Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

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
Mechanisms of twitch summation
x
26
Are tendons contractive?
No but have passive elasticity
27
What does the shortening of sarcomeres do to tendon?
Stretches tendon
28
What is the effect of twitch summation on tendons? (series elastic component)
Greater tension produced in tendon since muscle has not completely relaxed before a new wave of contraction occurs
29
How can muscle size be increased?
By short bursts of high intensity training
30
What does muscle size increase act as a stimulus for?
For hypertrophy of mainly fast-glycolytic fibres
31
What causes hypertrophy?
Increased actin and myosin synthesis
32
Does an increase in muscle size have an effect on endurance?
No
33
Defn fatigue
Inability to maintain muscle tension at a given level
34
Muscle fatigue purpose
Purpose is to prevent muscle from reaching a point where it can no longer produce ATP; rigor
35
Defn central fatigue
Inadequate activation of motor neurons?
36
What does increased levels of phosphate cause? (muscle fatigue)
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?
37
What occurs in muscle fatigue?
- Increased levels of phosphate - Leakage of Ca2+ out of cell so it cannot be re-sequestered into sarcoplasmic reticulum - Depletion of glycogen energy reserves
38
What are three types of muscle fibres?
- Slow-oxidative (type I) fibres - Fast-oxidative (type IIa) fibres - Fast-glycolytic (type IIx) fibres
39
What makes a muscle fibre fast/slow?
The rate of myosin ATPase activity
40
What is the speed of contraction and enzymatic machinery used for?
ATP formation
41
ATP in oxidative versus Glycolytic fibres
Net ATP is greater in oxidative fibres, less fatiguable
42
NBBB!!! Give the steps in ATP formation
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
V basic three steps of ATP formation
1. Transfer of high-energy phosphate from creatine phosphate to ADP 2. Oxidative phosphorylation (relatively slow process) 3. Glycolysis (anaerobic/high intensity exercise)
44
What is the Myosin-ATPase activity in slow-oxidative (Type I) fibres like?
Low
45
What is the Myosin-ATPase activity in fast-oxidative (Type IIa) fibres like?
High
46
What is the Myosin-ATPase activity in fast-glycolytic (Type IIx) fibres like?
High
47
What is the speed of contraction in Slow-Oxidative (Type I) fibres like?
Slow
48
What is the speed of contraction in Fast-Oxidative (Type IIa) fibres like?
Fast
49
What is the speed of contraction in Fast-Glycolytic (Type IIx) fibres like?
Fast
50
What is the resistance to fatigue in Slow-Oxidative (Type I) fibres like?
High
51
What is the resistance to fatigue in Fast-Oxidative (Type IIa) fibres like?
Intermediate
52
What is the resistance to fatigue in Fast-Glycolytic (Type IIx) fibres like?
Low
53
What is the Oxidative Phosphorylation Capacity like in Slow-Oxidative (Type I) fibres like?
High
54
What is the Oxidative Phosphorylation Capacity like in Fast-Oxidative (Type IIa) fibres like?
High
55
What is the Oxidative Phosphorylation Capacity like in Fast-Glycolytic (Type IIx) fibres like?
Low
56
Quantity of enzymes for anaerobic glycolysis in Slow-Oxidative (Type I) fibres
Low
57
Quantity of enzymes for anaerobic glycolysis in Fast-Oxidative (Type IIa) fibres
Intermediate
58
Quantity of enzymes for anaerobic glycolysis in Fast-Glycolytic (Type IIx) fibres
High
59
Quantity of mitochondria in Slow-Oxidative (Type I) fibres
Many
60
Quantity of mitochondria in Fast-Oxidative (Type IIa) fibres
Many
61
Quantity of mitochondria in Fast-Glycolytic (Type IIx) fibres
Few
62
Quantity of capillaries in Slow-Oxidative (Type I) fibres
Many
63
Quantity of capillaries in Fast-Oxidative (Type IIa) fibres
Many
64
Quantity of capillaries in Fast-Glycolytic (Type IIx)
Few
65
Myoglobin content in Slow-Oxidative (Type I) fibres
High
66
Myoglobin content in Fast-Oxidative (Type IIa) fibres
High
67
Myoglobin content in Fast-Glycolytic (Type IIx)
Low
68
Colour of Fibre of Slow-Oxidative (Type I) fibres
Red
69
Colour of Fibre of Fast-Oxidative (Type IIa)
Red
70
Colour of Fibre of Fast-Glycolytic (Type IIx)
White
71
Glycogen content of Slow-Oxidative (Type I) fibres
Low
72
Glycogen content of Fast-Oxidative (Type IIa) fibres
Intermediate
73
Glycogen content of Fast-Glycolytic (Type IIx)
High
74
What muscles are Slow-oxidates?
Muscles of posture
75
What muscles are Fast-glycolytic?
Muscles of arms
76
Reason for fatigue in CNS
- Malfunction of neurons - Inhibition of voluntary effort (motor cortex) - Psychological factors
77
Three sites of fatigue in peripheral nervous system
- NMJ - T tubules - Contractile elements
78
Proposed mechanism of fatigue in NMJ
- Inhibition of axonal terminal - Depletion of neurotransmitter - Altered neurotransmitter binding to receptors
79
Proposed mechanism of fatigue in T tubules/SR
- Inability to release Ca2+ | - Inability of Ca2+ to bind to troponin
80
Proposed mechanism of fatigue in contractile elements
- Depletion of ATP - Depletion of phosphocreatine - Depletion of glycogen - Accumulation of lactate H+, PO4-, etc
81
What are the three types of contraction
- Isotonic - Isometric - Isokinetic
82
What occurs in isotonic contraction?
Load remains constant and muscle length changes
83
What occurs in isometric contraction?
Muscle is prevented from shortening so tension develops at constant muscle length i.e. trying to lift something heavy
84
What occurs in isokinetic contraction?
Velocity of shortening remains constant as muscle length changes
85
What are the two types of isotonic contractions?
- Concentric contraction | - Eccentric contraction
86
What occurs in concentric contraction?
The muscle tension rises to meet the resistance, then remains the same as the muscle shortens.
87
What occurs in eccentric contraction?
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
What happens to the muscle length in isometric contraction?
It remains constant
89
Isotonic vs isometric contraction
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
What happens to the length of muscle in isometric contraction?
Remains the same
91
What happens to the length of muscle in isotonic contraction?
Shortens
92
What happens to the tension in isometric contraction?
Rises during contraction
93
What happens to the tension in isotonic contraction?
No change
94
Is there external work in isometric contraction?
No external work down
95
Is there external work in isotonic contraction?
Work down?
96
Give an example of isometric contraction
Trying to lift heavy weights (when weights are not actually lifted)
97
Give an example of isotonic contraction
Lifting of weights
98
What does the velocity of shortening of a muscle relate to ?
The load (weight)
99
When does isotonic contraction become isometric?
When the maximal tension generated in the muscle is not sufficient to overcome the load (weight of the object)
100
What is most skeletal muscle attached to?
Bone across joints
101
What is the lever in the lever system?
Rigid structure moving around a pivot (e.g. forearm)
102
What is the fulcrum in the level system?
The pivot (e.g. elbow joint)
103
Lever system example (forearm) - most common type of lever system in body
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
At point of insertion how much force must a muscle exert?
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.
© 2025 Bold Learning Solutions. Terms and Conditions