Muscular System Almost 700 muscles in the human body Types of muscle: Attach to bones (skeletal muscle) Muscles of the heart (cardiac muscle) Muscles of internal organs (smooth muscle) Function *Movement *Heat production (e.g. shivering) *Maintain posture

Organs Systems Directly Involved in Movement Muscular System Move bones Skeletal System Bones moved at joints by muscles Nervous System Transmits impulses to muscles to cause contractions Nerve supply to the muscle is vital to the function of the muscle Respiratory Exchanges oxygen and carbon dioxide between air and blood Circulatory Transports oxygen to muscles and removes carbon dioxide and other waste products from the blood

5 Characteristics of Muscle Tissue Contractibility: ability to shorten and thicken Extensibility: ability to stretch Elasticity: ability to return to original length Irritability: ability to respond to a stimulus Tone: slight tension in muscle at all times, even at rest

Types of Muscle Tissue Smooth Muscle Found in walls of internal organs No striations Involuntary control (controlled by ANS) *Example: smooth muscle propels substances along the GI tract

Types of Muscle Tissue Cardiac Muscle Found only in the heart Striated Involuntary control (controlled by ANS; Autonomic Nervous System) Contraction of myocardium creates blood pressure and keeps blood circulation throughout the body

Types of Muscle Tissue Skeletal Muscle Makes up muscles that are attached to bones Striated Voluntary control (controlled by CNS)

Muscle Structure Muscle cells are specialized for contraction Skeletal muscle cells are called muscle fibers Fascia = connective tissue covering muscles Tendons= fibrous connective tissue that anchor muscles to bones

Action of Movement When muscles contract, one bone remains stationary and the other bone moves Origin: site where muscle is attached on stationary bone Insertion: site where muscle is attached on bone that moves

How Muscles Move Muscles move by contraction Muscles cannot push Muscles pull as they contract Skeletal muscles move bones by pulling on them Muscles are arranged so that whatever one muscle/group can do (agonist), another muscle/group can do the opposite movement (antagonist) Usually the muscle above a bone moves the bone below it

Muscle Movement Agonist (*prime mover*) Muscle with primary responsibility for movement Synergist Muscle that assists with movement Antagonist Muscles that oppose or reverse movement Every muscle has an antagonist

Classification of Muscles *Abductors: muscles that move body parts away from the midline of the body *Adductors: muscles that move body parts toward the midline of the body Levators: Muscles that raise a body part Depressors: Muscles that lower a body part *Flexors: Muscles that bend a limb at a joint Extensors: Muscles that straighten a limb at a joint *Sphincters: Muscles that regulate the size of an opening

How Skeletal Muscles are Named Size: vastus (huge), maximus (large), minimus (small) Shape: deltoid (triangular), latissimus (wide) Direction of fibers: rectus (straight), oblique (diagonal), transverse (across) Location: pectoralis (chest), gluteus (buttocks), hypoglossal Number of divisions forming them: biceps (2), triceps (3), quadriceps (4) Action: named for action, like flexing or extending (erector spinae) Origin and insertion: joint name of place of origin to name of place of insertion

Muscle Tone Skeletal muscles have tone (condition where some muscle fibers are always contracted) Muscle tone helps maintain posture Muscle atrophy with no activity and hypertrophy with forceful contraction Tetanus is sustained contraction (it is a normal state)

Exercise Improves muscle tone *Isotonic exercise Muscles contract and bring about movement against set resistance with varying speed Examples: swimming, jogging, weight lifting Improves aerobic and anaerobic fitness *Isometric exercise Contraction without bodily movement Example: push palms flat against a surface such as a wall Improves strength at that specific joint angle and give or take 10 degrees *Isokinetic exercise Muscles contract and bring about movement against a set speed with varying resistance Examples: Isokinetic resistance machine used in rehabilitation of an injury to work on strength through a full ROM

Energy Source *ATP is direct energy source for muscle contraction Muscle fibers are stimulated by nerve impulses to contract at neuromuscular junctions Nervous stimulation causes contractions

All or None “All or None” law of physiology Applies to muscle cell, not the whole muscle State a muscle cell will contract to its fullest extent when stimulated, it never partially contracts Muscles are organs of thousands of cells, all cells may not be stimulated at the same time

Actions of Muscles *Flexion – decrease angle of joint, brings bones together Typical of hinge joints (knee or elbow) Common with ball and socket, (hip or shoulder) *Extension – movement that increases the angle or distance between bones Straighten leg at knee, stand/sit up straight

Actions of Muscles *Abduction – moving a limb away from the midline or median plane body *Adduction – movement of limb toward midline *Rotation – movement of bone around its longitudinal axis *Example: shaking head “no”

Actions of Muscles Circumduction – combines flexion, extension, abduction, and adduction Seen in ball and socket and saddle joints Proximal end of limb is stationary while distal end moves in a circle Example: move thumb in a circle without moving the hand

Actions of Muscles Supination: moving palm from posterior position to anterior position (anatomical position – palms up, like holding a bowl of soup) Pronation: moving palm from anterior to posterior position (palms down)

Actions of Muscles Actions of the foot Inversion: turn sole of foot so faces medially (inward) Eversion: turn sole of foot laterally Dorsiflexion: movement at the ankle, moves instep of foot up and dorsal to shin (standing on heels) Plantarflexion: straighten ankle joint, point toes downward (standing on toes)