Muscle Tissue Flashcards
(136 cards)
1
Q
What are the two most important characteristics of the muscle tissue?
A
contractility and conductivity
2
Q
Contractility is due to the presence of what three things?
A
actin, myosin, ATP
3
Q
Conductivity allows muscle cells to do what?
A
transmit electrical impulse to other cells and receive impulses from nerve cells
4
Q
Are skeletal muscles voluntary?
A
yes
5
Q
skeletal muscles exhibit distinctive _______ that are due to the arrangement of filaments in the cytoplasm
A
cross-striations
6
Q
skeletal muscles are attached to bones and used primarily for what?
A
locomotion, respiration, and other functions
7
Q
visceral muscles are present where?
A
tongue, pharynx, and in the upper part of the esophagus
8
Q
skeletal muscles of the eye are responsible for precise eye movement. true or false?
A
true
9
Q
Smooth muscles are primarily found where?
A
the walls of internal organs
10
Q
Are smooth muscles voluntary?
A
no
11
Q
True or false? smooth muscles who striations in the cytoplasm
A
false; they do not
12
Q
Describe cardiac muscle
A
found in heart, striated, involuntary
13
Q
The specialized plasmalemma of muscles cells is the ____, the cytoplasm of muscle cells is the ____, and the specialized smooth ER of muscles cells is the ______
A
sarcolemma; sarcoplasm; sarcoplasmic reticulum
14
Q
Skeletal muscles are quick, but usually get tired fast. True or false?
A
true
15
Q
Skeletal muscle fibers originate from ____
A
myoblasts
note: myoblasts then fuse with each other to form long multinucleate post mitotic myotubles
16
Q
Each of the cells of the skeletal muscle is actually a _____ ___
A
multinucleate syncytium
note: more commonly called a skeletal muscle fiber
17
Q
Sarcolemma of skeletal muscle fibers forms long process called ____-_____ that extend into the cytoplasm
A
T-tubules
18
Q
What do the T-tubules do?
A
important for carrying the wave of depolarization deep into the sarcoplasm
19
Q
____ of the skeletal muscle cells are peripheral in location and are found immediately beneath the sarcolemma
A
nuclei
20
Q
The sarcoplasm of skeletal muscles contains what three things?
A
myofibirils, filamentous mitochondria, myoglobin
21
Q
In regards to sarcoplasm of muscle cells, the arrangement of contractile filaments within the myofibrils is regular and gives the myofibril “____” appearance
A
striated
note: the whole fiber exhibits characteristic transverse striations
22
Q
In regards to sarcoplasm of muscle cells, the filamentous mitochondria lie between myofibrils and close to the sarcolemma. They represent the source of ____ for the myofibrils
A
ATP
23
Q
Myoglobin is what type of protein found where?
A
oxygen-binding protein found in skeletal muscle cells
24
Q
The sarcoplasmic reticulum is a highly specialized form of smooth ER and is used as a depot of ____.
A
Ca2+
note: when excited, the sarcoplasmic reticulum releases Ca2+ into cytoplasm initiating the muscular contraction
25
Named skeletal muscles (e.g. the biceps) consist of ____ or bundles of skeletal muscle fibers surrounded by a connective tissue sheath
fascicles
26
Each ____ is formed by groups of skeletal muscle fibers. Each skeletal muscle fiber is formed by many ____ that extend the whole length of the muscle fiber
fascicle; myofibrils
27
What are the two components of the myofibril?
thick and thin filaments
28
Within the myofibril, the thin (actin) filaments are arranged in a _____ array with 6 thin filaments surrounding 1 thick (myosin) filament
hexagonal
29
Thin filaments are composed of several proteins including:
F-actin, Tropomyosin, troponin complex
30
F-Actin forms a double-stranded helical filament and is the polymerization of what?
G-Actin
31
Tropomyosin forms filaments that lie in the grooves between what?
two actin monomers
32
In the resting muscle, tropomyosin masks the ____ binding sites on the actin filament
myosin
33
What are the 3 globular subunits of the troponin complex and what do they bind to?
