Skeletal Muscle Flashcards
1
Q
skeletal msucle is what kind of muscle
A
voluntary
2
Q
cardiac and smooth muscle is what kind of muscle
A
involuntary
3
Q
cardiac and skeletal fall into what kind of category
A
striated
4
Q
smooth muscle falls into what category
A
unstriated
5
Q
skeletal muscle fibers are made up of
A
myofibrils
6
Q
myofibril composed of
A
1500 thick and 3000 thin filament
7
Q
what is sarcomere
A
end to end chain of repeating units in myofibril
8
Q
list the skeletal muscle heirarchy structure
A
look up to confirm
9
Q
each myofibril in muscle fiber is surrounded by
A
sarcoplasmic reticulum
10
Q
what is the smallest contractile unit of skeletal muscle
A
multinucleated, elongated cell called a muscle fiber
11
Q
multinucleated, elongated cell called a muscle fiber is surrounded by
A
cell membrane: sarcolemma
12
Q
what is the sksletal muscle cell membrane called
A
sarcolemma
13
Q
a bundle of linearly aligned muscle fibers form what
A
a fasicle
14
Q
bundles of fasicles form what
A
muscle
15
Q
An individual skeletal muscle cell contains a densely arranged parallel array of cylindrical elements called
A
myofibrils
16
Q
what is a myofibril
A
essentially an end-to-end chain of regular repeating units, or sarcomeres, that consist of smaller interdigitating filaments called myofilaments, which contain both thin filaments and thick filaments.
17
Q
invaginations of sarcolemma are called
A
t tubules
18
Q
T tubules are in contact with
A
extracellular space
19
Q
the portion nearest the t tubule is caleld the
A
terminal cisternae
20
Q
terminal cisternae is the site of
A
Ca2+ release
21
Q
Draw the parts of a sarcomere
A
pg 9
22
Q
what is the ultimate function of t tubules
A
coordinated contraction
23
Q
what is function of terminal cisternae
A
sac-like ends of SR; acts like a storage of the Ca2+ ions that release in excitation-contraction coupling
24
Q
what is the triad
A
the close apposition of two terminal cisternae against T-tubule; important in electrochemical coupling
25
the two dark lines on sarcomere is caleld the
Z lines
26
on either side of z line is what
I band
27
I band contains what
thin filaments composed primarily of the protein, actin.
28
what is I band primarily composed of
actin
29
what is the area b/w two I bands called
A band
30
A band contains
thick filaments composed primarily of the protein myosin
31
A band is primarily composed of
myosin
32
the dark area at end of A band represents
region of overlap between thick and thin filaments
33
light area in the center of sarcomere is called
H band
34
What is H band
area of the A band that only contains thick myosin filaments
35
where do thin actin filaments extend
from the Z line to the edge of the H band and overlap a portion of the filament in the A band
36
what is the dark line in the center of the sarcomere called
M line
37
What is function of M line
appear to be critical for organization and alignment of the thick filaments in the sarcomere.
38
Sarcomere
Basic contractile unit – delineated by Z disks or lines: contains full A band and ½ an I band on either side of A band
39
A band
contain thick filaments; overlapping of thick and thin filaments (potential sites of cross-bridge formation
40
I band
Contain actin (thin) filaments, Z disks and no thick filaments
41
Z disc
Run down middle of each I band defining the end of each sarcomere
42
H zone
Center of each sarcomere. No thin filaments (no overlap of thick and thin filaments/cross-bridge formation in this region
43
M line
Bisects the H zone linking the central portion of the thick filaments together
44
describe the structure of myosin
6 polypeptide chains, head function as an ATPase enzyme
& actin binding
site
45
what binds to myosin
ATP and actin
46
the head region of myosin extends in what direction
away from thick filament
47
region of myosin extends towards
actin thin filament
48
the part of myosin that binds to ATP does what specifially
binds and hydrolyses ATP
| aka it is a ATPase
49
aggregation of actin molecules is called
globular actin
| or G actin
50
what is another name for globular actin
G actin
51
describe the structure of actin in skeletal muscle
two stranded helical structure - called F-actin
52
What is another name for F-actin
filamentous actin
53
what does tropomyosin do
extend over the entire actin filament and cover myosin binding sites on the actin molecules
54
a tropomyosin extends over how many actin molecules
7
55
what are the three subunits of troponin
T, I, C
56
what is function of troponin
binds to tropomysoin and blocks the binding sites so the muscle won't move unless calcium binds to troponin and moves it out of the way so tropomyosin can move
57
what happens when clacium is released into muscle cells
calcium binds to troponin C so myosin binding site is exposed
58
watch her ppt of sliding mechanism contractinon as well as kahn academy and draw diagram to help remember
pg 13
| do itt
59
during contraction what part of myofibril shortens
sarcomere
I band
H zone
60
during contraction what part of myofibril stays the same
A band - same width
| thick and thin filaments - same width
61
thick myosin filaments are tethered to z lines by what
titin
62
what is titin
a very large elastic protein that extends from the Z line to the center of the sarcomere and appears to be important for organization and alignment of the thick filaments in the sarcomere. Titin appears to play a role in stabilizing thin filament length during muscle development in an isometric contraction.
