Test 3 -Skeletal Muscle Flashcards
(126 cards)
1
Q
Muscle
A
Little mouse
2
Q
Muscle functions
A
- movement
- maintenance of posture
- join stabilization
- heat generation
3
Q
movement of muscle
A
skeletal muscle attaches to the skeleton and moves the body by moving the bones
4
Q
maintenance of posture
muscle function
A
certain skeletal muscles contract continuously to maintain posture, enabling the body to remain in standing or sitting position
5
Q
join stabilization (muscle function)
A
muscle tone is a constant, low level of contractile force that is generated by a muscle even when it is not causing movement
6
Q
muscle tone stabilizes joints by?
A
keeping tension on the muscle tendons that cross over joints just external to the join capsule
7
Q
heat generation (muscle function)
A
muscle contractions produce heat that plays a vital role in maintaining normal body temperature at 98.6 F (37 C)
8
Q
what are some special functional characteristics of muscle tissue that distinguish it from other tissues
A
contractility
excitability
extensibility
elasticity
9
Q
contractability of muscles
A
- muscle cells shorten and generate a strong pulling force as they contract
- actin and myosin
10
Q
excitability of muscles
A
nerve signals or other factors excite muscle cells, causing electrical impulses to travel along the cell’s plasma membrane, causing the cells to conract
11
Q
extensibility of muscles
A
muscle tissue can be stretched by the contraction of an opposing muscle
12
Q
elasticity of muscles
A
after being stretched, muscle tissue can recoil passively and resume its resting lenght
13
Q
what are the three types of muscle tissue?
A
skeletal
cardiac
smooth
14
Q
each type of muscle tissues can be characterized by what two main features?
A
- the presence or absence of striations in the muscle cells
2. whether control is voluntary or involuntary
15
Q
striated vs nonstriated
A
- striated muscle tissue has stripes extending transversely across the muscle cells
- nonstriated muscle does not have the distinctive bands of striation
16
Q
in muscles voluntary and involuntary refers to?
A
to the innervation of the muscle tissue
17
Q
voluntary muscle
A
innervated by voluntary motor nerves and subject to conscious control
- you can control this muscle tissue at will
18
Q
involuntary muscle
A
innervated by the involuntary portion of the nervous system and cannot be controlled consciously
19
Q
skeletal muscle tissue
A
-located in the skeletal muscle, discrete organs that attach to and move
the skeleton
- make up 40% of the body weight
- cells are striated
- contractions is subject to voluntary control
20
Q
cardiac muscle tissue
A
- occurs only in the walls of the heart
- cells are striated
- contractions is subject to involuntary control
- visceral muscle
21
Q
smooth muscle tissue
A
- most found in the walls of hollow internal organs
- cells lack striations
- contractions is subject to involuntary control
- visceral muscle
22
Q
what is an important similarities between skeletal and smooth muscles only
A
the cells of skeletal and smooth muscle tissu (only) are called fibers because they are elongated
23
Q
in all three types of muscle tissue, muscle contractions depend on?
A
myofilaments
- specific types of microfilaments that are responsible for the shortening of muscle cells
24
Q
the plasma membrane of muscle cells are called?
A
sarcolemma
25
the cytoplasm of muscle cells are called?
sarcoplasm
26
does the function of cytoplasm in comparison to sarcoplams or plasma membrane to sarcolemma differ?
no. they are the same, just different name
27
what holds the fibers of a skeletal muscles together?
several sheath of connective tissue
from external to internal:
- epimysium -> perimysium -> endomysium
28
epimysium
- "outside the muscle"
| - an overcoat of dense, irregular C.T that surrounds the whole skeletal muscle
29
perimysium
- "around the muscle"
| - a layer of fibrous C.T. that surrounds each fascicle
30
fascicle
a group of muscle fibers
31
endomysium
- "within the muscle"
| - a fine sheath of C.T. consisting mostly of reticular fibers that surrounds each muscle fiber within each fascicle
32
What are the function of the fibrous connective tissue of skeletal muscles?
binds muscle fibers together and hold them in parallel alignment so they can work together to produce force
33
all three sheaths are continuous with?
with the tendon
34
tendon
the connective tissue structure that joins skeletal muscle to bones
35
what happens when muscle fibers contract?
they pull on the surrounding endomysium
36
Because of the continuity between sheath what happens after the surrounding endomysium is pulled?
the pull is then exerted on the perimysium, epimysium, and tendon
37
what else does the sheath provide?
provide a muscle with much of its elasticity and carry the blood vessels and nerves that serve the muscle fibers
38
in general, each skeletal muscle is supplied by?
one nerve, one artery, and one or more veins
39
where does the nerve, artery, and veins all enter or exit the muscle?