Troponin T: binds to tropomyosin, anchoring the troponin complex
Troponin I: binds to actin
Troponin C: smallest subunit, binds to Ca2+
34
Thick filaments are formed by what?
hundreds of myosin II molecules
35
What do Myosin II molecules consist of?
two heavy chains - have globular heads that exhibit ATPase and motor activity and have binding sites for actin and ATP
two light chains - attach to the heads
36
In regards to the microstructure of a myofibril, most of the ___ band contains both thick and thin filaments
A
37
the ___ zone is a pale area in the middle of the A-band that contains only thick filaments and no thin filaments
H
38
the ___ line is a dense line bisecting H-zone of the A-band
M
39
What is the M-line formed by?
accessory protein, myomesin - holds the thick filaments in register
40
In regards to the microstructure of a myofibril, this is a pale area formed primarily by thin filaments. It is bisected by a dense line, the Z-line
I-band
41
That is the Z-line composed of? What is its major function?
accessory proteins, alpha-Actinin; major function: provide anchoring points for thin filaments and to support the architecture of the myofibril
42
The ____ is a portion of the myofibril between two adjacent Z-lines. It is the basic contractile unit of skeletal muscle
sarcomere
43
The sarcomeres of individual myofibrils are in register in one muscle fiber, so the entire muscle cell exhibits ____-____
cross-striations
44
Skeletal muscle contraction is due to the sliding of filaments which results in what?
shortening of the sarcomere while the length of individual filaments does not change
45
The length of the ___ band does not change during contraction but the ___ band and ____ zone shrink during contraction due to the increase of overlap between thick and thin filaments
A; I; H
46
__-___ is a short bipolar, rod-shaped actin-binding protein that bundles thin filaments into parallel arrays and anchors them at the Z-line
alpha-Actinin
47
Accessory proteins are essential in regulating the spacing, attachment, and alignment of _____
myofilaments
48
Accessory proteins - structural protein components constitute less than ___% of the total protein of the muscle fiber
25
49
____ is an elongated, inelastic protein attached to the Z lines and runs parallel to the thin filaments.
Nebulin
50
Nebulin does what?
helps alpha-actinic anchor thin filaments to Z lines and is thought to regulate the length of thin filaments during muscle development
51
Tropomodulin, a small actin-binding protein is attached to the free portion of the thin filament. This actin-capping protein does what?
maintains and regulates the length of the sarcomeric actin filament
52
_____, a large protein, forms an elastic attic that anchors thick filaments in the Z lines
Titin
53
____ has two spring-like portions of the protein adjacent to the thin filaments to help stabilize the centering of the myosin-containing thick filament, preventing excessive stretching of the sarcomere
Titin
54
____, a myosin-binding protein, holds thick filaments in register at the M line
myomesin
55
___ protein, a myosin-binding protein serves the same function as myomesin and forms several distinct transverse stripes on either side of the M line
C
56
Describe Desmin. What does it do?
a type of intermediate filament, forms a lattice that surrounds the sarcomere at the level of the Z lines, attaching them to one another and to the plasma membrane, thus forming stabilizing cross-linked between neighboring myofibrils
57
Dystrophin, a large protein, linkes _____, which resides in the external lamina of the muscle cell, to ___ filaments
laminin; actin
58
Mutations of structural proteins of the skeletal muscle can cause severe disorders called ____ ____, which result in severe muscle weakness, atrophy and destruction.
muscular dystrophies
59
absence of dystrophin protein is associated with progressive muscular weakness, a genetic condition called?
Duchenne's muscular dystrophy
60
Membrane triads consist of one __-____ and two _____ of sarcoplasmic reticulum running parallel to it
T-tubule; cisternae
61
T-tubules allow for the impulse to travel down into the cell and excite the of the sarcoplasmic reticulum
terminal cisternae
62
T-tubules run at the junction of ___ and ___ bands
A; I
63
The sarcoplasmic reticulum forms long chambers called?
terminal cisternae
64
Terminal cistern run parallel to the __-___ on both sides of it, forming the triads. They contain high concentrations of ___ ions.
T-tubules; Ca2+
65
As the action potential travels along the membrane, it descends down into the cell along the T-tubules, which causes excitation of the sarcoplasmic reticulum and release of ____ into the sarcoplasm
Ca2+
66
In regards to skeletal muscle contraction, in the resting muscle cell the myosin-binding site on the actin filament is concealed by _____
tropomyosin
67
In regards to skeletal muscle contraction, in the presence of high concentration of Ca2+ ions, Ca2+ binds to ____ __
troponin C
68
In regards to skeletal muscle contraction, binding of Ca2+ to troponin C changes the spatial configuration of the troponin molecule and causes the tropomyosin filament to shift which opens up what?
opens up the myosin-binding site on the actin filament
69
In regards to skeletal muscle contraction, myosin starts "walking" along the ____ fibers
actin
70
In regards to skeletal muscle contraction, myosin uses ATP energy to slide the actin along, so myosin is an ____
ATPase
71
Describe stage 1 of the contraction cycle (attachment)
at the beginning of contraction cycle, the myosin head is tightly bound to the actin molecule of the thin filament, and ATP is absent. This arrangement is called rigor configuration. ATP binds to the myosin head at the end of this step.
