The Muscular System Flashcards
1
Q
what control do we have over skeletal muscle
A
voluntary control
2
Q
what skeletal muscles don’t all attach to the skeleton
A
many facial muscles
3
Q
what are the functions of skeletal muscle
A
- movement
- posture
- joint stability
- thermogenesis
4
Q
describe this muscle function: movement
A
muscles produce tension to move things by pulling or squeezing
5
Q
how do cells produce tension
A
rapidly contracting
6
Q
what type of muscle are sphincters made of
A
- smooth muscle
- skeletal muscle
7
Q
what are example of skeletal sphincter muscles
A
- sphincter at the anus
- sphincter at the urethra
- orbicularis oris
- orbicularis oculi
8
Q
describe this muscle function: posture
A
- baseline tension exerted at all times
- holds the body is a certain position against the force of gravity
9
Q
when do muscles have posture control
A
when conscious
10
Q
describe this muscle function: joint stability
A
constant tension holds joints together
11
Q
define diarthrotic joints
A
freely moveable joints
12
Q
where are most diarthrotic joints found
A
in the limbs
13
Q
examples of diarthrotic joints
A
- shoulder
- hip
- elbow
- knee
14
Q
what is the relationship between joint mobility and stability
A
inverse relationship
15
Q
what are the 3 factors of joint stability
A
- ligaments holding the joint together
- snugness of fit of the bones comprising the joint
- contribution from muscles crossing over the joint
16
Q
what type of joint are both the shoulder and hip joint
A
ball and socket
17
Q
describe the joint stability of the shoulder joint in comparison to the hip joint
A
- shallower fit/less snugness of the humerus in the glenoid cavity
- more mobile
- less stable
18
Q
describe the joint stability of the hip joint in comparison to the hip joint
A
- deeper fit/more snugness of the femur in the acetabulum
- less mobile
- more stable
19
Q
what joints are the easiest to dislocate
A
- shoulder
- mandible
20
Q
when is the shoulder joint most vulnerable to dislocation
A
when extended laterally and posteriorly
21
Q
what muscles help to stabilize the shoulder joint
A
rotator cuff muscles
22
Q
define rotator cuff muscles
A
- 4 muscles surrounding the shoulder joint
- stabilize the humerus head in the glenoid cavity
- insert onto a cuff-like tendon
23
Q
what are the 4 rotator cuff muscles
A
- subscapularis
- supraspinatus
- infraspinatus
- teres minor
24
Q
describe this muscle function: thermogenesis
A
skeletal muscles can be stimulated by impulses from the hypothalamus to shiver which warms you up
25
what is the difference between a muscle cell and a muscle fiber
nothing, they are synonymous
26
what are the 4 characteristics of muscle cells
- excitable
- contractile
- extensible
- elastic
27
describe this characteristic of muscle cells: excitable
respond to chemical and mechanical stimuli by generating organized wave-like movement of electrical charge across membranes
28
define resting membrane potential
- voltage across the cell membrane under normal circumstances
- all cells have resting membrane potential
29
what is a synonym for voltage
electrical potential
30
what type of cells can use resting membrane potential as a platform to create action potentials
- excitable cells
- ex: muscle cells
31
what is a synonym for action voltage
action potential
32
define muscle potential
action potentials in muscles
33
define action potential in muscle cells
- muscle potential
- the resting membrane potential can have a wave-like change in voltage to create action
34
what do muscle cells need to have before they can contract
action potential
35
contraction is ________ by a previous action potential
predicated
36
what comes first: contraction or action potential
action potential
37
describe this characteristic of muscle cells: contractile
muscle cells can shorten to produce force
38
describe this characteristic of muscle cells: extensible
muscle cells can tolerate stretching
39
what muscle type has the most extensibility
- smooth muscle
- can tolerate the most stretching
40
skeletal muscle is considered extensible and elastic when compared to ____________
other organs
41
describe this characteristic of muscle cells: elastic
muscle cells can snap back into position after they stretch
42
are ligaments extensible or elastic
no, neither extensible or elastic
43
how far can ligaments stretch
1-2% of their resting length
44
what happens if ligaments stretch
- not elastic
- won't snap back into position
- why one dislocation can cause it to be easier to dislocate that joint in the future
45
list the order of components of muscles from smallest to largest
- myofilaments
- myofibrils
- muscle fibers
- muscle fascicles
- whole muscle
46
how long can each muscle fiber be
- over 1cm
- as long as the whole muscle
47
are muscle fibers thick enough to see
no
48
what is the longest muscle
sartorius
49
how wide can each muscle fiber be
up to 0.1millimeters (100 micrometers)
50
what are the strongest muscles in the body
- hamstrings
- quadriceps
51
what is the relationship between the cross sectional area of a muscle and the strength of the muscle
directly proportional (more area = more strength)
52
where are the thickest muscle fibers found
in the thickest muscles
53
how are muscle fibers formed
fusion of myoblasts in embryo
54
describe myoblasts
- small cells with a single nucleus
- fuse together to become muscle fibers in utero
- myo=muscle; blast=building
- muscle stem cells in a sense
55
when do we have all the skeletal muscle fibers that we will ever have
at birth
56
how to muscle cells grow
hypertrophy (NOT hyperplasia)
57
what hormones cause muscle cells to hypertrophy
anabolic hormones (growth hormone, testosterone)
58
women produce __% of the amount of testosterone than men produce
5%
59
how are damaged muscles repaired by the body
- myoblasts are maintained in each muscle fiber throughout life
- myoblasts will fuse together to create new muscle cells if needed
60
what do sarco- and myo- mean
muscle
61
define myofilaments
- protein filaments in muscle
- slide past each other during contraction
62
what is the term for the cytoplasm in muscle cells
sarcoplasm
63
what is the term for the cell membrane in muscle cells
sarcolemma
64
what is the old term used for plasma membrane
plasmolemma
65