near the middle of its lenght
40
the nerves and vessels branch repeatedly where?
branch repeatedly in the intramuscular CT, with the smallest branches serving individual muscle fibers
41
capillaries of the skeletal muscle form a network within the
endomysium
42
the rich blood supply to muscles reflects the?
high demand that contracting muscle fibers have for nutrients and oxygen
43
the smallest nerve branches serve?
individual muscle fibers
44
what is neuromuscular joints?
interface between nerve and muscle fiber
| synaptic cleft between neuron and muscle fibers
45
what is a muscle attachement
the location on a bone where a muscle connects to the bone
46
each skeletal muscle extends from?
one bone to another crossing at least one movable join
47
what happens when a muscle contracts?
it causes one of the bones to move while the other bone usually remains fixed
48
the attachment of the muscle on the less movable bone is called?
the origin of the muscle
49
the attachment on the more moveable bone is called?
(the muscle's) Insertion
50
when muscle contracts what happens between insertion and origin?
muscles insertion is pulled towards its origin
51
in the muscle of the limbs, the origin is?
the more proximal attachment of the muscle
52
in the muscles of the limbs, the insertion is?
the more distal attachment
53
the origin and insertion of a given muscle can be at either attachment of the muscle, depending on?
a. what position of the body is in
| b. the movement is produced as the muscle contracts
54
muscles attach to their origins and insertions via?
strong fibrous periosteum of the bone
55
what happens in direct or fleshy attachments
the attaching strands of the CT are so short that the muscle fascicles themselves appear to attach directly to the bone
56
in indirect attachments, the ct?
Connective tissues extends well beyond the end of the muscle fibers to form either a cordlike tendon or a flat sheet called aponeurosis
57
Which are more common attachments?
indirect attachments are more common than direct attachments and most muscles have tendons
58
raised bone markings are often present where?
where tendons meet bones (eg Greater trochanter)
59
microscopic anatomy of skeletal muscle fiber
skeletal muscle fibers are long, cyndrical cells
- diameter 10 - 100 um
- lenght: several cm (short muscles) to dozens of cm (long muscles
60
each skeletal muscle fiber is formed by?
the fusion of hundreds of embryonic cells.
| - contains many nuclei
61
where are the nuclei located in skeletal muscle fibers?
they lie in the periphery of each fiber, just deep to the sacrolemma
62
the striations of skeletal muscle fibers are the result from?
from the internal structure of long, rod-shaped organelles called myofibrils
63
myofibrils
specialized contractile organelles unique to muscle tissue that make up more than 80% of the sacroplasm
- a long row of repeating segments called sarcomeres
64
sarcomeres
- "muscle segments"
| - the basic unit of contraction
65
Z-discs or Z-lines
the boundaries at the two ends of each sarcomere are called?
66
where are actin filaments located?
attached to each Z-disc and extending towards the center of the sacromere
67
actin filaments
- (fine myofilaments) thin filaments which consist primarily of the protein actin
68
myosin filaments
cylindrical bundle of thick filaments that consists primarily of myosin molecules
69
where are myosin molecules located?
in the center of the sacromere and overlapping the inner ends of the thin filaments
70
myosin filaments also contains what enzyme?
ATPase enzymes that split ATP to release the energy required for muscle contractions
71
the sarcomere structrue explains?
the pattern of striations in skeletal muscle fibers
72
the dark bands are created by?
the full length of the thick filaments in the sarcomeres, along with the inner ends of the thin filaments
73
what region is dark bands in?
the A band
74
H zone
- central part of an A band,
| - no thin filaments reach
75
M line
- in the center of the H-zone
| - contains tiny rods that hold the thick filaments together
76
I bands
the two regions on either side of the A band, which contains only thin filaments
77
I bands forms which bands?
light bands
78
each skeletal muscle fiber contains two sets of?
two sets of tubules that participate in the regulation of muscle contraction
79
what are the two set of tubules in the skeletal muscle fiber
1. sarcoplasmic reticulum (SR)
| 2. T tubules
80
Sarcoplasmic reticulum (SR)
an elaborate smooth endoplasmic reticulum whose interconnecting tubules surround each myofibril and run longitudinally along the myofibril
81
terminal cisternae
- "end sacs"
| - larger perpendicular cross-channels over the junction between the A bands and I bands
82
The sacroplasmic reticulum stores ?
large quantities of calcium ions Ca2+
83
when are calcium ions released?
when the muscle is stimulated to contract
84
Ca2+ ions actions
- diffuse through the cytosol to the thin filaments, where they trigger the sliding filament mechanism of contraction
- after the contraction, the Ca@+ ions are pumped back into the SR for storage
85
muscular contraction in skeletal muscle is controlled by?
