation (the main source when O2 is present), fueled by glucose derived from muscle glycogen storesor by glucose and fatty acids delivered by the blood
    - Glycolysis (the main source when O2 is not present). Pyruvate, the end product of glycolysis, is converted to lactate when lack of O2 prevents the pyruvate from being further processed by the oxidative phosphorylation pathway
43
Q

V basic three steps of ATP formation

A
  1. Transfer of high-energy phosphate from creatine
    phosphate to ADP
  2. Oxidative phosphorylation (relatively slow process)
  3. Glycolysis (anaerobic/high intensity exercise)
44
Q

What is the Myosin-ATPase activity in slow-oxidative (Type I) fibres like?

A

Low

45
Q

What is the Myosin-ATPase activity in fast-oxidative (Type IIa) fibres like?

A

High

46
Q

What is the Myosin-ATPase activity in fast-glycolytic (Type IIx) fibres like?

A

High

47
Q

What is the speed of contraction in Slow-Oxidative (Type I) fibres like?

A

Slow

48
Q

What is the speed of contraction in Fast-Oxidative (Type IIa) fibres like?

A

Fast

49
Q

What is the speed of contraction in Fast-Glycolytic (Type IIx) fibres like?

A

Fast

50
Q

What is the resistance to fatigue in Slow-Oxidative (Type I) fibres like?

A

High

51
Q

What is the resistance to fatigue in Fast-Oxidative (Type IIa) fibres like?

A

Intermediate

52
Q

What is the resistance to fatigue in Fast-Glycolytic (Type IIx) fibres like?

A

Low

53
Q

What is the Oxidative Phosphorylation Capacity like in Slow-Oxidative (Type I) fibres like?

A

High

54
Q

What is the Oxidative Phosphorylation Capacity like in Fast-Oxidative (Type IIa) fibres like?

A

High

55
Q

What is the Oxidative Phosphorylation Capacity like in Fast-Glycolytic (Type IIx) fibres like?

A

Low

56
Q

Quantity of enzymes for anaerobic glycolysis in Slow-Oxidative (Type I) fibres

A

Low

57
Q

Quantity of enzymes for anaerobic glycolysis in Fast-Oxidative (Type IIa) fibres

A

Intermediate

58
Q

Quantity of enzymes for anaerobic glycolysis in Fast-Glycolytic (Type IIx) fibres

A

High

59
Q

Quantity of mitochondria in Slow-Oxidative (Type I) fibres

A

Many

60
Q

Quantity of mitochondria in Fast-Oxidative (Type IIa) fibres

A

Many

61
Q

Quantity of mitochondria in Fast-Glycolytic (Type IIx) fibres

A

Few

62
Q

Quantity of capillaries in Slow-Oxidative (Type I) fibres

A

Many

63
Q

Quantity of capillaries in Fast-Oxidative (Type IIa) fibres

A

Many

64
Q

Quantity of capillaries in Fast-Glycolytic (Type IIx)

A

Few

65
Q

Myoglobin content in Slow-Oxidative (Type I) fibres

A

High

66
Q

Myoglobin content in Fast-Oxidative (Type IIa) fibres

A

High

67
Q

Myoglobin content in Fast-Glycolytic (Type IIx)

A

Low

68
Q

Colour of Fibre of Slow-Oxidative (Type I) fibres

A

Red

69
Q

Colour of Fibre of Fast-Oxidative (Type IIa)

A

Red

70
Q

Colour of Fibre of Fast-Glycolytic (Type IIx)

A

White

71
Q

Glycogen content of Slow-Oxidative (Type I) fibres

A

Low

72
Q

Glycogen content of Fast-Oxidative (Type IIa) fibres

A

Intermediate

73
Q

Glycogen content of Fast-Glycolytic (Type IIx)

A

High

74
Q

What muscles are Slow-oxidates?

A

Muscles of posture

75
Q

What muscles are Fast-glycolytic?

A

Muscles of arms

76
Q

Reason for fatigue in CNS

A
  • Malfunction of neurons
  • Inhibition of voluntary effort (motor cortex)
  • Psychological factors
77
Q

Three sites of fatigue in peripheral nervous system

A
  • NMJ
  • T tubules
  • Contractile elements
78
Q

Proposed mechanism of fatigue in NMJ

A
  • Inhibition of axonal terminal
  • Depletion of neurotransmitter
  • Altered neurotransmitter binding to receptors
79
Q

Proposed mechanism of fatigue in T tubules/SR

A
  • Inability to release Ca2+

- Inability of Ca2+ to bind to troponin

80
Q

Proposed mechanism of fatigue in contractile elements

A
  • Depletion of ATP
  • Depletion of phosphocreatine
  • Depletion of glycogen
  • Accumulation of lactate H+, PO4-, etc
81
Q

What are the three types of contraction

A
  • Isotonic
  • Isometric
  • Isokinetic
82
Q

What occurs in isotonic contraction?

A

Load remains constant and muscle length changes

83
Q

What occurs in isometric contraction?

A

Muscle is prevented from shortening so tension develops at constant muscle length i.e. trying to lift something heavy

84
Q

What occurs in isokinetic contraction?

A

Velocity of shortening remains constant as muscle length changes

85
Q

What are the two types of isotonic contractions?

A
  • Concentric contraction

- Eccentric contraction

86
Q

What occurs in concentric contraction?

A

The muscle tension rises to meet the resistance, then remains the same as the muscle shortens.

87
Q

What occurs in eccentric contraction?

A

The muscle lengthens due to the resistance being greater than the force the muscle is producing. i.e. the muscle fibres are contracting to resist the passive stretching by the load

88
Q

What happens to the muscle length in isometric contraction?

A

It remains constant

89
Q

Isotonic vs isometric contraction

A

Isotonic: Muscle contracts, shortens and creates enough force to move the load
Isometric: Muscle contracts but does not shorten. Force cannot move the load

90
Q

What happens to the length of muscle in isometric contraction?

A

Remains the same

91
Q

What happens to the length of muscle in isotonic contraction?

A

Shortens

92
Q

What happens to the tension in isometric contraction?

A

Rises during contraction

93
Q

What happens to the tension in isotonic contraction?

A

No change

94
Q

Is there external work in isometric contraction?

A

No external work down

95
Q

Is there external work in isotonic contraction?

A

Work down?

96
Q

Give an example of isometric contraction

A

Trying to lift heavy weights (when weights are not actually lifted)

97
Q

Give an example of isotonic contraction

A

Lifting of weights

98
Q

What does the velocity of shortening of a muscle relate to ?

A

The load (weight)

99
Q

When does isotonic contraction become isometric?

A

When the maximal tension generated in the muscle is not sufficient to overcome the load (weight of the object)

100
Q

What is most skeletal muscle attached to?

A

Bone across joints

101
Q

What is the lever in the lever system?

A

Rigid structure moving around a pivot (e.g. forearm)

102
Q

What is the fulcrum in the level system?

A

The pivot (e.g. elbow joint)

103
Q

Lever system example (forearm) - most common type of lever system in body

A

Skeletal muscle provides the force to move the lever (bone) around the fulcrum (joint) by coupling muscle contraction to displacement of the lever (bone) by the tendon.

104
Q

At point of insertion how much force must a muscle exert?

A

Force 7 times greater than the load to maintain position and greater to actually lift the load

Physiology (28 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions