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MED 310A > muscle physiology > Flashcards

muscle physiology Flashcards

1
Q

which muscles are striated?

A

skeletal and cardiacw

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2
Q

which muscles are involuntary?

A

cardiac and smooth muscle

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3
Q

what are muscle fibers in the skeletal msucle held together by?

A

connective tissue

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4
Q

what is a single muscle cell called?

A

muscle fiber

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5
Q

what is a myofibril?

A

the contractile element of skeletal muscle

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6
Q

is myosin in thick or thin filaments?

A

thickwh

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7
Q

what shape is used to described myosin?

A

golf club

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8
Q

what 2 sites in skeletal muscle are critical for cross bridge formation?

A

Actin-binding site and Myosin ATPase site

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9
Q

is actin in thick or thin filaments?

A

thin

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10
Q

what are the 3 molecules are in thin filaments of skeletal muscle?

A

tropomyosin, actin, troponin

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11
Q

what is special about tropomyosin for cross bridge formation?

A

it needs to be moved from blocking the actin site

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12
Q

what does troponin do once bound to Ca2?

A

moves tropomyosin away from blocking the actin site

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13
Q

what is a sarcomere?

A

functional unit of striated muscle. Found between 2 Z lines (connects thin filaments of adjoining sarcomeres)

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14
Q

what is the A band?

A

made up of thick filaments along with portions of thin that overlap

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15
Q

what is the H zone?

A

lighter area within middle of A band where thin filaments don’t reach

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16
Q

what is the M line?

A

extends vertically down the middle of the A band within the center of H zone

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17
Q

what is the I band?

A

consists of remaining portion of thin filaments that do not project into the A band

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18
Q

what are the characteristics of the sliding filament mechanism?

A

Increased Ca2 starts the sliding
Decrease Ca2 turns off the sliding
Thin filaments on each side of the sarcomere slide inward.
This pulls Z lines closer
Sarcomere shortens

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19
Q

what are the characteristics of a power stroke?

A

Activated cross bridging = rowing in thin filament
Sarcoplasmic reticulum releases Ca2 into sarcoplasm
Myosin heads bind to actin
Myosin head swivel toward center of sarcomere
ATP binds to myosin head and detaches it from actin

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20
Q

how does a cross bridge form?

A

Ach released by motor neuron axon generates an action potential across surface membrane and down T tubules
Action potential in T tubule triggers Ca2 release from SR
The Ca2 binds to troponin which moves tropomyosin from the actin site and initiates binding
causes bridge cycling

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21
Q

how does a muscle relax?

A

Depends on uptake of Ca2 by SR
Acetylcholinesterase breaks down the Ach at the junction
Muscle fiber action potential halts and Ca2 goes back to SR

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22
Q

what is a motor unit?

A

motor neuron + muscle fibers it innervates

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23
Q

does a muscle producng a precise movement have lots or few motor units?

A

few

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24
Q

does a muscle producing a powerful movement have lots or few motor units?

