Physiology Lab - Skeletal Muscle

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Smooth muscle

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47 Terms

1

Smooth muscle

  • no striation

  • uninucleated

  • nucleus centrally located

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2

skeletal muscle

  • striated

  • multinucleated

  • nucleus peripherally located

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3

cardiac muscle

  • striated

  • uninucleated or binucleated

  • nucleus centrally located

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4

epimysium

surround the muscle group

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5

perimysium

surrounds fasicle

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6

endomysium

surrounds muscle fiber/cell

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7

sarcomere

functional unit of muscle

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8

striation

comes from arrangement of myofilaments within myofiber

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9

myofilament

actin and myosin

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10

myofiber

muscle cell

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11

I-band

actin only; light region of sarcomere

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12

A-band

myosin plus overlapping actin; dark region of sarcomere

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13

H-band

myosin only; center of A-band

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14

M-line

center of A band

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15

thick filaments

myosin

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16

thin filaments

actin

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17

z-line

how sarcomeres are divided from each other, found in center of I band

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18

sarcolemma

muscle plasma membrane

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19

T tubules

extension of sarcolemma into muscle fiber; carry action potential to interior myofibrils

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20

Sarcoplasmic reticulum

stores calcium ions

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21

excitation-contraction coupling

pairs depolarization of neuron with depolarization of a muscle cell

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22

steps of excitation-contraction coupling

  • Ach is released into neuromuscular junction and binds to receptor site on sarcolemma

  • action potential travels down T tubules causing Ca2+ channels to open

  • intracellular Ca2+ concentration increases

  • Ca2+ binds to troponin on thin filaments

  • Tropomyosin moves away to allow myosin to attach to actin

  • cross-bridge cycling begins and force is generated

  • Ca2+ is reaccumulated by SR and muscle relaxes

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23

Ca2+ is low

tropomyosin blocks myosin binding site on actin; no contraction

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24

Ca2+ is present

Ca2+ binds to troponin complex which changes tropomyosin to allow myosin to bind to actin; contraction can occur

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25

sliding filament theory

  • ATP binds to myosin and causes myosin head to detach

  • ATP hydrolyzed into ADP and P; myosin is in resting cocked position

  • myosin binds to actin monomer forming crossbridge

  • P is released; filaments slide past each other (powerstroke)

  • ADP is released

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26

motor unit

single motor neuron and the muscle fibers it innervates

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27

small motor units

fine motor activities

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large motor units

gross motor activities

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29

recruitment

start using small motor units and add more as needed

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30

isometric action

muscle contract and length remains; force generated is insufficient to overcome load

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31

isotonic action

contraction tension remains constant and muscle changes length and moves the load

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32

concentric action

muscle contracts and shortens

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eccentric action

muscle contracts and lengthens

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34

agonist

primary mover

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synergist

muscle that assist agonist group

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antagonist

muscles that oppose the agonist

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37

Slow Twitch - Type I

  • mostly aerobic respiration, not large amount of force, fatigue resistant, efficient, lots of mitochondria

  • endurance athlete

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38

Fast Twitch - Type IIX

  • anaerobic glycolysis or direct phosphorylation of ADP

  • less resistant to fatigue, high power output, rich in glycolytic enzymes, small number of mitochondria

  • 100m sprint

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39

Fast Twitch - Type IIA

  • intermediate fibers, mix of Type I and Type IIX

  • 800m sprint

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40

hypertrophy

increase in muscle fiber diameter due to increase in myofibril size; muscle can exert more force due to proportionality of cross-sectional area and force

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41

Muscle soreness

  • from microscopic injury to muscle fibers

  • 24-48 hrs after injury

  • not from lactic acid accumulation

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42

Rigor mortis

postmortem muscle stiffness due to rigor cross-bridges in absence of ATP

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43

Sarcopenia

age related decline in muscle mass beginning around age 25 and occurs across lifespan

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44

slow phase sarcopenia

10% muscle mass loss from age 25-50

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rapid phase sarcopenia

additional 40% muscle mass loss from age 50-80

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46

Muscular dystrophy

  • group of hereditary muscle diseases that weaken skeletal muscle

  • no cure and respiratory failure usually occurs early in life

  • lack dystrophin protein

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47

dystrophin protein

helps maintain structural integrity of sarcolemma

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