SKELETAL MUSCLE MAIN FUNCTIONS: 1. POSTURE

SKELETAL MUSCLE MAIN FUNCTIONS: 1. POSTURE 2. LOCOMOTION 3. HEAT PRODUCTION 4. DEFENCE 5. RESPIRATION 6. 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 Triade sarcolemma SPR actin Z myosin Z-disc Z

Latent Contraction Relaxation period phase AP

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 FAST MUSCLE FIBERS CHARACTERISTICS: RED WHITE WEAK STRONG AEROBIC ANAEROBIC MYOGLOBIN CONTENT CREATINE PHOSPHATE, TRIGLYCERIDES (FUEL) GLYCOGEN (FUEL) RESISTANT TO FATIGUE FATIGABLE PROVIDE CONTINUOUS PROVIDE LOCOMOTION, MUSCLE TONE 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