Muscle Flashcards
1
Q
what is a myocyte
A
an individual muscle cell
2
Q
what is the sarcoplasm
A
cytoplasm of a muscle cell
3
Q
what is the sarcolemma
A
plasma membrane of a muscle cell
4
Q
what are the 3 types of muscles
A
skeletal, smooth, and cardiac
5
Q
what is are muscle cells derived from
A
mesoderm
6
Q
what is the function of skeletal muscle
A
movement of skeleton, under voluntary motor control
7
Q
describe skeletal muscle cells
A
-multinucleate, large cytoplasm, striations, “irregular polygon shaped”
8
Q
what are syncytia
A
muscle cells formed from fusion of myoblasts into multinucleate myotubes
9
Q
what do myotubes do
A
synthesize contractile proteins which assemble into sarcomeres
10
Q
what happens when nuclei of skeletal muscle cells move to the periphery of the cell
A
they lose their ability to proliferate
11
Q
what are the layers in skeletal muscle organization
A
endomysium, perimysium, and epimysium
12
Q
what does the endomysium cover
A
individual muscle fibers
13
Q
what does the perimysium surround
A
fascicles
14
Q
what are fascicles in muscle cells
A
several muscle fibers bound together
15
Q
what makes up muscle
A
many fascicles together
16
Q
what does the epimysium surround
A
the entire muscle
17
Q
where are blood vessels and nerves found in skeletal muscle cells
A
they follow the epimysium and perimysium
18
Q
what type of nerve innervate fast muscle fibers
A
fast nerves
19
Q
what type of nerves innervate slow twitch muscle fibers
A
slow nerves
20
Q
what types of myosin are there
A
fast and slow
21
Q
describe type 1, slow twitch muscle fibers
A
-small fibers
- large amounts of myoglobin
- large number of mitochondria
-resistant to fatigue but only generate moderate muscle tension
- common in peripheral limbs
22
Q
what type of respiration do type 1 slow twitch muscle fibers use
A
aerobic respiration for oxidative metabolism
23
Q
describe type 2, fast twitch muscle fibers
A
-large fibers with less myoglobin and fewer mitochondria
- lots of glycogen
- extensive sarcoplasmic reticulum for rapid Ca release
- fatigue rapidly but generate high tension for short bursts of activity
24
Q
what type of respiration do type 2 slow twitch fibers use
A
anaerobic glycolysis
25
why do type 2 fibers fatigue rapidly
because they use anaerobic respiration and have a low amount of mitochondria
26
what color are type 1 fibers
dark red
27
what color are fast twitch fibers
pink/tan
28
what are the intermediate muscle fibers
-type 2a
-type2b
29
describe type 2a fibers
oxidative and fatigue resistant
30
describe type 2b fibers
glycolytic and fatigue resistant
31
what type of respiration do both muscle fiber types use in peak periods of exertion and why
anaerobic respiration because they cant get enough oxygen
32
what does lactic acid build up do to muscle
forms crystal precipitates in muscle tissue that tear the fibers causing soreness after heavy exertion
33
what does severe oxygen debt cause
ischemia, muscle cramps, and even cell death
34
what is rhabdomyolysis
breakdown of actin and myosin as a result of extreme exertion
35
what can rhabdomyolysis be followed by and how
kidney failure (myoglobinuric nephrosis) due to release of myoglobin and clogging of glomeruli
36
how do muscle cells increase in size/hypertrophy
increase in number of mitochondria, and increase in volume of contractile proteins causes splitting/branching of individual muscle fibers
37
how often are new muscle fibers produced
relatively rarely
38
what is atrophy caused by
immobilization, denervation, and age
39
what happens in sacropenia
loss of skeletal muscle fibers that are not replaced. decrease in number of fibers and muscle mass
40
what do satellite cells do
regenerate skeletal muscle, they are small myogenic cells adjacent to sarcolemma
41
what do satellite cells do following injury
proliferate and differentiate into myoblasts
42
what are the types of proprioceptors in muscle cells
neuromuscular spindles and neurotendinous spindles
43
what are intrafusal fibers
modified skeletal muscle fibers associated with modified nerve endings
44
what do neuromuscular spindles sense and where are they located
sense changes in length and are located within the belly of muscle
45
what do neurotendinous spindles sense and where are they located
the sense changes in tension and they are located within the tendon
46
what do mechanoreceptors in muscle tissue do
prevent overstretching and tearing of muscles, used in postural reflexes and coordination
47
what is the ultrastructure in muscle cells
individual muscle fibers composed of myofibrils
48
