Muscular System

Facts Myology: study of muscles Kinesiology: study of voluntary muscles and their actions Human body has more than 600 muscles Most abundant tissue in the human body Can only pull not push

Facts cont. Makes up 40-50% of body weight Long excitable cells capable of contraction All muscle cells are muscle fibers Larger the fibers the greater the force Muscles attach to bones by tendons

Functions Responsible for movement “MACHINES OF THE BODY” Maintains posture Stabilizes joints Generates heat

Characteristics EXCITABILTIY- reacts to stimuli CONTRACTIBILITY- can become shorter and thicker when work is done EXTENSIBILITY- can become longer and thinner ELASTICITY- ability to return to its normal length after the force applied has been removed

Muscle Groups AGONISTS- ANTAGONISTIC Prime movers Cause particular movement Several muscles contract at same time causing a movement ANTAGONISTIC Usually arranged in pairs – one contracts and one extends

Types of Contractions ISOMETRIC ISOTONIC Muscles do not change shape Tension produced never exceeds the resistance Examples Pushing against a locked door Trying to pick up a car ISOTONIC Muscles change shape Tension rises and exceeds the resistance Two types Concentric contractions Eccentric contractions

Isotonic contractions Concentric Shortening Positive work is done Energy is released to exert force or lift a weight

Isotonic contractions cont… Eccentric Lengthening Peak tension is less than the resisitance Requires less energy to accomplish task Examples: walking down stairs & weight

Muscle Groups Antagonistic Relaxes Opposite or reversed Prime mover is active then antagonistic Change automatically Example: hold your arm out in front of you then bend the elbow while feeling the biceps in the front & the tricep in the back with the other hand

Types of Antagonistic Muscles Flexion Decreases angle of the joint & brings 2 bones together Extension Increases the angle or distance between 2 bones Extend greater than 180o is hyperextension

Types of Antagonistic Muscles Abduction Move a limb away from the midline Fanning movement of fingers and toes Adduction move a limb toward the midline

Types of Antagonistic Muscles Circumduction Combination of flexion, extension, abduction, & adduction Rotation Movement of bone around its longitudinal axis

Types of Antagonistic Muscles Supination Moving the palm from a posterior position to an anterior position Pronation Move the palm from an anterior position to a posterior position

Types of Antagonistic Muscles Eversion Turn the sole of the foot laterally Inversion Turn the sole of the foot so it faces medially

Types of Antagonistic Muscles Plantar Flexion Straightens the ankle joint Toes point downward Standing on your toes Dorsiflexion Moves instep of foot up and dorsally toward the shin Standing on your heels

Types of Antagonistic Muscles Elevation Raising the scapula Depression Pulling the scapula to an inferior position