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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
Troponin
3 polypeptides keep tropomyosin in blocking position 1 binds to tropomyosin 1 binds to actin 1 binds with Ca++
26
Muscle proteins
myosin and actin contractile proteins but don't actually contract not unique to skeletal muscle each myosin molecule surrounded by 6 actin molecules
27
Titin
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
Two important roles of Titin
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
Sarcoplasmic Reticulum
modified ER in muscle cell interconnected compartments that surround myofibril wrapped around each A and I band
30
Tranverse T tubules
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
Motor Unit
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
Neuromuscular junction
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
Sliding filament mechanism
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
Actin molecules in thin myofilament
BINDING POWER STROKE DETACHMENT ATP BINDING
35
Binding 1
Myosin cross bridge binds to actin molecule
36
Power stroke
cross bridge bends, pulling thin myofilament inward
37
Detachment ATP
attaches to ATPase sire; cross bridge detaches at end of poer stroke and returns to original conformation
38
Binding 2
cross bridge binds to more distal actin molecule; cycle repeated
39
Cross Bridge Cycle
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
Power stroke
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
ATP during contractions
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
Relaxation
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
Rigor and Muscle Tone
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
Tension
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
Two types of contraction
isotonic | isometric
46
Isotonic
muscle tension remains constant as muscle changes length
47
isometric
muscle is prevented from shortening | tension develops at constant muscle length
48
cardiac muscle
``` heart interconnected by gap junctions ANS CN X Hormones Local factors more sarcoplasm and mitochondria larger T-tubules but less developed SR ```
49
Cardiac muscle
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
Smooth Muscle
``` 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
Smooth muscle
contraction/relaxation controlled by ANS CN X Hormones Local factors longer to initiate and terminate contraction Ca2+ dissociation required enzyme phosphatase
52
Muilti-Unit smooth muscle
many separate muscle units function independently and are separately stimulated to contract
53
Neurogenic
contraction only in response to stimulation of ANS nerves supplying the muscle
54
Multi-Unit smooth muscle found in
``` 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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