Functions of Muscles

• Body movement • Maintenance of posture • Ventilation • Thermogenesis • Communication • Constriction of organs and lumens • Heartbeat

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Tendon

Fascia

Skeletal muscle

Muscle fascicle Nerve Blood vessels Epimysium

Perimysium Endomysium Muscle fiber

Muscle fascicle

Perimysium

Muscle fiber 5 6 (a) 7 8

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Nucleus

Sarcomere

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Z disc M line 4

H band 3

I band A band I band 2 Individual myofibrils

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(a)

Sarcomere I band A band I band H band

Thick filament Thin filament M line Tin Z disc Elasc filament (b) Z disc

a: Visuals Unlimited

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Muscle fiber

Nucleus

A band

I band

Z disc

Mitochondria Openings into transverse tubules

Sarcoplasmic reculum

T riad: T erminal cisternae T ransverse tubule

Sarcolemma Myofibrils Sarcoplasm

Myofilaments

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Terminal T tubule cisterna of SR

T tubule Sarcoplasmic reculum

Ca2+

Ca2+

6 Acon potenals propagated 7 Calcium released from down T tubules terminal cisternae

Acve sites Troponin 2+ Ca Tropomyosin Acn Thin filament

Myosin Ca2+

8 Binding of calcium 9 Shiing of tropomyosin; to troponin exposure of acve sites on acn

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproducon or display. Spinal cord

Motor neuron 1 Motor neuron 2

Neuromuscular juncon

Skeletal muscle fibers

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Threshold Smulus voltage

1 2 3 4 5 6 7 8 9 Smuli to nerve

Proporon of nerve fibers excited

Maximum contracon

Tension

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25 Responses of muscle 26

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Muscle develops Muscle shortens, Muscle lengthens tension but does tension remains while maintaining not shorten constant tension Movement No movement Movement

(a) Isometric contracon (b) Isotonic concentric contracon (c) Isotonic eccentric contracon

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