Muscle Flashcards
(180 cards)
1
Q
individual muscle cell is called
A
myocyte
muscle fiber
2
Q
muscle cytoplasm=
A
sarcoplasm
3
Q
muscle plasma membrane/plasmalemma=
A
sarcolemma
4
Q
3 types of Mm
A
skeletal
smooth
cardiac
5
Q
all three types of muscle are derived from the
A
mesoderm
6
Q
skeletal muscle is responsible for the
A
movement of skeleton
7
Q
skeletal muscle is under
A
voluntary motor control
8
Q
–% of the body mass is skeletal mm
A
40%
9
Q
skeletal mm cells nuclei are
A
multinucleate
10
Q
multinucleate cells form
A
syncytial
11
Q
syncytial forms due to
A
fusion of myoblasts into a multinucleate myotube during development
12
Q
myotubes synthesize
A
contractile proteins which assemble sarcomeres
13
Q
skeletal muscle nuclei migrate to the
A
periphery of the cell
14
Q
skeletal muscle nuclei lose the ability to
A
proliferate
15
Q
individual muscle fibers are surrounded by connective tissue called
A
endomysium
16
Q
several fibers bound together into
A
fascicles
17
Q
fascicles surrounded by connective tissue
A
perimysium
18
Q
many fascicles together form
A
muscle
19
Q
entire muscle surrounded by
A
epimysium
20
Q
epimysium is continuous with
A
tendinous attachment
21
Q
blood vessels and Nn tend to follow connective tissue epi and perimysial for
A
support
22
Q
two types of skeletal muscle fibers
A
fast twitch
slow twitch
23
Q
Early in development of myotubes, “fast” Mm fibers are innervated by “—” Nn & “slow” Mm fibers by “—” Nn
A
fast
slow
24
Q
Also differences in development of contractile proteins
A
“fast” myosin & “slow” myosin
25
slow myosin are --- fibers with a large amount of ---
small
| myoglobin
26
type 1 uses --- --- --- for oxidative metabolism
1' aerobic respiration
27
type 1 have a large number of mitochondria, used for
ATP
28
type 1 muscle fibers are resistant to
fatigue
29
type 1 muscle fibers generate --- muscle tension
moderate
30
where are type 1 slow fibers common?
in peripheral limbs
31
color of type 1 slow twitch fibers
dark red, almost black bc they're rich in myoglobin
32
type 2 fibers are --- fibers with --- myoglobin and --- mitochondria
large
less
fewer
33
how do type 2 fibers use --- --- --- for energy production
1' anaerobic glycolysis
34
type 1 fibers have abundant
glycogen
35
type 2 have extensive sarcoplasmic reticulum for rapid
ca release
36
type 2 fibers fatigue
readily
37
type 2 fast twitch fibers generate --- muscle tension for short bursts of activity
high
38
intermediate filaments (2)
type 2a
| type 2b
39
type 2a
oxidative and fatigue resistant
40
type 2b
glycolytic and fatigue sensitive
41
most muscles are
mixed
42
during peak periods of exertion, both type 1 and 2 fibers metabolism glycogen via
anaerobic glycolysis to produce ATP
43
intermediate metabolites (lactic acid) predicate as crystals in muscle, leading to
tearing of muscle fibers and pain after heavy exertion
44
if oxygen debt is severe, it can lead to (3)
ischemia
muscle cramps
cell death
45
extreme exertion may lead to (2) due to the release of myoglobin and clogging of glomeruli
acute rhabdomyolysis and subsequent myoglobinuric nephrosis
46
acute rhabdomyolysis
breakdown of actin and myosin
47
myoglobinuric nephrosis
kidney failure
48
during normal exercise, muscle fibers develop
microtears
49
hypertrophy
with exercise, muscle cells increase in size
50
why do muscle fibers increase in size? (3)
increase in number of mitochondria
increase in volume of contractile proteins
splitting/branching of individual muscle fibers
51
production of new muscle fibers is relatively
rare
52
atrophy
with disuse, muscle cells decrease in size
53
why do muscle cells decrease in size? (2)
immobilization (splint, cast)
| denervation (never damage least to muscle atrophy)
54
sarcopenia
with increased age, progressive loss of skeletal muscle fibers `
55
lost muscle fibers are not replaced, therefore
increase in number and decrease in size of muscle mass
56
skeletal muscle ability to regenerate following injury
limited ability
57
primary source of regeneration
satellite cells
58
satellite cells
small myogenic cells adjacent to sarcolemma
59
after injury, cells proliferate and differentiate into
myoblasts
60
-- types of proprioceptors located within mm
2
61
intrafusal fibers
modified skeletal muscle fibers associated with modified nerve endings
62
neuromuscular spindles
muscle spindles
| located within belly of mm
63
neuromuscular spindles are sensitive to changes in
length
64
neurotendinous spindles
Golgi tendon organs
| located within tendon
65
neurotendinous spindles are sensitive to changes in
tension
66
both prevent overstretching and tearing of mm; used in (2)
postural reflexes
| coordination
67
individual muscle fibers are composed of
myofibrils
68
myofibrils are composed of numerous
