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Physiology > Muscle Physiology > Flashcards

Muscle Physiology Flashcards

1
Q

What are the muscle characteristics

A

Excitability which is the ability to generate atp
contractility which shortens the muscle
extensibility which allows the muscle to stretch without tearing
elasticity which is the ability to recoil or return to original length

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2
Q

What are some muscle functions

A

They produce movements
Maintain posture and body position
Stabilize joints
Generate heat and electricity

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3
Q

What are characteristics of cardiac muscles

A

Involuntary control
Uninucleated and highly branched
Contains intercalated disks
Striated

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4
Q

What are characteristics of skeletal muscle

A

Voluntary
Multi-nucleated
Banded and striated
Surrounds bone

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5
Q

Characteristics of smooth muscle

A

Surround hollow organs or glands and tubes in body
Involuntary control
Uninucleated and not striated
Cigar or spindle shaped

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6
Q

Characteristics of red muscle

A

High mitochondria
High blood supply
High oxygen content
Uses oxidative phosphorylation
Sustained atp content
Low power, low fatigue
No large amount of force

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7
Q

Characteristics of white muscle

A

Low mitochondria content
Low blood supply and low oxygen content
Uses glycolysis
Fatigues quickly and uses high power

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8
Q

From outside to inside name the layers of a muscle

A

Epimysium, fascicle, perimysium, endomysium

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9
Q

What is the cell membrane of a myofiber

A

Sarcolemma

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10
Q

What are the major myofibrils in this unit

A

Actin and myosin

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11
Q

What does thick filaments contain

A

Myosin

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12
Q

What do thin filaments contain

A

Actin, troponin and tropomyosin

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13
Q

What do elastic filaments contain

A

Titin

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14
Q

What is myosin

A

Two globular heads with a long braided tail
Contains atp and actin binding sites
Binds to actin during muscle contraction

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15
Q

What is actin

A

Filamentous protein made of globular subunits knows as g actin
Two filament strands which form the thin filament
Binds to myosin during muscle contraction

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16
Q

What is tropomyosin

A

Filamentous protein that spirals around actin
Inhibits myosin by blocking the myosin binding site on actin

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17
Q

What is troponin

A

Interacts with tropomyosin
Made up of TnI, TnT, and TnC
TnI is the inhibitory subunit that covers the myosin binding site on actin
TnT is what binds to tropomyosin
TnC is the calcium binding subunit

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18
Q

What is dystrophin

A

Stabilizing protein that anchors the thin filament to the sarcolemma and aids in membrane stability

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19
Q

What is titin

A

Binds thick filament to Z disc of sarcomere and allows for extensibility

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20
Q

What is the sarcoplasmic reticulum characteristics

A

Tubules run along the axis of the myofibrils
Terminal cisterns run perpendicular to the A and I band junction
Regulates intracellular Ca levels