what is the term for the smooth endoplasmic reticulum in muscle cells
sarcoplasmic reticulum
66
define muscular fascia
- surrounds individual muscles and groups of muscles
- connects muscles to each other
67
define epimysium
- surrounds each muscle
- connective tissue
- bundles fascicles together
68
define perimysium
- surrounds each fascicle
- connective tissue
- bundles muscle fibers together
69
define endomysium
- surrounds each muscle fiber
- connective tissue
70
can muscle fibers be seen with the naked eye
no
71
what do the epimysium, perimysium, and endomysium converge to form
components of the tendon
72
define myofibrils
- organelles in each muscle fiber
- contain myofilaments
- each muscle cell has many myofibrils
- takes up most of the muscle cell volume -
73
describe what happens to the actin and myosin myofilaments during contraction
- do NOT change length
- actin myofilaments slide past the stationary myosin myofilaments
74
how many myofibrils are in a single muscle fibers
hundreds to thousands
75
what takes up most of the muscle cell volume
myofibrils
76
describe the position of the nuclei in a muscle fiber
- pushed to the outer edge of the cell
- makes the cell membrane (sarcolemma) pucker out
77
define triad in a muscle fiber
- repeating structure composed of 3 elements
- 2 terminal cisterns and 1 T tubule
78
what is the opening of the T tubule called
pore
79
what is the plural of cisterna/cistern
cisternae/cisterns
80
what is the full name of the T tubule
transverse tubule
81
describe why T tubules are called transverse tubules
the tubule extends across and into the muscle fiber
82
describe T tubules
- follows the contours of myofibrils from one side of the muscle fiber to the other
- extension of the sarcolemma that helps to communicate action potentials from the sarcolemma to the myofibrils
83
describe terminal cisterns
specialized portion of the sarcoplasmic reticulum
84
where are terminal cisterns located
on either side of the T tubule
85
what ion do terminal cisterns store in high concentrations
calcium
86
when do terminal cisterns release calcium
when the action potential travels down the T tubule
87
how much does calcium concentration spike within the cell once the terminal cisterns begin releasing it
10x increase in calcium
88
what is the chemical link between electrical action potentials and mechanical sliding of actin/thin filaments
calcium ions
89
describe the path of an action potential from an axon to a sarcomere
- action potential moves from axon terminal to the sarcolemma
- action potential moves down the sarcolemma
- action potential splits in 2 as it hits a T tubule (moves further down the sarcolemma and down the T tubule towards the sarcomeres)
90
why is it necessary for capillaries to be attached to muscle fibers
muscle fibers need good blood supply to get nutrients needed to convert ATP during movement
91
what is the atomic unit of contraction
sarcomere
92
what is the smallest element that can contract in a skeletal muscle cell
sarcomere
93
list the contractile elements of muscle from smallest to alrgest
- sarcomere
- myofibrils
- muscle fiber
- muscle fascicles
- muscle
94
how many axons connect to a single muscle fiber
one axon per muscle fiber
95
where do axons typically connect to the muscle fiber
near the middle of the muscle fiber
96
how much can sarcomeres contract
up to 2/3 their resting length
97
list all the steps of a muscle contraction
- action potential moves down the axon which induces the fusion of vesicles containing acetylcholine
- acetylcholine moves into the synaptic cleft through exocytosis
- acetylcholine binds to protein receptors on the motor end plate
- binding of acetylcholine leads to the opening of sodium protein channels
- sodium begins moving from outside the muscle cell to inside causing depolarization of the sarcolemma which stimulates the action potential
- more sodium channels begin to open up as the action potential moves across the sarcolemma
- action potential moves down the T tubule and calcium is released from the terminal cisterns
- calcium will bind to the troponin on actin filaments allowing for myosin binding and therefore contraction
98
define acetylcholine
neurotransmitter inducing muscle contraction
99
define synaptic cleft
area between the axon terminal and sarcolemma
100
define motor end plate
area of the sarcolemma that is opposite of the axon terminal
101
where is a sarcomere located
between Z discs
102
define I band
- lighter area of the sarcomere
- less dense
- only contains thin filaments
- 1/2 I band on either side of the Z disc
- split by the sarcomere
103
define A band
- darker area of the sarcomere
- denser
- contains both thick and thin filaments
- also contains the H zone and the M line
104
define H zone
- lighter region within the A band
- still darker than the I band
- contains only thick filaments
105
define M line
- proteins attach thick filaments together
- darker line than H zone
106
what is the significance of the M line
proteins attach thick filaments together so they can't slide
107
describe the organization of thick and thin filaments in the lateral portion of the A band
- thick filaments have hexagonal relationship with thin filaments
- each thick filament associates with 6 thin filaments
108
describe the structure of each myosin filament
composed of 8 repeating structures of myosin each containing 2 globular heads
109
describe the structure of each myosin protein within a myosin filament
- 2 myosin polypeptides coiled around each other
- each polypeptide has 1 globular head
110
how many myosin proteins make up a thick filament
few hundred
111
what are thin filaments made of
2 chains of actin polymers wrapped around each other
112
describe a single actin protein that makes up thin filaments
each actin polypeptide is spherical and has its own active site for myosin heads to bind
113
what are the 2 proteins attached to thin filaments
- tropomyosin
- troponin
114
describe the structure of tropomyosin
- composed of 2 thin protein threads wrapped around each other
- each protein strand is not long, but they splice together to form a tropomyosin filament
115
how many tropomyosin filaments are there per thin filament
2, one for each actin strand
116
where is tropomyosin located when a muscle is relaxed
covering the active sites on actin so myosin heads can't bind
