General Biology II: Musculoskeletal System

This set of vocabulary flashcards covers the musculoskeletal system, including muscle fiber organization, the sliding filament model, contraction types, and skeletal structures as presented in Chapter 38.

Musculoskeletal System

A system made up of bones, joints, muscles, cartilage, tendons, ligaments, and other connective tissue that supports the body, allows motion, and protects vital organs.

Muscle Fiber

An individual muscle cell that contains contractile proteins known as actin and myosin.

Actin

A contractile protein that forms the thin filaments within a myofibril.

Myosin

A contractile protein that forms the thick filaments within a myofibril.

Myofibrils

Rod-like units that make up muscle fibers, organized into thick and thin filaments.

Tropomyosin

A protein that exists as a double helix surrounding the thin actin filaments.

Z-disc

A protein backbone to which thin actin filaments are attached within the myofibril.

Sarcomere

The contractile unit of a muscle, spanning the area from one Z-disc to the next.

Power Stroke

A conformational change in the myosin head that occurs after it binds to actin and releases $ADP$ and $P_i$, resulting in muscle contraction.

Cross-bridge

The structure formed when a myosin head binds to an active site on an actin filament.

Motor Unit

A single motor neuron and all of the muscle fibers (myofibers) that it connects to.

Sarcoplasmic Reticulum

The specialized endoplasmic reticulum of a muscle cell that stores and releases $Ca^{2+}$ in response to an action potential.

Acetylcholine

A neurotransmitter released from the axon terminal that binds to receptors on the sarcolemma to initiate muscle excitation.

Troponin

A protein that binds with $Ca^{2+}$ to move tropomyosin, thereby exposing the actin binding sites for myosin.

Excitation-Contraction Coupling

The process by which the electrical excitation of a muscle cell is linked to its mechanical contraction.

Calmodulin

A protein used by smooth muscle instead of tropomyosin to control the formation of cross-bridges.

Antagonist Muscles

Paired muscles that cause the exact opposite movement of each other when they contract.

Flexion

A muscle contraction result that causes a bending movement at a joint.

Extension

A muscle contraction result that causes a straightening movement at a joint.

Agonists

Muscles that contract to provide the main force required to move or rotate a bone through its joint.

Isometric Contraction

A type of contraction in which the muscle produces force without changing its length.

Lengthening Contraction

A contraction that occurs when the force applied to a muscle exceeds the force the muscle is producing, causing it to lengthen.

Twitch

A muscle contraction of a specific force produced by a single action potential from a motor nerve.

Tetanus

A long, sustained muscle contraction that occurs when action potentials stimulate the muscle at very high rates.

Slow-twitch Fibers

Red muscle fibers that contract and consume $ATP$ slowly, utilize aerobic respiration, and are used for posture.

Fast-twitch Fibers

White muscle fibers that contract rapidly, burn through $ATP$ quickly, and are used for anaerobic rapid movements.

Myoglobin

An oxygen-binding protein prevalent in slow-twitch fibers that carries oxygen to mitochondria for aerobic respiration.

Hydrostatic Skeleton

A type of skeleton consisting of fluid-filled compartments, found in animals like earthworms.

Exoskeleton

A rigid external covering for the body in some invertebrate animals, providing support and protection.

Chitin

Polysaccharide fibers reinforced by proteins that make up the exoskeleton.

Molting

The process by which an organism sheds its cuticle or exoskeleton to allow for growth.

Endoskeleton

A internal skeleton made of extracellular matrix such as bone, tooth enamel, dentine, tendon, and cartilage.

Tendons

Specialized connective tissue made of collagen that connects muscles to bone.

Axial Skeleton

The part of the endoskeleton that includes the skull, ossicles, hyoid bone, vertebral column, and rib cage.

Appendicular Skeleton

The part of the endoskeleton that includes the shoulder girdle, pelvic girdle, arms, hands, legs, and feet.

Osteoblasts

Cells responsible for the production and formation of new bone.

Osteoclasts

Cells that remove bone tissue to reshape bone or repair damaged regions.

Hydroxyapatite

The calcium phosphate mineral that constitutes the primary inorganic component of bone.

Spongy Bone

Bone composed of small plates and rods called trabeculae, found at the ends of bones to reduce weight.

Compact Bone

Dense mineralized bone that forms the walls of bone shafts and contains a network of blood vessels.

Diaphysis

The central shaft of a long bone.

Epiphysis

The rounded ends of a long bone.

Growth Plate

An area of cartilage located between the epiphysis and the diaphysis where bone growth occurs.

Ball-and-socket Joint

A joint type that allows for a three-dimensional range of motion but is more prone to dislocation.

Hinge Joint

A stable joint type that allows for a two-dimensional range of motion.