L13, 14 & 15: Muscle Physiology Flashcards
(116 cards)
1
Q
three types of muscle?
A
skeletal, cardiac, smooth
2
Q
skeletal properties?
A
multinucleate, unbranched, voluntary activity
3
Q
cardiac properties?
A
1 or 2 nuclei, branched, non-voluntary
4
Q
smooth
A
single nucleus, unbranched, non-voluntary
5
Q
skeletal muscles are connected
A
to at least two bones
6
Q
an exception of the two-bone rule
A
biceps
7
Q
muscles are connected to bones with
A
tendons, connective elastic tissue
8
Q
muscle bodies are covered by
A
epimysium
9
Q
muscle bodies are divided into
A
fascicles
10
Q
fascicles are covered by
A
perimysium
11
Q
fascicles contain
A
muscle fibers
12
Q
muscle fibers are covered by
A
endomysium
13
Q
a muscle fiber semifluid cytoplasm
A
sarcoplasm
14
Q
contractile machinery in sarcoplasm
A
myofibrils
15
Q
plasma membrane of a musle fiber
A
sarcolemma
16
Q
surrounds each myofibril
A
sarcoplasmic reticulum
17
Q
fundamental unit of myofibril
A
sarcomere
18
Q
sarcomere elements
A
a band, i band, z line, m line, h zone
19
Q
z line
A
end of sarcomere, links thin filaments
20
Q
m line
A
middle of sarcomere, links thick filaments
21
Q
i band
A
thin filaments only
22
Q
h zone
A
thick filaments only
23
Q
a band
A
thick filaments + overlap
24
Q
which band is dark?
A
a band
25
which band is light?
i band
26
myosin parts
head, neck, tail
27
myosin types
myosin I inside the cell, myosin II in muscles
28
muscle contracts by
a sliding filament mechanism
29
cross-bridge steps
cross-bridge formation, power stroke, cross-bridge detachment, reactivation of myosin
30
cross-bridge formation?
activated myosin head with ADP and Pi binds to actin site, then Pi is released, the bond becomes stronger
31
power stroke?
ADP is released, sliding microfilament due to pivoting of the head
32
cross-bridge detachment?
ATP binds the head, the actin-myosin bond weakens, myosin head detaches
33
you got this!
you got this!
34
reactivation of myosin?
ATP is hydrolyzed to ADP and Pi, the energy activates the head, moves to the cocked position
35
does the H zone length change due contraction?
yes
36
does the Z distance change due to the contraction?
yes
37
does the A band length changes due to the contraction?
no
38
does the I band length change due to contraction?
yes
39
tropomyosin is
a rod-shaped protein, overlaps 7 actin monomers, covering myosin-binding sites
40
troponin is
a 3 subunit protein with TnC subunit doing Ca2+ binding
41
what causes uncovering of myosin-binding sites?
Ca2+ to TnC of troponin results in a conformational change of tropomyosin
42
what works together to coordinate contraction
transverse (t-)tubules and sarcoplasmic reticulum
43
what carries electrical information in muscle fibers?
by T-tubules
44
what releases calcium?
sarcoplasmic reticulum
45
muscle contraction step 1
action potential stimulates the muscle
46
muscle contraction step 2
muscle action potential goes to the T-tubule
47
muscle contraction step 3
t-tubules make SER release Ca2+
48
muscle contraction step 4
ATP and Ca2+ are required for thick-thin filament
49
muscle contraction step 5
electrical potential returns to normal, Ca2+ is pumped back to SER by Ca2+ pump proteins
50
what releases Ca2+ ions into the cytoplasm from SER
ryanodine receptors
51
what activates ryanodine receptors
voltage-gated protein, dihydropyridine (DHP) receptor in the T-tubule membrane
52
what triggers the DHP receptor?
muscle action potential
53
the only mechanism to stimulate an action potential
activation of motor neuron
54
motor neurons are located in
ventral horn
55
motor neuron axons are
myelinated and largest diameter
56
do motor neurons have a delay?
no
57
motor unit
motor neuron plus all muscle fiber it innervates
58
neuromuscular junction
junction of an axon terminal with the muscle fiber plasma membrane
59
the first major difference between interneuronal synapses and NMJs
a single depolarization of motor endplate is much larger
60
why is the depolarization of NMJ is larger than of interneuronal synapse?