63
what is function of nebulin
extends along the length of the thin filament and may participate in regulation of the length of the thin filament.
64
what is function of alpha actinin
associated with the Z lines, serves to anchor the thin filaments to the structure of the Z line.
65
what is function of dystrophin
connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane.
66
what is normal values of serum creatine kinase for men
25-90 U/L
67
what is normal values of serum creatine kinase for women
10-70 U/L
68
what is treatment for DMD
corticosteroids
anticonvulsants
immunosuppressants
69
what is purpose of corticosteroids for treating DMD
slow muscle degeneration
70
what is purpose of anticonvulsants for treating DMD
control seizures and some muscle activity
71
what is purpose of immunosuppressants for treating DMD
delay some damage to dying muscle cells, and antibiotics to fight respiratory infections.
72
draw out the mechanism of muscle contraction in order
pg 24
73
watch video for calcium release and muscle contraction
pg 25
74
watch video for calcium reuptake and muscle relaxation
pg 26
75
where does motorneuron synapse with muscle cell
motor end plate
76
The association of a T-tubule with two opposing terminal cisternae is the
triad
77
Ach binds to what when it is released from motorneuron
nicotinic receptors on muscle fiber
78
when Ach binds to nicotinic receptors on muscle fiber it produces what
large depolarization called EPP
79
EPP triggers what
opening of nearby voltage-gated Na+ and K+ channels which underlie the muscle action potential.
80
watch animation for crossbridge cycling
pg 27
81
what is isometric contraction
stimulation without shortening the muscle length - still causes increase in tension
82
what is an example of an isometric contraction
individual pushing against an immovable object such as the wall of a house
83
what is an isotonic contraction
muscle tension remains constant a smuscle changes length
| creates force to generate movement
84
what is an example of a isotonic contraction
individual lifting a 10 lb weight
85
how do you develop enough force to lift a load
want to do just a little bit more than needed to lift the load
86
what is a way to increase force or tension development
recruitment
frequency summation
muscle length prior to stimulation
87
what is recruitment
multiple fiber summation → you are summing tension (more motor units)
88
in recruitment you sum
tension
89
what is frequency summation
twitch, summation, tetanus
90
increased frequency of firing for AP you will get
frequency summation
91
describe how you can use muscle length prior to stimulation to regulate force
if you stretch out muscle beforehand, can get more force. like stretching a rubber band
92
before stimulatino called
preload
93
after stimulation called
total force
94
the force of skeletal muscle contraction in vivo is regulated by
recruitment
frequency summation
when you depol. you get maximum out of muscle b/c they are optimally overlapped
95
in tetanus what is happening that keeps the tension in muscle
calcium atpase isn't work up and can't keep up with the frequency of firing. it doesn't have time to sequester the calcium completely
96
what is preload
is the load on a muscle in a relaxed state, that is, prior to contraction.
(pre-stretch, haven't depol. yet)
97
when preload is applied to muscles what two things does it do
causes muscle to stretch
| and to develop passive tension
98
the greater the preload added, the greater the
stretch of the muscle
99
why dont you see length change in isometric contraction
b/c of the elastic elements - that is what is stretching so the msucle length doesnt actually change
100
the bigger the pre-stretch, the more passive tension, but all the passive tension
cannot be used to move a load
| there is a point where if you keep increasing pre-stretch it will start to decrease the total force
101
passive tension generated by
stretching non-muscular, elastic elements within the whole muscle
102
active tension generated by
crossbridge cycling in contractile elements is transmitted to the load and movement occurs
103
total tension is sum of
the active tension developed by the crossbridge cycling In the sarcomeres and the passive tension caused by stretching the muscle
104
what is afterload
amount of force development generated after depol
| it is the force the muscle must develop to shorten and lift the load.
105
F max is the
maximum load
106
the heaviest load that can be listed is
Vb
107
the lightest load that can be lifted
Vd
108
Vmax denotes
max velocity cycling rate
109
If Fmax is 25 lbs and preload is stretched and Fmax is 15, can I lift buddy?
