Muscular System

Excitability

Ability to respond to a stimulus such as a nerve impulse

Contractibility

Ability of muscle fibers to shorten and thicken causing movement

Extensibility

Ability of a muscle to be stretched

Elasticity

Ability of a muscle to return to its original shape after stretching or contracting

Tendon

Fibrous connective tissue that connects muscle to bone

Fascia

Fibrous membrane that covers supports and separates muscles

Origin

End of a muscle that remains stationary during contraction

Insertion

End of a muscle that moves during contraction

Muscle tone

State of partial muscle contraction that keeps muscles ready to act

Contracture

Tightening or shortening of a muscle

Number of muscles in the body

More than 600 muscles

Muscle structure

Bundles of muscle fibers held together by connective tissue

Three types of muscle

Cardiac visceral (smooth) and skeletal

Involuntary muscles

Cardiac and visceral (smooth) muscle

Cardiac muscle location

Walls of the heart

Cardiac muscle function

Contracts to circulate blood

Cardiac muscle characteristics

Short branching fibers with faint striations and a centrally located nucleus

Visceral (smooth) muscle location

Internal organs such as digestive tract respiratory system blood vessels and eyes

Visceral muscle function

Moves substances through organs and allows expansion and contraction

Smooth muscle striations

None (unstriated)

Skeletal muscle location

Attached to bones

Skeletal muscle control

Voluntary

Skeletal muscle appearance

Striped with alternating light and dark striations

Skeletal muscle functions

Movement heat production posture maintenance organ protection

Thermogenesis

Production of heat by muscles

Muscle attachment methods

Tendons or fascia

Adduction

Movement of a body part toward the midline

Abduction

Movement of a body part away from the midline

Flexion

Decreasing the angle between two bones (bending)

Extension

Increasing the angle between two bones (straightening)

Rotation

Turning a body part around its own axis

Circumduction

Moving a body part in a circular motion

Pronation

Turning a body part downward

Supination

Turning a body part upward

Dorsiflexion

Bending the foot toward the knee

Plantar flexion

Bending the foot away from the knee

Muscle tone at rest

Muscles are partially contracted at all times

Muscle atrophy

Shrinking and loss of muscle strength due to lack of use

Fibromyalgia

Chronic widespread muscle pain

Fibromyalgia symptoms

Muscle stiffness fatigue numbness tingling sleep memory and mood problems headaches depression

Muscular dystrophy

Group of inherited diseases causing progressive muscle weakness

Duchenne muscular dystrophy

Most common type affects boys symptoms begin age 2 to 3

Myasthenia gravis

Chronic disease causing muscle weakness from impaired nerve impulses

Early signs of myasthenia gravis

Drooping eyelids and double vision

Muscle spasms

Sudden painful involuntary muscle contractions

Muscle strain

Overstretching or injury to a muscle or tendon

Tendonitis

Inflammation of a tendon