Understanding Muscle Structure and Function

Human muscle count

Approximately 600 muscles in the human body.

Muscle Composition

Muscles consist of bundle fibers, size of hair.

Muscle Contraction

Muscles contract and relax alternately for movement.

Motor Neurons

Axons supply muscle cells, controlling contractions.

Motor Unit

Group of muscle cells and motor neurons.

Muscle Twitch

Single contraction event caused by stimulus.

Muscle Contraction Phases

Includes delay, peak, and relaxation stages.

Tetanus

Continuous stimulation causing cramps and spasms.

Muscle Recruitment

Adjusts active motor units based on activity.

Glycogen Storage

Carbohydrates stored as glycogen in muscles.

Energy Source

Glycogen converts to glucose during muscle activity.

Heat Production

Heat released as glycogen is used.

Muscle Support

Muscles hold body structures and maintain posture. The muscles along the back, shoulders, and neck hold the trunk and head erect while permitting great flexibility in movement.

Muscle Protection

Protects blood vessels and organs from injury.

Skeletal Muscle

Attached to bones, allows voluntary movement.

Smooth Muscle

Involuntary muscle in internal organs.

Myocardial Muscle

Heart muscle tissue with intercalated discs.

Intercalated Discs

Connect myocardial cells for synchronized contraction.

Skeletal Muscle Action

Muscles shorten and thicken during contraction (When the biceps contracts to bend the elbow, the shorter and thicker muscle causes a bulge in the upper arm)

Flexor

Muscle that bends a joint.

Extensor

A muscle that straightens at a joint (triceps)

Muscle Team

Pair of muscles working together at joints.

Abduction

Movement away from the body's center line.

Adduction

Movement toward the body's center line.

Muscle Tone

Partial contraction of muscles for posture.

Atrophy

Progressive wasting of muscle tissue.

Contracture

Permanent shortening of flexor muscles.

Tendon

Connective tissue attaching muscle to bone.

Achilles Tendon

Strongest tendon, connects calf muscle to heel.

Ligament

Connective tissue connecting bone to bone.

Fascia

Membrane covering and protecting muscle tissue.

Aponeurosis

Flat tendon or fascia type of attachment.

Origin

Muscle attachment closest to body center.

Insertion

Movable end of muscle attachment.

Bursa

Fluid-filled sac reducing friction in joints.

Sheath

Membrane reducing friction around tendons.

Peristalsis

Involuntary muscle contractions moving food.

Circular Layer

Smooth muscle layer narrowing the esophagus.

Longitudinal Layer

Smooth muscle layer shortening the esophagus.

CNS Assessment

Evaluating muscle tone for nerve function.

Muscle Fibers

Individual muscle cells contracting for movement.

Sphincters

Doughnut-shaped muscles controlling flow in systems.

Stomach Sphincters

Muscles at stomach ends securing contents during digestion.

Diaphragm

Primary muscle for breathing, separates chest and abdomen.

Sternocleidomastoid

Neck muscle aiding head movement and posture.

Trapezius

Muscle supporting head and moving shoulders.

Pectoralis Major

Main chest muscle enabling arm flexion across body.

Intercostal Muscles

Muscles aiding diaphragm by enlarging thoracic cavity.

External Oblique

Outer abdominal muscle layer protecting organs.

Internal Oblique

Middle abdominal muscle layer beneath external oblique.

Transversus Abdominis

Innermost abdominal muscle layer providing stability.

Rectus Abdominis

Long muscle extending from pubis to rib cage.

Latissimus Dorsi

Large back muscle extending and adducting the arm.

Deltoid

Shoulder muscle abducting the arm, used for injections.

Gluteus Maximus

Largest buttock muscle supporting body weight.

Gluteus Medius

Buttock muscle preferred for intramuscular injections.

Hiccups

Spasmodic contractions of the diaphragm causing involuntary sounds.

Iris Muscles

Smooth muscles controlling pupil size in response to light.

Light Reflex

Pupil response to light assessing brain function.

Sartorius

Longest muscle, flexes hip and knee.

Quadriceps Femoris

Four-part muscle, powerful knee extensor.

Tibialis Anterior

Front leg muscle, enables heel walking.

Hamstring Group

Muscles flexing knee, includes biceps femoris.

Gastrocnemius

Calf muscle, aids in plantar flexion.

Frontalis

Forehead muscle expressing surprise or sternness.

Orbicularis Oris

Facial muscle for whistling and kissing.

Masseter

Jaw muscle responsible for chewing.

Bursitis

Inflammation of bursa around joints.

Tendonitis

Inflammation of tendons, often in joints.

Epicondylitis

Inflammation of forearm tendon at elbow.

Fibromyalgia Syndrome

Chronic pain condition with tender points characterized by widespread musculoskeletal pain, affecting an estimated 6-12 million people in the U.S. It often occurs alongside autoimmune and arthritis disorders.

Ice Application

Initial treatment for inflammation in injuries.

Heat Therapy

Used for pain relief after inflammation subsides.

Physical Therapy

Rehabilitation to maintain joint function.

Calcified Tendonitis

Tendonitis with calcium deposits visible on X-rays.

Joint Pain

Discomfort in any joint of the body.

Fatigue

Extreme tiredness affecting daily functioning.

Muscle Fatigue

Decline in muscle performance from exertion.

Muscle Strain

Injury from overstretching or tearing muscle fibers.

Muscular Dystrophy

Group of genetic disorders causing muscle weakness.

Duchenne's Dystrophy

Severe form of muscular dystrophy affecting young boys.

Limb-Girdle Muscular Dystrophies (LGMD)

Slowly progressive muscular dystrophy affecting limbs.

Torticollis

Neck deformity causing head tilt and rotation.

Congenital torticollis

Neck deformity present at birth.

Acquired torticollis

Neck deformity developed due to injury or spasms.

Physical therapy

Treatment using physical methods to improve mobility.

muscular dystrophy

group of hereditary diseases characterized by degeneration of muscle and weakness. An X-[inked disorder affecting males