Ch 14 Muscular System

Fibers

Specialized cells that make up muscle

Skeletal muscle

-Produce and stop movement

-Located at the opening of internal tracts to control the movement of substances

-Allow functions to be under voluntary control

-Protect internal organs such as abdominal and pelvic organs

-Contribute to the maintenance of homeostasis by generating heat

Cardiac muscle

-Found only in the heart (myocardium)

-Similar in appearance to skeletal muscle

-Striated and organized into sarcomeres

-Extensively branched and connected at their ends by intercalated discs, allowing the cells to contract in wave-like patterns so the heart can work as a pump

Smooth muscle

-Also called visceral muscle

-Cells do not have striations

-Involuntary muscle movements (breathing)

-Can be found:

• In the walls of hollow organs

• In the walls of passageways

• In the respiratory, urinary and reproductive tracts

• In the eyes

• In the skin

Fascia

Fibrous connective tissue that encloses muscle

Muscle contraction

-One muscle contracts while the other relaxes

-Contraction shortens the muscle fibers

-Influenced by the nervous system

Muscle relaxation

Lengthens the muscle fibers

Functions of the muscular system

-Assist with movement

-Maintain posture

Flexion

-Bending a limb

-Decreasing the angle between two bones

Extension

-Straightening out a limb

-Increasing the angle between two bones

Dorsiflexion

Opposite movement of stepping on the gas pedal

Plantar flexion

Stepping on the gas pedal

Supination

-Outward roll of the foot/ankle

-Turning the palm up when the elbow is bent

Pronation

-Inward roll of the foot/ankle

-Turning the palm down when the elbow is bent

Muscular dystrophy

-Weakens muscles and decreases mobility

-Duchenne/Becker muscular dystrophy is the most common type

Cerebral palsy (CP)

-Interruption to the normal development of the brain, leading to weak muscles

-It becomes hard to balance and coordinate movements

Carpal tunnel syndrome

Caused by pressure on the median nerve

Localized paralysis vs Generalized paralysis

Localized paralysis affects specific areas while generalized paralysis affects a larger area

Paresis

-Generalized paralysis

-Partial paralysis with some control of muscles

Paraplegia

-Generalized paralysis

-Affects both legs and lower part of the body

Quadriplegia

-Generalized paralysis

-Affects both arms, both legs and sometimes from the neck down

Hemiplegia

Affects one side of the body

Sprain

Injury to a joint where a ligament is torn

Strain

Injury to a muscle where a tendon is torn