what are myofibrils composed of
myofilaments or contractile proteins in parallel bundles
49
what are the 2 types of myofilaments
actin (thin) and myosin (thick)
50
what is the ratio of actin to myosin in skeletal muscle
2:1
51
what gives rise to the striated appearance of muscle tissue
parallel arrangement of contractile proteins
52
where do actin and myosin overlap
in the A band
53
what are sarcomeres
functional units of muscle cells that are arranged myofibrils
54
what do Z-discs do
act as anchoring points for actin myofilaments
55
what happens in the sliding filament theory of muscle contraction
during muscle contraction, sarcomeres shorten, but myofilaments remain the same length
56
what happens when thick and thin filaments slide over one another
-use energy via ATP
- shortening of sarcomere from binding and unbinding of actin and myosin filaments
57
what is the NMJ
site where skeletal muscle innervated by motor nerves
58
what is the motor end plate
the dilated terminal portion of the axon surrounded by myelin
59
what is the difference between a motor end plate and a terminal bouton
the motor end plate is myelinated
60
what is the synaptic cleft
space between motor end plate of nerves and sarcolemma of muscles
61
what neurotransmitter is released at the synaptic cleft on the NMJ
generally acetylcholine
62
what happens in the electrical stimulation of a neuron
-influx of Na+ into neuron
-wave of depolarization down axon
- release of NT
- binding to receptor proteins
-wave of depolarization of muscle fiber
63
what do transverse tubules do (T tubules)
extensive network of tubules continuous with sarcolemma that indirectly links extracellular space with ER and intracellular environment
- carries depolarization wave to the inside of the muscle cell cytoplasm
64
what are the ends of t tubules bound by
terminal cisternae of ER on both sides
65
what makes up a triad
a t tubule surrounded on both sides by cisternae
66
what act as Ca resevoirs in muscle tissue
sarcoplasmic reticulum and terminal cisternae
67
what is the mechanism for Ca release from ER and terminal cisternae into cytoplasm
influx of Na+ ions into cytoplasm from T tubules triggers depolarization of sarcolemma which triggers release of Ca
68
what does the sliding filament mechanism result in
muscle contraction
69
what are the steps in the sliding filament mechansim
- Ca causes conformational change in troponin, which interacts with tropomyosin molecules on actin to expose myosin binding sites on the 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 presence of Ca and Pi, causing contraction
70
what is a graded response
the strength of the overall contraction calculated by the total number of muscle fibers contracting at any given time
71
what is a motor unit
a group of muscle fibers supplied by single motor neuron
72
what does the stimulation of a motor neuron result in
contraction of all muscle fibers within that motor unit
73
what is recruitment
increase in number of motor units firing within a muscle
74
what does recruitment lead to
a graded response
75
what is muscular dystrophy
-degenerative wasting disease
- muscle weakness due to genetic defect in muscle protein and then muscle cell death
- most commonly affected muscle protein: dystrophin-
76
what is myasthenia gravis
autoimmune disease cause by production of antibodies to Ach receptors which leads to muscle weakness
77
how is myasthenia gravis treated
with AcHase inhibitors
78
describe inherent contractility in skeletal muscle
rhythmic, wave-like contractions independent of neurological stimulation
79
describe the orientation of smooth muscle fibers and function
highly irregular branching fascicles specialized for long contractions with low force
80
describe the size of smooth muscle fibers and the nuclei
smaller than skeletal muscle and the nucleus is long, single and central
81
how do you tell the difference between smooth muscle and skeletal muscle
the nucleus in smooth muscle is single and central
82
how do you distinguish between connective tissue and smooth muscle
-nuclei are long and ovular, the ends of nuclei are rounded and fibers are uniform in size in smooth muscle
83
what is the ratio of actin to myosin filaments in smooth muscle
15:1, randomly arranged
84
why are there no striations in smooth muscle
because myofilaments are not arranged in sarcomeres
85
what are dense bodies
functionally equivalent to z-discs in smooth muscle, provide attachment sites for actin
86
what does smooth muscle fibers use that controls myosin binding
calmodulin
87
what are caveolae