No
110
if there is increased preload or decreased proload the graph will
shift left
| can see pg 73
111
how do you get a different myosin ATPase
with a different muscle
112
skeletal muscle, even if slow twitch, will have faster myosin ATPase then smooth muscle?
yes, faster skeletal muscle ATPase
113
in relaxed skeletal muscle, what inhibits contraction
tropomyosin- troponin complexes - they prevent cross bridging
114
when muscle shortens what happens to sarcomere
length is reduced
115
thick myosin filaments are tethered to z lines by what
titin
116
what is titin
cytoskeletal protein, extends from z line to center of sarcomere, important for organizing and aligning thick filaments
117
titin helps stabilize thin filament during
isometric contraction
118
what is purpose of nebulin
cytoskeletal protein, extends along length of thin filament and helps regulate the thin filament length
119
what is function of alpha-actinin
associated with the Z lines, serves to anchor the thin filaments to the structure of the Z line
120
what is function of dystrophin
connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane.
121
what disease is there lack of dystrophin
DMD
122
what does DMD stand for
duchenne muscular dystrophy
123
gower's sign is a symptom of
DMD
124
Pts with DMD usually die due to
respiratory failure or heart failure
125
what does corticosteroids do to treat DMD
slow muscle degeneration
126
what does anticonvulsants do to treat DMD
controls seizures and some muscle activity
127
what does immunosuppressants do to treat DMD
delays some damage to dying muscle cells
128
draw out the steps of muscle contraction
pg 24
129
when AP arrives at NM junction it triggers what
release of Ach by exocytosis
130
when Ach is released in NM junction it produeces what
EPP → depolarization
131
when muscle cell has EPP then what happens
voltage gated Na and K channels open → muscle AP
132
surface electrical activity on muscle cells is carried to central parts of muscle fiber by what
T tubules
133
association of T tubule w/ two opposing terminal cisternae is
triad
134
what is the name of the protein that bridge the gap b/w t tubule and terminal cisternae
feet
135
RYR stands for
Ryanodine receptor
136
the feet - what do they do
Ca2+ release channels in the membrane of the terminal cisternae that are responsible for the elevation in intracellular [Ca2+] in response to the action potential.
137
what is another name for the feet
ryanodine receptor
138
why is the channel called ryanodine receptor
it binds the drug ryanodine
139
where is the RYR located
a portion embedded in SR membrane
| most of it in myoplasm b/w terminal cisternae & t-tubule
140
DHPR stands for
dihydropyridine receptor
141
what protein does RYR interract with at the t-tubule membrane
DHPR
142
what is an L-type voltage gated Ca2+ channel
DHPR
143
what is the function of one of the subunits of DHPR
binds dihydropyridine class of channel blocking drugs
144
DHPR (especially subunit) is needed for what
induce release of calcium from SR
145
for calcium to be released from SR is DHPR needed
no
146
explain the steps for calcium release from the SR
conformational change in DHPR → opens RYR → Ca released into myoplasm
147
what protein stores calcium in SR
calsequestrin
148
what initiates relaxation of skeletal msucle
acetylcholinesterase removes Ach from NM junction
149
what are the two ways calcium is removed from cell
sent across plasma membrane
| sequestered into intracellular compartments
150
how is calcium extruded - what does the cell use to do this?
Na-Ca exchangers
| Ca ATPase pumps
151
how is calcium pumped back into SR
sarcoplasmic endoplasmic reticulum Ca2+ ATPase (SERCA) pumps
152
what does SERCA stand for
sarcoplasmic endoplasmic reticulum Ca2+ ATPase (SERCA) pumps
153
what is the most important mechanism for returning calcium to resting levels
SERCA
154
what are the funcions of the SR
Ca storage
Ca release
Ca uptake
155
if there is high free Ca in the lumen of SR, what does this do to SERCA
inhibits it
156
what acts as a buffer and allows more uptake of calcium and a much higher capacity of calcium inside SR
calsequestin
157
draw out the powerstroke
pg 31
158
explain what causes rigor mortis
ATP depletion in muscle cells
| it's rigid b/c cells can no longer remove calcium, so actin-myosin binding, but can't do power stroke b/c no ATP
159
what is tension in terms of muscle
when muscles contract and the attachment points are both pulled towards each other
160
what is an isometric contraction
increase in tension but not shortening
| muscle length is fixed -
161
what creates force without generating movement
tension
162
an individual pushing against an immovable object such as the wall of a house is an example of what
tension
163
if the force of the muscle is slightly greater than the load what kind of contraction is it
isotonic contraction
164
describe isotonic contraction
constant load, tension in is greater than the load
| the muscle will change length
165
muscle tension remaining constant as muscle changes length is an example of what
isotonic contraction
166
an individual lifting a ten pound weight is an example of what
isotonic contraction
167
what regulates force of skeletal muscle contraction in vitro
* Recruitment (multiple fiber summation)
* Frequency summation (twitch, summation, tetanus)
* Muscle length prior to stimulatio
168
what regulates the force of skeletal muscle contraction in vivo
CNS regulates:
• Recruitment
• Frequency summation
169
why is muscle length prior to stimulation minor in vivo
attachment to skeleton limit the changes in length
170
a motor unit consists of what
a number of muscle fibers innervated by the same alpha motorneuron
171
how is increasing force of contraction done in vivo
recruits more muscle fibers (via motor units)
172
activation of a single alpha motor neuron leads to what
synchronous twitching of all fibers it innervates
173
if muscle is allowed to relax fully prior to second shock what will it result in
twitch
174
if second shock is delivered before muscle can fully relax it will result in
summation
175
what is incomplete tetany
muscle is stimluated again before it had a chance to fully relax. but intracellular calcium has the chance to return to baseline
176
what is tetany
high level of stimluation & intracellular Ca doesn't go down, it just increases.