myofilaments or contractile proteins in parallel bundles
69
two types of myofilaments
actin
| myosin
70
actin
thin filament
| 6-8 nm in diameter
71
myosin
thick filament
| 15 nm in diameter
72
actin and myosin ratio is skeletal muscle
2:1
73
striated muscle
parallel arrangement of contractile proteins which give a striated appearance in longitudinal section
74
actin and myosin overlap in the - band but not the - band
A band
I band
(striations)
75
skeletal muscles are stopped in C-S due to
hexogonal array of microfilaments
76
myofibrils are arranged in
sarcomeres
77
sarcomeres
the functional units of muscle cells
78
z discs act as anchoring points for
actin myofilaments
79
during muscle contraction, sarcomeres shorten, but --- remain the same length -
myofilaments
80
due to thick and thin filaments sliding over one another via energy from ATP,
shortening of sarcomere, via repeated binding and unbinding of actin and myosin filaments
81
neuromuscular junction (NMJ)
the site where skeletal muscle is innervated by motor neurons
82
motor end plate
dilated terminal portion of axon surrounded by myelin
83
the motor end plate rests on
sarcolemma
84
terminal button is similar to the motor end plate, except
unmyelinated
85
synaptic cleft
the space between the motor end plate of neurons and sarcolemma of muscle
86
which chemical neurotransmitter is the neuromuscular junction typically bridged by?
acetylcholine
87
what does the depolarization of the muscle fiber travel down?
transverse tubule system (t tubules)
88
t tubules
extensive network of tubules continuous with the sarcolemma
89
t tubules indirectly links the extracellular space with (2)
ER
| intracellular environment
90
ends of t tubules are bounded by enlarged
terminal cistern of either side
91
triad
2 terminal cisternal and one t tubule
92
sarcoplasmic reticulum and terminal cisternal act as -- reservoirs when muscle is relaxed
ca
93
-- is necessary for muscle contraction
ca
94
influx of sodium ions into the cytoplasm from t tubules trigger depolarization of
sarcolemma
95
depolarization of sarcolemma releases -- from the ER and terminal cisternae into the cytoplasm during contraction
ca
96
what do ca ions activate?
sliding filament mechanism during contraction
97
how does ca activate the sliding filament mechanism?
ca causes conformational change in troponin which interacts with tropomyosin molecules (bound to actin), exposing myosin binding site on actin filament. myosin binding causes conformational change in myosin head and sliding of myosin past actin. myosin heads repeatedly bind and unbind to actin in the presence of ca and pi causing contraction
98
all or none response
muscle fiber either contracts or it doesn't
99
total number of muscle fibers contracting at any given time determines the
strength of overall contraction
100
graded response
strength of overall contraction
101
motor unit
a group of muscle fibers supplied by a single motor neuron
102
stimulation of a motor neuron results in contraction of --- muscle fibers within the motor unit
all
103
-- of motor units varies
size
104
recruitment increases the number of
motor units firing within a muscle
105
muscular dystrophy
degenerative wasting disease
muscle weakness due to genetic defect in muscle protein
cell dead
106
what form of muscular dystrophy affects protein?
dystrophin
107
myasthenia graves
autoimmune disease caused by production of antibodies to act receptors resulting in muscle weakness
108
treatment of myasthenia graves
achase inhibitors
109
inherent contractility
rhythmic, wave like contractions independent of neurological stimulation
110
smooth muscle organization
endothelial peri epi
111
smooth muscle fibers are bound together into highly irregular, branching fascicles specialized for
prolonged contractions with low force
112
smooth muscle nucleus
single, long, central
113
are skeletal or smooth muscle fibers larger?
skeletal
114
actin and myosin ratio in smooth muscle
15:1
| randomly arranged
115
arrangement of smooth muscle
random
myofilaments are not arranged in sarcomeres
no striations
116
dense bodies
equivalent functionally to z discs
| provide attachment sites for actin
117
smooth muscle lacks
troponin complex that controls myosin binding
118
instead of troponin, smooth muscle uses
calmodulin
119
calmodulin
binds ca and activates myosin cross binding
120
smooth muscle lacks t tubule system and terminal cisternal of ER. instead, cell membrane has
caveolae
121
caveolae
pockets/ divets in the membrane
122
what does smooth muscle rely on for contraction?
extracellular ca
123
what is smooth muscle influenced by? (3)
autonomic nervous system
hormones
local metabolites
124
smooth muscle autonomics
most has dual sympathetic and parasympathetic innervation
125
is smooth muscle voluntary?
