Unit 2: Muscle Physiology Flashcards
1
Q
What are the 3 types of muscle tissue?
A
1) Skeletal
2) Visceral/Smooth
3) Cardiac
2
Q
The biggest quantity of muscle type (about 40% body mass) is:
A
skeletal muscle
3
Q
Skeletal muscle is found:
A
Attached to skeleton
4
Q
Skeletal muscle plays an important role in:
A
moving/positioning bones within the skeleton
5
Q
Under the microscope, skeletal muscle is:
A
striated [striped pattern]
voluntary [has the potential to be controlled]
6
Q
Which muscle type is voluntary?
A
Only skeletal
7
Q
The 2nd most wide-spread muscle type is:
A
visceral muscle
8
Q
Most of the _________ muscle type is associated with hollow internal structures/organs like intestines/airways
A
visceral
9
Q
Under the microscope, visceral muscle:
A
NONstriated/ smooth muscle
involuntary
10
Q
Cardiac muscle is only found-
A
within the structure of the heart
11
Q
Under the microscope, cardiac muscle:
A
is striated [less so than skeletal muscle]
involuntary
12
Q
What are the 3 basic muscle functions?
A
1) produce movement
2) maintaining posture [prevent movement]
3) heat generation
13
Q
What are the 4 key characteristics of muscle?
A
1) Excitability
2) Contractibility
3) Extensibility
4) Elasticity
14
Q
Muscle excitability is
A
the ability for the cells to change their electrical charge
15
Q
_________ is responsible for electrical signaling within cells
A
Excitability
16
Q
Contractility is the ability to
A
shorten the muscle
17
Q
Extensibility is
A
After contraction, the muscle relaxes and lengthens again
18
Q
Elasticity means
A
when a muscle is stretched, it will spring back to its original shape [force that opposes stretching]
19
Q
the outer layer of the muscle cell is the
A
plasma membrane [sarcolemma]
20
Q
The muscle’s plasma membrane is called
A
sarcolemma
21
Q
The sarcolemma gets its unique name because
A
it forms invaginations [modifications of membrane called Transverse Tubules]
22
Q
The Transverse Tubules pass right up against some key organelles:
A
smooth endoplasmic reticulum
AKA sarcoplasmic reticulum
&
Myofibril
23
Q
The sarcoplasmic reticulum has been highly specialized for the purpose of
A
storing calcium
~internally holds large quantities of calcium
24
Q
The 1-2-3 pattern associated with every T tubule is called
A
a triad
25
The Transverse tubule (really the whole triad) wraps around
a myofibril
26
The myofibril is made up of
Filament proteins [myofilaments]
~thick & thin overlapping filaments
27
The muscle cells are filled with ____________ that are responsible for production of ATP by way of aerobic mechanisms to fuel muscle contraction activity
mitochondria
28
The I band zone is ______ in color
Light
29
The A band zone is ______ in color
dark
30
The dark line in the center of the I band is the
Z line
31
The A band has a lighter center region called
H zone
32
The dark line in the center of the H zone is the
M line
33
The Z line represents the point where
All of the thin myofilaments are bound to each other
34
The M line represents the point where
all of the thick myofilaments are bound to each other
35
The repeating element from Z line to Z line is
Sarcomere
36
The segment where thin and thick myofilaments overlap is called
the zone of overlap
37
Contraction occurs in the
zone of overlap
38
The zone of overlap is responsible for
contraction
39
The area with just thin filaments is the
I band
40
The area with thick filaments is the
A band
41
There are 3 proteins making up the structure of a thin myofilament:
~Actin [looks like a string of pearls/little balls]
~Troponin [responsible for linking tropomyosin complex to actin proteins & can interact w/ calcium]
~Tropomyosin [fibrous; linked to troponin; lays on actin binding sites]; behaves like a competitive inhibitor.
