MEDTERM CH6

Muscles

Muscles make up approximately 42% of body weight.

Muscle fibers

Long, slender cells that make up muscles.

Muscle structure

Each muscle consists of a group of fibers held together by connective tissue and enclosed in a fibrous sheath of fascia.

Muscle fibers and energy

Muscle fibers receive nerve impulses and store glycogen, which is used for energy.

Types of muscles

Skeletal, smooth, and cardiac.

Skeletal muscle

Also known as voluntary or striated muscle; controlled by the conscious part of the brain and attached to bones.

Striated muscle

Muscle that has a cross-striped appearance.

Skeletal muscle characteristics

Varies in size, shape, arrangement of fibers, and means of attachment to bones.

Contractility

Ability of a muscle to contract or shorten.

Extensibility

Ability of a muscle to be stretched or extended.

Excitability

Ability of a muscle to respond to stimulation.

Elasticity

Ability of a muscle to return to its original shape after being stretched or contracted.

Three distinguishable parts of a muscle

Body, origin, and insertion.

Body of a muscle

Main portion of a muscle.

Origin

Fixed attachment of a muscle to a bone.

Insertion

Point of attachment of a muscle to the bone that it moves.

Tendon

Structure that attaches skeletal muscle to bone.

Aponeurosis

Wide, thin, sheet-like tendon.

Antagonist

Muscle that counteracts another muscle's action.

Prime mover (agonist)

Muscle that is primarily responsible for a given movement.

Synergist

Muscle that acts with another muscle to produce or assist movement.

Smooth muscle

Also called involuntary, visceral, or unstriated muscle; not consciously controlled and is regulated by the autonomic nervous system.

Locations of smooth muscle

Internal organs of the digestive, respiratory, and urinary tracts and certain muscles of the eye and skin.

Cardiac muscle

Muscle of the heart, or myocardium; involuntary but striated in appearance.

Cardiac muscle control

Cardiac muscle is under control of the autonomic nervous system.

Cardiac pacemaker cells

Specialized cells that allow cardiac muscle contraction to occur without initial nervous input.

Cardiac muscle blood supply

Provides oxygen and nutrients to cardiac muscle cells and removes waste products such as carbon dioxide.

Functions of muscles

Movement, locomotion, propulsion of substances, changing the size of openings, maintaining posture, and producing heat.

Locomotion

Movement in which chemical energy is changed into mechanical energy.

Muscle propulsion

Movement of substances through tubes, such as in circulation and digestion.

Muscle control of openings

Contraction and relaxation of muscles can change the size of body openings, such as the iris of the eye.

Sternocleidomastoid

Anterior muscle that rotates and laterally flexes the neck.

Trapezius

Anterior/posterior muscle that draws the head backward and to the side and rotates the scapula.

Deltoid

Anterior/posterior muscle that raises and rotates the arm.

Rectus femoris

Anterior muscle that extends the leg and assists in flexion of the thigh.

Tibialis anterior

Anterior muscle that dorsiflexes the foot and increases the arch during the beginning process of walking.

Sartorius

Anterior muscle that flexes and rotates the thigh and leg.

Pectoralis major

Anterior muscle that flexes, adducts, and rotates the arm.

Biceps brachii

Anterior muscle that flexes the arm and forearm and supinates the forearm.

External oblique

Anterior muscle that contracts the abdomen and viscera.

Rectus abdominis

Anterior muscle that compresses or flattens the abdomen.

Gastrocnemius

Anterior/posterior muscle that plantar flexes the foot and flexes the knee.

Soleus

Anterior muscle that plantar flexes the foot.

Triceps

Posterior muscle that extends the forearm.

Latissimus dorsi

Posterior muscle that adducts, extends, and rotates the arm.

Gluteus medius

Posterior muscle that abducts and rotates the thigh.

Gluteus maximus

Posterior muscle that extends and rotates the thigh.

Biceps femoris

Posterior muscle that flexes the knee and rotates it outward.

Semitendinosus

Posterior muscle that flexes and rotates the leg and extends the thigh.

Semimembranosus

Posterior hamstring muscle that flexes the knee and extends the thigh.

Achilles tendon

Posterior tendon involved in plantar flexion of the foot and extension of the ankle.

Aldolase (ALD) blood test

Blood test performed on serum to measure the ALD enzyme present in skeletal and heart muscle.

Calcium blood test

Blood test performed on serum to determine calcium levels.

Creatine kinase (CK) blood test

Blood test used to determine creatine kinase levels.

Electromyography (EMG)

Test used to measure electrical activity across muscle membranes by means of electrodes attached to a needle inserted into muscle.

Lactate dehydrogenase (LDH, LD) blood test

Blood test used to determine LDH enzyme levels.

Muscle biopsy

Surgical removal of a small piece of muscle tissue for examination; may be a needle biopsy or open biopsy.

Aspartate aminotransferase (AST) blood test

Blood test used to determine AST enzyme levels, which may increase with skeletal muscle damage and myocardial infarction.

Alanine aminotransferase (ALT) blood test

Blood test used to determine ALT enzyme levels, which may increase with skeletal muscle damage.

Amputation

Surgical or traumatic removal of a limb, part, or other appendage.

Contracture

Muscle shortening that renders the muscle resistant to the normal stretching process.

Dermatomyositis

Acute or chronic connective tissue disease with systemic pathology characterized by edema, dermatitis, and inflammation of the muscles.

Diaphragm

Major muscle of breathing.

Fibromyalgia syndrome

Chronic widespread musculoskeletal pain and fatigue.

Muscular dystrophy

Group of genetic diseases characterized by progressive weakness and degeneration of skeletal or voluntary muscles that control movement.

Myofibroma

Tumor that contains muscle and fibrous tissue.

Polyplegia

Paralysis affecting many muscles.

Torsion

Process of being twisted.

Skeletal muscle relaxants

Drugs used to relax skeletal muscles.

Anti-inflammatory agents

Drugs used to reduce inflammation.

Analgesics

Drugs used to relieve pain.

ACR

American College of Rheumatology.

AE

Above elbow.

AK

Above knee.

ALD

Aldolase.

ALT

Alanine aminotransferase.

AST

Aspartate aminotransferase.

BE

Below elbow.

BK

Below knee.

Ca

Calcium.

CK

Creatine kinase.

EMG

Electromyography.

FMS

Fibromyalgia syndrome.

FROM

Full range of motion.

IM

Intramuscular.

LDH / LD

Lactate dehydrogenase.

MD

Muscular dystrophy.

MG

Myasthenia gravis.

MS

Musculoskeletal.

NCI

National Cancer Institute.

NIH

National Institutes of Health.

ROM

Range of motion.

SOB

Shortness of breath.