LEC43: Muscle Tissue Flashcards
1
Q
3 types of muscle tissue
A
smooth, skeletal, cardiac
2
Q
general functions of muscle tissue
A
1) movement
2) maintenance of posture
3) joint stabilization
4) heat generation
3
Q
special functional characteristics of muscle
A
1) contractility
2) excitability
3) extensibility
4) elasticity
4
Q
contractility means
A
muscle only has 1 action: to shorten
shortening generates pulling force
5
Q
excitability means
A
muscle can be excited; nerve fibers cause electrical impulse to travel
6
Q
extensibility means
A
muscle can stretch w/ contraction of an opposing muscle
7
Q
elasticity means
A
muscle recoils passively after being stretched
8
Q
skeletal muscle location
A
attach to, move skeleton
9
Q
how much of body weight does skeletal muscle comprise?
A
40%
10
Q
are skeletal muscle contractions voluntary or involuntary?
A
voluntary
11
Q
which muscle types are striated?
A
skeletal, cardiac
12
Q
where is cardiac muscle found?
A
only in wall of the heart
13
Q
are cardiac muscle contractions voluntary or involuntary?
A
involuntary
14
Q
where is smooth muscle found?
A
walls of hollow organs
15
Q
are smooth muscle contractions voluntary or involuntary?
A
involuntary
..although some voluntary as well
16
Q
what does each skeletal muscle have associated w/ it?
A
1 nerve, 1 artery, 1 vein, which branch repeatedly
17
Q
what do skeletal muscles connect
A
1 bone to another
18
Q
what do skeletal muscles span
A
at least 1 movable joint, but can span 2 or more joints
19
Q
where is skeletal muscle origin/insertion re: movement?
A
origin: the less movable attachment
insertion: pulled toward the origin
20
Q
do both bones move when skeletal muscle contracts?
A
no, usually 1 bone moves other remains fixed
21
Q
where is origin re: insertion (proximal, distal)
A
origin is proximal to insertion
22
Q
what is biarticular muscle?
A
multijoint muscle, when muscles span 2 or more joints, cause movements at 2 joints
23
Q
what are “fleshy” attachments?
A
aka direct attachment
attachment so short muscle appears to attach directly to bone
24
Q
what is indirect attachment?
A
when connective tissue extends well beyond the muscle
eg: tendon
25
what do most skeletal muscles have attached to them?
tendonous attachment - cordlike
26
characteristics of skeletal muscle
1) moves skeleton
2) voluntary/conscious control
3) limited regeneration
27
muscle cell plasma membrane?
sarcolema / plasmalemma
28
muscle cell ER?
sarcoplasmic reticulum
29
muscle cell cytoplasm?
sarcoplasm
30
what comprises a skeletal muscle's motor unit?
1 motor nerve + all the muscle fibers it innervates
31
how many fibers in a muscle cell?
1
32
how is skeletal muscle nucleus?
multinucleated, nuclei are peripherally located, surrounded by endomysium
33
arrangement of skeletal muscle fiber
fiber surrounded by endomysium
34
how are skeletal muscle fibers bundled?
fibers grouped into fasicles; surrounded by perimysium
35
how are several skeletal muscle fasicles grouped?
bundles of fasicles make up a muscle, surrounded by epimysium
36
what are endomysium, perimysium, epimysium made of?
connective tissue
37
what is a muscle cell made of?
many myofibrils
38
what are myofibrils made of?
bundles of myofilaments (thin-actin, thick-myosin), organized into sarcomeres
39
which tissue types are present in a skeletal muscle
all!
- arteries/veins have endothelial cell lining
- nerves have nervous tissue
- CT surrounds muscle cell fibers
40
what is connective tissue function re: skeletal muscle?
necessary for muscle function, continuous with tendons, muscle attachments distributing force of muscle to bone, skin, etc
41
what surrounds myofibril?
sarcoplasmic reticulum
42
what are A and I bands named for?
how they rotate polarized light
I: isotropic: same in all drxns
A: anisotropic: diff in all drxns
43
sarcomere
basic unit of a muscle/myofiber, what allows us to flex
| segment between 2 neighboring Z lines
44
subdivisions of sarcomere?
A band, I band, Z line, H band, M line
45
A band?
dark band
| actin, myosin filaments
46
I band?
light band
| only actin
47
Z line?
bisects I band
| anchors actin, defines border of adjacent sarcomeres
48
H band?
light band, bisects A band
| only myosin
49
M line?
dark line, bisects H band
| anchors myosin
50
what type of filaments make up myofibrils?
1) thick-myosin
2) thin-actin
3) elastic-titin
51
structure of myosin
2 light chains + ATPase domain + actin-binding domain
52
how does myosin filament assemble? what is rod structure?
self-assembles into a-helical tail, large bipolar aggregate or filament
53
what does troponin connect? what is troponin complex made of?
connects to actin a-helices, to tropomyosin between actin filaments
1) calcium binding part
2) inhibitory part-troponin I
3) troponin T, binds to tropomyosin
54
what covers actin's myosin-binding site?
tropomyosin
55
what is driving force for movement in myosin?
myosin II heads, thru ATPase activity move along actin filament
56
what connects actin to Z disc?
a-actinin
57
what connects myosin to Z disc?
titin
58
where is a-actinin?
incorporated into Z disk
| attaches actin to the disk
59
what is sarcoplasmic reticulum made of?
smooth ER
60
sarcoplasmic reticulum function?
store Ca++, release it when muscle stimulated to contract
61
what is continuous with sarcolemma? what is the result?
t-tubules
| therefore whole muscle contracts simultaneously (including deep parts)
62
what are terminal cisternae
cross-channels in sarcoplasmic reticulum
63
what makes troponins change conformation?
high [Ca++]
64
what binds to troponin in muscle contraction? what is result?
