Muscles Flashcards
1
Q
What are the functions of muscles?
A
Produce movement
Stabilise body positions
Store and move substances (myocardium)
Generate heat
2
Q
What is thermogenesis?
A
The process of generating heat as a result of muscle contraction
3
Q
What is the importance of thermogenesis?
A
Maintain body temperature
4
Q
What are the key properties of muscle tissue?
A
Electrical excitability
Contractility
Extensibility
Elasticity
5
Q
Explain the muscle property of electrical excitability:
A
Respond to electrical stimuli (action potentials) cause contraction of the muscle
6
Q
Explain the muscle property of contractility:
A
The muscles have the ability to shorten creating tension causing movement
7
Q
Explain the muscle property of extensibility:
A
Myocardium and smooth muscle can relax and extend when required
8
Q
Explain the muscle property of elasticity:
A
Muscles can return to their original position after stretching
9
Q
What are the different types of muscle tissue?
A
Cardiac
Smooth
Skeletal
10
Q
Where is smooth muscle located?
A
Within the walls of hollow internal organs, e.g. blood vessels, airways and abdominal organs
11
Q
Smooth muscle is non-striated, what does this mean?
A
There is no specific tissue pattern
12
Q
Smooth muscle is non-voluntary, what does this mean?
A
It is innervated by neurons in the autonomic nervous system so muscle contraction is non voluntary
13
Q
Compare / Contrast the 3 muscle types in relation to voluntary contraction:
A
Cardiac = involuntary Smooth = involuntary Skeletal = voluntary
14
Q
Compare / Contrast the 3 muscle types in relation to striation:
A
Cardiac = striated Smooth = non-striated Skeletal = striated
15
Q
Where is cardiac muscle tissue found?
A
Only in the heart, especially the walls of the heart
16
Q
Cardiac muscle is striated, what does this mean?
A
The muscle proteins are formed in well organised bundles (sarcomeres)
17
Q
Cardiac muscle is involuntary, what does this mean?
A
The muscle is stimulated by the Sinoatrial node which creates the action potential for contraction to begin
18
Q
Where are Intercalated discs found and what is their function?
A
Found in cardiac muscle, they aid in transmitting action potentials through myocardium to increase contraction
19
Q
Skeletal muscle is striated, what does this mean?
A
The muscle proteins are formed in an organised fashion, through alternating dark and white bands
20
Q
Skeletal muscle is voluntary, what does this mean?
A
Contraction is controlled by neurons as part of the somatic nervous system (although most contractions are subconscious)
21
Q
Compare / Contrast the 3 muscle types in relation to contraction speed:
A
Cardiac = moderate Smooth = slow Skeletal = fast
22
Q
Compare / Contrast the 3 muscle types in relation to size:
A
Cardiac = Large Smooth = Small Skeletal = Very large
23
Q
Compare / Contrast the 3 muscle types in relation to regulator proteins for contraction:
A
Cardiac = Troponin and Tropomyosin Smooth = Calmodulin and Myosin Skeletal = Troponin and Tropomyosin
24
Q
Compare / Contrast the 3 muscle types in relation to autorhythmicity:
A
Cardiac = Yes Smooth = Yes Skeletal = No
25
What is a sarcolemma?
An excitable plasma membrane surrounding a muscle fiber
26
What is sarcoplasm?
The cytoplasm of the muscle fiber
27
Where is the sarcoplasm found?
Within the sarcolemma
28
What substances are found within sarcoplasm which aid muscular contraction?
Glycogen (for ATP)
| Myoglobin (O2 receiver)
29
What is the function of mitochondria in muscle fibers?
They breakdown glycogen into ATP
30
Many myofibers combine to form a _____:
Muscle fiber
31
What are sarcomeres?
The smallest component of a myofiber
32
What are the main contractile proteins of a myofiber?
Myosin (thick filament)
| Actin (thin filament)
33
What is the M line?
The middle of a sarcomere
34
What is the Z disc?
The end of a sarcomere
35
What is the A band?
The middle of the sarcomere extending the entire length of the thick filament (myosin), including overlap
36
What is the H zone?