42
Actin is shaped in a way so it can interact with :
myosin
43
When __________, the myosin heads latch on to actin and undergo power strokes that pull in the direction towards the middle of the sarcomere [left to right; right to left]
contracting
44
Cross-bridge formation occurs when myosin heads attach to binding sites on _______ which is part of the _______ filaments.
actin
thin
45
The T-tubule is a part of:
the cell membrane
46
identify B
I band
47
In a muscle cell at rest the sarcoplasmic reticulum contains an abundance of calcium, while the ________ does not contain any calcium.
sarcoplasm
48
Which of muscle types is described "involuntary"?
multiunit smooth muscle
single unit smooth muscle
cardiac muscle
49
The image above depicts a skeletal muscle cell. The structure labeled C (in yellow) is a tubular structure. What flows through that tube?
nothing "flows" through the tube, but it is filled with cytosol
50
Myosin molecules have binding sites for binding with:
ATP
Actin
51
the excitation event in the transverse tubule triggers the sarcoplasmic reticulum to
release its calcium and flood the sarcoplasm
[triggering ion channels in the SR to open]
52
The calcium attaches to binding sites on
the troponin component of the troponin-tropomyosin complex
53
When the ________ & _______bind to each other, this is the trigger releasing energy of the spring
myosin and actin
54
____ is necessary to get the muscle to relax
ATP
55
The next contraction occurs by adding:
calcium
[not ATP]
56
Excitation of a skeletal muscle cell depends on:
a triggering event coming from outside, specifically from a neuron
[Somatic Alpha motor neuron]- will connect to a muscle cell
57
what is a synapse composed of?
Axon
Axon terminal
Synaptic vesicles
Synaptic cleft
Motor end plate
58
Nerve impulses/action potentials travel down the axon towards the:
terminal
59
Inside the axon terminal, it is filled with membrane bubbles called
synaptic vesicles
60
Synaptic vesicles are filled with
neurotransmitters [chemical signals]
61
The extracellular gap between the axon terminal and another cell is called
synaptic cleft [aka synapse]
62
The entire synapse [of skeletal muscle] is also called
neuromuscular junction
63
___________ is a common neurotransmitter inside synaptic vesicles that determines whether a target cell becomes excited or not
Acetylcholine (ACH)
64
The membrane of the post-synaptic muscle cell is called
motor end plate
65
The _____ _______ _____ has receptors that can respond to neurotransmitter release by the neuron
motor end plate
66
The combination of one neuron and all of the muscle cells it is connected to, so has control over, is called
a motor unit
67
Motor units ______ overlap
do not
68
Each muscle cell is responding to one single __________, but each ________ can be controlling multiple muscle cells
1. neuron
2. neuron
69
If all 3 motor units stimulate their muscle cells at the same time, contracting in unison, this phenomenon is called ___________ which produces progressively increasing forces of contraction
recruitment/ spatial summation
70
Spatial summation is when
the contractile forces of 3 motor units are added together
71
The neuron (alpha motor neuron) excitation/ action potential arrives at the axon terminal and results in
exocytosis and release of neurotransmitter into synaptic cleft
72
The neurotransmitter released into the synaptic cleft will bind to a receptor producing a __________________which will then travel along the membrane
transduction event (such as an electrical change)
73
There are membrane channels within the T Tubule wall called:
L-type/ DHP membrane channels
74
L-type/ DHP membrane channels go through a shape change and open in response to
excitation
75
The ____________ is sometimes called the excitation-contraction coupler
calcium
[it couples the 2 events of excitation and contraction]
76
The addition of calcium moves the troponin-tropomyosin complex so that myosin can now latch on to actin. This triggers:
the power stroke to occur
77
_________ is necessary to get the myosin head released from actin and also to drive the energy of pulling the myosin head back into its high energy state
ATP
78
After the excitation is over, all of the _________ is back in the sarcoplasmic reticulum
calcium
79
A muscle twitch has _______________ contractile behavior
all or none
[rule can be broken]
80
A muscle twitch has 3 parts:
1. Latent period
2. contractile interval
3. relaxation interval
81
It takes ___________________________ to shorten the sarcomere enough so we see movement of the Z-lines shortening the muscle and producing force.
hundreds of power strokes
82
Muscle cells/ motor units don't contract continuously, they only:
twitch
83
muscles rarely ever fully ______
relax
84
muscle tone ________ during sleep
decreases
85
When muscle is relaxed, the myosin head will be in its ______________________________ state.
cocked and ready (high potential energy)
86
Contraction of motor units in a(n) ________ manner allows a muscle to maintain a smooth level of force for a duration of time without fatiguing.
asynchronous / alternating
87
Following a contraction, what is required to return the muscle to the relaxed state?
