Lecture Exam 3 Review Flashcards
1
Q
What are the functions of muscle tissue?
A
produce movement, stabilize body position/posture, regulate organ volume, generate heat, propel fluids and food matter through various body systems
2
Q
What is the scientific study of muscles?
A
myology
3
Q
Describe skeletal muscle tissue
A
moves bones of the skeleton, striated, mainly voluntary, controlled by somatic neurons
4
Q
Describe cardiac muscle tissue
A
makes up most of the heart wall, striated, involuntary, autorhythmic, regulated by autonomic neurons and hormones
5
Q
Describe smooth muscle tissue
A
located in the walls of hollow internal structures such as blood vessels, airways, and most organs in the abdominopelvic cavity, and in the skin attached to hair follicles, nonstriated, involuntary, autorhythmic in some digestive muscles, regulated by autonomic neurons and hormones
6
Q
What are the properties of muscle tissue?
A
electrical excitability, contractility, extensibility, elasticity
7
Q
What is electrical excitability?
A
the ability to respond to certain stimuli by producing electrical signals called action potentials
8
Q
What is contractility?
A
the ability of muscular tissue to contract forcefully when stimulated by a nerve impulse
9
Q
What is extensibility?
A
the ability of muscular tissue to stretch, within limits, without being damaged
10
Q
What is elasticity?
A
the ability of muscular tissue to return to its original length and shape after contraction or extension
11
Q
What are muscle cells called?
A
myocytes/muscle fibers
12
Q
How does subcutaneous tissue relate to the muscles?
A
it separates muscle from skin, is composed of areolar connective tissue and adipose tissue, provides a pathway for nerves, blood vessels, lymphatic vessels to enter and exit muscles
13
Q
What is fascia?
A
a dense sheet or broad band of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other organs of the body
14
Q
What are the functions of fascia?
A
holds muscles with similar functions together, allows free movement; carries nerves, blood vessels, and lymphatic vessels; fills spaces between muscles
15
Q
What are the 3 protective layers of connective tissues in muscles?
A
epimysium, perimysium, endomysium
16
Q
What is the epimysium?
A
outer layer, encircling the entire muscle, dense irregular connective tissue
17
Q
What is the perimysium?
A
dense irregular connective tissue, surrounds groups of 10-100+ muscle fibers separating them into fascicles
18
Q
What is the endomysium?
A
penetrates the interior of each muscle fascicle and separates individual muscle fibers from one another; mostly reticular fibers
19
Q
What is a tendon?
A
attaches a muscle to the periosteum of a bone
20
Q
What is an aponeurosis?
A
when connective tissue elements extend as a broad, flat sheet
21
Q
What is sarcolemma?
A
plasma membrane of a muscle fiber
22
Q
What are T tubules?
A
tiny tube-shaped invaginations of the sarcolemma that tunnel in from the surface toward the center of each muscle fiber, filled with interstitial fluid
23
Q
What is sarcoplasm?
A
the cytoplasm of a muscle fiber, includes a lot of glycogen
24
Q
What is glycogen?
A
a large molecule composed of many glucose molecules that can be used for ATP synthesis
25
What is myoglobin?
inside the sarcoplasm, only in muscles, binds oxygen molecules that diffuse into muscle fibers from interstitial fluid, releases oxygen when it is needed by the mitochondria for ATP production
26
What are myofibrils?
contractile organelles of skeletal muscle
27
What is the sarcoplasmic reticulum?
fluid-filled system of membranous sacs that encircle each myofibril
28
What are terminal cisterns?
dilated end sacs of SR that butt against the T tubule from both sides forming a triad; release of Ca2+ from the terminal cisterns triggers a muscle contraction
29
What are filaments?
smaller protein structures within myofibrils
30
What are thin filaments composed of?
actin
31
What are thick filaments composed of?
myosin
32
What are sarcomeres?
basic functional units of a myofibril
33
What 3 types of proteins form myofibrils?
contractile, regulatory, structural
34
What do contractile proteins do?
generate force during contraction; myosin and actin
35
What do regulatory proteins do?
help switch the contraction process on and off
36
What do structural proteins do?
keep the thick and thin filaments in the proper alignment, give the myofibrils elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix
37
What do motor proteins do?
pull various cellular structures to achieve movement by converting the chemical energy in ATP to the mechanical energy of motion
38
What 2 binding sites are located on myosin heads?
actin and ATP
39
What is ATPase?
an enzyme that hydrolyzes ATP to generate energy for muscle contraction
40
What are Z discs?
narrow, plate-shaped regions of dense material that separate one sarcomere from the next
41
What is the A band?
dark, middle part of sarcomere that extends the entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments
42
What is the I band?
lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments; a Z disc passes through center of each I band
43
What is the H band?
narrow region in center of each A band that contains thick filaments but no thin filaments
44
What is the M line?
region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere
45
What is actin?
main component of thin filaments, on each actin molecule is a myosin-binding site where a myosin head can attach
46
What are the two regulatory proteins in muscles?
troponin and tropomyosin
47
What is tropomyosin?
a component of thin filament; when skeletal muscle fiber is relaxed, tropomyosin covers myosin-binding sites on actin molecules, thereby preventing myosin from binding to actin
48
What is troponin?
component of thin filament; when calcium ions binds to troponin, it changes shape, this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds on actin
49
What is titin?
a structural protein that connects Z disc to M line of sarcomere, thereby helping stabilize thick filament position; it can stretch and then spring back unharmed, and thus accounts for much of the elasticity and extensibility of myofibrils
50
What is α-actinin?
structural protein of Z discs that attaches to actin molecules of thin filaments and to titin molecules
51
What is myomesin?
structural protein that forms M line of sarcomere; binds to titin molecules and connects adjacent thick filaments to one another
52
What is nebulin?
structural protein that wraps around entire length of each thin filament; helps anchor thin filaments to Z discs and regulates length of thin filaments during development
53
What is dystrophin?
structural protein that links thin filaments of sarcomere to integral membrane proteins in sarcolemma, which are attached in turn to proteins in connective tissue matrix that surrounds muscle fibers; thought to help reinforce sarcolemma and help transmit tension generated by sarcomeres to tendons
54
Define skeletal muscle
organ made up of muscle fascicles that contain muscle fibers, blood vessels and nerves; wrapped in epimysium
55
Define muscle fascicle
bundle of muscle fibers wrapped in perimysium
56
Define muscle fiber
long cylindrical cell covered by endomysium and sarcolemma; contains sarcoplasm, myofibrils, many peripherally located nuclei, mitochondria, T tubules, sarcoplasmic reticulum, and terminal cisterns; has a striated appearance
57
Define myofibril
threadlike contractile elements within sarcoplasm of muscle fiber that extend entire length of fiber; composed of filaments
58
Define filaments/myofilaments
contractile proteins within myofibrils that are of two types: thick filaments composed of myosin and thin filaments composed of actin, tropomyosin, and troponin; sliding of thin filaments past thick filaments produces muscle shortening
59
What is the sliding filament mechanism?
the process of skeletal muscle shortening during contraction by thick and thin filaments sliding past one another
60
What is the contraction cycle?
repeating sequence of events that causes the filaments to slide
61
What is step 1 of the contraction cycle?
ATP hydrolysis- myosin head hydrolyzes ATP and becomes energized and oriented
62
What is step 2 of the contraction cycle?
attachment of myosin to actin- myosin head binds to actin, forming a cross-bridge
63
What is step 3 of the contraction cycle?
power stroke- myosin head pivots, pulling the thin filament past the thick filament toward the center of the sarcomere
64
What is step 4 of the contraction cycle?
detachment of myosin from actin- as myosin head binds ATP, the cross-bridge detaches from actin
65
Where is calcium stored?
sarcoplasmic reticulum
66
What are voltage-gated Ca2+ channels?
located in the T tubule membrane; arranged in tetrads; serve as voltage sensors that trigger the opening of the Ca2+ release channels
67
What are Ca2+ release channels?
release calcium from the SR for muscle contraction
68
What is the length-tension relationship?
forcefulness of muscle contraction depends on the length of the sarcomeres within a muscle before contraction begins
69
What is the neuromuscular junction (NMJ)?
the synapse between a somatic motor neuron and a skeletal muscle fiber; includes all synaptic end bulbs on one side of synaptic cleft, the synaptic cleft, motor end plate of muscle fiber on the other side
70
synapse
a region where communication occurs between 2 neurons or between a neuron and a target cell
71
synaptic cleft
a small gap that separates the 2 cells at most synapses
72
neurotransmitter
chemical messenger that allows the cells to communicate across the gap
73
axon terminal
end of a motor neuron
74
synaptic end bulbs
in clusters, neural part of NMJ
75
synaptic vesicles
membrane-enclosed sacs suspended in the cytosol within each synaptic end bulb, contains thousands of molecules of acetylcholine
76
acetylcholine (ACh)
neurotransmitter released at the NMJ
77
motor end plate
region of the sarcolemma opposite the synaptic end bulbs, muscular part of NMJ, contains ACh receptors
78
acetylcholine receptors
integral transmembrane proteins to which ACh specifically binds, abundant in junctional folds
79
junctional folds
deep grooves in the motor end plate that provide a large surface area for ACh
80
what type of channel are ACh receptors?
ligand-gated ion channels
81
What is step 1 of generating a muscle action potential?
nerve impulse stimulates voltage-gated channels to open and release Ca2+, synaptic vesicles release ACh into the synaptic cleft
82
What is step 2 of generating a muscle action potential?
