Muscle Tissue & Physiology Flashcards
(97 cards)
1
Q
What are the 3 types of muscle tissue?
A
Skeletal muscle.
Cardiac muscle.
Smooth muscle.
2
Q
A muscle bundle is also known as a muscle ________.
A
fascicle.
3
Q
A single skeletal muscle cell is also known as a muscle ______.
A
fibre.
4
Q
Are skeletal muscle cells mononucleated or multinucleated?
A
Multinucleated.
5
Q
Describe the shape of a muscle fibre.
A
Long/elongated, cylindrically shaped.
6
Q
What is a muscle fibre made out of?
A
Myofibrils.
7
Q
What is each myofibril made out of?
A
Myofilaments.
8
Q
What are the two different types of myofilaments?
A
Thick filaments & thin filaments.
9
Q
Thick filaments are also known as _______.
A
myosin.
10
Q
Myosin is ____ in colour.
A
dark.
11
Q
Thick filaments make up the _ band.
A
A.
12
Q
Thin filaments are also known as _____.
A
actin.
13
Q
Actin is _______ in colour.
A
lighter.
14
Q
Thin filaments make up the _ band.
A
I.
15
Q
What is the functional unit of a muscle fibre?
A
Sarcomere.
16
Q
What is each sarcomere bordered by?
A
Z-lines.
17
Q
What do Z lines do?
A
Connect thin filaments of adjoining sarcomeres.
18
Q
What is the A-band made out of?
A
Thick filaments (myosin) + portions of thin filaments (actin) of adjoining sarcomeres.
19
Q
What is the H-zone in a sarcomere?
A
Only thick filaments (myosin) in these zones
20
Q
What is the M-line in a sarcomere?
A
A line that extends vertically down the middle of the A-band within the centre of the H-zone (think “M for Middle”).
21
Q
What is the I-band in a sarcomere?
A
It contains the remaining portion of thin filaments (actin) that do not project into the A-band.
22
Q
What is a sarcolemma?
A
Plasma membrane of a muscle.
23
Q
The T-tubules are connected to the ___________.
A
sarcolemma.
24
Q
T-tubules run ______________ from the surface of the _________ into central portions of the muscle fibre.
A
perpendicularly, sarcolemma.
25
What is the function of T-tubules?
Quick spread of action potentials.
26
The __________ is essentially the cytoplasm of muscle cells.
sarcoplasm.
27
The ____________ _________ is a modified ER found in muscle cells that surround the __________.
sarcoplasmic reticulum, myofibrils.
28
The ends of SR segments form _______ ____.
lateral sacs.
29
What is the function of lateral sacs?
Calcium storage.
30
What are the 3 types of dense connective tissue muscle coverings?
Epimysium, perimysium & endomysium.
31
What is the epimysium?
The outermost muscle membrane that surrounds the entire muscle.
32
What is the perimysium?
A membrane that wraps around each muscle fascicle.
33
What is the endomysium?
The innermost muscle membrane that surrounds each muscle fibre.
34
What is titin?
A giant, highly elastic protein (largest protein in the body).
35
What are the 2 main functions of titin?
1. Helps stabilize the position of the thick filaments in relation to thin filaments.
2. Greatly augments muscle's elasticity by acting like a spring.
36
Titin extends in both directions from the _ line to _ lines at opposite ends of the sarcomere.
M, Z.
37
Myosin has _ identical subunits shaped like a ____ ____.
2, golf club.
38
What the 2 components of a myosin subunit?
Tails & globular heads.
39
Myosin heads form _____ _______ between thick & thin filaments.
cross bridges.
40
What are the 2 important sites for muscle contraction on the cross bridge?
Actin binding site & ATPase site.
41
What are the 4 components of thin filaments?
Filamentous actin (F-actin), nebulin, tropomyosin & troponin.
42
F-actin is a twisted strand, composed of _ rows of globular _-_____ molecules.
2, G-actin.
