Jan 31st Content Flashcards
(172 cards)
1
Q
Muscle classifications
A
skeletal, smooth, cardiac
2
Q
Characteristics of skeletal muscle
A
multinucleated, has mitochondria, transverse tubules (t-tubules), myofibrils, sarcomeres, intracellular structures (sarcolemma, sarcoplasm, sarcoplasmic reticulum)
3
Q
Sarcolemma =
A
plasma membrane
4
Q
Sarcoplasm =
A
cytoplasm
5
Q
Sarcoplasmic reticulum =
A
smooth ER
6
Q
What transfers force to the tendon then force to bone resulting in movement?
A
connective tissue
7
Q
Force produced at the level of the
A
sarcomere
8
Q
Epimysium
A
surrounds entire muscle
9
Q
Perimysium
A
middle; surround bundles of muscle fibers
10
Q
Endomysium
A
surrounds individual muscle fibers
11
Q
Satellite cells
A
myogenic stem cells located within the sarcolemma
12
Q
Satellite cells help with
A
regenerative cell growth
13
Q
Satellite cells may play a role in
A
hypertrophy
14
Q
Through donation of what do muscle fibers continue to grow
A
nuclei
15
Q
Structures that give skeletal and cardiac muscle their striated appearance
A
myofibrils
16
Q
Myofibrils consist of orderly arrangements of
A
actin (thin) & myosin (thick)
17
Q
Structure of the sarcomere
A
I-band (Z-line, titin), A-band (thin filament, m-line, thick filament), I-band (titin, z-line)
18
Q
Myofibrils lead to
A
sarcomeres
19
Q
Tropomyosin is locked onto
A
actin
20
Q
Troponin is the lock that attaches to
A
tropomyosin
21
Q
Troponin pulls away when
A
calcium attaches to it
22
Q
A molecule spring that provides tension
A
Titin
23
Q
Myofibrils inside
A
endomysium
24
Q
Myosin filaments are oriented with their trials pointed
A
toward the center of the sarcomere
25
Proportion of actin to myosin in myofibril =
density
26
Myosin is
thick
27
Actin is
thin
28
Actin consists of
tropomyosin and troponin
29
Skeletal Muscle Mass
75% water, 20% protein, 5% other
30
Arteries and veins lie parallel to
individual muscle fibers
31
Extensive branching of blood vessels ensures each muscle fiber an
adequate oxygenated blood supply from the arterial and rapid removal of CO2 in venous circulation
32
Trained muscle increased capillary to muscle fibers ratio helps explain
improved exercise capacity with endurance training
33
Enhanced capillary microcirculation expedites removal of
heat and metabolic byproducts from active tissues in addition to facilitating delivery of oxygen, nutrients, and hormones
34
Enhanced vascularization at capillary levels proves beneficial during activities that require
high level steady-rate aerobic metabolism
35
Vascular stretch and shear stress on the vessel walls from increased blood flow during exercise stimulates _____________ __________ with ____________ __________ ___________
capillary development; intense aerobic training
36
Capillary to fiber ratio
fibers grow more than added capillaries; ratio decreases
37
Motor units are made up of
a motor neuron and the skeletal muscle fibers innervated by the motor neuron's axon terminals
38
Groups of motor units work together to
coordinate contractions of a single muscle
39
All motor units within a muscle are considered a
motor pool
40
What moves down the axon arriving at the nerve terminak?
action potential
41
Action potential ________ the nerve terminal
depolarizes
42
Depolarization of the nerve terminal activates
voltage-gated calcium channels
43
Calcium enters the synaptic terminal and increases
cytosolic calcium concentration
44
Increased cytosolic calcium causes release of
neurotransmitter from vesicles
45
Neurotransmitter enters into __________ _________ through ____________
synaptic cleft; exocytosis
46
Neurotransmitter dissociates from receptor and is removed from synpase by (3)
metabolism, reuptake into nerve terminal, or diffusion away from synapse
47
Neurotransmitter =
Acetylcholine
48
Postsynaptic receptor
nicotinic-cholinergic receptor (NAChR)
49
What is nicotinic-cholinergic receptor (NAChR)?