117
describe the structure of troponin
- made of 3 unidentical proteins, each with a different job
- one end protein: spherical, attaches to actin
- middle protein: where calcium binds
- one end protein: oval-shaped, attached to tropomyosin
118
how often are troponin proteins located on actin
every 90 nm
119
which protein making up troponin causes troponin to contract
middle protein where calcium binds
120
describe what happens when calcium binds to troponin
- troponin contracts
- tropomyosin moved towards the end attached to myosin
- myosin heads can bind to actin and pull the thin filaments
121
what is the "origin" and "insertion" points of troponin when calcium binds
- origin: protein attached to actin, part that doesn't move
- insertion: protein attached to tropomyosin, part that does move
122
describe how thick filaments are indirectly attached to Z discs
attached via the protein titin
123
describe titin
- spring-like protein
- attaches thick filaments to Z discs
- 1 polypeptide made of 30,000 amino acids (very long)
- limits the compression of the sarcomere to 2/3 its resting length
124
where is titin located in a contracted sarcomere
between the Z disc and the A band
125
what happen to titin in the sarcomere after contraction
extends back to normal position
126
what protein makes muscles compressible and extensible compared to other oragns
titin
127
what happens to Z discs as a sarcomere contracts
move towards each other/towards the middle
128
what happens to the I band as a sarcomere contracts
- I band collapses
- still some I band left in areas where titin is compressed to full extent
129
what happens to the H zone as a sarcomere contracts
- goes away completely
- no region left without thin filaments
130
describe dystrophin proteins
- located under the sarcolemma
- keep the sarcolemma from breaking
131
the lack of what protein causes muscular dystrophy
dystrophin proteins
132
when are you no longer able to hold a muscle in a contracted position
once you feel fatigue
133
define complete tetanus
complete contraction of sarcomeres and therefore the muscle
134
define incomplete tetanus
any range of muscle contraction between completely relaxed and completely contracted
135
what happens when someone has the disease tetanus
- all skeletal muscles are in complete uncontrolled tetanus
- you cannot relax your muscles
136
how do people die from tetanus
breathing muscles cannot relax leading to respiratory failure and asphyxiation
137
what causes the disease tetanus
the bacteria clostridium tetani
138
how does clostridium tetani often enter the body
through a puncture wound
139
how does clostridium tetani cause the disease tetanus
- releases a toxin that migrates up nerve axons to the spinal cord
- toxin stops motor neurons from being able to be inhibited so motor neurons have uncontrolled activity
140
how long is the delay of symptoms for the disease tetanus
2-3 weeks
141
what predicates tension developed via filament sliding
an electrical impulse (action potential) that radiates from the neuromuscular junction
142
what is another term for voltage
potential
143
what happens to pressure and current as voltage increases
- pressure increases
- current increases
144
what helps to move a current from one place to another
electrical pressure
145
describe an electrical current
- electrons flowing across a membrane
- energy conversion across a membrane
146
do all cell membranes have a resting membrane potential
yes
147
what cell was used to first determine resting membrane potential
neurons in the loligo squid
148
why were neurons in the loligo squid used to first determine resting membrane potential
- had a large axon that can be seen with the naked eye
- excitable cell
- similar on the molecular level to human neurons
149
what instrument was used to measure the resting membrane potential
oscilloscope
150
where are the microelectrodes placed to determine resting membrane potential
- measurement electrode: inside cell membrane
- reference electrode: outside cell membrane
151
which electrode on an oscilloscope is set to the baseline of 0
reference electrode placed outside the cell membrane
152
describe what it means that voltage is relative in terms of the resting membrane potential
the voltage of the inner surface of the cell membrane is measured with respect to the voltage of the outer surface of the cell membrane
153
what is the resting membrane potential neurons
-70 mv
154
what is the resting membrane potential for human skeletal muscle
-85 mv
155
what is the resting membrane potential for red blood cells
-10 mv
156
what is the sign of resting membrane potentials (+ or -)
always negative
157
how do excitable cells produce action potentials
using resting membrane potential
158
define leakage channels
- protein channels in cell membranes that allow a specific substance to move through (selective)
- open all the time, allowing substances to move across the membrane constantly
159
examples of two leakage channels in cell membranes
- Na+
- K+
160
which type of leakage channel is more abundant
100x more K+ channels than Na+ channels
161
what are the only substances than can move through Na+ leakage channels
Na+ ions
162
what are the only substances that can move through K+ leakage channels
K+ ions
163
where is Na+ concentrated (inside or outside cell)
more Na+ outside the cell
164
where is K+ concentrated (inside or outside cell)
more K+ inside the cell
165
describe the concentration difference between Na+ and K+ inside and outside of the cell
- more Na+ outside the cell
- more K inside the cell
166
describe how ions move through leakage channels
- facilitated diffusion
- moving from an area of high concentration to low concentration
167
why are leakage channels necessary
- ions are hydrophilic while cell membranes are hydrophobic (on the inside)
- ions need to move through specialized protein channels to be able to cross the cell membrane
168
list the brief steps of establishing and maintaining the resting membrane potential
1. sodium potassium pump moves Na+ out of the cell and K+ into the cell
2. ions move down their concentration gradient
3. an electrical gradient is produced
4. gradients move into an equilibrium state
5. resting membrane potential is created
169
