Muscle Tissue Flashcards
(129 cards)
1
Q
How does muscle tissue contribute to homeostasis?
A
produce body movements, moving substances through the body, and produce heat to maintain body temp
2
Q
What is authorhythmicity?
A
built in rhythm of the cardiac and some smooth muscle
3
Q
No Mr. Rose
A
.
4
Q
4 Special properties of muscle tissue
A
electrical excitability, contractility, extensibility, elasticity
5
Q
What is electrical excitability?
A
ability to respond to certain stimuli by producing electrical signals called action potentials
6
Q
Purpose and composition of hypodermis
A
protects muscle, composed of areolar and adipose tissue
7
Q
Fascia
A
dense sheet of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other organs; holds muscles with similar function together
8
Q
3 Layers of connective tissue that extend from fascia to protect and strengthen skeletal muscle
A
epimysium, perimysium, endomysium
9
Q
Epimysium
A
outer layer, encircles entire muscle, consists of dense irregular connective tissue
10
Q
Perimysium
A
dense irregular connective tissue, surrounds groups of 10 to 100 muscle fibers- separtes them into fascicles
11
Q
Endomysium
A
penetrates the interior of each fascicle and separates individual muscle fibers from one another; mostly reticular fibers
12
Q
Aponeurosis
A
connective tissue elements extend as a broad, flat sheet
13
Q
What neuron stimulates skeletal muscle? What provides blood supply?
A
somatic motor neuron (axon branches and connects to muscle), capillaries
14
Q
Sarcolemma
A
plasma membrane of a muscle cell
15
Q
Transverse (T) tubules
A
invaginations of the sarcolemma, tunnel in from the surface toward the center of each muscle fiber, filled with interstitial fluid
16
Q
What is the sarcoplasm and what does it contain?
A
cytoplasm of muscle fiber; much glycogen, myoglobin
17
Q
What is myoglobin?
A
protein that binds O2 that diffuses into muscle from ISF, releases O2 when it is needed by mitochondria
18
Q
Myofibrils
A
contractile organelles of skeletal muscle; stuffed inside sarcoplasm
19
Q
Sarcoplasmic reticulum
A
fluid-filled system of membranous sacs that encircle each myofibril
20
Q
Terminal cisterns
A
dilated end sacs of the sarcoplasmic reticulum; butt afaints the T tubule from both sides; releases calcium ions in muscle contractions
21
Q
Triad
A
a T tubule and the 2 terminal cisterns on either side of it
22
Q
2 Myofilaments of myofibrils
A
thin and thick filaments
23
Q
Thin filaments
A
composed of the protein actin
24
Q
Thick filaments
A
composed of the protein myosin
25
Sarcomere
basic functional unit of a myofibril, extend from one Z disc to the next
26
Z discs
narrow, plate-shaped region of dense protein that separate one sarcomere from the next
27
A band
darker middle part of the sarcomere, extends the entire length of the thick filaments
28
I band
lighter, less dense area that contains the rest of the thin filaments (no thick)
29
H zone
center of each A band, contains only thick filaments
30
M line
supporting proteins that hold the thick filaments together at the center of the H zone
31
What are the two contractile proteins in muscle fibers?
actin and myosin
32
Myosin
make up thick filaments, motor protein (pulls on structures to achieve movement); myosin tail points toward the M line and the 2 myosin heads have binding sites
33
What are the binding sites on myosin heads?
actin-binding site and ATP-binding site
34
How many thin filaments surround each thick filament?
6
35
Actin
make up thin filaments, each molecule has a myosin-binding site
36
Tropomyosin
regulatory protein in thin filaments, covers myosin binding site in relaxed muscle
37
Troponin
regulatory protein in thin filaments, moves tropomyosin out of the way
38
List the structural proteins of myofibrils
titin, α-actinin, myomesin, nebulin, dystrophin
39
What is the 3rd most plentiful protein in skeletal muscle?
titin
40
Titin
connects a Z disc to the M line, helps stabilize the position of the thick filament; very elastic- helps sarcomere return to its resting position
41
Level of organization of skeletal muscle
skeletal muscle -> fascicle -> muscle fiber -> myofibril -> filaments
42
Sliding filament mechanism
myosin heads pull the thin filaments toward the M line; the I band and H zone narrow and then disappear when muscle is maximally contracted
43
What initiates the contraction cycle?
release of calcium ions from the sarcoplasmic reticulum which binds to troponin which moves tropomyosin out of the way
44
4 Steps in the contraction cycle
(1) ATP hydrolysis (2) attachement of myosin and actin (3) power stroke (4) detachement of myosin and actin
45
What is excitation-contraction coupling?
sequence of events that links excitation (muscle action potential) to contraction (sliding of the filaments)
46
Process of excitation-contraction coupling
AP enters T tubules and opens voltage gated calcium channels, once voltage channels are open calcium release channels release calcium from SR into sarcoplasm, calcium binds to troponin which moves tropomyosin; calcium-ATPase pumps pump calcium back into SR
47
Calsequestrin
protein inside SR that bind calcium and allow even more calcium to be stored in the SR
48
T/F calcium is 10 000 times higher in the sarcoplasm of a relaxed muscle than in the SR
False. It's 10 000 times higher in the SR than the sarcoplasm
49
What is the length-tension relationship in skeletal muscles?