43
Active sites on _-_____ bind to myosin.
G-actin.
44
What is the function of nebulin?
Holds F-actin strand.
45
Tropomyosin & troponin are ________ proteins.
regulatory.
46
Tropomyosin looks like a ______.
Thread.
47
Troponin is composed of _ units. What does each one bind to?
3.
One binds to tropomyosin.
One binds to actin.
One binds with Ca2+.
48
Muscle contraction is powered by ___.
ATP.
49
What are the 5 steps in muscle contraction?
1. Activated cross bridge bends towards the centre of thick filament
2. SR releases Ca2+ into the sarcoplasm.
3. Myosin head binds to an actin molecule.
4. Myosin head swivels towards the centre of the sarcomere, pulling thin filament inward.
5. ATP binds to myosin head & detaches it from actin.
50
An ________ in Ca2+ starts the filament sliding.
increase.
51
A ________ in Ca2+ turns off the sliding process.
decrease.
52
During muscle contraction, ____ filaments on each side of the sarcomere slide inwards (towards centre of the _ band) while _____ filaments are stationary.
thin, A, thick.
53
As thin filaments slide inwards, they pull _ lines closer together. This cases the _ band to get shorter, so the _ zone gets shorter too.
Z, I, H.
54
The _ line and _ band of the sarcomere are unchanged in length during contraction.
M, A.
55
The stronger the power stroke, the ______ the Z lines will be together and the ______ the sarcomere.
closer, shorter.
56
_________ of ATP transfers energy to the myosin head to reorient it.
Hydrolysis.
57
What are the 5 steps to initiate muscle contractions?
1. ACh released & binds to ACh receptors on sarcolemma.
2. Action potential generates & reaches T-tubule.
3. SR releases Ca2+.
4. Active sites exposed (Ca2+ binds to troponin) & cross bridges form by binding to active sites.
5. Contraction begins, powered by ATP.
58
What are the 5 steps that end muscle contractions?
1. ACh is broken down by acetylcholinesterase, ending action potential generation.
2. SR reabsorbs Ca2+, decreasing Ca2+ concentration in the cytosol.
3. Active sites are covered by tropomyosin, stopping cross-bridge formation.
4. Contraction ends (no cross-bridges).
5. Muscle relaxation occurs (return to resting length).
59
Rigor occurs between the ____ _______ and __________.
power stroke, attachment.
60
Why does rigor mortis occur?
When we die, our body cells aren't producing anymore ATP so our muscles can't relax once they've entered rigor. Thus, the cross bridge cycle gets stuck, causing rigid contractions.
61
What is a motor unit composed of?
1 motor neuron and the muscle fibres it innervates.
62
Muscles that produce precise, delicate movements often contain ______ fibres per motor unit.
fewer.
63
Muscles performing powerful, coarsely controlled movement have ____ fibres per motor unit.
more.
64
Some motor units of muscle contract continuously, producing a resting tension called _______ ____.
muscle tone.
65
___________ recruitment of motor units helps to delay & prevent _______.
Asynchronous, fatigue.
66
What are the 4 factors that influence the extent to which muscle tension can be developed?
Frequency of stimulation.
Length of fibre @ onset of contraction.
Extent of fatigue.
Thickness of fibre.
67
Where is tension produced?
Internally, within sarcomeres.
68
Tension must be transmitted to ____ via __________ tissue & tendons before movement can occur.
bone, connective tissue.
69
Muscle is usually attached to at least _ different bones across a joint. What is each one called?
2, origin & insertion.
70
Which end of the muscle is attached to the more stationary part of the skeleton?
The origin.
71
Which end of the muscle is attached to the part of the skeleton that moves?
The insertion.
72
Treppe produces a series of contractions with __________ tension.
increasing.
73
Where is treppe usually seen?
Cardiac muscle.
74
When do twitch summations occur?
Muscle fibre is restimulated before it can completely relax, so the second twitch is added onto the first resulting in summation of tension.
