Muscular System

Word Parts

fasci/o: fibrous membrane

fibr/o: fiber

kinesi/o: movement

ligament/o: ligament

muscul/o: muscle

my/o: muscle

-paresis: incomplete paralysis

-plegia: paralysis

quadri: four

sthen/o: strength

tend/o: tendon

tendin/o: tendon

Abbreviations

ALS: amyotropic lateral sclerosis

EMG: electromyoprahy; electromyogram

Fx: fracture

IM: intramuscular

MD: muscular dystrophy

MG: myasthenia gravis

MRI: magnestic resonance imaging

NSAID: nonsteroidal anti-inflammatory drug

PT: physical therapy

RICE: rest, ice, compression, elevation

ROM: range of motion

CTD: cumulative trauma disorder

Abduction - movement away from the midline of the body

Adduction - movement towards the midline of the body

Flexion - decreasing the angle of a joint; movement that bends a limb

Extension - increasing the angles of a joint; movement that straightens a limb

Hyperextension - excessive extension beyond normal anatomical position; movement could not be done without incurring damage, such as whiplash

Circumduction - movement in a circular direction from a central point

Rotation - turning a body part on its own axis

Pronation - turning the palm posteriorly (facing down)

Supination - turning the palm anteriorly (facing up)

Dorsiflexion - bending the sole foot upward toward the shin

Plantar - bending the sole of the foot downward or pointing the toes downward

Eversion - turning the sole of the foot outward

Inversion - turning the sole of the foot inward

Structure and Function

Muscular system has 600 muscles

Skeletal:

• attaches to bone

• voluntary movement

• striated (striped)

• controls movement of bones

Smooth (visceral):

• acts involuntarily

• walls of hollow organs (except heart) in the blood vessels, respiratory passages, urinary system, and digestive system

Cardiac:

• acts involuntarily

• responsible for heart’s pumping action

• striated (striped)

• forms most of the heart

Voluntary: happens on command

Involuntary: happens without thinking

Muscle fiber: muscle cell

Muscles are characterized by: location, control action, and cell characteristics

Function of the muscle:

• Produce movement

• Maintain posture

• Stabilize joints

• Generate heat

Skeletal muscles:

• Enclosed in fibrous sheath called fascia

• Tendons attach muscle to bone

• Ligaments attach bone to bone and provide support to muscle

Prime mover or agonist: contracts and produces movement

Antagonist: opposes the movement

Tendon: attaches a bone to a muscle

Ligaments: connects bone to bone

Fascia: attach muscle to muscle

Electromyography: the electrical recording of muscle activity

Muscles must receive stimulation from the nervous system

The nervous system helps to communicate and control movement in relation to skeletal muscle.

If communication from the nervous system to the skeletal muscles are severed, the body will experience paralysis.

Muscle Contraction

Neurotransmitter for muscle contraction: Acetylcholine (ACH) → neurotransmitter that diffuses across a synapse and produces an impulse in the cell membrane of a muscle cell

Energy needed for muscle contraction: stored ATP

Calcium: enables muscle proteins to lock together and pull the muscle fibers tight

Excitability: ability of an electrical impulse to stimulate a muscle cell to contract

Contractility: ability of muscle cells to shorten and generate a pulling force

Sliding filament model of contraction: involved actin and myosin sliding past each other but not shortening

Neuromuscular junction: point of contact between a motor neuron and a skeletal muscle cell

Most important ions: sodium, potassium, and calcium

• Sodium rushes inside the cell during action potential, while potassium rushes outside to prepare for next impulse

Muscle Fatigue

Factors:

• Muscles response to signals from the brain

• Ion (sodium, potassium, and calcium) depletion

Resting allows sodium, potassium, and calcium ions to replenish in and around muscle cells restoring their ability to contract

Exercise: helps improve muscle endurance, improves ion efficiency, enhances waste clearance, delay fatigue

Disorders

Muscular dystrophy (MD): hereditary, progressive degenerative disorder that causes skeletal muscle weakness

• Most common childhood muscular dystrophy: Duchenne muscular dystrophy

Myasthenia gravis (MG): immunologic disorder characterized by fluctuating weakness

Fibromyalgia: widespread aching and stiffness of muscles and soft tissues, fatigue, tenderness, sleep disorders

Amyotropic lateral sclerosis (ALS) (Lou Gehrig’s disease): progressive degeneration of the nerve tracts

Musulcar atrophy: muscle shrinking and wasting → wasting away of muscles from nonuse

Dysphagia: difficulty swallowing

Tendonitis: inflammation of a tendon

Repetitive, work-related motions that damage muscles, tendons, joints, or nerves

• Carpal tunnel syndrome: painful conditions resulting from compression of the median nerve within the carpal tunnel

• Rotator cuff injury

• Epicondylitis

• Plantar fasciitis

• Hamstring injury

• Shin-splints: tenderness and pain in the muscles in the lower leg following athletic overexertion

Paralysis: loss of voluntary muscle movement caused by injury or disease

Paresis: partial or incomplete paralysis

• Hemiparesis: weakness or paralysis affecting one side of the body

• Hemiplegia: total paralysis of one side of the body

• Paraplegia: paralysis of both legs and lower trunk

• Quadriplegia: paralysis of all four extremities

For many chronic muscle conditions, there is not cure, only treatment of symptoms

• Steroids

• Antiacetylcholineterase medications

• Immunosuppressant agents

• Rest, ice, compression, elevation (RICE)

Ice Bucket Challenge: celebrities took this challenge to spread awareness for ALS

Practice and Practitioners

Myology: branch of science concerned with study of muscles and accessory strucutres

Medical specialists:

• Orthopedic surgeon

• Kinesiologist

• Occupational therapist

• Physical therapist

• Orthopedic physician

Kinesiology: study of movement