Muscle

Muscle Tissue

• Skeletal Muscle

• Cardiac Muscle

• Smooth Muscle

www.freelivedoctor.com

Skeletal Muscle

• Long cylindrical cells• Many nuclei per cell• Striated• Voluntary• Rapid contractions


Cardiac Muscle

• Branching cells

• One or two nuclei per cell

• Striated

• Involuntary

• Medium speed contractions


Smooth Muscle

• Fusiform cells

• One nucleus per cell

• Nonstriated

• Involuntary

• Slow, wave-like contractions


Microanatomy of Skeletal Muscle



Z line Z line





H Band


Sarcomere Relaxed


Sarcomere Partially Contracted


Sarcomere Completely Contracted




Binding Site Tropomyosin

Troponin


Myosin



Neuromuscular Junction



Acetylcholine Opens Na+ Channel



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


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


Muscle Contraction Continued

• Myosin head attach to binding sites and create a power stroke

• ATP detaches myosin heads and energizes them for another contaction

• When action potentials cease the muscle stop contracting


Motor UnitAll the muscle cells controlled by one

nerve cell


Motor Unit Ratios

• Back muscles– 1:100

• Finger muscles– 1:10

• Eye muscles– 1:1


ATP


Creatine

• Molecule capable of storing ATP energy

Creatine + ATP Creatine phosphate + ADP


Creatine Phosphate

• Molecule with stored ATP energy

Creatine + ATPCreatine phosphate + ADP


Muscle Fatique

• Lack of oxygen causes ATP deficit

• Lactic acid builds up from anaerobic respiration


Muscle Atrophy

• Weakening and shrinking of a muscle

• May be caused– Immobilization– Loss of neural stimulation


Muscle Hypertrophy

• Enlargement of a muscle

• More capillaries• More mitochondria• Caused by

– Strenuous exercise

– Steroid hormones


Steroid Hormones

• Stimulate muscle growth and hypertrophy


Muscle Tonus

• Tightness of a muscle

• Some fibers always contracted


Tetany

• Sustained contraction of a muscle

• Result of a rapid succession of nerve impulses


Tetanus


Refractory Period

• Brief period of time in which muscle cells will not respond to a stimulus


Refractory


Skeletal Muscle Cardiac Muscle

Refractory Periods


Isometric Contraction

• Produces no movement

• Used in– Standing– Sitting– Posture


Isotonic Contraction

• Produces movement

• Used in– Walking– Moving any part of the body


Documents

Muscle