the forcefulness of muscle contraction depends on the length of the sarcomeres within a muscle before contraction begins
50
What does the neuromuscular junction consist of?
synaptic end bulbs, synaptic cleft, motor end plate of the muscle fiber
51
What neuron stimulates skeletal muscle fibers?
somatic motor neurons
52
Synapse
a region where communication occurs between 2 neurons or between a neuron and target cell
53
Synaptic cleft
gap in synapse that separates 2 cells
54
What is the axon terminal?
end of the motor neuron at the NMJ
55
Synaptic end bulbs
clusters of the end of the axon terminal
56
Synaptic vesicles
membrane enclosed sacs suspended in the cytosol within each synaptic end bulb, contain acetylcholine
57
Motor end plate
region of the sarcolemma opposite the synaptic end bulbs
58
ACh receptors
integral transmembrane proteins on motor end plate, ligand-gated ion channels
59
Junctional folds
deep groves in the motor end plate that provide a large surface area for ACh receptors
60
4 Steps in muscle action potential
(1) release of ACh (2) activation of ACh receptors (3) production of muscle AP (4) termination of ACh activity
61
3 Ways muscle fibers produce ATP
creatine phosphate, anaerobic glycolysis, aerobic respiration
62
Which form of ATP production is unique to muscle fibers?
creatine phosphate
63
What is creatine?
small, amino-acid like molecule that is synthesized in the liver, kidneys, and pancreas and then transported to muscle fibers
64
T/F Creatine phosphate is the first source of energy when muscle contractions begin
True
65
How does creatine phosphate work to produce ATP?
creatine phosphate is plentiful in the sarcoplasm; when muscle contractions begin, creatine kinase catalyzes the transfer of a phosphate group from creatine phosphate back to ADPx; occurs very rapidly
66
How long do the stores of creatine phosphate and ATP provide energy for muscles to contract?
15 seconds
67
Where does glycolysis occur and how much net ATP does it produce?
cytosol, 2 ATP
68
What is are the products of anaerobic glycolysis?
2 lactic acid and 2 ATP
69
How long does anearobic glycolysis provide energy for muscle contraction?
2 minutes
70
What does that catabolism of glucose produce (glycolysis)?
2 pyruvic acid
71
Aerobic respiration
When sufficient oxygen is present, the pyruvic acid formed by glycolysis enters the mitochondria where is undergoes aerobic respiration
72
What to reaction cycles/chains make up aerobic respiration?
the Krebs cycle and electron transport chain
73
How much ATP is produced from the catabolism of 1 glucose via aerobic respiration?
30-32 ATP
74
What are the 2 sources of oxygen for muscle tissue?
oxygen that diffuses into muscle fibers from the blood and oxygen released by myoglobin within muscle fibers
75
Muscle fatigue
the inability of a muscle to maintain force of contraction after prolonged activity
76
Mechanisms that cause muscle fatigue
inadequate calcium in sarcoplasm, depletion of creatine phosphate, insufficient oxygen, depletion of glycogen and other nutrients, buildup of lactic acid and ADP, failure of AP's to release enough ACh
77
How does extra oxygen restore metabolic conditions to the resting level?
convert lactic acid back into glycogen stores in the liver, resynthesize creatine phosphate and ATP in muscle fibers, replace the oxygen removed from myoglobin
78
Oxygen debt
added oxygen, over and above the resting oxygen consumption, that is taken into the body after exercise
79
Recovery oxygen uptakes
better term than oxygen debt for the elevated use oxygen after exercise
80
Motor unit
consists of a somatic motor neuron plus all of the skeletal muscle fibers it stimulates
81
T/F All the muscle fibers in one motor unit contract in unison
True
82
What does the total strength of a contraction depend on?
size of the motor units and the number that are activated at a given time
83
Twitch contraction
brief contraction of all muscle fibers in a motor unit in response to a single AP in its motor neuron
84
Latent period
time between stimulus application and muscle contraction; muscle AP sweeps over sarcolemma and calcium is released from SR; 2 msec
85
Contraction period
calcium binds to troponin, myosin-binding sites on actin are exposed, and cross-bridges form; 10-100 msec
86
Relaxation period
calcium actively transported back into SR, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle decreases; 10-100 msec
87
Refractory period
period of lost excitability in which another contraction cannot occur
88
Wave summation
stimuli arriving at different times causes larger contractions
89
Unfused (incomplete) tetanus
sustained wavering contraction, occurs when a skeletal muscle is stimulated 20-30 timers per sec and the muscle can only partially relax
90
Fused (complete) tetanus
sustained contraction in which individual twitches cannot be detected; occurs when a skeletal muscle is stimulated 80-100+ times per sec and the muscle does not relax
91
When does wave summation and tetanus occur?
