Muscle: Structure and Function Flashcards
1
Q
skeletal muscle generally attach to bones through what?
A
tough connective tissue tendons
2
Q
a muscle attaches to the more fixed bone at its
A
origin
3
Q
a muscle attaches to the more movable bone at its
A
insertion
4
Q
decrease angle of joint
A
flexors
5
Q
increase angle of joint
A
extensors
6
Q
prime mover of any skeletal movement
A
agonist
7
Q
muscles that act on the same joint to produce opposite actions
A
antagonists
8
Q
fibrous connective tissue from tendons forms sheaths called ( ) that extend around and into skeletal muscle
A
epimysium
9
Q
inside the muscle, the epimysium divides muscle into columns called ( )
A
fascicles
10
Q
connective tissue around fascicles
A
perimysium
11
Q
muscle fibers are ensheathed by a thin connective tissue layer called the ( )
A
endomysium
12
Q
the plasma membrane of the muscle is called what?
A
sarcolemma
13
Q
muscles are similar to other cells except they are ( )
A
multinucleate and striated
14
Q
what does the NMJ include?
A
1) the single synaptic ending of the motor neuron that’s innervating each muscle fiber
2) underlying specializations of sarcolemma
15
Q
the place on the sarcolemma where the NMJ occurs is the
A
motor end plate
16
Q
Ach release can be inhibited by what?
A
Botulinum toxin (botox)
17
Q
The Ach transduces the signal and it can be inhibited by what?
A
curare
18
Q
what inhibits AchEsterase release?
A
neostigmae
19
Q
each fiber contains bundles of subunits called ( ), which make up about 80% of the fiber volume
A
myofibrils
20
Q
myofibrils are packed with ( ), which are composed of thin and thick filaments
A
myofilaments
21
Q
give rise to bands which underlie striations
A
thick and thin filaments
22
Q
dark and contains thick filaments (mostly myosin)
A
A band
23
Q
light area at the center of the A band
A
H band
24
Q
the area where actin and myosin don’t overlap
A
H band
25
light and contains thin filaments (mostly actin)
I band
26
at the center of I band is ( ), which is where actins attach
Z disc/line
27
contractile units of skeletal muscle consisting of components b/w 2 Z discs
sarcomeres
28
structural proteins that anchor myosin during contraction
M line
29
an elastic protein attaching myosin to Z disc that contributes to elastic recoil of muscle
Titin
30
which ones shorten and why: I, H, or A band
I and H bands because they are relatively thin filaments
31
what is the Sliding Filament Theory of Contraction?
the muscle contracts because myofibris get shorter
32
cross bridges are formed by heads of myosin molecules that extend toward and interact with ( )
actin
33
the sliding of filaments is produced by the actions of ( )
cross bridges
34
Each myosin head (cross bridge) contains an ATP-binding site which functions as an
ATPase
35
Myosin can't bind to actin unless it is ( )
"cocked" by ATP
36
After binding, myosin undergoes a conformational change (power stroke) which exerts force on ( )
actin
37
what happens after a power stroke?
myosin detaches
38
the control of cross bridge attachment to actin is through what?
troponin-topomyosin system
39
what filament lies in grove between double row of G-actins (which make up actin thin filament)
tropomyosin
40
what is attached to tropomyosin at intervals of every 7 actins?
troponin
41
in relaxed muscle, what blocks binding sites on actin so crossbridges can't occur?
tropomyosin
42
when does tropomyosin block site on actin so crossbridges can't occur?
when Ca2+ levels are low
43
Ca2+ levels decrease because it is continually pumped back into the ( )
sarcoplastic reticulum
44
calcium reservoir in muscle
sarcoplastic reticulum
45
most ca2+ in the SR is in ( )
terminal cisternae
46
running along terminal cisternae are ( )
T tubules
47
contraction can occur only when ( )
binding sites are exposed
48
when Ca2+ levels rise, Ca2+ binds to ( ) causing conformational changes that moves tropomyosin and exposes binding sites
troponin
49
Release of Ach at the NMJ causes large depolarizing ( ) and ( ) in the muscle
end-plate potentials and APs
50
APs race over the sarcolemma and down into the muscle through
T tubules
51
T tubules are extensions of
sarcolemma
52
Ca2+ in the SR are mechanically linked to channels in the ( )
T tubules
53
APs in the T tubules cause release of Ca2+ from the cisternae through what? what is it called?
Voltage gated and Ca2+ release channels---it's called electromechanical release
54
When APs cease, the muscle relaxes bc Ca2+ channels close and the Ca2+ is pumped back into the SR by ( )
Ca2+ ATPase pumps
55
Is ATP needed for relaxation or for contraction?
