Muscle Function

3 Types of Muscle Tissue Skeletal muscle Smooth or Visceral Muscles Cardiac muscle The body has more than 600 muscles that make up 40 to 45% of the body’s weight

Skeletal Muscle Tissue Striated Dark and light bands in fibers Voluntary Conscious control over these muscles

Smooth or Visceral Muscle Tissue Unstriated No dark and light bands Involuntary Under control of the autonomic nervous system Located: Walls of internal organs Respiratory and digestive tracts Digestive tract=peristalsis Wavelike movement Causes contents to be propelled onward

Cardiac Muscles Indistinctly striated Involuntary

Muscle Function

Muscle Function Aid in movement Provide and maintain posture Protect internal organs Provide movement of blood, food and waste products Open and close body openings Provide heat Muscle Function

Our Muscles

How Muscles are Named Muscle origin Muscle insertion Place where muscle begins More fixed end nearest midline where movement does not occurs Muscle insertion Place where muscle ends End where movement occurs Farthest from midline How Muscles are Named

How Muscles are Named Location Size Shape Number Direction of fibers Anterior Posterior Bone Number Bi Tri Quad Size Maximus Minimus Shape Deltoid Trapezius Direction of fibers Rectus Oblique How Muscles are Named

Characteristics of Muscles Irritability Ability to respond to stimulus Contractibility Ability to shorten Extensibility Ability to stretch and lengthen Elasticity Ability to return to original length at rest

Muscular System Flaccid Muscle tone or tonus Soft when not contracted Normal state of balanced muscle tension required to hold body in awake position Partial state of contraction Muscles are ready for action Muscular System

Flaccid and Tone

Tendons Strong, fibrous connective tissue that connect muscle to bone Achilles tendon Located bottom of the calf (gastrocnemius muscle) Secures that muscle to heel of bone (calcaneus)

Fascia Fibrous membrane that covers, supports, and separates muscle

Structures of Muscles Made of bundles of muscle fibers Basic unit causing contraction: sarcomeres made of actin & myosin myofibrils

Contraction of Muscles Sliding filament theory Contain bundles of muscle fibers Single fiber: Fibrils containing actin & myosin filaments During contraction, actin & myosin filaments move close together to shorten muscle

Contraction of Muscles Results from: Myoneural stimulation Glucose fuels ADP-ATP cycle for release of energy Calcium needed for reaction to occur Produces: Muscle contraction Heat Lactic acid Carbon dioxide & water Contraction of Muscles

Types of Muscle Contractions Isotonic: shortening produces movement Isometric: does not produce shortening or movement Twitch: quick, jerky movement Tetanic contraction (tetany): sustained contraction caused by stimuli in rapid succession Types of Muscle Contractions

Types of Muscle Contractions Fibrillation: uncoordinated contractions Convulsions: contractions of groups of muscles in abnormal manner Spasms: involuntary, sudden, prolonged Types of Muscle Contractions

Muscle Movement Pull never push on bones Always cross a joint Work in pairs: Prime mover (agonist): pulls to cause movement Antagonist: relaxes when agonist pulls Synergists & fixators: keep muscle & bone stable during movement Muscle Movement

Body Movements Caused by Skeletal Muscle Flexion: Decrease angle between two bones or bending a limb at a joint Elbow bent and lower arm brought upward Knee bent and lower leg backward Extension Increase angle between two bones or straightening out a limb Elbow straightened and lower arm downward Body Movements Caused by Skeletal Muscle

Body Movements Caused by Skeletal Muscle Abduction Movement away from body midline Arm moves outward, away from side of body Adduction Movement toward midline of body Arm moves inward, toward side of body Rotation Circular or semi-circular movement around an axis Turning the head when saying no Body Movements Caused by Skeletal Muscle

Body Movements Caused by Skeletal Muscle Pronation: Turning hand downward Supination: Turning hand upward Body Movements Caused by Skeletal Muscle