Chapter 9 Flashcards
1
Q
Name 3 types of muscle tissue
A
- skeletal
- cardiac
- smooth
2
Q
Does the skeletal muscle tissue have the following:
- striations
- attachment sites…what are they?
- are they voluntary?
- how strong are they?
A
- yes to stripes
- attached to bones
- voluntary conscious control
- powerful
3
Q
Does the cardiac muscle tissue have the following:
- striations
- what is their function?
- are they voluntary?
A
- yes to stripes
- pumps blood
- involuntary
4
Q
Does the smooth muscle tissue have the following:
- striations
- where are they located?
- are they voluntary?
A
- no to stripes
- located in walls of hollow organs
- involuntary
5
Q
Name 4 characteristics of muscle tissue
A
- excitability - responsiveness
- contractility - able to decrease in length
- extensibility - able to stretch
- elasticity - is able to recoil to original length
6
Q
Name 4 muscle functions:
A
- movement of bones or fluid
- maintaining posture
- stabilizing joints
- heat generation
7
Q
Name the 3 connective tissue sheaths that muscles are wrapped in
A
- epimysium
- perimysium
- endomysium
8
Q
What does epimysium surround and what type of connective tissue is it?
A
surrounds the whole muscle
dense regular
9
Q
What does the permysium surround and what type of connective tissue is it?
A
surrounds each fascicle
fibrous
10
Q
What does the endomysium surround and what type of connective tissue is it?
A
surrounds each muscle fiber
areolar
11
Q
What is the origin vs the insertion?
A
origin: attachment to bone that doesn’t move (usually proximal)
insertion: attachment to bone that does move (usually distal)
12
Q
Describe how a muscle attaches directly.
A
the epimysium of muscle is fused to the periosteum of bone or perichondrium of cartilage
13
Q
Describe how a muscle attaches indirectly
A
connective tissue wrappings extend beyond the muscle as a ropelike tendon or sheet-like aponeurosis
14
Q
Which is the most common attachment method:
direct or indirect
A
indirect
15
Q
What are bundles of actin and myosin myofilaments that are enclosed in sarcoplasmic reticulum called?
A
myofibrils
16
Q
What is the membrane around the outside of the muscle cell (muscle fiber) called? and where is it located?
A
sarcolemma
located inside endomysium
17
Q
Name 4 things the muscle cell cytoplasm contains and what is their function?
A
- mitochondria - ATP production
- glycosomes - stores glycogen
- myoglobin - stores oxygen
- myofibrils - for contraction
18
Q
What is the name of the cytoplasm of the muscle cell?
A
sarcoplasm
19
Q
What has terminal cisternae that store calcium ions?
A
sarcoplasmic reticulum
20
Q
What are the channels from the sarcolemma into the cells called? and where are they located?
A
t-tubules
located at A and I band junctions
21
Q
What are a pair of terminal cisternae and a t-tubule called?
A
triad
22
Q
What volume of a cell does the myofibrils take up?
A
80%
23
Q
Describe the striations exhibited by myofibrils and what are they called?
A
A bands - dark
I bands - light
24
Q
What are the thick filaments in the myofibrils called?
A
myosin
25
What are the thin filaments in the myofibrils called?
actin
26
What are the two proteins called that act as a control switch for muscle contraction?
tropomysin
| troponin
27
Described the functions of tropomysin vs. troponin.
tropomysin blocks the binding sites on actin in relaxed muscle
troponin holds tropomysin in position
28
What is the smallest contractile unit of a muscle fiber? and where is it located?
sarcomere
| located in the region of a myofibril between two Z discs
29
What is a sarcomere composed of?
thick and thin myofilaments made of contractile proteins
30
What produces striations?
arrangement of myofilaments
31
What is the light band with Z disc in middle?
I band
32
What is the sheet of alpha actinin that anchors actin filaments?
Z disc
33
What are the dark bands that contain both myosin and actin?
A band
34
What is the lighter band in the middle of A band where there is only myosin present?
H zone
35
What is the middle of H zone; dark line containing myomesin which anchors myosin filaments?
M line
36
What protein are the elastic filaments composed of?
titin
37
Where does the elastic filaments stretch from and what is their purpose?
stretch from Z disc to M line through myosin
help sarcomere return to original length after being stretched
38
When does shortening occur in the contraction of a muscle?
only occurs when tension generated by cross bridges on the thin filaments exceeds forces opposing the shortening
39
Describe the sliding filament model of contraction
1. myosin heads bind to actin, detach and bind again to propel actin towards the M line
2. as H zone shorten and disappear, sarcomeres shorten, muscle cells shorten and whole muscle shortens
40
What are the 2 requirements for skeletal muscle contraction?