ATP binding to myosin
88
Starting with a muscle at rest, what must happen to initiate a contraction (aka power stroke)?
Binding of calcium (Ca2+) to troponin on the thin myofilament
89
The image above depicts a muscle twitch. The time interval labeled A (in yellow) represents the:
latent period
90
The image above depicts a muscle twitch. The time interval labeled C (in blue) represents the:
relaxation interval
91
A single neuron can connect to and control multiple muscle cells. This is called a:
motor unit
92
What are the 2 types of muscle fibers?
Type 1- slow-twitch: aerobic
Type 2- fast-twitch: anaerobic
93
The _____________ muscle cell fibers have the greatest density of capillaries surrounding them, so have a continuous exchange of oxygen, Co2, etc.
type 1 (slow-twitch) aerobic
94
the_________fibers are darker in color due to myoglobin; fatigue-resistant
~also smaller in diameter
slow-twitch
95
Fast-twitch fibers are lighter in color, and larger in diameter because they accumulate:
glycogen
this can be converted into glucose and burned during glycolysis to generate ATP anaerobically
96
The distribution of muscle fiber types is determined how?
genetically disposed
(not based on training much).
97
why do muscles fatigue? [primary factor]
the more you rely on anaerobic metabolism> more lactic acid is made> lactic acid acidifies the cell and changes protein shape> reduces muscle function> decreases ability of thin and thick filaments to interact> weaker muscle response
~fatigue may also be due to dependency on NS; NMJ running low on NTs>not enough NTs to stimulate muscles
~later on, may also be due to lack of ATP
98
The ______________________ is found in the tendon and responds to anything that causes the tendon to stretch [force must be applied]
golgi tendon organ
99
muscle spindles are housed in
inside the muscle
100
muscle spindles are partially made of muscle cells and they respond to :
changes in the length of the muscle
[is it getting longer or shorter]
101
the muscle group or muscle cells/fibers making up the muscle itself are called :
extrafusal cells/fibers
99.9% of muscle mass
102
Enclosed in a wrapping of perimysium, the muscle fibers within the spindles are called:
intrafusal cells/fibers
103
sensory receptors are always made from:
dendritic ends of neurons
104
sensory endings are affiliated with intrafusal muscle cells within the spindle and they detect:
changes in length
105
What are the 2 lower motor neuron types?
1. alpha motor neurons [extrafusal fibers]
2. gamma motor neurons [intrafusal fibers]
106
The alpha motor neurons are the only neurons that connect to the
extrafusal cells
107
__________ is the only muscle type without striations
smooth/visceral
108
___________ are a consequence of the arrangement of thin and thick myofilaments
striations
109
What are the 2 types of smooth muscle?
1. single-unit [cells work as a collective group; "gap junctions"
2. multi-unit [each cell functions independently]
110
Single-unit smooth muscle is characterized by:
having lots of gap junctions
[causing cells to be intimately linked to each other, excitation of one cell leads to excitation of all cells> all cells contract]
111
Smooth muscles are uniquely activated by
influx of calcium
[causes phosphorylation of myosin]
112
smooth muscles have an active range, meaning
they can contract over a long range of stretch
113
Smooth muscle has myogenic contraction, meaning
it can in itself (without nervous system intervention) respond to something that stretches it by contracting
114
Single-unit smooth muscle may exhibit autorhythmic regulation, meaning
automatic generation of rhythym
115
cardiac muscle is found :
exclusively in the heart
[not even in blood vessels]
116
Cardiac muscles have less defined striations than skeletal muscles due to
Lower concentration of thin and thick myofilaments within cardiac muscle cells
117
____________ in cardiac muscle cells intimately and strongly link cells together
Desmosomes [many of them]
118
Interspersed with desmosomes, in cardiac muscle cells, there are lots of smaller protein junctions connecting the cells called
gap junctions
119
________________ muscle cells contain abundant myoglobin
type 1 (slow-twitch) aerobic
120
All muscles are induced to contract by excitation which is coupled to contraction. What serves as the coupler between excitation and contraction?
calcium (Ca2+)
121
Muscles contain sensory receptors. The sensory receptor that would provide the necessary information to prevent excessively strong muscle contractions:
Golgi tendon organs
122
___________________ muscle fibers fatigue quickly
Fast twitch (type II) anaerobic
123
Which of the following muscle types may exhibit autorhythmicity?
slow twitch muscle
smooth muscle
fast twitch muscle
cardiac muscle
skeletal muscle
smooth
cardiac
124
Activation of contraction in smooth muscle is unique.