no, involuntary
126
response of smooth muscle depends on
receptor tupe (alpha or beta)
127
sympathetic stimulation in the gut leads to
inhibitory and parasympathetic stimulation, then stimulation to Smooth muscle
128
smooth muscle as a single unit
tonic smooth muscle
fibers contract as a unit
ex. visceral smooth muscle of the gut, most common
129
smooth muscle as a multi unit
phasic smooth muscle
individual muscle fibers contract independently
ex. ciliary body of iris, erector pili muscle
130
smooth muscle retains the ability to divide and repair itself following
injury
131
smooth muscle cells can develop from (3)
endothelial cells
pericytes of blood vessels
fibroblasts
132
glandular epithelial cells can also differentiate into
myoepithelial cells
133
pericardium
sac like, fibrous connective tissue surrounding the heart
134
layers of the heart (2)
fibrous connective tissue layer
| inner serous layer (continuous with epicardium)
135
inner serous layer contains
mesothelial cells
136
pericardium contains
pericardial fluid for lubrication
137
heart layers
epicardium
myocardium
endocardium
138
epicardium
outermost layer, simple squamous mesothelium on the external surface of the heart
139
epicardium is supported by
underlying fibroblastic connective tissue and adipose tissue
140
blood vessels and nerves are located within
subepicardial layer
141
the heart is surrounded by a protective layer of
adipose tissue
142
myocardium
cardiac muscle itself, thicker in ventricles than atria
143
what is particularly present in the myocardium?
endo, peri, epimysium
144
the myocardium is composed of
fibroblasts and collagen
145
cardiac muscle intermediate between skeletal and smooth muscle both
structurally and functionally
146
cardiac muscle myocyte nucleus
one centrally located, occasionally two
147
cardiac muscle fibers are ---, but ----
striated
| involuntary
148
arrangement of contractile p[roteins into sarcomeres similar to skeletal muscle, but cardiac myocytes contain intracellular ---, not ---
diad
149
diad
composed of one t tubule and one cisternal of ER located at the z disc
150
endocardium
lines atria and ventricles, covers heart valves
151
cell type of endothelium
simple squamous
152
endocardium is supported by
sub endothelial fibroblastic connective tissue, interspersed with reticular fibers and smooth muscle
153
endocardium is thicker in
atria than ventricles (greater turbulence in atria)
154
where are purkinje fibers located?
within subepi and endocardial layers
155
cardiac valves contain layer of fibrous connective tissue called --- --- covered by endothelium
lamina fibrosa
156
valves are surrounded by tough, fibrous rings at the
base of the aorta and pulmonary artery (~AV valves) and extending into IVS
157
occasionally ossify to form body rings at the base of AV values called
os cordis
158
individual cardiac myocytes exhibit
inherent automaticity
159
ends of fibers abut at
intercalated discs
160
intercalated discs
unique to cardiac muscle, specialized connections between cells
161
intercalated discs enhance speeds of
contractile stimulus between cells and allow synchronous contractions
162
intercalated discs also provide increased --- --- for attachment of myofibrils between adjacent cells
surface area
163
what junctions make up intercalated discs? (3)
desmosomes
fascia adherents
gap junctions
164
desmosomes
macula adherents
| bind individual myocytes together laterally and on the ends
165
fascia adherents
adherent junctions
| like zonula adherents but join ends of muscle fibers
166
gap junctions
located laterally, provide iconic communication between cells, synchronize contractions, and allow muscle to behave as a syncytium
167
condition system of the heart consists of (4)
SA node
AV node
bundle of His
purkinje fibers
168
all consist of highly modified cardiac myocytes that coordinate conduction, joined by extensive
gap junctions
169
calls larger than surrounded cardiac muscle cells conduct impulses ~-x faster
4x
170
paler staining than surrounding muscle due to
higher glycogen content
171
SA node
pacemaker
172
SA node is located at junction of the
superior vena cava and RA
173
SA node generates impulses that induce
contraction of atria
174
as impulses travel across atria, this stimulates the
AV node
175
AV node is located between
RA and V
176
the AV node delays atria, giving time to
contract
177
travels down inter ventricular septum (IVS) via
bundle of His
178
branches into
Land R AV bundles within IVS
179
fibers further subdivide in ventricular myocardium and ramify into --- --- within subendo and subepicardium of ventricular free wall, gradually merge with myocardium, initiate ventricular contraction
purkinje fibers
180
inherent rhythm of SA node modulated by autonomic nervous system
sympathetic stimulation from:
parasympathetic stimulation from:
sympathetic stimulation from dympethic ganglia increase heart rate
parasympathetic stimulation from vagus nerve decrease heart rate