what is needed to establish the concentration gradient of Na+ and K+
sodium potassium pump
170
what is another name for concentration gradient
chemical gradient
171
what is another name for the sodium potassium pump
sodium potassium ATPase
172
what type of movement occurs in the sodium potassium pump
active transport
173
what does active transport in the sodium potassium pump require
energy, ATP
174
how much ATP is needed for one pump of the sodium potassium pump
1 ATP
175
what is pumped during one cycle of the sodium potassium pump
- 3 Na+ pumped out of the cell
- 2 K+ pumped into the cell
176
which has a greater effect on the resting membrane potential: sodium potassium pump OR ions moving through leak channels
ions moving through leak channels
177
describe how the sodium potassium pump helps to create an electrogenic effect (voltage across the cell membrane)
- there is not an equal distribution of Na+ and K+ inside and outside of the cell
- sodium potassium pump moves more Na+ outside of cell (3) than K+ inside the cell (2)
- makes the outside of the cell more positive than inside the cell
178
describe the movement of K+ in response to both the electrical gradient and concentration gradient
- electrical gradient: K+ moving into the cell
- concentration gradient: K+ moving out of the cell
179
what is the overall charge of cytoplasm within the cell
neutral
180
why is the inner surface of the cell near the cell membrane slightly negative in charge
- negative anions are concentrated near the cell membrane
- anions are not neutralized here because K+ moves out of the cell due to the concentration gradient
181
describe what happens to K+ in terms of the electrical gradient
- K+ move out of the cell following the concentration gradient
- leaves anions inside the cell creating a negative environment (electrical gradient)
- K+ begins to move back into the cell following the electrical gradient
182
define equilibrium potetnail
electric potential needed to attract an ion into a cell to balance the ions moving out of the cell
183
describe the equilibrium potential for potassium
- when the K+ moving into the cell due to the electrical gradient is equal to the K+ moving out of the cell due to the concentration gradient
- -90 mv
184
describe how Na+ moves across the cell membrane
moves down the concentration gradient into the cel
185
what is the equilibrium potential for sodium
+65 mv
186
what is the resting membrane potential for a skeletal muscle cell based on the equilibrium potentials of sodium and potassium
- EP K+ = -90 mv
- EP Na+ = +65 mv
- RMP = -85 mv
187
how is the resting membrane potential of a membrane determined
based on the equilibrium potentials of all ions moving across the cell membrane
188
define voltage gated channels
- not always open
- opens when a change in voltage moves through it (such as an action potential)
- quickly open and close
189
define ligand gated channels
capable of binding smaller molecules that change the large channel protein, allowing it to open
190
define acetylcholine
- neurotransmitter
- small molecule
- acetate (2 carbons) covalently linked to choline
191
how does the diameter of an axon relate to the speed of an action potential
- directly related
- larger axon diameter = faster movement of action potential
192
define motor end plate
portion of the sarcolemma where the axon terminal connects at the neuromuscular junction
193
what happens when an action potential moves down the axon to the axon terminal
- causes depolarization of the axon membrane
- leads to the opening of voltage gated calcium channels on the axon terminal
- calcium will enter the axon terminal
194
describe the movement of calcium when an action potential moves down an axon
- calcium moves through voltage gated channels down its concentration gradient
- higher concentration of calcium outside of the axon, so calcium will move into the axon
- spike of calcium levels inside the axon terminal
195
what does calcium do in the axon terminal
begins the exocytosis of acetylcholine vesicles into the synaptic cleft
196
what does acetylcholine do in the synaptic cleft
binds to ligand gated sodium channel proteins on the motor end plate to open them
197
how many acetylcholine bind to one ligan gated sodium channel for the channel to open
2
198
what happens as sodium moves into the muscle cell through ligand gated channels on the motor end plate
depolarization of the motor end plate
199
define end plate potential
the depolarization of the motor end plate as sodium enters the cell
200
describe how the end plate potential moves to generate an action potential
- end plate potential spreads to the sarcolemma from both sides of the motor end plate
- generates an action potential
201
define acetylcholinesterase
- enzyme that breaks down (hydrolyzes) acetylcholine in the synaptic cleft after it has binded to sodium channels
- off switch that stops overstimulation of cell
202
what does acetylcholinesterase hydrolyze acetylcholine into
- acetic acid
- choline
203
what is acetylcholinesterase in terms of acetylcholine
inhibitor of acetylcholine
204
define toxins
- blocks physiological pathways necessary for life
- often understood to be bad
205
how are toxins and medicines related
toxins can be used in some circumstances as a treatment for a condition
206
define acetylcholinesterase inhibitors
- toxins
- inhibit acetylcholinesterase; stimulate acetylcholine
- many different types with different potencies
207
what acetylcholinesterase inhibitor is considered extremely strong
sarin
208
define sarin
- strong acetylcholinesterase inhibitor
- toxin
- aka nerve gas
209
what is sarin often used for illegally
- weapon of war
- poison gas
210
what recent war was sarin used against civilians in
syrian war
211
what happens when someone inhales sarin
- acetylcholinesterase in inhibited
- acetylcholine levels rise dramatically
- causes uncontrolled contractions, leading to respiratory failure and death
212
what acetylcholinesterase inhibitor is considered mild
neostigmine
213
define neostigmine
- mild acetylcholinesterase inhibitor
- toxin
- soluble compound
214
what condition is neostigmine often used as a treatment
myasthenia gravis
215
define myasthenia gravis
- autoimmune disease
- body attacks protein channels in the synaptic cleft of skeletal muscle cells