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21
Q

What is the region between a discs

A

The sarcomere

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22
Q

What is the m line

A

Where myosin fuses with myomesin
Myosin abuts

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23
Q

What is the Z disc

A

When actin aligns

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24
Q

What is the I band

A

Made up of only thin filaments

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25
What is the A band
Overlapping thick and thin filaments
26
What is the H zone
Only thick filaments
27
What gives muscles the banded appearance
Alternating thick and thin filaments of actin and myosin
28
What are t tubules
Deep invaginations in the sarcolemma They increase surface area Place the sarcolemma in close association with sarcoplasmic reticulum Carries action potentials deep within the muscle fiber
29
What is the triad
Terminal cistern, t tubule, terminal cistern
30
What do integral proteins on the t tubule act as
Voltage sensors Example is the DHP receptor DHP receptor connected to the SR receptor
31
What do integral proteins of the sarcoplasmic reticulum act as
Calcium channels such as the rhyandine receptor
32
What does myosin do to actin during contraction
Myosin grabs the actin filament and the actin filament slides over the top of myosin which increases the degree of overlap
33
What is the motor end plate
Allows chemical signaling between the muscle and motor neuron Portion of the myofiber that receives the synaptic bulb
34
What is a motor unit
One neuron and all the muscle fibers it communicates with
35
What is a motor neuron
Signal sent from brain to tell skeletal muscle fiber to contract This signal is sent as an action potential
36
What is the neuromuscular junction
Synapse between a somatic motor neuron and a muscle fiber
37
What is the portion of a motor neuron at the neuromuscular junction called
The synaptic bulb
38
What is the synoptic cleft
Space between the motor end plate and synaptic bulb
39
What forms the doyeres eminence
The lateral edges of a motor end plate meeting the Schwann cell of a motor neuron
40
What important receptor is on the motor end plate
Achetocoline receptor
41
Explain the nerve stimulus at a neuromuscular junction
Synaptic vesicles with acetylcholine are found in the synaptic bulb An action potential reaches the synaptic bulb Voltage gates calcium channels open and Ca2+ influxes Calcium binds to acetylcholine containing vesicles and these vesicles fuse to SNAPs on the neurolemma Acetylcholine is exocytosed into synaptic cleft and binds to ligand gated Na channel on the motor end plate
42
What does a highly folded sarcolemma at the motor end plate allow for
More acetylcholine receptors
43
Explain how an action potential is generated in a myofiber
Acetylcholine in the synaptic cleft binds to its receptor on ligand gated Na channels which causes influx of Na Then depolarization which causes threshold to be reached at the motor end plate and voltage gated Na and K channels activated Influx of Na caused M.P to go up which causes generation of action potential
44
How do you generate an action potential in a motor neuron
Ligand binds to ligand gated channel and it opens which causes Na influx Na diffuses across cell and threshold is reached which opens the Na V.G activation gate Na influxes again and m.p reverses polarities which generates the action potential Action potential is propagated down the motor neuron and reaches the axon terminal
45
How is Ca released from the sarcoplasmic reticulum
Action potential propagates down sarcolemma and reaches DHP receptor in t tubule There is a confirmation change in the DHP receptor which causes confirmation change in ryanodine receptor (DHP is connected to ryanodine on SR) Ryanodine receptor acts as gated channel and opens which allows Ca to efflux from SR to sarcoplasm
46
Explain how you make a cross bridge and what is is
Ca is released from SR and binds to TnC receptor on troponin and troponin undergoes confirmation change which causes confirmation change in tropomyosin Tropomyosin then slides around actin, exposing myosin binding site allows myosin to bind The actin myosin interaction is the cross bridge
47
Explain cross bridge cycling
Myosin has an ADP and inorganic phosphate attached to it but then myosin binds to actin which causes the phosphate to be released Myosin undergoes confirmation change and bends at the elbow which pulls on the actin filament This causes ADP to be released and opens ATP binding site on myosin ATP binds to myosin which causes myosin to detach from actin ATP is then hydrolyzed into ADP and Pi which returns myosin to cocked position
48
What does myosin do when it rebinds to actin
It binds at a location further up on the actin filament
49
How do you stop a cross bridge cycle
There is no longer a signal so acetylcholine is cleared from the synaptic cleft and an AP in the myofiber is stopped Ca stops being released in the SR and is pumped back into SR using Ca ATPase Ca is also no longer bound to troponin and tropomyosin can return to normal confirmation of blocking myosin binding site
50
As you move away from a blood vessel what happens
The overall concentration of O2 lessens
51
What is anoxia
Concentration of oxygen dies off
52
What is muscle tension
Force exerted by a muscle The opposing force this is called the load
53
What is isometric contraction
Muscle contracts but doesn’t shorten
54
What is isotonic contraction
Muscle contracts and shortens
55
What is concentric contraction
Muscle contracts and shortens but the force exceeds the load
56
Eccentric contraction is what
When a muscle contracts but lengthens and the load exceeds the force
57
How many neurons innervate muscle fibers
Multiple Each muscle has one nerve but each nerve has multiple neurons
58
What increases force of contraction
An increase in the number of myofiber activated
59
A neuron plus an associated fiber is what
Motor unit
60
What is motor unit recruitment
Generates more force by activating more motor units
61
When and why do motor units oscillate
They oscillate during sustained contraction to reduce fatigue This is why you shake during strong forcible contraction
62
When you activate a motor unit what happens to the force of the muscle
It increases
63
What is subthreshold stimulus
A stimulus sent to the muscle but no observable contraction
64
What is threshold stimulus
Stimulus sent to muscle and results in observable contraction
65
What is maximal stimulus
All motor units recruited which results in maximal tension
66
What are the three phases of a muscle twitch
Latent period Period of contraction Relaxation
67
What is a muscle twitch
A motor units response to a single action potential
68
What is wave summation
An increase in frequency of action potentials which results in an increase in twitches Muscle tension increases due to increased stimulus frequency
69
What is unfused tetanus
Sustained but quivering contraction which results in partial relaxation in between stimuli
70
What is fused tetanus
Maximal tension sustained which is the result of no relaxation between stimulus
71
What causes muscle tone
Caused by feedback mechanism involving stretch receptors
72
What phosphorylated ADP directly to make ATP
Creatine phosphate
73
What is lactic acid fermentation
ATP from glucose via glycolysis produces pyruvic acid and in absence of oxygen pyruvic acid is converted to lactic acid
74
How many ATP per creatine phosphate? What about per glucose?
1 per creatine phosphate 2 atp per glucose
75
What is aerobic respiration
ATP from glucose from glycolysis and aerobic respiration which usually provides hours of energy
76
How many ATP per glucose molecule are made in aerobic respiration
28
77
What is muscle fatigue
Physiological inability to contract in the presence of a stimulus most likely causes with a lack of atp
78
What is physiological contracture
State of fatigue where neither contraction or relaxation can occur due to lack of atp
79
What is rigor
Muscle state where the muscles are locked in the contracted state which is caused by a lack of atp that operates the calcium atpase so calcium can’t be cleared from the sarcoplasm
80
What is rigor mortis
Calcium atpase breaks down and calcium leaks out of the SR
81
What is EPOC
Excessive post exercise oxygen consumption where oxygen reserves in myoglobin are depleted and need to be replenished Lactic acid needs to be converted to pyruvic acid and glycogen stores need replenished ATP and creatine phosphate stores also need to be replenished
82
What determines speed of contraction
How fast the myosin atpase splits atp
83
What are characteristics of slow fibers
Slow muscle twitch but more fatigue resistant
84
What are characteristics of fast fibers
Fast twitch but fatigue more readily
85
What are oxidative fibers
Use aerobic respiration
86
What do glycolysis fibers use
Anaerobic pathway

Physiology (13 decks)

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