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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?

A

lots

25
Q

what is twitch summation?

A

sustained elevation of cytosolic calcium

26
Q

what is tetanus?

A

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
Q

where is tension produced?

A

internally within sarcomeres

28
Q

how is tension trasnmitted to bone?

A

connective tissue and tendons

29
Q

is the bone stationary or moving at the origin end of the muscle?

A

stationary

30
Q

is the bone stationary or moving at the insertion end of the muscle?

A

moving

31
Q

what is the series elastic component?

A

connective tissue
tendons
etc…

32
Q

what happens during a concentric contraction and what is an example?

A

muscle shortens. I.e standing from sat. flexion

33
Q

what happens during a concentric eccentric and what is an example?

A

muscle lengthens. I.e sitting. extension

34
Q

what is an isometric contraction?

A

tension develops without change in joint angle

35
Q

what is Henneman’s size principle?

A

within each muscle there is great diversity of size and properties of motor units

36
Q

what are the characteristics of the slow oxidative unit?

A

low threshold, thin axon, slow, weak, energy efficient, fatigue resistant, not interconvertable

37
Q

what are the characteristics of the fast oxidative unit?

A

medium threshold and axon, medium fast,strong, efficient, fatigue resistant, interconvertable with fast glycolytic

38
Q

what are the characteristics of the fast glycolytic unit?

A

high threshold, thick axon, very fast, very strong, poor efficiency and poor fatigue resistance, interconvertable with fast oxidative

39
Q

what is hypertrophy?

A

increase in mass or girth of muscle. Can be induced by resistance exercise, increases myofibrils and based on the injury-regeneration cycle

40
Q

what is atrophy?

A

loss of muscle

41
Q

what is disuse atrophy?

A

skeletal muscles not being physically stressed regularly

42
Q

what is denervation atrophy?

A

nerve supply to muscle is lost

43
Q

what are characteristics of skeletal muscle?

A

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
Q

what are characteristics of multi-unit smooth muscle?

A

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
Q

what are characteristics of single-unit smooth muscle?

A

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
Q

what are characteristics of cardiac muscle?

A

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
Q

what is the functional syncytium?

A

a group of interconnected muscle cells that function electrically and mechanically

48
Q

do filaments in smooth muscle cells form myofibrils?

A

no

49
Q

how are cells in smooth muscle arranged?

A

in sheets

50
Q

do the thin filaments of smooth muscle have all 3 molecules that skeletal do?

A

no - they dont have troponin

51
Q

does tropomyosin block the active site in smooth muscle?

A

no

52
Q

what is the response to Ca2 in smooth msucle?

A

Ca2 binds to calmodulin to activate MLCK
MLCK phosphorylates myosin activating myosin ATPase activity which initiates cross bridging

53
Q

what is pacemaker potential?

A

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
Q

what are slow wave potentials?

A

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
Q

what are varicosities?

A

sites of transmitter release

56
Q

how does the heart pump blood into the body?

A

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
Q

what does the sympathetic nervous system do to the heart?

A

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
Q

what does the parasympathetic nervous system do to the heart?

A

releases acetylcholine which binds to muscarinic receptors
Hyperpolarizes the SA cells and reduces firing slowing the heart rate

59
Q

what is starlings law of the heart?

A

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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