- because acetylcholine cannot bind to protein channels, the body has a hard time activating muscles leading to muscle weakness
216
what are treatments for myasthenia gravis
- cortisol
- neostigmine
217
describe how cortisol is a treatment for myasthenia gravis
- cortisol suppresses the immune system
- myasthenia gravis is caused by an overactive immune system
218
what is the oral form of cortisol
prednisone
219
describe how neostigmine is a treatment for myasthenia gravis
- neostigmine inhibits acetylcholinesterase so there is more acetylcholine in the synaptic cleft
- has more opportunities for acetylcholine to find protein channels that are healthy and stimulate them
220
what toxins stimulate muscle contraction
acetylcholinesterase inhibitors
221
what toxins are paralytics to muscles
- botulinum toxin
- curare
222
what produces botulinum toxin
bacterium clostridium botulinum
223
what is one of the most toxic compounds on earth
botulinum toxin
224
how much botulinum toxin will kill someone
2 nanograms
225
what does botulinum toxin do
- interrupts the fusion of acetylcholine filled vesicles with the axon terminal membrane
- no exocytosis of acetylcholine into the synaptic cleft
- leads to weak muscles, paralysis, respiratory failure, and death
226
how do people end up ingesting botulinum toxin
through poor canning sanitation processes
227
what are the medical benefits of botulinum toxin
- can treat spastic paralysis
- can be used to smooth out wrinkles
228
define spastic paralysis
- motor neurons in the spinal cord are not well regulated
- often caused by a stroke
- person has no control over a particular muscle
229
how does botulinum toxin treat spastic paralysis
- can be injected into the muscle that has spastic paralysis
- will inhibit the contraction of that muscle
230
what is the name for botulinum toxin when it is being used to smooth out wrinkles
botox
231
how does botulinum toxin treat wrinkles
- lightly paralyzes muscles of the face
- smooths out the face but also lessens control of facial muscles
232
define curare
- plant neurotoxin
- causes muscle weakness
233
how was curare first used
hunting in old tribes to paralyze animals before killing them
234
does curare have an effect on humans when taken orally
no
235
how was curare first used in medicine
- gateway drug for anesthesiology
- relaxes muscles to allow for surgery, specifically relaxing tracheal muscles to allow for intubation
236
what type of toxin is curare
antagonist
237
describe what curare does
- almost identical structure to acetylcholine
- can bind to protein channels in the synaptic cleft but cannot open them; blocks acetylcholine from binding
- muscles won't react to action potentials causing muscle weakness
238
what are the two voltage gated ion channels in the sarcolemma that propagate action potentials
- Na+
- K+
239
which voltage gated ion channels open first following an action potential
Na+
240
describe what happens as Na+ voltage gated channels open in the sarcolemma
- open immediately after action potential arrives
- depolarization of sarcolemma as Na+ moves into the cell
- polarity flips from -85 mv to slightly positive
- channels close after 1/2 millisecond
241
what part of the action potential wave is created when Na+ voltage gated channels open
first half
242
describe what happens as K+ voltage gated channels open in the sarcolemma
- open 1/2 millisecond after action potential arrives (happens to be right when Na+ channels close)
- repolarization of sarcolemma as K+ moves out of the cell
243
what part of the action potential wave is created when K+ voltage gated channels open
back half
244
define threshold potential
- the potential needed for voltage gated Na+ channels to open
- -55 mv
245
how long are voltage gated Na+ channels open after detecting an action potential
1/2 millisecond
246
at what polarity do voltage gated K+ channels open
+20 mv
247
define after hyperpolarization
following the closing of voltage gated K+ channels after an action potential, the sarcolemma gets too negative (lower than -85 mv)
248
how is after hyperpolarization addressed
sodium potassium pump re-establishes the RMP
249
describe what it means that an action potential is a self-reinforcing chain reaction
uses positive feedback to move the action potential down the sarcolemma
250
when does the self-reinforcing chain reaction of an action potential end
when it reaches the end of the sarcolemma
251
what would happen if voltage gated Na+ and K+ channels opened at the same time after an action potential
- nothing
- depolarization and repolarization at the same time would cancel out
252
what happens to the thick and thin filaments during muscle contraction
thin filaments are pulled and slide past the stationary thick filaments
253
what are the 2 positions of the myosin head
- high energy
- lower energy
254
describe the high energy position of the myosin head
- energy in stored
- myosin head is holding ADP or ADP+P
255
describe the low energy position of the myosin head
- no energy is stored
- myosin head is holding nothing or ATP
256
list the steps of cross bridge cycling
- exposure of active sites
- cross bridge formation
- power stroke
- cross bridge release
- hydrolysis of ATP
- recovery stroke
257
describe this step of cross bridge cycling: 1. exposure of active sites
- calcium levels must increase intracellularly
- calcium binds to troponin
- tropomyosin moves to expose the active sites on actin
258
describe this step of cross bridge cycling: 2. cross bridge formation
- myosin head binds to active site
- phosphate detaches from the myosin head
259
describe this step of cross bridge cycling: 3. power stroke
- movement of the myosin head
- actin filaments pulled past stationary myosin filament
- ADP detaches from the myosin head
260
describe this step of cross bridge cycling: 4. cross bridge release
- ATP binds to the myosin head
- myosin head detaches from the active site
261
describe this step of cross bridge cycling: 5. hydrolysis of ATP
ATP is broken down into ADP and P
262
describe this step of cross bridge cycling: 6. recovery stroke
- breakdown of ATP supplies energy for recovery stroke
- myosin head returns to high energy position
- myosin head rebinds to an active site farther down on the actin filament
263