invaginations in membrane of smooth muscle cells. smooth muscle cells use these instead of the t-tubule/terminal cisternae system. rely on extracellular calcium for contraction
88
what type of innervation does skeletal muscle have
sympathetic and parasympathetic
89
what does a single unit of muscle fibers do and what is the example
fibers contract as a unit ex: visceral smooth muscle of gut
90
what does a multi unit of smooth muscle do and example
individual muscle fibers contract independently ex: erector pili muscle
91
can smooth muscle repair itself after injury
yes
92
what does smooth muscle develop from
endothelial cells, pericytes of blood vessels, fibroblasts
93
what can glandular epithelial cells differentiate into
myoepithelial cells
94
what is the CT layer called that surrounds the heart
pericardium
95
what are the layers of the pericardium and what do they contain
outer fibrous CT layer and inner serous layer containing mesothelial cells
96
what does the pericardium contain and what is its function
pericardial fluid for lubrication
97
what are the 3 layers of the heart
epicardium, myocardium and endocardium
98
what is the epicardium of the heart made of
simple squamous mesothelium
99
what is the epicardium supported by
the underlying fibroblastic CT and adipose tissue
100
where are the blood vessels and nerves located
within the subepicardial layer
101
what is the heart surrounded by
adipose tissue
102
where is the myocardium thickest
in the ventricles compared to atria
103
describe the myocardium
thick, collagenous, connective tissue skeleton made of fibroblasts and collagen
104
describe cardiac muscle fibers
have one centrally located nucleus (occasionally 2), fibers are striated but involuntary
105
describe the arrangement of cardiac muscle
contractile proteins are arranged into sarcomeres, contain a diad of one t-tubule and one cisterna of ER located at z-disc
106
where is endocardium found and what kind of cells are they
lines atria and ventricles, ccovers heart valves; simple squamous endothelium
107
what supports endocardium
subendothelial fibroblastic CT, with reticular fibers and smooth muscle
108
where is the endocardium the thickets
in atria compared to ventricles
109
where are purkinjie fibers located
subepi and endocardial layers
110
what do cardiac valves contain
layer of fibrous connective tissue called lamina fibrosa covered by endothelium
111
what are valves surrounded by
tough, fibrous rings at base of aorta and pulmonary artery, AV valves and extending into IVS
112
what is os cordis
at the base of AV valves when valves occasionally ossify to form bony rings
113
what is inherent automaticity
cardiac myocytes can contract themselves without external stimulation
114
what are intercalated discs
unique to cardiac muscle, special connections between the cells
115
what do intercalated discs do
enhance spread of contractile stimulus between cells and allow synchronous contractions, increase SA for attachment of myofibrils between adjacent cells
116
what are the types of cell junctions
desmosomes, fascia adherens, and gap junctions
117
what do desmosomes do
bind individual myocytes together laterally and on ends
118
what do fascia adherens do
like zonuls adherens but joins ends of muscle fibers
119
what do gap junctions do and where are they located
located laterally, provide ioninc communication between cells, synchronize contractions and allow muscles to behave as a syncitium
120
what does the cardiac conduction system look like
SA node, AV node, Bundle of His, and purkinje fibers
121
describe the cells surrounding the conduction system of the heart
they are larger surrounding cardiac conduction systems and conduct impulses 4x faster
-paler staining around these structures due to higher glycogen content
122
what is the pacemaker of the cell and where is it located
SA node located at junction of superior vena cava and RA
123
what does the SA node do
generates impulses that induce contraction of atria
-as impulses travel across atria, stimulate AV node
-delays impulses, give atria time to contract
-impulse travels down IVS via bundle of His, branches into L and R AV bundles within IVS
- fibers divide into ventricular myocardium and ramify into purkinje fibers within subendo and subepicardium of ventricular free wall, gradually merge with myocardium, initiate ventricular contraction
124
what does sympathetic and parasympathetic stimulation do in the SA node
-sympathetic stimulation from sympathetic ganglia increase HR
- parasympathetic stimulation from vagus nerve decreases HR
