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Muscle Physiology

Human Anatomy and Physiology IIOklahoma City Community College

Dennis Anderson

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Muscle Tissue

Skeletal Muscle

Cardiac Muscle

Smooth Muscle

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Skeletal Muscle

Long cylindrical cells

Many nuclei per cell

Striated

Voluntary

Rapid contractions

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Cardiac Muscle

Branching cells

One or two nuclei per cell

Striated

Involuntary

Medium speed contractions

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Smooth Muscle

Fusiform cells

One nucleus per cell

Nonstriated

Involuntary

Slow, wave-like contractions

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Microanatomy of Skeletal

Muscle

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Z line Z line

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H Band

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Sarcomere Relaxed

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Sarcomere Partially

Contracted

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Sarcomere Completely

Contracted

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Binding Site Tropomyosin

Troponin

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Myosin

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Neuromuscular Junction

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Acetylcholine Opens Na+

Channel

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Muscle Contraction Summary

Nerve impulse reaches myoneural junction

Acetylcholine is released from motor

neuron

Ach binds with receptors in the muscle

membrane to allow sodium to enter

Sodium influx will generate an action

potential in the sarcolemma

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Muscle Contraction Continued

Action potential travels down T tubule

Sarcoplamic reticulum releases calcium

Calcium binds with troponin to move the

troponin, tropomyosin complex

Binding sites in the actin filament are

exposed

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Muscle Contraction Continued

Myosin head attach to binding sites and

create a power stroke

ATP detaches myosin heads and energizesthem for another contaction

When action potentials cease the muscle

stop contracting

M t U it

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Motor UnitAll the muscle cells controlled by one

nerve cell

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Motor Unit Ratios

Back muscles

1:100

Finger muscles

1:10

Eye muscles

1:1

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ATP

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Creatine

Molecule capable of storing ATP energy

Creatine + ATP Creatine phosphate + ADP

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Creatine Phosphate

Molecule with stored ATP energy

Creatine + ATPCreatine phosphate+ ADP

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Muscle Fatique

Lack of oxygen causes ATP deficit

Lactic acid builds up from anaerobic

respiration

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Muscle Atrophy

Weakening and shrinking of a muscle

May be caused

Immobilization

Loss of neural stimulation

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Muscle Hypertrophy

Enlargement of a

muscle

More capillaries More mitochondria

Caused by

Strenuous exercise

Steroid hormones

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Steroid Hormones

Stimulate muscle growth and hypertrophy

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Muscle Tonus

Tightness of a muscle

Some fibers always contracted

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Tetany

Sustained contraction of a muscle

Result of a rapid succession of nerve

impulses

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Tetanus

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Refractory Period

Brief period of time in which muscle cells

will not respond to a stimulus

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Refractory

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Skeletal Muscle Cardiac Muscle

Refractory Periods

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Isometric Contraction

Produces no movement

Used in

Standing

Sitting

Posture

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Isotonic Contraction

Produces movement

Used in

Walking

Moving any part of the body

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THE END