a ligand-gated channel
50
Nicotinic-cholinergic receptor (NAChR) is selective for
sodium and potassium
51
Activation of nicotinic-cholinergic receptor (NAChR) allows
diffusion of sodium into the cell and potassium out of the cell
52
Acetylcholine esterase (AChE) is localized in
folds of the endplate
53
Acetylcholine esterase (AChE) hydrolyses the Ach to
choline and acetate
54
What is taken back into the nerve terminal by sodium dependent co-transporter
choline
55
Choline taken back into the nerve terminal is used to
synthesize new Ach
56
What diffuses away from the synaptic cleft
acetate
57
Acetate is taken up by _______ and enters __________ ___________
cells; metabolic pathways
58
Duration of synaptic transmission
1 ms
59
Only channels present at endplate
nicotinic-cholinergic receptor (NAChR)
60
Endplate is/is not electrically excitable
is not
61
The membrane surrounding the endplate is/is not electrically excitable
is
62
Membrane surrounding the endplate contains
voltage-gated sodium and potassium channels
63
Current produced by EPP spread to surrounding muscle membrane and ________ it to _________
depolarized; threshold
64
Current activates ________________ __________ __________ and produces an
voltage-gated sodium channels; action potential
65
Ratio correspondence of motor neuron action potentials and action potentials in muscle
1:1
66
Voltage-dependent calcium channels (DHP receptors) located in
t-tubules
67
Activation of what channels allows calcium to flow out of the SR into cytoplasm
calcium release channels
68
What is in the SR membrane that pumps cytosolic calcium into the SR
calcium ATPase
69
Action potentials travel down sarcolemma from endplate into the ____________ and activate ___________ __________ ____________
t-tubules; voltage-gated calcium channels
70
Activation of voltage gated calcium channels activates
calcium release channels
71
Activation of calcium release channels causes release of
calcium from lateral sacs of SR
72
Calcium binds to
troponin
73
Troponin removes blocking action of
tropomyosin
74
Myosin cross-bridge bind to
actin
75
Sequestration of calcium into the SR decrease
cytosolic calcium concentrations
76
Calcium dissociates from
troponin
77
Once calcium dissociates from troponin, what ceases
cross-bridge cycling
78
One cross-bridge cycling ceases, the sarcomere
extends to resting length
79
Force generation produces shortening of skeletal muscle fiber, overlapping of filaments in each sarcomere, propelled by movements of cross-bridges
Sliding filament theory
80
Ability of muscle fiber to generate force and movement depends on
interaction of contractile proteins actin and myosin
81
Cross-Bridge Cycle
1. energized cross-bridge binds to actin
2. phosphate release from myosin for power stroke pulli actin towards center of sarcomere
3. ATP binds to myosin head causes detach
4. ATP hydrolyzed into ADP + Pi for new cross-bridge
82
If no ATP available for cross-bridge, it remains
attached to actin producing rigor mortis
83
Rigor mortis peaks
12 hours after death
84
rigor mortis disappears
48-60 hours after death due to breakdown of muscle
85
Regulator proteins
tropomyosin and troponin
86
Protein that intertwines with actin and covers myosin binding sites on actin
tropomyosin
87
protein binds to tropomyosin and holds it over myosin binding site
troponin
88
Subunits of troponin
inhibitory, calcium-binding, tropomyosin-binding
89
Calcium-binding sites are on
troponin
90
Binding of calcium to calcium-binding sites causes
change of troponin to move tropomyosin and expose myosin binding sites on actin
91
Endoplasmic reticulum-like organelles that store calcium in skeletal muscle (and cardiac) muscle fibers
sarcoplasmic reticulum (SR)
92
The SR surrounds the
myofibrils
93
Enlargements at the end of SR and is associated with the transverse tubule
lateral sacs
94
Invaginations of the muscle plasma membrane (sarcolemma)
transverse tubules (t-tubules)
95
Activation of motor neuron cell body leads to
an action potnetial
96
Action potential at nerve terminal of motor neurons causes release of
acetylcholine at neuromuscular junction
97
Acetylcholine activates
nicotinic receptors in endplate
98
Activation of nicotinic receptors produces a
end-plate potential
99
End-plate potential depolarizes the ____________ ___________ ___________ and produces an _________ ______________
surrounding muscle membrane; action potential
100
Action potential propagates to the
end of the muscle fiber
101
Action potential enters t-tubule and activates
voltage-gated calcium channels (DHP receptors)
102
Calcium is released from sarcoplasmic reticulum via
calcium release channels
103
Calcium binds to
troponin
104
Tropomyosin moves to uncover
myosin binding sites on actin
105
Once myosin binding sites are uncovered
cross bridge cycling begins
106
Calcium ATPase pumps calcium back into
sarcoplasmic reticulum
107
Once calcium ATPase pumps calcium back to the SR, calcium dissociates from
troponin
108
Once calcium dissociates from troponin, tropomyosin
covers myosin binding sites and cross bridge cycling ends
109
The plateau and descending limb of the isometric/concentric force-length relationship are well predicted and explained by the amount of
overlap between actin and myosin filaments
110
When muscle is stretched while activated and held at a final length long enough for force transients to cease, steady force achieved is higher than steady force developed when muscle is activated while already held isometrically at same final length
Residual Force Enhancement
111
Force enhancement after active muscle stretching was maintained when muscles were deactivated
Passive Force Enhancement
112