Ca++ binds
Ca++ moves tropomyosin out of the way, bonds to troponin
allows myosin to bind to actin, muscle contraction
65
what happens if [Ca++] is low?
troponin returns to standard conformation
tropomyosin blocks myosin
no muscle contraction
66
role of neurotransmitters in muscle contraction, re: calcium?
1) neurotransmitters from motor end plate cause depolarization of sarcollema, including T-tubules
2) depolarization extends to membranes of sarcoplasmic reticulum
3) Ca++ released into sarcoplasm
67
what happens when Ca++ in sarcoplasm?
binds to Tpn C, separates Tpn I from actin, exposes myosin binding site, contraction cycle begins
68
what surrounds T tubule and skeletal muscle?
2 terminal cisternae
69
what makes up the "triad" of the sarcoplasm? where is it?
2 terminal cisternea + T tubule
| at the A-I junction
70
what is the nature of the "triad" in cardiac muscle?
it is a diad
71
motor end-plate function?
motor end plate of neuromuscular junction impinges on muscle fiber
72
what happens to A-I band length when muscle contracts?
it shortens
73
what kind of movement when actin-myosin bind?
RATCHET
74
cause of contraction of muscle fiber?
1) Ca++ influx
| 2) ATP hydrolyzed to ADP + Pi
75
role of satellite cell in skeletal muscle?
lie within basal lamina
| migrate up, make filaments to fill in damaged areas when skeletal muscle damaged
76
what is myasthenia gravis?
autoimmune disease
antibodies against Ach receptor bind to receptor, prevent Ach from binding to it, blocks normal nerve-muscle interaction, no muscle firing
clinically, ppl suffer from progressive muscular weakness
77
how are the fibers in cardiac muscle?
fibers branch
78
position of nucleus in cardiac muscle?
1-2 central nuclei
79
do cardiac muscles have satellite cells?
no
80
what are features within cardiac muscles?
1) intercalated disks
2) T-tubules at Z lines
3) cross-striations
81
how many cells make up a cadiac muscle?
many cells/muscle
82
where do cardiac muscle cells join
interalated disc
83
what is a cardiac muscle "fiber"
long row of joined cardiac muscle cells
84
what is myocardium
thick bundles of cardiac muscle
85
what is inherent rhythmicity?
characteristic of cardiac muscle whereby each muscle cell beats separately, without stimulation
86
syncitium
cardiac muscle cells are interconnected by specialized membranes with gap junctions which are synchronized electrically in an action potential
87
how is terminal cisternae arrangement in cardiac muscle?
diad of terminal cisternae join with T tubule at Z line
88
how does intercalated disc join together cardiac muscle cells?
1) macula adherens
2) gap junction
3) fascia adherens
89
6 major locations of smooth muscle
1) inside eye
2) walls of vessels
3) respiratory tubes
4) digestive tubes
5) urinary organs
6) reproductive organs
90
shape of smooth muscle cells?
spindle-shaped
91
how many nuclei in smooth muscle cell?
1
92
how are smooth muscle cells grouped?
into sheets; often run perpendicular to each other
93
how do smooth muscles move?
slow, sustained contractions that're resistant to fatigue
94
which type of muscles do peristalsis?
smooth muscle
95
what stimulates smooth muscle to contract?
can be stretching, hormones; doesn't have to be nervous signal
96
where is myenteric plexus, what kinds of cells found there?
GI
| neuronal ganglion cells
97
what feature of smooth muscle takes in calcium?
surface caveolae, endocytotic vesicles
98
what does calcium bind w/ in smooth muscle?
calmodulin
99
how does smooth muscle contraction cascade work?
Ca-calmodulin complexes > phosphorylation of myosin light chain kinase of myosin rod > conformational change exposing actin binding site of myosin > myosin binds actin > contraction
100
what are dense bodies?
analogous to z-disks, but in smooth muscle
101
where are dense bodies?
in smooth muscle
| beneath plasma membrane, in cytoplasm's intercytoplasmic surface
102
what do dense bodies contain?
alpha actinin site of insertion of actin filaments - holds actin in place
103
does smooth muscle have myosin filaments?
yes!
104
what must occur for myosin to be able to bind actin?
myosin light chain kinase phosphorylates light chains; tail extends; forms bipolar myosin filaments, myosin heads can now bind actin
105
which muscle tissue type cannot regenerate in adults?
cardiac muscle
106
can skeletal muscle tissue regenerate?
nuclei cannot undergo mitosis; tissue can undergo limited regeneration
107
what in skeletal muscle allows regeneration?
satellite cells
108
can smooth muscle tissue regenerate?
yes!
| i.e. uterus enlarges during pregnancy
109
how many known actin genes?
at least 4
1) cardiac actin
2) skeletal muscle actin
3) vascular smooth muscle actin
4) visceral smooth muscle actin
110
what causes myopathies
changes in actin gene structure
111
how to distinguish myopathy from neuropathy?
histology