Describe the regulation of contraction in smooth muscle
myosin binds to actin when triggered by ATP binding
125
The sensory receptors found in muscle that are sensitive to changes in muscle length:
muscle spindles
126
In smooth (aka visceral) muscle, calcium ions bind to ___________ in order to initiate contraction.
myosin light chain kinase (MLCK)
127
Starting with a muscle at rest, which of the following must happen to initiate a contraction (aka power stroke)?
Binding of calcium (Ca2+) to troponin on the thin myofilament
128
Myosin exhibits three different properties necessary to its role in contraction, what are they?
Tadpole like heads -uses energy to create movement
stiff rodlike sections intertwining to form a tail
elastic neck region joining the head to tail
129
What is the functional significance of the troponin-tropomyosin complex?
it will lay on top of the actin proteins and covering the binding site on actin that myosin can latch on to.
[actin binding site is covered, producing the resting state].
130
Describe the evidence supporting the sliding filament theory (as opposed to filament shortening)
electron micrographic imagery -
Electron microscopy studies have revealed the detailed structure of muscle cells, showing that myofibrils, the contractile units of muscle, contain repeating sarcomeres. Sarcomeres consist of thin (actin) and thick (myosin) filaments arranged in a highly organized pattern.
131
Steps of muscle contraction cycle
1) ATP binds to myosin; myosin releases actin
2) myosin hydrolyzes ATP; ATP rotates myosin head to cocked position; myosin binds weakly to actin
3) power stroke begins when calcium binds to troponin; tropomyosin moves off the binding site
4) myosin releases ADP at the end of power stroke; cycle can begin again
132
Explain in detail ALL of the events leading up to contraction beginning at the time the nerve impulse (action potential) arrives at the neuron terminal of the neuromuscular junction
[steps of calcium signals initiating skeletal muscle contraction]
1) Calcium levels increase in cytsol
2) Calcium binds to troponin
3) troponin-calcium complex pulls tropomyosin away from actin's myosin binding site
4) myosin binds strongly to actin and completes power stroke
5) actin filament moves
133
What is a muscle twitch?
a single contraction-relaxation cycle in a skeletal muscle fiber
134
Define and describe what is occurring during the latent, contraction and relaxation intervals of a muscle twitch
latent- time between stimulus and beginning of twitch
contraction- period of time where the actin-myosin molecules are binding and cycling and the sarcomere is shortening, producing force
relaxation- after the peak of contraction; fewer myosin heads are active
135
What does “all-or-none” mean?
in response to a single excitation from a neuron, we should get the same muscle response each time- a twitch of the same strength each time.
if no excitation, no twitch.
136
Define “temporal summation”. Describe temporal summation as it applies to a single muscle cell.
A single cell twitches, and continues to twitch in rapid succession, each twitch separated by a little bit of time
A muscle cell contracts repeatedly and rapidly, so that the next contraction occurs before the previous one has totally relaxed.
Twitches will piggyback, level of force increases
AKA piggyback phenomenon
137
Describe and explain how the initial length of the muscle cell (or sarcomere) influences the contractile strength of the muscle cell.