what factors are necessary for cross bridge cycling
- calcium (formation)
- ATP (release)
264
how many action potentials will generally run down the muscle cell compared to the number of action potentials that run down the neuron
- same number
- muscle cell action potentials generally mirror the number of action potentials in the neuron
265
describe how calcium is released for the formation of cross bridges
- action potential runs down sarcolemma and T tubule
- depolarization opens voltage-gated calcium channels
- calcium is released from the terminal cisterns
266
define calcium pump proteins in the terminal cisterns
- pump calcium back into the terminal cisterns
- rely on ATP to function
- always running to keep calcium levels high in concentration within the terminal cisterns
267
what causes calcium levels to drop following the recovery stroke in cross bridge cycling
calcium pump proteins in the terminal cisterns pump calcium back into the terminal cisterns
268
what is the "off switch" for cross bridge cycling
- calcium pump proteins in the terminal cisterns
- pump calcium back into the terminal cisterns, calcium will no longer bind to troponin, tropomyosin will cover active sites
269
describe what happens in 1 cross bridge cycle compared to multiple cycles
- 1 cycle: Z discs will move towards the M line slightly before titin pushes them back to the resting position
- multiple: Z discs will move incrementally with each cycle towards the M line until the sarcomere is at full tetanus (or the action potentials stop arriving)
270
what are the two requirements to maintain muscle contraction
- high sarcoplasmic calcium levels
- constant supply of ATP
271
describe why muscles contractions stop when there is no ATP available
- ATP is used to detach myosin heads from actin filaments
- if there is no ATP, myosin heads cannot detach and the filaments will stay fused together, making the muscle stiff
272
do skeletal muscle fibers store ATP
no
273
describe how skeletal muscle fibers get ATP
adjust the synthesis of ATP based on the need for ATP
274
what does skeletal muscle store and why is it important
- glucose and oxygen
- needed to make ATP when ATP is needed for muscle contraction
275
do muscles usually run out of ATP
no
276
what happens is a muscle runs out of ATP
- physiological contracture: muscles seize up as myosin heads can't detach from thin filaments
- damages the muscle
277
what usually happens before a muscle runs out of ATP
- the muscle fiber will lose the ability to keep calcium levels high
- stops the muscle from contracting, forcing relaxation
- does not damage the muscle
278
describe muscle fatigue and damage to muscle with the analogy of a car running out of gas and oil
- running out of gas: muscle losing ability to keep calcium levels high; doesn't damage muscle/car; needs to rest/refill
- running out of oil: muscle running out of ATP; damages the muscle/car
279
define rigor mortis
the body becoming stiff up to 12-16 hours after death
280
how long after death does the body loosen up and decay
after 24 hours
281
describe how/why rigor mortis occurs
- muscle cells die so the calcium pumps in the terminal cisterns stop working causing calcium levels to rise slowly within the cell
- there is some ATP still left within the cell
- muscle contractions in flexing and extending muscles will occur as calcium levels rise
- myosin heads will fuse to the thin filaments once the ATP runs out
282
describe how the concept of rigor mortis is used in forensic science
- can determine time of death based on level of rigor mortis if the temperature is known and a muscle sample is taken
- only useful within 24 hours of death (before body becomes limp)
283
what does the rate of rigor mortis depend on
temperature
284
what does each action potential in a muscle fiber result in
muscle twitch
285
what does myogram translate to
muscle chart
286
how is tension produced in a single twitch measured
force-tension myogram
287
what are the three phases of a muscle twitch
- latent phase
- contraction phase
- relaxation phase
288
how long is the latent phase of a muscle twitch
0-5 milliseconds
289
describe what is happening at a gross anatomical level during the latent phase of a muscle twitch
- nothing
- no apparent physical response
290
what triggers the start of the latent phase of a muscle twitch
action potential moving down the sarcolemma
291
what is happening at a microanatomical level during the latent phase of a muscle twitch
excitation-contraction coupling
292
describe excitation-contraction coupling
- action potential moving down the sarcolemma and T tubules
- voltage gated calcium channels in the terminal cisterns open and calcium diffuses into the muscle fiber
- calcium binds to troponin causing tropomyosin to reveal active sites on actin
- myosin heads bind to active sites on actin
293
how long is the contraction phase of a muscle twitch
20-100 milliseconds
294
describe what is happening during the contraction phase of a muscle twitch
power stroke: myosin filaments pulling actin filaments; sarcomere shortening
295
how long is the relaxation phase of a muscle twitch
20-100 milliseconds
296
describe what is happening during the relaxation phase of a muscle twitch
- myosin heads detach from the actin filaments
- sarcomere returns to a relaxed state
297
how long is the total time of a muscle twitch
40-200 milliseconds
298
define digital event
it either happens or it doesn't, no in between
299
define analog reponse
varying degrees or gradient of an event
300
is a muscle twitch a digital event or analog reponse
- digital event
- it either happens or it doesn't
301
is most muscle activity a digital event or analog reponse
- analog response
- muscle activity requires graded contractions with variations in time and force
302
what makes the analog response of a muscle movement possible
- the controlling neuron
- can send different frequencies of action potentials to change muscle contraction time and force
303
what happens to muscle tension as the frequency of action potentials increases
muscle tension increases
304
what frequency level will produce separate muscle twitches
- low frequency
- action potentials fired over 200 milliseconds apart
305
how long does it take an action potential to reach the muscle fiber to begin a muscle contraction
1 millisecond
