muscle physiology
TRANSCRIPT
Muscle Physiology
Muscle Tissue• Skeletal Muscle• Cardiac Muscle• Smooth Muscle
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
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 Fatigue
• 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
THE END