Chapter 5

Origin

The attachment of a muscle to a bone or structure that does not move when the muscle contracts.

Insertion

The attachment of a muscle to a bone or structure that does move when the muscle contracts.

Intrinsic muscle

A muscle that has its origin and insertion located in the same body region.

Extrinsic muscle

A muscle that has its origin in a different body region than the insertion.

Fixator

A muscle that holds an origin stable for another muscle.

Synergists

Muscles that have the same action.

Prime mover

The main muscle that performs the action, helped by synergists.

Antagonist

A muscle that has an opposing action.

Flexion

Action that bends a part of the body anteriorly.

Extension

Action that bends a part of the body posteriorly.

Abduction

Movement of a part of the body away from the midline.

Adduction

Movement of a part of the body toward the midline.

Protraction

A movement that brings part of the body forwards.

Retraction

Movement that brings part of the body backward.

Dorsiflexion

Position of standing on the heels with the toes pointing up off the floor.

Plantar flexion

Position of standing on tiptoes with the heels off the floor.

Lateral excursion

Movement of the jaw laterally to either side

Inversion

Position in which the soles of the feet are together, facing each other.

Eversion

Position in which the soles of the feet point away from each other.

Rotation

The act of spinning on an axis.

Circumduction

The act of making a circle with part of your body.

Supination

Rotation that turns the palms up.

Pronation

Rotation that turns the palms down.

Opposition

The act of bringing the thumb to the palm.

Reposition

The act of taking the thumb away from the palm.

Elevation

The act of closing the jaw or raising the shoulders.

Depression

The act of opening the jaw or lowering the shoulders.

Orbicularis oris

Closes and protrudes lips, as in kissing.

Orbicularis oculi

Closes eyes.

Frontalis

Raises eyebrow and wrinkles the skin of the forehead.

Masseter

Elevates mandible.

Sternocleidomastoid

Individually each muscle rotates the head, together, they bring the head forward and down.

Pectoralis major

Flexes and adducts humerus.

Diaphragm

Prime mover for breathing.

Latissimus dorsi

Extends, adducts, and medially rotates the humerus.

Gastrocnemius

Plantar-flexes foot.

Sliding Filament Theory

The theory that thick myofilaments grab thin myofilaments and pull them toward the center of the sarcomere during muscle contraction.

Aerobic respiration

Uses oxygen to produce 36 ATP molecules per glucose, supports long-duration activities.

Anaerobic respiration

Does not use oxygen, produces 2 ATP molecules per glucose, supports short bursts of intense activity.

Neuromuscular Junction (NMJ)

The site where stimulation of a muscle cell by a nerve occurs, involving the release of acetylcholine.

Threshold

A minimum amount of acetylcholine required to activate the muscle.

Medial Excursion

Movement of the jaw back to the midline

Occipitals

Fixes epicranial aponeurosis as an origin for the frontalis muscle

Temporalis

Elevates, retracts, and causes medial and lateral excursion of the mandible

Buccinator

Compresses cheeks

Platysma

Depresses mandible and draws the corner of the mouth and lip downward

Zygomaticus major

Draws mouths angle upwards and outwards

Pectoralis minor

Depresses and protracts shoulder

Serratus Anterior

Protracts shoulder

External Intercostals

Expand the thoracic cavity during inspiration

Internal Intercostals

Compress the thoracic cavity during forced expiration

Extrenal abdominal oblique

Compresses abdomen, flexes spine, and allows rotation at the waist, origin at ribs

Internal abdominal oblique

Compresses abdomen, flexes spine, and allows rotation at the waist, origin at Iliac Crest

Rectus abdominal

Flexes spine

Transverse abdominal

Compresses abdomen 

Trapezius

Extends head 

Erector spinae

Hold the spine erect for posture and extends spine

Gluteus medius

Abducts and medially rotates hip

Gluteus maximus

Extends and laterally rotates hip 

Deltoid

Abducts humerus

Biceps brachii

Flexes elbow, origin at scapula

Triceps brachii

extends elbow

Brachialis/ Brachioradialis

flexes elbow, origin at humerous

Extensor Carpi Radialis

Extends and abducts wrist

Extensor Carpi Ulnaris

Extends and adducts wrist

Palmaris Longus

Flexes wrist

Flexor Carpi Radialis

Flexes and abducts wrist

Flexor Carpi Ulnaris

Flexes and adducts wrist

Extensor Digitorum

Extends fingers

Flexor Digitorum

Flexes fingers

Tensor Fasciae Latae

Abducts and medially rotates hip

Gracilis

Flexes knee and adducts hip

Adductor Longus

Adducts hip

Pectineus

Adducts and flexes hip

Iliopsoas

Flexes hip

Soleus

Plantar-flexes foot

Tendon

Connects muscle to bone. Composed of tough connective tissue that transmits the force from muscle contraction to bones.

Epimysium

The outermost layer of connective tissue surrounding the entire muscle.

Perimysium

Connective tissue that surrounds groups of muscle fibers (fascicles).

Endomysium

A thin layer of connective tissue that encases individual muscle fibers (cells).

Fascicle

Bundles of muscle fibers wrapped together by the perimysium, Allows for strength and flexibility in muscle movement

Sarcolemma

The plasma membrane of a muscle cell, Encloses the muscle fiber and helps transmit electrical impulses.

Sarcoplasmic Reticulum

A specialized form of smooth endoplasmic reticulum in muscle cells, Stores and releases calcium ions necessary for muscle contraction.

Myofibrils

Cylindrical structures within muscle fibers, Contain repeating units of sarcomeres, which are the functional units of muscle contraction

Sarcomeres

Composed of overlapping thick filaments (myosin) and thin filaments (actin), Responsible for the striated appearance of skeletal muscles and their ability to contract.

Skeletal Muscle

Controls voluntary movements, appears striped, and is attached to bones for body motion.

Cardiac Muscle

Found only in the heart, it works involuntarily to pump blood and has specialized connections for coordination.

Smooth Muscle

Found in hollow organs, it works involuntarily to move substances like food or blood without conscious control.