72
If there is no ATP to bind with myosin, the muscle stays rigid and is known as ____ ____
rigor mortis
73
Describe stage 2 of the contraction cycle (release)
ATP induces conformation changes to myosin head, myosin becomes released form actin
74
Describe stage 3 of the contraction cycle (bending)
ATP is broken into ADP and inorganic phosphate; as a result of hydrolysis of ATP, the myosin head bends (5nm)
75
Describe stage 4 of the contraction cycle (force generation)
myosin head binds to actin again; release of Pi from the myosin head causes the myosin head to generate a force and returns to its initial unbent position, which is the power stroke; later ADP is lost from the myosin head
76
During the power stroke, the ___ filament is forced along the ____ filament
actin; thick
77
Describe stage 5 of the contraction cycle (reattachment)
myosin head is attached to new actin and is ready for a new cycle
78
Describe the process of skeletal muscle relaxation
Following the depolarization, Ca2+ activated ATPase membrane pumps transport Ca2+ back into SR. Ca2+ dissociates from troponin C. Troponin complex returns to original state and pulls tropomyosin filament over myosin binding site - stops contraction.
79
Skeletal muscle relaxation is a rapid action that only takes ____ msec
30
80
Regeneration of skeletal muscle cells is due to the presence of ___ cells scattered between the skeletal muscle fibers
satellite
81
After injury, satellite cells become activated, proliferate and give rise to new ____, which fuse to form a new ___
myoblasts; fiber
82
Muscles respond to aging by increasing the ____, to exercise by ____, and to disuse by ____
diameter; hypertrophy; atrophy
83
Skeletal muscle is surrounded by layers of connective tissue:
the ____ surrounds individual muscle fibers
the ___ surrounds fascicles
the ____ surrounds a group of fascicles (muscle)
endomysium
perimysium
epimysium
84
____ muscle is the simplest type of muscular tissue
smooth
85
Smooth muscles are mostly specialized for what type of contractions
slow/rhythmic contractions of internal organs
86
Where can smooth muscle provide rapid and precise contraction?
the eye
87
Smooth muscle cells are elongated spindle-shaped or _____ cells that are 20-200 um in length.
fusiform
88
The nuclei of smooth muscles cells are ____ placed and long with tapered ends
centrally
89
Myofilaments of smooth muscle cells are more randomly distributed throughout the cytoplasm than in the skeletal muscle and are poorly organized. True or false?
true
90
In regards to smooth muscle, thin filaments are attached to anchoring points called ____ bodies, formed primarily by the actin-binding protein alpha-actinin
Dense bodies
note: dense bodies of smooth muscle are somewhat analogous to the Z lines of skeletal muscle fibers
91
The sarcolemma of smooth muscle cells possesses processes of large invaginations that resemble ____
caveolae
92
In regards to smooth muscle, caveolae and the vesicles along with sER function to deliver ____ to the cytoplasm
Ca2+
93
True or false? Very few gap junctions are found in smooth muscle
false; numerous
94
smooth muscle cells are enclosed by the external lamina and a network of ____ fibers. These fibers play in important role in the force transaction in the smooth muscle tissue.
