Lesson 12: How do Animals Move?

Actin

A thin protein filament in muscle fibers that slides past myosin during contraction.

Aerobic respiration

Cellular respiration that uses oxygen to produce ATP.

Anaerobic respiration

Energy production without oxygen; produces less ATP and lactic acid.

Antagonist muscle

A muscle that opposes the action of another muscle (the agonist).

ATP

The main energy-carrying molecule in cells.

Bone

A hard, connective tissue that supports, protects, and helps move the body.

Bone remodeling

The process where osteoblasts build bone (deposit) and osteoclasts break it down (resorption).

Calcite

A calcium carbonate mineral found in shells and some skeletons.

Calcium

A mineral essential for bone strength, muscle contraction, and nerve signaling.

Canaliculi

Tiny channels in bone that allow nutrients and waste to move between cells.

Cardiac muscle

Involuntary muscle found only in the heart.

Cartilage

A flexible connective tissue that cushions joints and supports structures.

Central cavity

The hollow space inside some bones that contains marrow.

Chaetae

Bristle-like structures used by some invertebrates for movement.

Chitin

A tough polysaccharide found in exoskeletons of arthropods and fungal cell walls.

Chondrocytes

Cells that produce and maintain cartilage.

Compact bone

Dense, strong bone tissue that forms the outer layer of bones.

Complete tetanus

A sustained muscle contraction with no relaxation between stimuli.

Contraction

The shortening or tension generation of a muscle.

Cross bridge cycle

The attachment, movement, and release of myosin heads to actin during contraction.

Endochondral development

Bone formation that starts with a cartilage model (long bones).

Endoskeleton

An internal skeleton made of bone or cartilage.

Epiphysis

The enlarged end of a long bone.

Exoskeleton

A hard external skeleton that supports and protects the body.

Fast twitch muscle

Muscle fibers that contract quickly and fatigue rapidly.

Fatigue

A decrease in muscle performance due to prolonged activity.

Growth plate

A cartilage region where long bones grow in length.

Haversian system

The structural unit of compact bone, containing blood vessels and nerves.

Hydrostatic skeleton

Support provided by fluid pressure inside the body.

Hydroxyapatite

A calcium phosphate mineral that hardens bone.

Incomplete tetanus

Muscle contractions with partial relaxation between stimuli.

Intramembranous development

Bone formation directly from connective tissue (flat bones).

Lactic acid

A waste product formed during anaerobic respiration.

Matrix

The nonliving material surrounding cells in connective tissue.

Medullary cavity

The marrow-filled central cavity of a long bone.

Motor unit

A motor neuron and all the muscle fibers it controls.

Muscle

Tissue that contracts to produce movement.

Muscle fibers

Long, multinucleated cells that make up muscle tissue.

Myofibrils

Rod-like structures in muscle fibers made of repeating sarcomeres.

Myofilaments

Protein filaments (actin and myosin) within myofibrils.

Myoglobin

A protein that stores oxygen in muscle cells.

Myosin

A thick protein filament that pulls actin during contraction.

Neuromuscular junction

The synapse between a motor neuron and a muscle fiber.

Osteoblast

A bone-building cell.

Osteoclast

A bone-breaking cell.

Osteocyte

A mature bone cell that maintains bone tissue.

Osteoporosis

A disease where bones become weak and brittle.

Power stroke

The movement of the myosin head that pulls actin inward.

Rigor mortis

Muscle stiffening after death due to lack of ATP.

Sarcomere

The basic functional unit of a muscle fiber.

Sarcoplasmic reticulum

A membrane network that stores and releases calcium ions.

Skeletal muscle

Voluntary muscle attached to bones.

Sliding filament mechanism

Muscle contraction caused by actin sliding over myosin.

Slow twitch muscle

Muscle fibers that contract slowly and resist fatigue.

Smooth muscle

Involuntary muscle found in organs and blood vessels.

Spongy bone

Porous bone tissue found inside bones.

Summation

Increased muscle force caused by repeated stimulation.

Suture line

An immovable joint between skull bones.

Transverse tubules

Channels that carry electrical signals into muscle fibers.

Tropomyosin

A protein that blocks myosin-binding sites on actin.

Troponin

A protein that moves tropomyosin when calcium binds.

Twitch

A single, brief muscle contraction.