1. activation
| 2. excitation-contraction coupling
41
Describe activation
every muscle cell is in contact with a neuron
42
Describe excitation-contraction coupling
1. generation and propagation of an action potential along the sarcolemma
2. final trigger: brief rise in intracellular calcium levels
43
Where is the neuromuscular junction?
located half way along the muscle cell
44
What are the synaptic vesicles in the axon terminal called?
acetylcholine (ACH)
45
What contains the receptors for the ACH in the synaptic cleft?
sarcolemma
46
Where does the initiation of a contraction start?
neuromuscular junction
47
Describe what happens at the start of a contraction up to the release of ACH.
1. nerve is stimulated (action potential) along axon to neuromuscular junction
2. calcium channels in membrane of axon terminal open and calcium enters axon
3. calcium ions trigger synaptic vesicles to release ACH by exocytosis into synaptic cleft
48
Describe what happens during the process of muscle contraction from when ACH is released into synaptic cleft and the action potential happens at the sarcolemma
1. ACH diffuses across synaptic cleft and binds to receptors on sarcolemma of motor end plate
2. permeability of sarcolemma changes and an action potential is initiated in the muscle cell
49
Where does the action potential travel?
along the muscle cell sarcolemma
50
What is ACH terminated by?
enzyme acetylcholinesterase
51
What is prevented in the destruction of ACH?
continued fiber contraction in absence of additional stimulation
52
What 2 things are happening during the latent period?
1. time when E-C coupling events occur
| 2. time between AP initiation and the beginning of contraction
53
Describe the first 5 steps of the sliding filament model of muscle contraction (up to the binding of mysosin on actin)
1. AP is propagated along sarcomere to t-tubules and calcium release from SR
2. calcium binds to troponin
3. troponin shape change moves tropomysin away
4. ATP binds to myosin head and is hydrolyzed into ADP and Pi
5. myosin heads are cocked and form cross bridges with action
54
Described steps 6-10 of the sliding filament model of muscle contraction (from where mysosin binds to action)
6. myosin head changes shape to produce a power stroke
7. ADP and Pi released from myosin head and new ATP binds
8. myosin head detaches from actin and reattaches to new site on actin
9. ATP hydrolyzed, head changes shape and new power stroke, etc...
10. contractions continue as long as enough calcium ions are present and ATP available
55
What is the interval after a muscle contraction before another one can begin where the membrane needs to be repolarized before it can be stimulated again?
refractory period
56
Describe what happens at low intracellular calcium levels
1. tropomysin blocks the active sites on actin
2. myosin heads cannot attach to actin
3. muscle fiber relaxes
4. calcium levels are kept low in sarcoplasm
57
What proteins control the level of calcium in the sarcoplasm?
1. calsequestrin
| 2. calmodulin
58
Describe what happens at higher intracellular
1. calcium binds to troponin
2. troponin changes shape and moves tropomysin away from active sites
3. events of the cross bridge cycle occur
4. when nerve stimulation stops calcium ions are pumped back into SR and contraction ends
59
Describe the 3 roles played by calcium in contraction
1. action potential from neuron triggers calcium gates at axon terminal to open which then triggers release of ACH into cleft
2. action potential in tubule and terminal cisternae triggers release of calcium from SR and removes inhibition by tropomysin
3. when calcium binds to calmodulin it activates kinases - it then converts glycogen to glucose which is fuel for ATP production
60
What is it called when there is no shortening of a muscle. The muscle tension increases but does not exceed the load.
isometric contraction
61
What is is called when the muscle shortens. Muscle tension exceeds the load.
isotonic contraction
62
What is the most common isotonic contraction? and what does it do?
concentric isotonic
| muscle shortens as it contracts
63
What type of isotonic contraction happens when the muscle is stretched by another muscle? What does it do and what is it important in maintaining?
eccentric isotonic
muscle contracts as it lengthens
maintains balance
64
What is a motor neuron and all muscle fibers it supplies?
motor unit
65
What do small motor units control?
muscles controlling fine movements (eg. fingers & eyes)
66
What do large motor units control?
large weight bearing muscles (eg. thighs & hips)
67
What is it called when all motor units do not fire at the same time? and why is this?
asynchronous
| prevents fatigue
68
Name the 3 phases of a twitch and what happens during each phase
1. latent - excitation contraction coupling
2. contraction - cross bridge formation, tension increases
3. relaxation - calcium ions reenter SR, tension declines to zero
69
What is a muscle twitch?
response of a muscle to a single brief threshold stimulus
70
What is a graded muscle response?
variation in the degree of muscle contraction
71
What are muscle responses graded by?