reticular
95
Thin filaments of smooth muscle cells resemble the thin filaments of skeletal muscle fibers but without the ___ ____
troponin complex
96
___-____ is the principal component of thin filaments in the smooth muscle
F-actin
97
No ___ is present in the thin filaments of smooth muscle
troponin
98
_____ is a smooth muscle-specific actin-binding protein that masks the myosin-binding site on the actin fibers
Caldesmon
99
In regards to smooth muscle, thick filaments are formed by ____
myosin II
note: composed of 2 heavy chains and 4 light chains
100
Smooth muscle myosin binds to actin only when ____
phosphorylated
101
The neural stimulation of smooth muscle occurs through the _____ fibers of the ANS
postganglionic
102
Not all smooth muscle cells receive terminal nerves and terminal nerves and impulse transmission from cell to cell occurs through ____ junctions
gap
103
____ stimulation of a smooth muscle contraction can be elicited by various hormones, angiotensin II, vasopressin, and other agents
chemical
104
____ stimulation of smooth muscle, such as passive stretching of the organ can lead to the initiation of a muscular contraction
mechanical
105
In regards to smooth muscle contraction, during the excitation, Ca2+ is released into the sarcoplasm where it binds to ____
calmodulin
106
In regards to smooth muscle contraction, the Ca2+-calmodulin complex binds to ____, releasing it from actin and opening the myosin-binding site on F-actin
caldesmon
107
In regards to smooth muscle contraction, the Ca2+-calmodulin complex activates ____ ___-____
myosin light-chain kinase
108
In regards to smooth muscle contraction, myosin light-chain kinase phosphorylates the ____ (light) chain of the myosin molecule
regulatory
109
In regards to smooth muscle contraction, when the light regulatory chain is phosphorylated, myosin molecule unfolds and actin-binding site on the myosin head becomes open and ____ bind to ___
myosin; actin
110
In regards to smooth muscle contraction, the filaments slide. The cell shortens. Nucleus folds and becomes ____-shaped
corkscrew
note; this is a slow action and it often takes over a second
111
True or false? the sequence of events that takes place as smooth muscle is relaxing:
Ca2+ is pumped back into SR
Ca2+levels in sarcoplasm drop
Calmodulin dissociates from the light-chain kinase
Myosin is dephosphorylated, becomes inactive
Caldesmon binds to myosin-binding site on actin filament
true
112
Smooth muscle relaxation is slow but has a prolonged effect on the tissue and requires only ___% of the ATP that would have been used by skeletal muscle
10
113
Smooth muscles process a secondary mechanism that allows them to maintain long-term contractions with minimum energy spent. This is called a ____ state of the smooth muscle
latch
114
The latch state of smooth muscle is caused by the decrease of ATP activity while the myosin head is attached to actin. This causes prolonged contraction used to sustain the ____ of blood vessels
tone
note: similar to rigor mortis in skeletal muscle
115
Smooth muscles can be found in the walls of what?
larger hollow organs
116
Smooth muscle cells are found in the iris and ciliary body where they are responsible for what?
constriction and dilation of pupil
117
Smooth muscle fibers are present in the dermis of the skin where they are attached to hair follicles and form so called ___ ____ muscles
arrectores pilorum
118
Smooth muscles have moderate blood supply. True or false?
true
119
Smooth muscle is capable of ____ ____ response.
active regenerative
120
Cardiac muscle has limited regeneration. The number of dividing cells is ____%
0.1
121
Localized injury to the cardiac muscle results in the replacement of muscle cells with fibrous connective tissue that forms a scar. As a result, the cardiac muscle function is lost in the area of the injury. This type of injury and repair is seen in the ____ ____
myocardial infarction
122
How are cardiac muscle fibers formed?
by numerous cylindrical cells arranged end to end that are about 100 um long
123
Cardiac muscle cells have centrally placed, rounded nuclei. True or false?
true
124
The connections between individual cardiac muscle cells are marked with ______ _____
intercalated disks
125
When two cardiac muscle cells attach to one end of another cardiac muscle cell, one can observe ____ of muscle fibers. This is not seen in other types of muscle
branching
126
What type of junctions are found in the transverse portion of the intercalated disks?
adherens, desmosomes
127
What type of junctions are found in the lateral portion of the intercalated disks?
gap junctions
128
Cardiac muscle cells have large T-tubules that are found where?
at the Z-disks and not at the junction of A and I bands
129
In cardiac muscle there are small terminal cisternae that run parallel to the T-tubules only on one side of the tubule forming ____
diads
130
Cardiac conducting cells called the ______ ____ are cardiac muscle cells modified for the conduction of electric impulses in a way similar to nerve cells
purkinje
131
Purkinje fibers form nodes and bundles including the ____ and ____ nodes and the bundle of ____
SA; AV; His
132
Arteries have thicker ____ and tend to have narrower ____
walls; lumens
133
Arteries are composed of circularly arranged ____ muscle fibers
smooth
134
Walls of ____ are not distinctly separated
veins
135
Veins are ____ of smooth muscle instead of a continuous band
bundle
136
These vessels have very thin walls and only endothelial lining. They may contain valves.
lymphatic vessels
