Muscle Physiology

Functions of Muscular Tissue Producing Body Movements Stabilizing Joints Maintaining Posture Producing heat Properties of Muscular Tissue Excitability Contractility Extensibility Elasticity

Types of Muscle

Connective Tissue Wrappings

Insertion - attachment to a movable bone Origin - attachment to stationary bone Attachment - connective tissue layers extend to attach to bone (tendon or aponeurosis) Muscle Attachments

Anatomy of a Muscle Fiber

Sarcomere Dark(A) & light(I) bands visible with an electron microscope

Sarcomere

Thick and Thin Filaments

Sliding Filament Mechanism Relaxed Muscle Contracte d Muscle

The Contraction Cycle

Stimulation and Contraction

Neuromuscular Junction

Summary

Motor Unit: A motor neuron and all the muscle fibers it innervates. Motor Unit

Muscle Tone Involuntary contraction of a small number of motor units which leads to partial state of contraction of relaxed muscles Keeps muscles firm even though relaxed Essential for maintaining posture

Contraction of a Skeletal Muscle Muscle Twitch: Response of a muscle to a single stimulus

Graded Muscle Responses 1. Frequency of stimulation Wave summation and Tetanus 2. Strength of the stimulus Motor Unit Recruitment Graded - variation in degree of contraction Contraction of a Skeletal Muscle More motor units stimulated which leads to more muscle fibers responding.

Wave Summation and Tetanus

Isotonic and Isometric Contractions Isotonic - muscle changes length load is moved Isometric - muscle applies tension but does not move the load

Muscle Metabolism

Types of Skeletal Muscle Fibers

Muscle Fatigue Inability to contract after prolonged activity –central fatigue is feeling of tiredness and a desire to stop (protective mechanism) –depletion of creatine phosphate –decline of Ca 2+ within the sarcoplasm Factors that contribute to muscle fatigue –insufficient oxygen or glycogen –buildup of lactic acid and ADP –insufficient release of acetylcholine from motor neurons