1. changing in the frequency of the stimulus
| 2. changing in the strength of the stimulus
72
What does a single stimulus produce?
a single twitch
73
What is it called when the muscle does not have time to relax completely between stimuli?
wave summation
74
What is it called when there is a further increase in frequency?
unfused (incomplete) tetanus
75
What is it called when stimuli are given quickly enough?
fused (complete) tetanus
76
What is the minimum stimulus strength that causes the first visible contraction?
threshold stimulus
77
What is the stimulus strength at which maximum contraction occurs?
maximum stimulus
78
What happens during recruitment?
stimulus strength increases
| increasing number of motor units contract
79
Describe muscle tone
constant, slightly contracted state of muscles
| even when resting
80
What is the function of muscle tone?
keeps muscles firm, healthy and ready to respond
81
What is the only source of energy used for muscle contraction?
ATP energy
82
What is ATP generated by?
phosphorylation of ADP by creatine phosphate
creatine PO4 -> PO4 + creatine
ADP + PO4 -> ATP
83
What are two components of muscle metabolism?
1. anaerobic pathway
| 2. aerobic respiration
84
What is the physiological inability to contract and respond to stimulus?
muscle fatigue
85
When does muscle fatigue occur?
1. ionic imbalance
2. calcium depletion
3. lack of ATP
86
What is caused when there is a total lack of ATP, during states of continuous contraction?
contractures or cramps
87
What is needed after excercise for replenishment of:
1. oxygen reserves and myoglobin
2. glycogen stores
3. ATP and CP reserves
extra oxygen
88
How much of the energy produced during muscle activity is given off as heat?
60%
89
What 4 factors affect the force of muscle contraction?
1. number of muscle fibers stimulated (recruitment)
2. size of the fibers-hypertrophy of cells increase strength
3. frequency of stimulation
4. length-tension relationship-muscles contract most strongly when muscle fibers are 80-120% of their normal resting length
90
Muscle fiber are classified according to two characteristics. What are they?
1. speed of contraction
| 2. metabolic pathways
91
Which type of fibers use aerobic pathways?
oxidative fibers
92
Which type of fibers use anaerobic glycolysis?
glycolytic fibers
93
What is influenced by muscle fiber type, load and recruitment?
velocity and duration of contraction (how fast and how long it contracts)
94
Name the 3 types of of muscle fibers?
1. slow oxidative fiber
2. fast oxidative fiber
3. fast glycolytic fiber
95
At what rate does slow oxidative fibers work and what type of excercise would they be good for?
slow contracting & fatiguing
| good for endurance - marathons
96
At what rate does fast oxidative fibers work and what type of excercise are they good for?
intermediate
| good for walking, sprinting
97
At what rate does fast glycolytic fiber work and what type of excercise are they good for?
fast contracting & fatiguing
| good for short term, high energy activites
98
Describe influence of load
increased load -> increased latent period, decreased contraction, and decreased duration of contraction
99
Describe influence of recruitment
increased recruitment -> faster contraction and increase in duration of contraction
100
What type of exercise leads to increased muscle capillaries, number of mitochondria, myoglobin synthesis?
aerobic exercise
101
What will aerobic exercise convert?
fast glycolytic fibers into fast oxidative fibers
102
What does aerobic exercise result in?
greater endurance, strength and resistance to fatigue
103
What type of exercise increases mitochondria, myofilaments, glycogen stores and connective tissue?
resistance exercise (typically anaerobic)
104
What is it called when muscles weaken and degenerate if not used regularly?
disuse atrophy
105
What shape is smooth muscle?
spindle shaped
106
What does resistance exercise result in?
muscle hypertrophy due to increased fiber size
107
What type of connective tissue does smooth muscle have?
endomysium only
108
Where is calcium stored in smooth muscle?
caveolae
109
What is caveolae?
indentations in the plasma membrane
110
What does smooth muscle not have in comparison to skeletal muscle?
does not have striations, sarcomeres, myofibrils and t-tubules
111
Where do the nerve fibers innervate smooth muscle?
diffuse junctions
112
What do the varicosities (bulbous swellings) of nerve fibers in smooth muscle release?
neurotransmitters
113
How does smooth muscle contract?
like a corkscrew
114
When the smooth muscle contracts cells are electrically coupled by what?
gap junctions
115
Describe stress-relaxation response.
responds to stretch briefly, then adapts to new length (ie. stomach filling up with food)
