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Physiology 150 > Unit 4 - Muscle Physiology > Flashcards

Unit 4 - Muscle Physiology Flashcards

1
Q

Three types of muscles

A

skeletal
cardiac
smooth

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2
Q

skeletal

A

voluntary/striated

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3
Q

cardiac

A

heart/involuntary/striated

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4
Q

smooth

A

involuntary/unstriated

internal organs

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5
Q

controlled muscle contraction allows

A

purposeful movement
manipulation of external objects
movement of contents through hollow internal organs
removal of wastes

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6
Q

Skeletal muscle

A

muscle fibres lying parallel to one another
single skeletal muscle cells
held together by dense, connective tissue
multinucleated
large, elongated, and cylindrically shaped
fibres usually extend entire length of muscle

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7
Q

Structure of skeletal muscle

A 
each muscle covered by dense connective tissue
3 anatomic connective tissues
1.epimysium
2.perimysium
3.endomysium
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8
Q

Epimysium

A

covers whole muscle

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9
Q

Perimysium

A

divides muscle fibers into bundles(fascicles)

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10
Q

Endomysium

A

innermost

covers each muscle fiber and cell

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11
Q

Muscle cell terminologies

A

Sarcoplasmic reticulum: endoplasmic reticulum

sarcolemma: plasma membrane of a muscle cell
sarcoplasm: cytoplasm

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12
Q

Structure of Muscle fibres

A

myofibrils are contractile elements of a muscle fibre

protein fibers run parallel to cell’s long axis

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13
Q

Myosin

A

thick filaments

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14
Q

Actin

A

thin filaments

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15
Q

Dark band

A

A band - thick

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16
Q

Light band

A

I band - thin

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17
Q

Sarcomere

A

functional unit for muscle contraction
along myofibril
between two Z lines (connects thin filaments of 2 adjoining sarcomeres)

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18
Q

A band

A

thick filaments and portions of thin filaments that overlap on both ends of thick filaments

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19
Q

H zone

A

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

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20
Q

I band

A

remaining portion of thin filaments that don’t project into A band

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21
Q

M line

A

extends vertically down middle of A band within center of H zone to stabilize thick filament

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22
Q

Thick filaments

A 
composed of protein myosin
Golf club
lie parallel
tail ends point toward centre
globular heads project out at one end
form cross bridges with 2 binding sites
ATPase and Actin
23
Q

Thin filaments

A

composed of protein actin (two strands twisted together)

two other proteins, tropomyosin and troponin

24
Q

Tropomyosin

A

lies along groove of actin spiral

cover binding sites -> actin can’t bind to myosin -> no contraction

25
Q

Troponin

A

3 polypeptides keep tropomyosin in blocking position
1 binds to tropomyosin
1 binds to actin
1 binds with Ca++

26
Q

Muscle proteins

A

myosin and actin
contractile proteins but don’t actually contract
not unique to skeletal muscle
each myosin molecule surrounded by 6 actin molecules

27
Q

Titin

A

giant, highly elastic protein
largest protein in body
extends in both directions from M line along length of thick filament to Z lines at opposite ends of sarcomere

28
Q

Two important roles of Titin

A

with M line proteins helps stabilize position of thick filaments in relation to thin filaments
augments muscle’s elasticity by acting like a spring

29
Q

Sarcoplasmic Reticulum

A

modified ER in muscle cell
interconnected compartments that surround myofibril
wrapped around each A and I band

30
Q

Tranverse T tubules

A

extension of sarcolemma to spread action potential and release Ca2+
run perpendiculary from sarcolemma into central portions of muscle fibre
Sepment ends form sacs - lateral sacs store calcium

31
Q

Motor Unit

A

one motor neuron and the muscle fibres it innervates
1 motor neuron innervates a varied number of muscle fibres, but each muscle fibre supplied by only 1 motor neuron
muscles that produce precise, delicate movements contain fewer fibres per motor unit
muscles performing powerful, coarsely controlled movement have larger number of fibres per motor unit

32
Q

Neuromuscular junction

A

space between motor unit axon terminal and muscle cell
Ach diffused across synaptic cleft
ACh binds with specific receptors sites on sarcolemma -> action potential
AP speads down muscle fibre into T-tubule
Ca+ released from lateral sacs to sarcoplasm

