Chapter 6 (not on exam)

Muscular System

System responsible for body movements, stabilizing joints, and generating heat through muscle contractions.

Muscle Tissue

The three types are skeletal, smooth, and cardiac, differing in structure and function.

Skeletal Muscle

Striated, multinucleate muscles that are voluntary and responsible for moving the skeleton.

Smooth Muscle

Involuntary, non-striated muscle found in the walls of hollow organs; controls the movement of substances within the body.

Cardiac Muscle

Striated, branched, involuntary muscle found in the heart; responsible for pumping blood.

Endomysium

Delicate connective tissue sheath that surrounds each muscle fiber.

Perimysium

Connective tissue that groups muscle fibers into bundles called fascicles.

Epimysium

Connective tissue that surrounds the entire muscle.

Tendon

A cord-like structure that connects muscle to bone.

Aponeurosis

A sheet-like fibrous tissue that connects muscles to the parts they move.

Motor Unit

A motor neuron and all muscle fibers it innervates.

Neuromuscular Junction

The synapse where a motor neuron communicates with a muscle fiber.

Action Potential

An electrical impulse that transmits a signal for muscle contraction.

Sliding Filament Theory

Theory explaining that muscle contraction occurs by myosin heads pulling actin filaments toward the center of the sarcomere.

Isometric Contraction

A type of muscle contraction where the muscle does not shorten but tension increases.

Isotonic Contraction

A type of muscle contraction where the muscle shortens and movement occurs.

Muscle Fatigue

The decline in ability of a muscle to generate force; often due to exhaustion of energy sources.

Lactic Acid

A metabolic byproduct that accumulates during anaerobic respiration, leading to muscle soreness.

Graded Response

Variability in the strength of muscle contraction based on the number of motor units activated.

Atrophy

The wasting away or decrease in size of muscle fibers primarily due to disuse.

Hypertrophy

The increase in the size of muscle fibers due to regular and intense physical activity.

Acetylcholine

A neurotransmitter that stimulates muscle contraction at the neuromuscular junction.

Calcium Ions (Ca2+)

Essential ions released from the sarcoplasmic reticulum that trigger muscle contraction by binding to troponin.

Muscle Tone

The state of slight tension in muscles at rest; assists in posture and readiness for action.

Synergists

Muscles that work together to produce a movement.

Antagonists

Muscles that oppose or reverse a movement.

Five Golden Rules of Muscle Movement

1. Muscles pull, never push. 2. The bulk of the muscle lies proximal to the joint it acts upon. 3. Muscles cross at least one joint. 4. During contraction, the muscle insertion moves toward the origin. 5. Muscles work in pairs (antagonist and agonist).

Flexion

A movement that decreases the angle between two body parts.

Extension

A movement that increases the angle between body parts, returning them to the anatomical position.

Abduction

Movement away from the midline of the body.

Adduction

Movement toward the midline of the body.

Circumduction

A circular movement of a limb that creates a cone shape.

Rotation

Movement of a bone around its own long axis.

Supination

Rotational movement that turns the palm upward.

Pronation

Rotational movement that turns the palm downward.

Elevation

Movement that raises a body part superiorly.

Depression

Movement that lowers a body part inferiorly.

Opposition

Movement of the thumb to touch the tips of the other fingers.

Reposition

Movement that returns the thumb to the anatomical position after opposition.

Muscle Movements

include flexion, extension, abduction, and adduction, opposition and reposition.

Fascicle Arrangement

The arrangement of muscle fibers within a muscle affects its movement and power.

Parallel Fascicles

Muscle fibers run parallel to the length of the muscle; they can shorten significantly but are not very powerful.

Pennate Fascicles

Muscle fibers attach diagonally to a central tendon, allowing for greater force production but less range of motion.

Convergent Fascicles

Muscle fibers converge to a single tendon; versatile in movement.

Orbicular Fascicles

Muscle fibers arranged in concentric rings; responsible for closing openings, like around the mouth.

Unipennate Fascicles

PSingle diagonal fiber arrangement; maximizes force with limited range of motion.

Bipennate Fascicles

Two rows of fibers facing opposite directions, allowing for more power.

Multipennate Fascicles

Multiple directions of fibers attached to multiple tendons, providing maximum strength.

Prime Mover (Agonist)

The primary muscle responsible for a specific movement.

Antagonist

A muscle that opposes the action of the agonist.

Synergist

A muscle that assists the prime mover in a movement.