75
When does tetanus occur?
When muscle fibre is stimulated so rapidly that it doesn't have a chance to relax at all between stimuli.
76
What are the 2 types of tetanus and how are they different?
1. Incomplete: produces near-maximum tension.
2. Complete: muscle in continuous, sustained contraction with no relaxation phase at all. Produces maximum tension and all potential cross-bridges form.
77
What is optimal muscle length?
The point at which maximum tension can be developed.
78
Define isotonic contraction.
Muscle tone remains constant while muscle length changes.
79
Define isometric contraction.
Muscle length doesn't change while tension developes (changes) at this constant length.
80
______ provides energy for the power stroke of the cross bridge by breaking down ATP.
ATP.
81
How does the cross-bridge detach from actin at the end of the powerstroke?
A fresh ATP molecule binds to myosin.
82
How is ATP related to the transport of Ca2+ into the SR during relaxation?
The Ca2+ must be actively transported back into the SR using energy derived from the breakdown of ATP
83
What are the 2 different types of muscle fatigue?
Central & peripheral fatigue.
84
When does central fatigue occur?
When the CNS no longer activates motor neurons supplying muscles.
85
What are some potential causes of peripheral muscle fatigue?
```
Lactic acid accumulation.
Glucose depletion.
Decreased levels of ACh.
Lack of O2.
Too much K+.
```
86
What are the main differences between fast & slow fibres?
Fast fibres have a quick onset but cannot perform at consistent levels for long periods of time.
Slow fibres take a longer time for onset but can sustain contractions for long periods of time.
87
What is hypertrophy?
Increase in mass or girth of muscles.
88
What is one stimulus that can induce muscle hypertrophy?
Resistance exercise (like weightlifting).
89
What is muscle atrophy?
Loss of muscle mass.
90
Describe the 2 types of muscle atrophy.
Disuse atrophy: skeletal muscles not physically stressed on a regular basis.
Denervation atrophy: nerve supply to a muscle is lost.
91
Compare the nuclei of skeletal, cardiac & smooth muscle tissue.
Skeletal: multinucleated, located near sarcolemma.
Cardiac: generally mononucleated but can be dinucleated, centrally located in the cell.
Smooth: mononucleated, centrally located in the cell.
92
Compare the filament organization of skeletal, cardiac & smooth muscle.
Skeletal & cardiac: in sarcomeres, along myofibrils (creates striated appearance).
Smooth: scattered throughout sarcoplasm (no organization = non-striated appearance.
93
Compare the control mechanisms (automacity or neural stimulation) for skeletal, cardiac & smooth muscle.
Skeletal: neural stimulation required at each neuromuscular junction.
Cardiac: autorhythmic (pacemaker cells), little neural stimulation involved.
Single-unit (myogenic) smooth: autorhythmicity (pacesetter cells).
Multi-unit (neurogenic) smooth: neural or hormonal stimulation.
94
Compare the Ca2+ source for skeletal, cardiac & smooth muscle.
Skeletal: released from SR.
| Cardiac & smooth: blood, ECF & released from SR (lack of a large SR).
95
Compare the mechanisms for Ca2+ regulation of skeletal, cardiac & smooth muscle.
Skeletal & cardiac: troponin on thin filaments.
| Smooth: calmodulin on myosin heads.
96
Compare the contraction mechanisms for skeletal, cardiac & smooth muscle.
Skeletal: rapid onset & rapid fatigue; may be tetanized.
Cardiac: slower onset; CANNOT be tetanized; resistant to fatigue.
Smooth: slow onset; may be tetanized; resistant to fatigue.
97
Compare the energy sources for skeletal, cardiac & smooth muscle.
Skeletal: aerobic during low-moderate activity; anaerobic during maximum activity (glycolysis).
Cardiac: aerobic with lipid or carbohydrate substrates.
Smooth: primarily aerobic.