The area of sarcomere where there is thick filament (myosin) only, so not the overlap area
37
In relation to M and Z, what happens during muscle contraction?
Z discs are pulled towards the M line, shortening the sarcomere
38
What is the I band?
The area of sarcomere where there is thin filament (actin) only, so not the overlap area
39
In a myofiber, what is the name for the protein in the THIN filament?
Actin
40
Which protein moves the Z disc towards the M line?
Actin (thin filament)
41
What is the structure of the thick filament?
```
Myosin tail
Myosin head (containing Actin-binding site and ATP-binding site)
```
42
What occurs during the second stage of the sliding filament theory?
Attachment of myosin to actin:
Myosin in the high-energy conformation attach to actin's binding site
Forming a cross bridge
43
What is the position of tropomyosin during a relaxed state?
It covers the myosin-binding site on the tin filament actin proteins
44
What causes troponin to become active?
Binding with calcium ions
45
What are the steps in the sliding filament theory?
ATP hydrolysis
Attachment of myosin to actin
Power stroke
Detachment of myosin from actin
46
What occurs during the first stage of the sliding filament theory?
ATP hydrolysis:
ATP attached to the ATP-binding site on myosin
ATP -> ADP + Pi (+energy)
Energy is stored in the myosin head
Head cocked into high-energy conformation (90 degrees)
47
What happens when calcium binds with troponin?
A change in the actin occurs moving the tropomyosin off the myosin-binding site allowing the myosin to bind to the actin
48
What is the structure of the thin filament?
Two actin strands helically around each other, clumps of troponin, myosin-binding site covered by tropomyosin
49
In a myofiber, what is the name for the protein in the THICK filament?
Myosin
50
What occurs during the fourth stage of the sliding filament theory?
Detachment of myosin from actin:
ATP attaches to myosin head
Link between actin and myosin weakens
Cross bridge detaches and actin slides back
51
What occurs during the third stage of the sliding filament theory?
Power stroke:
Pi is released initiating power stroke
Myosin head pivots and pulls actin towards M line
Then ATP is released
52
The sliding filament theory is continuous as long as what conditions are present?
There is sufficient ATP in the sarcoplasm and there is stimuli from the nervous system to contract
53
What are contractile proteins?
Proteins which generate force during muscle contractions
| Myosin, Actin
54
What are regulatory proteins?
Proteins which help control the muscle contraction process
| Tropomyosin, Troponin
55
What are structural proteins?
Proteins that maintain the alignment of the thick and thin filaments, provide myofibril elasticity and link myofibrils to sarcolemma
(Titin, α-Actinin, Myomesin, Nebulin, Dystrophin)
56
Where are regulatory proteins Tropomyosin and Troponin found?
On the thin filament (actin)
57
Explain how regulatory proteins aid muscle contraction:
When calcium ions bind to troponin, it changes shape and subsequently moves tropomyosin away from the myosin-binding site allowing myosin to bind to actin
58
Where are transverse tubules?
Run from the sarcolemma into the individual muscle fibres
59
Where are calcium ions located prior to their binding with troponin?
In the terminal cisterns of the sarcoplasmic reticulum
60
How do calcium ions get into the sarcoplasm from sarcoplasmic reticulum?
Through calcium release channels controlled by voltage
61
How do calcium ions get into the sarcoplasmic reticulum from the sarcoplasm?
Through the Calcium-ATPase pump
62
How does an action potential from a neuron trigger the contraction of a muscle?
The action potential travels down the transverse tubule and opens the voltage gated channels to release calcium into the sarcoplasm and sliding filament theory begins
63
Where does stimulation of the sarcolemma occur?
Neuromuscular junction
64
What is a neuromuscular junction?
The point where a somatic motor neuron meets a muscle fiber
65
What neurotransmitter diffuses across the synaptic cleft at the neuromuscular junction?
Acetylcholine (ACh)
66
Explain the process of synaptic transmission at the neuromuscular junction:
Acetylcholine (ACh) released from vesicle into synaptic cleft
Diffuses across and binds to ACh receptors
Muscle action potential is produced by release of sodium
ACh is broken down
67
When is Acetylcholine ACh broken down in synaptic transmission?