larger area, more N-AChRs
61
second major difference between interneuronal synapses and NMJs
no inhibitory potentials in NMJs
62
tubocurarine
nondepolarizing neuromuscular blocking agent, antagonists, relaxes muscles
63
nicotine
N-ACh-R agonist
64
muscarine
M-ACh-R agonist
65
atropine
M-ACh-R antagonist
66
isometric contraction
no shortening, static
67
isotonic contraction
change of length, dynamic
68
concentratic contraction
tension > load, result
69
eccentric contraction
load > tension, no result
70
latent period
onset of contraction, few msec
71
contraction phase
tension increasing, 10-100 msec, calcium levels increases, release exceeds reuptake
72
relaxation phase
tension decreasing, long, cytosolic calcium levels decrease, reuptake exceeds release
73
types of isotonic contraction
concentric, eccentric
74
as load increases, plateau times
decreases
75
as load increases, latent period
increases
76
eventually, isotonic movement becomes
isometric
77
summation
increase in muscle tension from successive action potentials
78
unfused tetanus
at low stimulation frequencies, the tension may oscillate as the fiber partially relaxes between stimuli
79
fused tetanus
at higher stimulation frequencies tension does not oscillate, it becomes 3-5 times greater than isotonic twitch
80
twitch
same tension over a period of time
81
during tetanus, Ca2+ concentration
persistently elevated
82
the magnitude of active tension depends on
muscle fiber length
83
shorter than optimum length
thin filaments overlap, causing a decline in tension
84
beyond optimum length
decreased overlap between thin and thick filaments, no binding of myosin heads to actin
85
ATP is used in the skeletal muscle to... reason 1
dissociate myosin heads from actin
86
ATP is used in the skeletal muscle to... reason 2
energize the myosin heads when hydrolyzed
87
ATP is used in the skeletal muscle to... reason 3
lower cytosolic Ca2+ levels via Ca2+ pump in the SER
88
ATP is used in the skeletal muscle to... reason 4
restore ions that cross the cell membrane to their original compartment the Na+ K+ ATPase
89
three ways of ATP formation
phophorylation of ADP by creatine phosphate, glycolysis, oxidative phosphorylation
90
fatigue
muscle is no longer able to generate or sustain the expected power output
91
fatigue depends on
intensity and duration of activity, metabolism, muscle composition, fitness level
92
two types of fatigue
central and peripheral
93
_ fatigue comes before physiological fatigue
phychological
94
central fatigue
changes proximal to motor neuron, motivation, recruitment
95
peripheral fatigue
motor unit itself, exhaustion of muscle energy supplies
96
high-frequency fatigue
fast fatigue, fast rest period
97
low-frequency
long duration, long rest period
98
extended submaximal exertion
depletion of glycogen stores, decreased Ca2+ release
99
short-duration maximal exertion
increased level of inorganic phosphate, altered power stroke
100
maximal exercise
K+ rise in the t-tubule ECF, altering the muscle fiber membrane potential
101
muscle fibers are classified on the basis of
maximal velocities of shortening and the major pathway used to form ATP
102
high ATPase activity
fast and type II fibers
103
low ATPase activity
slow and type I fibers
104
major pathways to form ATP
oxidative and glycolytic
105
oxidate fibers have lots of
myoglobin
106
myoglobin
oxygen-binding protein, gives fibers dark red color
107
fiber with glycolytic enzymes
white muscle fibers
108
three principal types of skeletal muscle fibers
slow-oxidative (type I), fast-oxidative glycolytic fibers (type IIa), fast-glycolytic fibers (type IIb)
109
type I fibers description
low myosin ATPase activity, high oxidative capacity
110
type IIa fibers description
high myosin ATPase activity, high oxidative capacity, intermediate glycolytic capacity
111
type IIb fibers description
high myosin ATPase activity with high glycolytic capacity
112
type I fatigue?
resistant to fatigue, maintain long periods of contractile activity
113
type IIa fatigue?
intermediate capacity to resist fatigue
114
type IIb
fatigue rapidly
115
singe motor unit is composed of
single fiber type
116
recruitment order
first type IIb, then type IIa, then type I