25
what is twitch summation?
sustained elevation of cytosolic calcium
26
what is tetanus?
if the muscle fiber is stimulated so rapidly that it does not have a chance to relax. 3-4x stronger than a single twitch
27
where is tension produced?
internally within sarcomeres
28
how is tension trasnmitted to bone?
connective tissue and tendons
29
is the bone stationary or moving at the origin end of the muscle?
stationary
30
is the bone stationary or moving at the insertion end of the muscle?
moving
31
what is the series elastic component?
connective tissue tendons etc...
32
what happens during a concentric contraction and what is an example?
muscle shortens. I.e standing from sat. flexion
33
what happens during a concentric eccentric and what is an example?
muscle lengthens. I.e sitting. extension
34
what is an isometric contraction?
tension develops without change in joint angle
35
what is Henneman's size principle?
within each muscle there is great diversity of size and properties of motor units
36
what are the characteristics of the slow oxidative unit?
low threshold, thin axon, slow, weak, energy efficient, fatigue resistant, not interconvertable
37
what are the characteristics of the fast oxidative unit?
medium threshold and axon, medium fast,strong, efficient, fatigue resistant, interconvertable with fast glycolytic
38
what are the characteristics of the fast glycolytic unit?
high threshold, thick axon, very fast, very strong, poor efficiency and poor fatigue resistance, interconvertable with fast oxidative
39
what is hypertrophy?
increase in mass or girth of muscle. Can be induced by resistance exercise, increases myofibrils and based on the injury-regeneration cycle
40
what is atrophy?
loss of muscle
41
what is disuse atrophy?
skeletal muscles not being physically stressed regularly
42
what is denervation atrophy?
nerve supply to muscle is lost
43
what are characteristics of skeletal muscle?
Attached to skeleton Movement of body in relation to environment Sliding filament mechanism Innervates somatic nervous system Under voluntary control Neurogenic Initiates contraction and accomplishes gradation Varying speed
44
what are characteristics of multi-unit smooth muscle?
Large blood vessels, small airways, eyes and hair follicles Variable function Sliding filament mechanism Innervates the ANS Under involuntary control Neurogenic Initiates contraction and contributes to gradation Very slow Not electrically connected with gap junctions. Polarization cannot spread from cell to cell contraction/relaxation is isolated solely to stimulated cell
45
what are characteristics of single-unit smooth muscle?
Walls of hollow organs in digestive, reproduction, and urinary tracts and in small blood vessels Movement of contents in the hollow organs Sliding filament mechanism Innervates ANS Under involuntary control Myogenic - self excitable Modifies contraction; can excite or inhibit and contributes to gradation Very slow - energy efficient Most smooth muscle is single unit/visceral smooth muscle Electrically connected with gap junctions Polarization can spread from cell to cell contraction/relaxation is synchronized across many cells
46
what are characteristics of cardiac muscle?
Heart only Pumps blood out Sliding filament mechanism Innervates the ANS Under involuntary control Myogenic Modifies contraction; can excite or inhibit and contributes to gradation Slow Cells connected by gap junctions Similar sarcomere structure to skeletal muscle The heart is spontaneously active The SA node is the pacemaker which spontaneously fires action potentials Voltage gated release of Ca2
47
what is the functional syncytium?
a group of interconnected muscle cells that function electrically and mechanically
48
do filaments in smooth muscle cells form myofibrils?
no
49
how are cells in smooth muscle arranged?
in sheets
50
do the thin filaments of smooth muscle have all 3 molecules that skeletal do?
no - they dont have troponin
51
does tropomyosin block the active site in smooth muscle?
no
52
what is the response to Ca2 in smooth msucle?
Ca2 binds to calmodulin to activate MLCK MLCK phosphorylates myosin activating myosin ATPase activity which initiates cross bridging
53
what is pacemaker potential?
membrane potential gradually depolarizes on its own due to shifts in passive ionic influx. When the membrane depolarizes to the threshold, an action potential is generated. Repolarizes only to depolarize again. Theses are self generating action potentials
54
what are slow wave potentials?
gradually alternating hyperpolarization and depolarization swings. Caused by automatic cycle changes in the rate at which sodium ions are actively transported across the membrane
55
what are varicosities?
sites of transmitter release
56
how does the heart pump blood into the body?
The atria and ventricles fill when the heart is relaxed The atria contract forcing more blood into ventricles After a delay the ventricles contract simultaneously pushing blood into the lungs and body
57
what does the sympathetic nervous system do to the heart?
released norepi and epi and bind to beta1 receptors Depolarizes the SA node cells causing them to beat faster Enhance Ca2 release which increase the force of contraction
58
what does the parasympathetic nervous system do to the heart?
releases acetylcholine which binds to muscarinic receptors Hyperpolarizes the SA cells and reduces firing slowing the heart rate
59
what is starlings law of the heart?
When the heart ventricles fill with blood the cardiac cells stretch which produces a more optimal orientation of actin and myosin and a greater contractile force to be generated

MED 310A (15 decks)

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