When there are no longer impulses coming down the axon terminal of the somatic motor neuron
68
What is a motor neuron consisted of?
A somatic motor neuron plus all of the muscle fibers it stimulates
69
When Acetylcholine (ACh) binds to the ACh receptors in the junctional fold, which ion is released to begin the muscular contraction?
Sodium / Na+
70
An action potential down one somatic neuron will stimulate how many muscle fibers?
It varies, averagely around 180 muscle fibers. It will stimulate all muscle fibers supplied by that neuron
71
How do muscle fibers reduce fatigue and allow recovery of other fibres?
Not all fibers within a muscle belly are contracted at the same time, some contract while others rest
72
What happens to suitable motor unit recruitment efficiency with age?
We learn how to recruit the fewest fibers to perform a function to allow other fibres to rest as fully as possible
73
What is wave summation?
When a second action potential occurs before the first muscle fibers have finished with contraction
74
What is unfused tetanus?
Multiple action potentials are generated, but there is relaxation of muscle fibers between so the contraction force is increased at a jagged rate
75
What is fused tetanus?
Many consecutive stimuli are sent per second, this produces a steady, sustained force of contraction
76
What is the relationship between number of action potentials and force of contraction?
More action potentials leads to a greater force of contraction
77
Explain what is meant by the Muscle Length-Tension Relationship:
The forcefulness of a contraction depends on the zone of overlap between thick and thin filaments
78
Why would a fully contracted or fully rested sarcomere contract with less force than one partially contracted?
There is less overlap between the thick and thin filaments
79
What is meant by muscle tone?
The tension in the relaxed muscle
80
How is muscle tone maintained?
A small number of fibers act in uniform (contract and relax)
81
When is muscle tone lost and the muscle is considered 'flaccid'?
When there is injury to the nervous system
82
What are the different types of muscle contraction?
Isotonic Eccentric
Isotonic Concentric
Isometric
83
What is the difference between an isotonic and isometric contraction?
```
Isotonic = Tension remains constant as muscle length decreases or increases
Isometric = Tension increases greatly without a change in muscle length
```
84
What are the different types of muscle fibers?
```
Slow oxidative (SO) fibers
Fast oxidative-glycolytic (FOG) fibers
Fast glycolytic (FG) fibers
```
85
Compare the myoglobin content of the different muscle fibers:
```
SO = many
FOG = many
FG = few
```
86
Compare the mitochondria content of the different muscle fibers:
```
SO = many
FOG = many
FG = few
```
87
Compare the colour of the different muscle fibers:
```
SO = red
FOG = red-pink
FG = white
```
88
Compare the capillaries of the different muscle fibers:
```
SO = many
FOG = many
FG = few
```
89
Compare the ATP generating capacities of the different muscle fibers:
```
SO = high, by aerobic respiration
FOG = intermediate, aerobic respiration and anaerobic glycolysis
FG = low, by anaerobic glycolysis
```
90
Compare the creatine kinase store of the different muscle fibers:
```
SO = low
FOG = intermediate
FG = high
```
91
Compare the glycogen store of the different muscle fibers:
```
SO = low
FOG = intermediate
FG = high
```
92
Compare the contraction velocity (speed) of the different muscle fibers:
```
SO = slow
FOG = fast
FG = fast
```
93
Compare the fatigue resistance of the different muscle fibers:
```
SO = high
FOG = intermediate
FG = low
```
94
Compare the rate of ATP hydrolysis of the different muscle fibers:
```
SO = slow
FOG = fast
FG = fast
```
95
How is ATP generated in slow oxidative (SO) fibers?
Aerobic respiration
96
What is the order of recruitment of the different muscle fibers?
```
first = slow oxidative (SO)
second = fast oxidative-glycolytic (FOG)
third = fast glycolytic (FG)
```
97
What is the primary function of slow oxidative (SO) fibers?
Maintaining posture and aerobic endurance
98
How is ATP generated in fast oxidative-glycolytic (FOG) fibers?
Aerobic respiration and anaerobic glycolysis
99
What is the primary function of fast oxidative-glycolytic (FOG) fibers?
Walking, sprinting
100
What is the primary function of fast glycolytic (FG) fibers?
Rapid movements of short durations