There is a curve showing the starting length of the sarcomere impacts contraction strength
if sarcomere is too short at the start, or too long at the start, we're not generating as much force as we could
but if the sarcomere is at its anatomic length, it is lined up so that it can generate the maximum force possible
138
Define “oxygen debt”.
anytime a muscle's endurance is pushed, oxygen debt is incurred
if muscles start borrowing from reserves to meet their metabolic needs (to be able to continue contracting), at the end of the activity, muscle has debt to pay back> need to maintain an elevated level of oxygen even after the activity ends to pay back the incurred oxygen debt
139
In multi-unit smooth muscle, all cells receive :
independent autonomic stimulation
140
The muscle characteristic of contractility is secondary to:
Excitability
141
________ is a motor protein with the ability to create movement
Myosin
142
the _______________ is the recipient of the excitation event/action potential that travels down the axon
axon terminal
143
The action potential triggers the axon terminal to :
undergo exocytosis and some of the synaptic vesicles will migrate to the membrane and release contents by exocytosis
144
The electrical/excitation events are limited to the-
membrane
145
When the skeletal muscle is in the resting stage, it is in a ________ energy state
high
[myosin head already in high energy state]
146
what triggers the power stroke?
myosin head latches onto actin
147
Muscle cells only _______, they do not contract continuously. But a whole muscle will contract continuously.
twitch
148
How does a whole muscle contract continuously?
by alternating timing between motor units
motor unit 1 twitches, relaxes
motor unit 2 twitches, relax
motor unit 3 twitches, relax
^^^alternating repeating pattern > steady state of contraction
149
Physiological tetanus is a state of:
continuous contraction induced by stimulating a muscle cell with very rapidly repeating stimuli; the cell will never have an opportunity to relax> stuck at high energy contraction
150
Physiological tetanus can be produced-
only in lab setting
151
what is muscle fatigue?
the muscle fails to continuously generate the same amount of power outlet over time
the muscle gets weaker and weaker with repetitive use
152
Explain how a muscle can contract continuously without any of the cells within the muscle contracting continuously.
asynchronous motor unit recruitment. This ensures that while some muscle fibers are contracting, others are relaxing, creating a coordinated and continuous muscle contraction.
153
Describe the pattern of motor unit recruitment as muscle contraction strength increases. How does this influence the fine control of a muscle as contraction strength increases?
the pattern of motor unit recruitment plays a crucial role in maintaining fine control of a muscle as contraction strength increases; It allows for a graded and precise response to varying strength demands while ensuring that the muscle remains adaptable, efficient, and resistant to fatigue during a wide range of activities.
154
During skeletal muscle contraction, Z lines:
move closer together
155
During skeletal muscle contraction, the I band:
gets smaller
156
During skeletal muscle contraction, overlap between ______________ increases
thick and thin filaments
157
Following death, rigor mortis occurs due to:
[2 reasons]
insufficient ATP is available to bind to myosin, without ATP myosin cannot detach from actin
increased accumulation of calcium in the sarcoplasm as SR calcium pumps shut down due to insufficient ATP, increased calcium results in exposure of actin-binding sites and actin-myosin binding
158
Transverse tubules (aka T-tubules) are membranous tubes that are continuous with (made of the same membrane as):
the sarcolemma
159
Most of the calcium ions in skeletal muscle are sequestered (stored) in the:
sarcoplasmic reticulum
160
Both cardiac muscle and single unit smooth muscle are characterized by an abundance of these intercellular structures:
gap junctions
161
Beginning from the resting state, skeletal muscle contraction begins when:
calcium ions (Ca2+) bind to troponin
162
The functional group composed of a single alpha motor neuron and all of the muscle cells the motor neuron controls (innervates) is called a:
motor unit
163
Following contraction, skeletal muscle relaxation cannot occur until:
ATP binds to myosin heads
164
What functions as the link (aka coupler) between the process of muscle cell excitation and muscle cell contraction?
calcium ions (Ca2+)
165
The process of sequestering (aka storing) calcium in muscle cells is due to active pumping of calcium ions that is occurring:
at all times
166
The sensory receptor that is sensitive to changes in muscle length (but not muscle tension) is the:
muscle spindle
167
The contraction of a single muscle fiber, called a twitch, is typically described as an all-or-nothing event. However, the strength of a single cells twitch can actually increase or decrease as a result of variations in:
the initial length of the cell
the frequency of the stimulus applied
168
What gets shorter when a muscle contracts:
I bands
H zone
Sarcomere
169
What is the name of the specific segment indicated by #2?
H zone
170
]Which transition (A->B, B->C....) represents the powerstroke?
B->C
171
What must be added at point 1 to transition from C to D?
ATP