306
which is faster: the electrical or mechanical event of muscle contraction
electrical event (action potential reaching muscle fiber)
307
what frequency level will produce incomplete tetanus
- intermediate frequencies
- action potential fired before muscle has completely relaxed
308
describe what happens to muscle tension during incomplete tetanus
- increases with each action potential sent
- the muscle doesn't have time to fully relax before another action potential is fired leading to a more intense contraction
309
are most muscle movements twitches, incomplete tetanus, or complete tetanus
incomplete tetanus
310
what frequency level will produce complete tetanus
- high frequency
- neuron firing at maximal frequency
311
describe the sarcomere during complete tetanus
maximally shortened
312
what does an electromyogram measure
compound muscle potentials from multiple motor units
313
what is the x-axis of both force-tension myograms and electromyograms
time (milliseconds)
314
how are force-tension myograms and electromyograms different
- force-tension myograms: measure tension directly
- electromyograms: measure compound muscle potentials (excitation as a product of force, not force directly)
315
what is a small motor unit
innervates 10-20 muscle fibers
316
what is an intermediate motor unit
innervates 20-100 muscle fibers
317
what is a large motor unit
innervates 1000s of muscle fibers
318
what happens to the electromyogram spike as larger motor units are recruited
increasing the amplitude
319
define Henneman's size recruitment prinicple
- small motor units will be recruited before larger motor units
- controls the gradient of force to make muscle contractions smooth
320
describe why we use electromyograms instead of force-tension myogrmas in clinical practice
- electromyograms are painless, give good data, and can be done noninvasively
- myograms must be done with a portion of the muscle taken out of the patient
321
what are the four metabolic pathways that can generate ATP for muscle contraction
- adenylate kinase
- creatine kinase
- anaerobic pathway
- aerobic pathway
322
what level of contraction are most daily muscle movements
minimal to moderate levels of contraction
323
what happens when ATP goes down
ADP goes up
324
what is the first metabolic pathway used for ATP generation for muscle contraction
adenylate kinase
325
define kinase
an enzyme that transfers a phosphate from one molecule to another
326
what does adenylate kinase do
- transfers a phosphate from one ADP to another ADP
- creates AMP (1 phosphate) and ATP (3 phosphates)
327
how long can adenylate kinase create ATP for muscle contraction
2-3 seconds
328
what is the second metabolic pathway used for ATP generation for muscle contraction
creatine kinase
329
what does creatine kinase do when your muscle is at rest
- transfers a phosphate group from ATP to creatine to make ADP and creatine phosphate
- done because the muscle cell can store creatine phosphate but not ATP
330
what does creatine kinase do when your muscle is contracting
transfers phosphate from creatine phosphate to ADP to make ATP
331
what is the fastest metabolic reaction for generating ATP for muscle contraction
creatine kinase
332
how long can creatine kinase create ATP for muscle contraction
5-7 seconds
333
how long can adenylate kinase and creatine kinase create ATP for muscle contraction
10 seconds
334
about how long does it take the aerobic pathway to be primed to create ATP
10-20 seconds
335
what is the purpose of adenylate kinase and creatine kinase pathways
- give muscle ATP while the aerobic or anaerobic pathway is getting ready to create ATP
336
what are the two pathways that could follow after adenylate kinase and creatine kinase
- aerobic pathway
- anaerobic pathway
337
when would the muscle use the aerobic pathway for ATP generation
- if adequate oxygen is available
- during mild to moderate muscle contraction
338
when would the muscle use the anaerobic pathway for ATP generation
- if adequate oxygen is not available
- during extreme movement and muscle contraction
339
what is the preferred metabolic pathway of ATP generation for muscle contraction
aerobic pathway
340
what is the general equation for the aerobic pathway of ATP generation for muscle contraction
glucose + oxygen = 36 ATP + carbon dioxide + water
341
list the general steps of the aerobic pathway of ATP generation
- glycolysis
- citric acid cycle
- electron transport chain and oxidative phosphorylation
342
where does glycolysis take place
in the cytoplasm
343
how many steps are in glycolysis
10
344
what is the general equation of glycolysis
glucose = 2 pyruvate + 2 ATP
345
where does the citric acid cycle take place
mitochondria
346
how many steps are in the citric acid cycle
8
347
how much ATP does the citric acid cycle produce
2 ATP
348
where does the electron transport chain and oxidative phosphorylation take place
mitochondria
349
how much ATP does the electron transport chain and oxidative phosphorylation produce
32 ATP
350
how much ATP does the aerobic pathway produce in total
36 ATP
351
what is the main downside to the aerobic pathway of ATP production
it's a very slow process because there are many steps that take place in different parts of the cell
352
how long can the aerobic pathway create ATP for muscle contraction
hours
353
describe the process of the anaerobic pathway of ATP production
glycolysis (and lactate formation)
354
how is glycolysis different in the anaerobic pathway of ATP production compared to the aerobic pathway
- glycolysis has an extra step in the anaerobic pathway
- pyruvate is converted to lactate
355
how many ATP are produced in the anaerobic pathway of ATP production
2 ATP
356
what is the upside to the anaerobic pathway of ATP production
- very fast process
- almost as fast at creatine kinase reactions
357
what is the downside to the anaerobic pathway of ATP production
- only makes 2 ATP
- not sustainable, cannot continue extreme contractions for long
- lactic acid formation lowers cell and blood pH
358
how long can the anaerobic pathway create ATP for muscle contraction
30-40 seconds
359
what happens to the pH of the cell and the blood during the anaerobic pathway of ATP production and why
- pH lowers (more acidic)
- lactic acid is created during this pathway which lowers pH