when additional calcium is released from the SR by subsequent stimuli while calcium is still high in the sarcoplasm from the first stimuli
92
Motor unit recruitment
process in which the number of active motor units increases
93
T/F motor unit recruitment contributes to smooth movements
true
94
T/F large motor units = smoother movements
false. Smaller = smoother
95
Muscle tone
small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units
96
Define flaccid and when does it occur
a state of limpness in which muscle tone is lost; when the motor neurons serving a skeletal muscle are damaged or cut
97
What do the motor units do to maintain muscle tone?
alternate being active and inactive in a shifting pattern
98
Isotonic contraction
the tension (force of contraction) developed in the muscle remains almost constant while the muscle changes length
99
What are isotonic contractions used for?
body movements and moving objects
100
2 Types of isotonic contractions
concentric and eccentric
101
Concentric isotonic reactions
tension generated is enough to overcome the resistance of the object being moved, the muscle shortens and produces movement eg. picking up a book from the table
102
Eccentric isotonic contraction
tension exerted by the myosin cross-bridge resists movement of a load; the length of the muscle increases during a contraction eg. lowering the book back onto the table
103
Isometric contraction
tension generated is not enough to exceed the resistance of the object being moved; the muscle does not change lengths eg. holding a book out in front of you
104
What are isometric contractions used for?
stabilize joints while others are moved
105
Red muscle fibers
skeletal muscle fibers that have a high myoglobin content, appear darker, contain more mitochondria, and are supplied by more blood capillaries
106
White muscle fibers
skeletal muscle fibers that have a low content of myoglobin and appear lighter
107
Slow oxidative (SO) fibers
contain large amounts of myoglobin and many blood capillaries, generate ATP mainly by aerobic respiration, ATPase hydrolyzes ATP slowly, contraction cycle is slow, very resistive to fatigue; for maintaining posture and aerobic endurance (marathon)
108
Fast oxidative-glycolytic (FOG) fibers
largest fibers, contain large amounts of myoglbin and capillaries, generate lots of ATP via aerobic respiration, high intracellular glyocogen level so also generate ATP by anaerobic glycolysis, ATPase hydrolyzes ATP 3-5 times faster than SO; for walking or sprinting
109
Fast glycolytic (FG) fibers
low myoglobin, few capillaries, few mitochondria; contain large amounts of glycogen and generate ATP mainly by glycolysis; contract strongly and quickly; for intense anaerobic movements for short duration eg. weight lifting, throwing ball
110
T/F About 1/2 the fibers in skeletal muscle are FOG fibers
false. SO fibers
111
T/F a motor unit contains a mixture of skeletal muscle fibers
false. All the same type of fiber
112
Intercalated discs
irregular transverse thickenings of the sarcolemma that connect the ends of cardiac muscle fibers to one another
113
What time of cell junctions are in the intercalated discs?
desmosomes (hold fibers together) and gap junctions
114
Which muscle tissue layer does cardiac muscle lack?
epimysium
115
T/F a cardiac muscle contraction lasts 10 to 15 times longer than a skeletal muscle contraction
true
116
Visceral (single-unit) smooth muscle tissue
contract in unison as a single unit, autorhythmic, connected via gap junctions; found in the skin, walls of small arteries, hollow organs (stomach, intestines, uterus, bladder)
117
Multi-unit smooth muscle tissue
consists of individual fibers, each with its own motor neuron terminals and with few gap junctions; stimulation of one fiber results in contraction of only that fiber; found in the walls of large arteries, airways, arrector pilli muscles, iris, and lens
118
What are caveolae?
small pouchlike invaginations of the plasma membrane in smooth muscle that contain extracellular calcium to be used in contractions
119
Dense bodies
thin filaments of smooth muscle attach to same, some dispersed throughout sarcoplasm, others are attache to sarcolemma; similar to Z discs
120
T/F Smooth muscle lacks T tubules
true
121
How does a smooth muscle contract?
thick and thin filaments generate tension thats transmitted to intermediate filaments, intermediate filaments pull on dense bodies attached to sarcolemma causing lengthwise shortening of the muscle fiber; as muscle contracts it rotates as a corkscrew turns
122
Differences of smooth muscle
contracts slower but longer, can shorten and stretch to a greater extent, smaller reservoir of calcium
123
Calmodulin
regulatory protein in smooth muscle that binds to calcium in the sarcoplasm; activates an enzyme called myosin light chain kinase which adds a phosphate group to the myosin head so it can contract
124
Smooth muscle tone
state of continued partial contraction caused by the prolonged presence of calcium in the cytosol
125
What initiates contraction/relaxation of smooth muscle?
autonomic nervous system, stretching, hormones, changes in pH, oxygen and carbon dioxide levels, temperature, ion concentrations
126
Stress-relaxation response
phenomenon in smooth muscle when a smooth muscle fiber is stretched it initially contracts and then the tension decreases
127
Hypertrophy
enlargement of existing cells
128
Hyperplasia
increase in the number of fibers
129
T/F Skeletal muscle fibers cannon undergo cellular division
true