ACh binds to the ACh receptor in a junctional fold, ion channel opens which allows Na+ to flow across the membrane
83
What is step 3 of generating a muscle action potential?
inflow of Na+ makes the inside of the muscle fiber more positively charged, change in membrane potential triggers a muscle action potential which propagates along the sarcolemma into the system of T tubules, SR releases stored Ca2+ into the sarcoplasm and the muscle fiber contracts
84
What 3 ways can muscle fibers produce ATP?
creatine phosphate, anaerobic glycolysis, and aerobic respiration
85
How does creatine phosphate produce ATP?
formed from ATP while the muscle is relaxed, transfers a high-energy phosphate group to ADP, forming ATP during muscle contraction
86
How long does energy produced from creatine phosphate last?
15 seconds
87
How does anaerobic glycolysis produce ATP?
breakdown of muscle glycogen into glucose and production of pyruvic acid from glucose via glycolysis produce both ATP and lactic acid; because no oxygen is needed, this is an anaerobic pathway
88
How does aerobic respiration produce ATP?
within the mitochondria, pyruvic acid, fatty acids, and amino acids are used to produce ATP via aerobic respiration, an oxygen-requiring set of reactions
89
How long does the energy produced from anaerobic glycolysis last?
2 minutes
90
How long does the energy produced from aerobic respiration last?
several minutes to hours
91
What two ways does muscle tissue receive oxygen?
diffused from the blood or released from myoglobin
92
What is muscle fatigue?
the inability of a muscle to maintain force of contraction after prolonged activity
93
What are some potential causes of muscle fatigue?
inadequate release of calcium ions from SR, depletion of creatine phosphate, insufficient oxygen, depletion of glycogen and other nutrients, buildup of lactic acid and ADP, failure of action potentials in the motor neuron to release enough ACh
93
What is oxygen debt/recovery oxygen uptake?
added oxygen, over and above, the resting oxygen consumption, that is taken back into the body after exercise
94
frequency of stimulation
number of nerve impulses per second
95
motor unit
a somatic motor neuron plus all of the skeletal muscle fibers it stimulates
96
twitch contraction
the brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron
97
myogram
record of a muscle contraction
98
latent period
brief delay between application of stimulus and the beginning of contraction
99
What happens during the latent period?
the muscle action potential sweeps over the sarcolemma and Ca2+ is released from the SR
100
What happens during the contraction period?
Ca2+ binds to troponin, myosin-binding sites on actin are exposed, cross-bridges form, peak tension develops in the muscle fiber
101
What happens during the relaxation period?
Ca2+ is actively transported back into the SR, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, tension in muscle fiber decreases
102
refractory period
a characteristic of all muscle and nerve cells where there is lost excitability
103
wave summation
stimuli arriving at different times causes larger contractions, second contraction stronger than the first
104
unfused tetanus
skeletal muscle fiber is stimulated between 20-30 times per second and only partially relaxes between contractions
105
fused tetanus
skeletal muscle fiber is stimulated between 80-100 times per second and does not relax at all; a sustained contraction in which individual twitches cannot be detected
106
motor unit recruitment
process in which the number of active motor units increases; weakest motor units recruited first, with progressively stronger motor units added if the task requires more force
107
muscle tone
a small amount of tautness or tension in the muscle at rest due to weak, involuntary contractions of its motor units
108
flaccid
state of limpness in which muscle tone is lost
109
isotonic contraction
the tension developed in the muscle remains almost constant while the muscle changes its length
110
concentric isotonic conctraction
if the tension generated is great enough to overcome, the resistance of the object to be moved, the muscle shortens and pulls on another structure such as a tendon, to produce movement and reduce the angle at a joint
111
eccentric isotonic contraction
the tension exerted by the myosin cross-bridges resists movement of a load and slows the lengthening process
112
isometric contraction
the tension generated is not enough to exceed the resistance of the object to be moved and the muscle does not change in length
113
mesoderm
what the muscles of the body are derived from
114
somites
columns of mesoderm that have undergone segmentation into a series of cube-shaped structures
115
myotome
forms the skeletal muscles of the trunk and limbs
116
dermatomal mesenchyme
forms the connective tissues including the dermis of the skin and subcutaneous tissue
117
schlerotome
gives rise to the vertebrae and ribs
118
intercalated discs
irregular transverse thickenings of the sarcolemma that connect the ends of cardiac muscle fibers to one another
119
hypertrophy
enlargement of existing cells
120
hyperplasia
increase in the number of fibers
