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Chapter 11. Physiology of the Muscular System. General functions:. Movement Heat Production Posture. Function of the skeletal muscle tissue. Muscle cell:. Bundles of muscle fibers (cells) Extends entire length of the cell Same structures as cells, but with different names

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chapter 11

Chapter 11

Physiology of the Muscular System

general functions
General functions:
  • Movement
  • Heat Production
  • Posture
muscle cell
Muscle cell:
  • Bundles of muscle fibers (cells)
  • Extends entire length of the cell
  • Same structures as cells, but with different names
  • Plasma membrane – sarcolemma
  • Cytoplasm – sarcoplasm
  • Many mitochondria and nuclei
  • Tubules and sacs – sarcoplasmic reticulum
  • Typical only to muscle cells – myofibrils bundles of fine fibers that allow contraction of the muscle
slide5
Cont.
  • Sarcomeres – fibers running lengthwise of the muscle and consist of A bands that look striped (striated)
  • T – tubules run transverse to the sarcomere fibers – allow for electrical signals to promote movement
  • Sarcoplasmic reticulum allows for calcium to be stored with in its sacs
  • Triad – these tubules ( T-tubules sandwiched between two SR sacs) allows for an electrical impulse to trigger movement
myofilaments
Myofilaments
  • Each muscle fiber has a thousand or more parallel subunits called myofibrils
  • Beside each myofibril are thousands of thick and thin myofilaments
  • Myofilaments composed of – myosin, actin, tropomysin, and troponin
contraction
Contraction
  • Shortening
  • Page 316 box 11-2
excitation of the sarcolemma
Excitation of the sarcolemma
  • Skeletal muscles normally at rest
  • Motor neurons receive message at the neuromuscular junction (synapse)
  • Can we say “gaposis”?
  • Neurotransmitter jumps the gap with messages and in turn releases acetylcholine
  • This initiates an electrical impulse causing excitation
contraction1
Contraction
  • The previously discussed impulse conducted down muscle fibers (sarcolemma) and to the T-tubules
  • This triggers release of Calcium ions from the SR
  • This combines with troponin and exposes actin molecules
  • Actin then binds with myosin – this bends the myosin heads and with great force, pulls the filaments past them
  • This shortens the myofibers (called the sliding filament theory)
relaxation
Relaxation
  • After the SR releases Ca into sarcoplasm, it begins to pull the Ca back into the sacs.
  • Only takes a few milliseconds
  • This shuts down the contraction process
slide12
ATP
  • Adenosine triphosphate
  • ENERGY!
  • Re-synthesis of this high energy bond must always take place since only small amounts are stored
  • Another high energy bond comes from creatine phosphate elevated with H.A.
  • Catabolism of both of these comes from catabolism of foods
glucose oxygen
Glucose / oxygen
  • Required for continued, efficient muscle function
  • Glucose is stored as glycogen
  • Oxygen can be stored by cells
  • During rest, oxygen is bound to protein molecules called myoglobin (red pigment) and contains iron to attract O-2
aerobic vs anerobic respiration
Aerobic vsanerobic respiration
  • Aerobic – oxygen
  • Anerobic – avoid the use of oxygen
  • Catabolic process that produces energy from glucose
  • Anerobic respiration results in lactic acid which causes a burning sensation during or after exercise
methemeglobinemia
Methemeglobinemia
  • Genetic flaw
  • Both parents must be carriers for the offspring to suffer from this abnormality.
  • Blood cannot bind to oxygen properly – blood is brown – not red in the arterial lumen
  • TMT: methylene blue q d
heat production
Heat production
  • Greatest source of heat production in the body is digestion
  • Next is muscle movement through exercise
tetanus
Tetanus
  • Smooth sustained types of contraction
  • Smooth/sustained – tetaniccontractions or tetanus
  • Can be incomplete (short periods of relaxation) or complete (sustained)
muscle tone
Muscle tone
  • Tonic ( tone) contraction – continual, partial contraction – also called muscle tone
  • Flaccid – reduced tone
  • Spastic – increased tone
strength
Strength
  • Graded strength principle – muscles contract at varying levels at various times
  • Variables - Metabolism, conscious stimuli, amount of load imposed
exercise effects on muscle structure
Exercise – effects on muscle structure
  • Disuse atrophy – wasting
  • Hypertrophy – enlargement
  • Strength training – mass
  • Endurance training (aerobic)- sustainability
isometric vs isotonic contractions
Isometric vs isotonic contractions
  • Isotonic – tone/tension remains same length of muscle elongates while moving against a load
  • Concentric contractions – results in shortening of the muscle (pick up a book)
  • Eccentric contraction – movement causes lengthening of the muscle while in a contracted state (lower the book back to the table)
  • Isometric contraction – opposite isotonic – muscle length remains the same during contraction – does’t produce movement – just tension (yoga)
abnormal contractions
Abnormal contractions
  • Cramp – involuntary twitches – inflammation, irritation, nutrition, fluid imbalance
  • Convulsion – abnormal, uncoordinated tetanic contraction – brain wave abnormality, fever, neurological damage
  • Fibrillation – fibers contract out of timing with each other – flutter – no productive movement occurs
cardiac muscle
Cardiac muscle
  • Exclusive to the heart
  • Striated involuntary muscle
  • Pericardium, myocardium, endocardium
smooth muscle
Smooth muscle
  • Involuntary
  • Visceral – walls of hollow organs – GI, U, Repro. – peristalsis
  • Multiunit – arrectorpili of the skin, small blood vessels
abnormalities
Abnormalities
  • Strain
  • Myalgia
  • Contusion
  • Infection – poliomyelitis
  • Muscular dystrophy – genetic – atrophy replaced by adipose tissue
  • Myasthenia gravis – muscle weakness
  • Hernia – inguinal, umbilical, abdominal