177
what is the best measure of preload length
sarcomere length
178
what is preload
the load on a muscle in a relaxed state, that is, prior to contraction.
179
applying preload to muscle does what two things
causes muscles to stretch
| causes muscle to develop passive tension
180
the greater the preload added the greater the
stretch of the muscle
pre-stretch of sarcomere
passive tension in muscle
181
what is passive tension
tension generated by stretching non-muscular, elastic elements within the whole muscle
think rubber band
182
what is active tension
tension generated by crossbridge cycling in contractile elements is transmitted to the load and movement occurs
183
what is total tension
the sum of the active tension developed by the crossbridge cycling In the sarcomeres and the passive tension caused by stretching the muscle.
184
the sum of active and passive tension is what
total tension
185
subtracting passive tension from total tension is what
active tension
186
the active tension developed is proportional to what
number of crossbridges that cycle
187
active tension is maximal when
maximal overlap of thick and thin filaments and maximal possible crossbridges
188
why is action tension reduced when muscle is stretched to longer lengths
the number of possible cross-bridges is reduced, and active tension is reduced
189
why is action tension reduced when muscle length is decreased
the thin filaments collide with each other in the center of the sarcomere, reducing the number of possible cross-bridges and reducing active tension.
190
what is optimal overlap in um
1.95-2.25 um
191
draw the optimal overlap chart comparing sarcomere length and relative force
pg 66
192
what is the bare zone
thick filaments at center of A band where no myosin heads are present
this is why b/w 1.95-2.25 um the isometric force capability doesn't change
193
understand and draw graph of iostonic contraction
pg 69
194
what is afterload
the force muscle must develop to shorten and lift the load
195
as afterload is decreased, velocity of shortening
increases
| velocity increases more and more as load is reduced
196
what is Fmax
if load is applied that is greater than the maximal force capacity of muscle
197
what is Vmax
maximum velocity - maximal cycling rate of cross-bridges
| this is theoretical velocity muscle could obtain if it didnt have to move any afterload
198
draw force-velocity curve
pg 71
199
velocity of shortening will be maximal when afterload on muscle is
0
200
draw out and understand the force-velocity relationship
pg 72
| the four bumps with the arrows
201
preload and afterload do not affect
Vmax
202
what are the two major ways the body converts nutrients to energy
aerobic metabolism
| anaerobic metabolism
203
is creatine phosphate aerobic or anaerobic
anaerobic
204
when is creatine phosphate system used, describe it
short bursts of energy - 10 seconds worth, like 100 meter sprint or weight lifting
it uses up any ATP stored in muscle (2-3 sec)
then sues CP to synthesize ATP (6-8 sec)
205
is glycolysis aerobic or anaerobic
anaerobic
206
describe how glycolysis works
creates ATP from carbohydrates
used during short, high intensity bursts of activity - like swimming 400 meter
used up in a few min.
207
what is by-product of glycolysis
lactic acid
208
is oxidative phosphorylation aerobic or anaerobic
aerobic
209
describe how ox-phos works
long duration activity
uses oxygen to convert nutrients to ATP
long-distance walking, jogging, swimming
210
what are the three types of muscle fibers
slow-oxidative
fast-oxidative
fast-glycolytic
211
what are the red and white fibers
slow-oxidative is red fiber
| fast-oxidative & fast-glycolytic are white fibers
212
Compare Vmax, myosin ATPase, glycolytic metabolism, oxidative metabolism, mitochondrial content, and myoglobin content b/w fast and slow twitch muscles
pg 76