360
describe how someone could run a 4 minute mile
- combining aerobic and anaerobic pathways of ATP production
- must have high aerobic capacity to continue aerobic respiration for a longer time during extreme movement
361
who was Robert Banister
- physician
- first person to break the 4 minute mile
362
what are the 3 types of fibers in muscles
- slow-twitch oxidative (SO) fibers (type I)
- fast-twitch oxidative glycolytic (FOG) fibers (type IIa)
- fast-twitch glycolytic (FG) fibers (type IIb)
363
describe what muscle fiber types are in every muscle and how they compare in proportions
- all muscles have all fiber types
- muscles differ in the proportion of each fiber type that is in them
364
describe slow-twitch oxidative fibers
- SO fibers
- type I
- use aerobic pathway
365
describe fast-twitch oxidative glycolytic fibers
- FOG fibers
- type IIa
- can use both aerobic and anaerobic pathways
366
describe fast-twitch glycolytic fibers
- FG fibers
- type IIb
- use anaerobic pathway
367
define myoglobin
- produced by muscle cells
- stores oxygen in muscle cells until it is needed for ATP production
368
describe the myoglobin content of slow-twitch oxidative (SO) fibers (type I)
- high
- need lots of oxygen for aerobic respiration
369
describe the mitochondria number of slow-twitch oxidative (SO) fibers (type I)
- many
- aerobic respiration takes place in mitochondria
370
describe the capillary number of slow-twitch oxidative (SO) fibers (type I)
- many
- needed to receive oxygen for aerobic respiration
371
describe the metabolism of slow-twitch oxidative (SO) fibers (type I)
- high aerobic capacity
- low anaerobic capacity
372
what is the relationship between power/speed and endurance
- inverse relationship
- high power/speed = low endurance
- low power/speed = high endurance
373
describe the endurance of slow-twitch oxidative (SO) fibers (type I)
- high
- slow and efficient so they can work for long periods of time
- low power/speed = high endurance
374
what are the two types of myosin ATPases in muscle fibers
- slow
- fast
375
what does myosin ATPase do
enzyme that performs hydrolysis on ATP during cross bridge cycling
376
describe the myosin ATPase activity of slow-twitch oxidative (SO) fibers (type I)
- slow
- slower cross bridge cycling because it takes longer for myosin ATPase to hydrolyze ATP
377
describe the glycogen concentration of slow-twitch oxidative (SO) fibers (type I)
- low
- less needed for aerobic respiration
378
what muscles are slow-twitch oxidative (SO) fibers (type I) most abundant in
- postural muscles -> muscles holding the head up
- core muscles in torso
- more in lower limbs than upper limbs
379
how much does the head weight
10 pounds
380
describe the functions of slow-twitch oxidative (SO) fibers (type I)
- maintenance of posture
- performance of endurance activities
381
describe the myoglobin content of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)
- high
- need lots of oxygen for aerobic respiration
382
describe the mitochondria number of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)
- many
- aerobic respiration takes place in the mitochondria
383
describe the capillary number of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)
- many
- needed to receive oxygen for aerobic respiration
384
describe the metabolism of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)
- intermediate aerobic capacity
- high anaerobic capacity
385
describe the endurance of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)
intermediate
386
describe the myosin ATPase activity of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)
- fast
- faster cross bridge cycling because it takes less time for myosin ATPase to hydrolyze ATP
387
describe the glycogen concentration of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)
- high
- need glucose for the anaerobic pathway (glycolysis)
388
what muscles are fast-twitch oxidative glycolytic (FOG) fibers (type IIa) most abundant in
lower limbs
389
describe the functions of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)
endurance activities in endurance-trained muscles
390
describe the myoglobin content of fast-twitch glycolytic (FG) fibers (type IIb)
- low
- anaerobic pathway doesn't require oxygen
391
describe the mitochondria number of fast-twitch glycolytic (FG) fibers (type IIb)
- few
- anaerobic pathways do not enter the mitochondria
392
describe the capillary content of fast-twitch glycolytic (FG) fibers (type IIb)
- few
- oxygen from capillaries is not needed in the anaerobic pathway
393
describe the metabolism of fast-twitch glycolytic (FG) fibers (type IIb)
- low aerobic capacity
- highest anaerobic capacity
394
describe the endurance of fast-twitch glycolytic (FG) fibers (type IIb)
low
395
describe the myosin ATPase activity of fast-twitch glycolytic (FG) fibers (type IIb)
- fast
- faster cross bridge cycling because it takes less time for myosin ATPase to hydrolyze ATP
396
describe the glycogen concentration of fast-twitch glycolytic (FG) fibers (type IIb)
- high
- need glucose for the anaerobic pathway (glycolysis)
397
what muscles are fast-twitch glycolytic (FG) fibers (type IIb) most abundant in
upper limbs
398
describe the functions of fast-twitch glycolytic (FG) fibers (type IIb)
rapid and intense movements of short duration
399
what type of muscle fiber is in high concentration in the soleus muscle and why
- high concentration of slow oxidative fibers
- soleus is an endurance muscle needed for walking
- needs less power/speed and more endurance
400
what type of muscle fiber is in high concentration in the gastrocnemius muscle and why
- high concentration of fast glycolytic fibers
- gastrocnemius is used for higher intensity movement such as running
- needs more power/speed and less endurance
401
do everyone's muscles have the same proportions of muscle fiber types
- no, there are variations in proportions between people
- why some people are better at power athletics and some are better at endurance
402
describe how exercise effects fast glycolytic fibers
- makes them hypertrophy
- get stronger through the hypertrophy
403
describe how exercise effects slow oxidative fibers
- won't hypertrophy
- get stronger by recruiting more mitochondria, myoglobin, and capillaries (more oxygen capacity)