Force enhancement has a passive component and part of that passive components originates in the
molecular spring titin
113
Hypothesized that titin is a molecular spring whose stiffness can be regulated by
activation and/or force production
114
Titin extends from
sarcomere's z-disc to m-band
115
Titin runs freely in the
I-band
116
Titin's extensibility provdes sarcomeres with
passive force
117
Passive force from titin is thought to
maintain thick filaments during contraction and provide stability and uniformity to adjacent sarcomeres
118
Structural arrangement of serially aligned spring elements indicates titin's stiffness can be
regulated
119
Skeletal muscles are activated by release of
calcium from SR
120
Stretching myofibrils within physiological limits results in
higher passive forces in presence of physiological levels of calcium
121
Deactivation of actively stretched myofibrils at an average sarcomere length of 5.0 um resulted in
no change in force
122
Passive structures of muscles are ________ and ________ when passively stretched out and become _________ and ___________ during active stretching
soft and compliant; hard and stiff
123
Titin forces increase when actin-myosin force
decrease
124
When titin is eliminated, all passive and active force transmission across sarcomeres is
lost
125
The long axis of a muscle determines the
arrangement of individual fibers
126
Differences in sarcomere alignment and length strongly affect a muscle’s
force and power generating capacity
127
Fibers run parallel to muscle's long axis and taper at tendinous attachment
fusiform
128
Fan-shaped fiber's fasciculi lie obliquely
pennate
129
Fusiform's fiber length and fiber force generation transmits directly to
tendon
130
Fusiform fiber arrangement facilitates
rapid muscle shortening
131
In fusiform, what are equal
physiological and anatomical
132
In pennate, anatomical misses
some fibers
133
In pennate, physiological contains
all fibers
134
Total cross-sectional areas of all fibers within a particular muscle
Physiologic Cross Sectional Area
135
How do pennate differ from fusiform?
contain shorter fibers, possess more individual fibers, exhibit less range of motion
136
Muscles with greater pennation are slower in _______ _________, and generate greater _________ and __________
contractile velocity; force and power
137
Series-fibered muscle features
individual fibers that run parallel to muscle's line of pull
138
Complex parallel arrangement features
muscle fibers that terminate in muscle's midbelly and taper to interact with connective tissue matrix or adjacent fibers
139
Arrangement enables parallel packing of
short fibers within a long muscle
140
Force exerted by muscle on object
tension
141
Force exerted by object on muscle
Load
142
Contraction under conditions in which it develops tension but does not change length
isometric
143
Contraction in which muscle changes length while load on muscle remains constant
isotonic
144
When tension is greater than load, muscle shortens
concentric
145
Load is greater than tension on an unsupported muscle
eccentric
146
Contraction of muscle fiber in response to a single action potential
twitch
147
Keep length constant and measure tension
isometric twitch
148
Keep load constant and measure muscle length
isotonic twitch
149
Following action potential, an interval of a few ms known as latent period before tension of muscle fiber begins to increase
latency
150
Time interval from beginning of tension development at the end of the latent period to peak tension
contraction time
151
The latent period is longer in which twitch
isotonic twitch
152
Isometric twitch experiment, twitch tension begins to rise as soon as
first cross-bridge attaches
153
Isotonic twitch experiment, the latent period includes both time for ________________________ and extra time to accumulate enough _______________ _________________
excitation-contraction coupling; attached cross-bridges
154
Characteristics of isotonic twitch depend upon magnitude of
load being lifted
155
At heavier loads
latent period is longer, velocity of shortening is slower, duration of twitch is shorter, distance shortened is less
156
Maximum velocity with
zero load
157
Zero velocity at
maximum load
158
Unloaded shortening velocity is determined by rate at which
individual cross-bridges undergo cyclical activity
159
One ATP splits during each cross-bridge cycle, the rate of ATP splitting determines
shortening velocity
160
Increasing the load on a cross-bridge slows its forward movement during
power stroke
161
If interval between stimuli is long enough for tension to return to baseline, the amplitude of the second twitch will be
similar to the first
162
Increases tension due to second stimulus occurring before the tension returns to baseline
summation
163
Unfused Tetanus
oscillating summated tension
164
Fused Tetanus
sustained summated tension
165
Maximal tetanic tension is about _______ the tension of a single twitch
5x
166
Tension developed is dependent on
overlap of thick and thin filaments
167
Maximal tension occurs when
all of the myosin cross bridges can bind to actin
168
As muscle fiber is stretched, fewer cross bridges can bind to actin until no cross bridges can bind, meaning
no tension is developed
169
As muscle fiber shortened, thin filaments on one side will interfere with cross bridge formation on opposite side and this will
reduce tension developed
170
At very short lengths, the z-lines collide with ends of relatively rigid thick filaments, creating an
internal resistance to sarcomere shortening
171
Initial length that produces maximal active tension
optimal length
172
Muscles normally operate at plus/minus what % of optimal muscle length
30%