nerve generated impulses that travel along the sarcolemma of the muscle cell then these impulses are further conducted by T tubules
86
T tubules
deep invaginations of the sarcolemma that run between each pair of terminal cisternae of the sarcoplasmic reticulum
87
Because T tubules are continuations of the sarcolemma they conduct each impulse to?
they conduct each impulse to the deepest regions of the muscle fiber
88
Triad
| T-tubules
the complext of a T tubule with flanked by two terminal cisternae at each A-I junction
89
the two types of muscle contraction involved in producing movements
1. concentric contraction
| 2. eccentric contraction
90
concentric contraction
the shortens and does work
91
eccentric contraction
a muscle generates force as it lengthens
| - essential for controlled movement and resistance to gravity
92
when muscles are acting "like a brake" they are contracting?
eccentrically
| - landing from a jump
93
what explains concentric contractions of skeletal muscle?
sliding filament mechanism
94
sliding filament mechanism
- actin + myosin + cross bridges
- contraction results as the myosin heads of the thick filaments attach to the thin filaments at both ends of the sarcomere and pull the thin filaments toward the center of the sarcomere by swiveling inward
95
sliding filament mechanism
| - what happens after a myosin head pivots at its hinges?
it lets go, returns to its original position, binds to the thin filament farther along its length and pivots again
96
the ratchet-like cycle of the sliding filament mechanism during a single contraction is?
repeated many times
| - the thick and thin filaments do not shorten, they merely slide past one another
97
the sliding filament mechanism is initiated by ?
the release of Ca2+ ions from the SR and the binding of those ions to the thin filaments
98
Sliding filament mechanism is powered by?
ATP
99
what does the action of the thick filaments do?
pulls the two Z discs closer together, causing each sarcomere to shorten
a) causing the I bands to shorten
b) causing the H zones to disappear completely
100
Why does the A bands stay the same lenght?
because the length of the thick filaments does not change
101
the optimal resting length for skeletal muscle fibers is?
the lenght that will generate the greatest pulling force when the muscle is contracted
102
what is the optimal resting length?
i dont know
103
When does the optimal length occurs?
when a fiber is slightly stretched so that its thin and thick filaments overlap only to a moderate extent..Why?
104
skeletal muscles range of optimal operational lenght
runs from about 80% of their normal resting lenght to about 120% of that length
105
joins normal actions
do not let any bone move so widely that its attached muscles could not shorten or stretch beyond their optimal range
106
titin
a spring like molecule in sarcomeres that resists overstretching
107
where does the titin molecules in a sarcomere extend from?
from the Z disc to the thick filament and run within the thick filament to attach to the M line
108
caridac muscle
the muscle tissue of the heart wall
109
myocardium
thick layer formed by the cardiac muscle
110
contraction of the cardiac muscle does what
pump blood through the blood vessels of the circulatory system
111
cardiac muscle - discription
striated like skeletal muscle and it contracts through the sliding filament mechanism
112
what kind of cell are cardiac muscles?
single cells separated from one another by a delicate endomysium
- each cell contains one or two neuclei in its center, not at periphery
113
are cardiac muscle cells called fibers?
no
114
what is unique to cardiac muscle?
its cells branch and join together at complex junctions called intercalated discs so that they form cellular network
115
what are the three types of cell junctions that intercalated discs have?
desmosomes
fasciae adherans
gap junction
116
fasciae adherans
long, desmosome-like junctions
117
desmosomes and fasciae adherans function
hold the cells together
118
gap junction function
allow ions to pass between cells
119
where are most smooth muscle of the body found?
walls of viceral organs that contracts via the slliding filament mechanism
120
six major location of smooth muscle
1. inside the eye
* ***in the walls of the
2. circulatory vessels
3. respiratory vessels
4. digestie tubes
5. urinary organs
6. reproductive organs
121
each smooth muscle fiber is a?
spindle shaped cell with one centrally located nucleus
- cells are separated by endomysium
- no s`triations or sarcomeres
122
what fills the sacroplasm of smooth muscle?
interdigitating thick and thin filaments
123
the fibers of smooth muscles in the walls of hollow viscera are?
grouped into sheets of smooth muscle tissue
| - often two sheets are present, with their fibers oriented at right angles to each other
124
smooth muscle layers
1. longitudinal layer
| 2. circular layer
125
circular layer and longitudinal layer of smooth muscle
- circular layer constricts the hollow organ
| - longitudinal layer shortens the organ's lenght
126
peristalsis
- around contraction
- a process by which the circular layer and longtitudinal muscle layers generate alternate waves of contraction and relaxation that propel substance through the organ