33
Q

Sliding filament mechanism

A

acetylcholine released at neuromuscular junction
sarcoplasmic reticulum releases Ca2+ into sarcoplasm
Ca2+ -> binds to troponin on actin filaments -> tropomyosin and troponin move aside to uncover binding site on actin -> myosin heads bind to actin
Myosin and actin cross bridge binding site moves inward -> actin ‘rowed’ inward -> muscle shortens (contracts)

34
Q

Actin molecules in thin myofilament

A

BINDING
POWER STROKE
DETACHMENT ATP
BINDING

35
Q

Binding 1

A

Myosin cross bridge binds to actin molecule

36
Q

Power stroke

A

cross bridge bends, pulling thin myofilament inward

37
Q

Detachment ATP

A

attaches to ATPase sire; cross bridge detaches at end of poer stroke and returns to original conformation

38
Q

Binding 2

A

cross bridge binds to more distal actin molecule; cycle repeated

39
Q

Cross Bridge Cycle

A

myosin heads swivel toward centre of sarcomere (power stroke) pulling actin inward
splitting of ATP gives energy for power stroke of cross bridge
binding of new ATP to myosin site lets bridge detach from actin filament at end of power stroke so cycle can be repeated

40
Q

Power stroke

A

cross bridges don’t power stroke in unison (asynchronous cycling -> prevent thin filaments from slipping back)
with cross bridge, thin filaments slide inward over stationary thick filaments toward centre of sarcomere
power stroke pulls thin filament inward

41
Q

ATP during contractions

A

ATP and Ca2+ (both available -> sliding mechanism and contraction, one or neither available -> sliding mechanism and contraction steps)
increase in Ca2+ starts filament sliding
decrease in CA2+ turns off sliding process

42
Q

Relaxation

A

Acetylcholinesterase breaks down ACh at neuromuscular junction
Muscle fibre action potential stops (when local action potential is no longer present Ca2+ moves back into sarcoplasmic reticulum
Troponin and tropomyosin cover actin binding sites
myosin can’t bind -> relaxation

43
Q

Rigor and Muscle Tone

A

between power stroke and detachment, myosin and actin tightly bound together
If no ATP produced, cross bridge cycle gets stuck at this step -> “rigor mortis”
Muscle tone
some of the motor units contract continuously, producing a resting tension in a skeletal muscle

44
Q

Tension

A

produced internally within sarcomeres during contraction
tension must be transmitted to bone via connective tissue and tendons during contraction before bone can move against load

45
Q

Two types of contraction

A

isotonic

isometric

46
Q

Isotonic

A

muscle tension remains constant as muscle changes length

47
Q

isometric

A

muscle is prevented from shortening

tension develops at constant muscle length

48
Q

cardiac muscle

A 
heart
interconnected by gap junctions
ANS
CN X
Hormones
Local factors
more sarcoplasm and mitochondria
larger T-tubules but less developed SR
49
Q

Cardiac muscle

A

initiates own AP potential without neuron stimulation ( AP travels throughout the entire cell network)
Limited intracellular Ca++ to sarcoplasm produces a contraction that last 10-15 times longer than in skeletal muscle

50
Q

Smooth Muscle

A 
hollow organs and tubes
no striations (thick and thin filaments don't form myofibrils, lack sarcomeres)
muscle fiber contracts and twists into a helix as it shortens (relaxes by untwisting)
51
Q

Smooth muscle

A

contraction/relaxation controlled by
ANS
CN X
Hormones
Local factors
longer to initiate and terminate contraction
Ca2+ dissociation required enzyme phosphatase

52
Q

Muilti-Unit smooth muscle

A

many separate muscle units function independently and are separately stimulated to contract

53
Q

Neurogenic

A

contraction only in response to stimulation of ANS nerves supplying the muscle

54
Q

Multi-Unit smooth muscle found in

A 
in walls of large blood vessels
in large airways
in muscle of eye that adjusts lens for near or far vision
in iris of eye
at base of hair follicles

Physiology 150 (11 decks)

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