Muscle Physiology and Anatomical Movements

Comprehensive vocabulary flashcards covering muscle anatomy, sliding filament mechanism, motor units, contraction types, and anatomical joint movements.

Muscle fiber

A muscle cell.

Motor unit

A single motor neuron and all the muscle fibers it innervates.

Sarcomere

The functional unit of muscle contraction, visible as a striated pattern in skeletal and cardiac muscle fibers.

Light band

The region of the sarcomere that only contains thin filaments.

Dark band

The region of the sarcomere determined by the length of the thick filaments.

Myosin

A muscle protein with a club head that can bind to actin and also serves as an ATPase.

Thick filament

A myofilament composed of several myosin proteins.

Actin

A globular muscle protein that forms two intertwining strands and has myosin-binding sites.

Thin filament

A myofilament composed of actin, tropomyosin, and troponin proteins.

Tropomyosin

A fibrous protein that wraps around the actin strands, covering actin's myosin-binding sites.

Troponin

A globular muscle protein located on actin strands that binds calcium.

Sarcoplasmic reticulum

A modified smooth endoplasmic reticulum found in muscle fibers that stores calcium.

Sliding filament mechanism

The contraction process in muscle fibers in which the thin and thick filaments move past each other while generating tension.

Excitation-contraction coupling

The linking of muscle fiber excitation (action potential) with the contraction of the muscle fiber that occurs as calcium is released from the sarcoplasmic reticulum.

Power stroke

The pivoting movement of the myosin head that pulls the thin filament toward the center of the sarcomere, increasing the overlap of the thin and thick filaments.

Recovery stroke

The resetting of the myosin head into cocked position; happens after the myosin head detaches from actin.

Crossbridge

A connection made between the thick and thin filaments when the myosin head binds to the actin.

Twitch contraction

A single contraction and relaxation of a muscle fiber produced by a single stimulatory action potential from the motor neuron.

Tetanus

A smoothly sustained muscle contraction caused by high frequency action potentials from the motor neuron.

Fusion

The maintenance of muscle contractions between stimulating action potentials that occurs during tetanus.

Summation

The increase in tetanic contraction strength above that of a twitch contraction.

Recruitment

An increase in the number of motor units that are stimulated in order to increase contraction strength.

Isometric contraction

A contraction in which a muscle doesn't change its length as it exerts force against an unmoving load.

Isotonic contraction

A contraction in which a muscle changes its length as it maintains a constant force against a load.

Concentric contraction

Muscle shortening that generates force. The identified action(s) of a muscle are concentric contractions.

Eccentric contraction

A contraction that generates force as the muscle lengthens. This lengthening contraction can be $50\%$ more forceful than a concentric contraction.

Delayed Onset Muscle Soreness (DOMS)

Pain or soreness which occurs several hours after an intense workout, particularly a workout that involved eccentric contractions.

Atrophy

Loss of muscle mass, generally due to inactivity.

Hypertrophy

Growth of muscle.

Flexion

Decreasing bone angle (bending).

Extension

Increasing bone angle to anatomical position (straightening).

Hyperextension

Increasing bone angle past anatomical position [not possible for all joints].

Abduction

Movement away from midline.

Adduction

Movement toward midline.

Circumduction

Rotational movement that forms a cone in space.

Internal rotation (medial rotation)

Anterior surface rotates toward midline.

External rotation (lateral rotation)

Anterior surface rotates away from midline.

Upward rotation

Scapular movement that rotates lateral edge upward.

Downward rotation

Scapular movement that rotates lateral edge downward.

Pronation

Movement of forearm that rotates palm to face down.

Supination

Movement of forearm that rotates palm to face up.

Plantar flexion

Movement of foot towards plantar (sole) surface.

Dorsiflexion

Movement of foot toward shin.

Inversion

Medial movement of foot's plantar surface.

Eversion

Lateral movement of foot's plantar surface.

Protraction

Moving a body part anteriorly.

Retraction

Moving a body part posteriorly.

Elevation

Lifting a body part superiorly.

Depression

Lowering a body part inferiorly.

Opposition

Thumb and another finger brought together.

Reposition

Thumb and finger brought back to original position.