SKELETAL MUSCLE MAIN FUNCTIONS: 1. 2. 3. 4. 5. 6. POSTURE LOCOMOTION HEAT PRODUCTION DEFENCE RESPIRATION VOCALIZATION
SKELETAL MUSCLE FIBER PROPERTIES: • EXCITABILITY • CONDUCTIVITY • CONTRACTILITY • ELASTICITY
STRUCTURAL UNIT OF A SKELETAL MUSCLE FIBER SARCOMERE • SARCOLEMMA • SARCOPLASMIC RETICULUM • MYOFIBRILS, WHICH CONSIST OF MYOSIN FILAMENTS ACTIN FILAMENTS
T-tubule sarcolemma SPR Z Triade myosin SPR Z-disc actin Z
Latent period AP Contraction phase Relaxation phase
DOUBLE STIMULUS LEAD TO MUSCLE TWITHES SUMMATION INCOMPLETE SUMMATION: THE SECOND STIMULUS IS APPLIED DURING RELAXATION PHASE
DOUBLE STIMULUS LEAD TO MUSCLE TWITHES SUMMATION COMPLETE SUMMATION: THE SECOND STIMULUS IS APPLIED DURING CONTRACTION PHASE
RHYTHMIC STIMULATION LEADS TO TETANIZATION INCOMPLETE (TOOTHED) TETANUS EACH FOLLOWING STIMULUS IS APPLIED DURING RELAXATION PHASE
RHYTHMIC STIMULATION LEADS TO TETANIZATION COMPLETE (SMOOTH) TETANUS EACH FOLLOWING STIMULUS IS APPLIED DURING CONTRACTION PHASE
MOTOR UNIT The functional unit in skeletal muscle is the motor unit which consists of • alpha-motor neuron in the spinal cord, • axon • and all the innervated muscle fibers.
MOTOR UNIT INCLUDES 1 -2 muscle fibers___in laryngeal muscles 5 -7 muscle fibers___in oculomotor m. 10 -15 muscle fibers_in finger muscles 200 -2000 muscle fibers – in large tonic muscles of legs, back, etc.
MOTOR UNIT CLASSIFICATION SLOW MUSCLE FIBERS CHARACTERISTICS: RED WEAK AEROBIC MYOGLOBIN CONTENT TRIGLYCERIDES (FUEL) RESISTANT TO FATIGUE PROVIDE CONTINUOUS MUSCLE TONE FAST MUSCLE FIBERS CHARACTERISTICS: WHITE STRONG ANAEROBIC CREATINE PHOSPHATE, GLYCOGEN (FUEL) FATIGABLE PROVIDE LOCOMOTION, MANIPULATION, SPEECH
SKELETAL MUSCLE TONE FORMATION low frequency of nerve impulses & asynchronic activity of motor units All the maximum fuse forming smooth continues contracton Weak skeletal muscle tone as a result