BOTH!
56
a single rapid contraction and relaxation of muscle fibers
twitch
57
if a 2nd stimulus occurs before muscle relaxes for 1st, the 2nd twitch will be greater; this is called what?
summation
58
contractions of varying strength are obtained by stimulation of varying numbers of fibers
graded contractions
59
if a muscles is stimulated by an increasing frequency of electrical shocks, its tension will increase to a maximum
incomplete tetanus
60
if the frequency is so fast that no relaxation occurs, a smooth sustained contraction results
complete tetanus/tetany
61
if a muscle is repeatedly stimulated with a max voltage to produce individual twitches, successive twithces get larger
treppe/staircase effect
62
what is treppe caused by?
accumulation of intracellular Ca2+
63
the exerted force does not cause load to move and length of fibers remains constant
isometric contraction
64
force remains constant throughout the process
isotonic contraction
65
2 ways length changes:
1) concentric contraction
| 2) eccentric contraction
66
Series-Elastic Component
tendons and connective tissue are elastic and absorb tension as muscle contracts, and recoil as muscle relaxes and spring back to resting length
67
strength of muscle contraction influenced by:
1) frequency of stimulation
2) thickness of each muscle fiber
3) inital length of muscle fiber
68
ideal resting length
that which can generate max force
69
if the exercise is moderate, aerobic respiration contributes the majority of the muscle requirements after how long?
the first 2 minutes
70
the percentage of VO2max at which there is significant rise in blood lactate levels
lactage (anaerobic) threshold
71
during light exercise, most of the energy is derived from
aerobic respiration of fatty acids
72
during moderate exercise, energy is derived
equally from fatty acids and glucose
73
during heavy exercise, energy is derived
2/3 from glucose and liver increased glycogenolysis and the GLUT-4 glucose carrier is moved to muscle cell's plasma membrane
74
when does O2 debt occur?
when O2 is withdrawn from hemoglobin and myoglovin and bc of the O2 needed for metabolism of lactic acid produced by anaerobic respiration
75
a source of high energy phosphate that allows the regeneration of ATP from ADP
Phosophocreatine
76
Type I fibers
slow-twich, slow-fatigue; slow oxidative
77
type: use mostly aerobic respiration, have rich capillary supply, many mitochondira, and aerobic enzymes
Type I
78
type: small motor neurons with small motor units
Type I
79
Type IIX fibers
fast twitch, fast fatigue; white fast glycolytic
80
type: adapted to contract fast using anaerobic
Type IIX
81
type: large stores of glycogen, few capillaries and mitochondria, little myoglobin
Type IIX
82
Type IIA
fast twitch, fast fatigue; fast oxidative
83
type: intermediate
Type IIA
84
sustained muscle contraction fatigue is due to an accumulation of ( )
extracellular K+
85
caused by changes in CNS rather than by fatigue in muscles themselves
central fatigue
86
the first "wall" an athlete must overcome in endurance exercise
central fatigue
87
endurance training improves aerobic capacity by ( ) and lactate threshold by ( )
20%; 30%
88
once a myofibril has attained certain thickness, what happens?
it may split into two myofibrils
89
allow AP to spread throughout cardiac muscle
intercalated disks (gap junctions)
90
has no sarcromeres
smooth muscle
91
contains 16X more actin than myosin which allows greater stretching and contracting
smooth muscle
92
smooth: actin filaments are anchored to ( )
dense bodies
93
smooth: contraction is controlled by Ca2+ but is different from striated muscle in that it ( )
has little SR and no troponin/tropomyosin
94
smooth: Ca2+-calmodulin complex activates what?
myosin light chain kinase (MLCK)
95
smooth: myosin is dephosphorylated by what and can no longer form cross bridges?
myosin phosphatase
96
smooth muscle has slower contractions than striated but can form a state of prolonged binding of myosin to actin called ( )
latch state
97
smooth muscle can be divided into:
1) single unit
| 2) multiunit
98
smooth type: spontaneously active (myogenic)
single unit
99
smooth type: have gap junctions to spread electrical activity
single unit
100
smooth type: some of these cells are pacemakers
single unit
101
smooth type: requires nerve stimulation by autonomic nervous system
multiunit
102
smooth type: NT is released along a series of synapses called variscosities
mulitunit
103
smooth muscle's variscosities are called ( )
synapses en passant
104
smooth type: ex: inestinal and uterine smooth muscles
single
105
smooth type: ex: arterial smooth muscle and the ciliary muscles attached to the lens of the eye
multi
