Exam 3 - Chapter 21

Testosterone

Hormone that increases muscle growth by stimulating protein buildup in muscle cells.

Human Growth Hormone (HGH)

Hormone that promotes muscle growth and repair.

Myostatin

Molecule that slows muscle growth; mutations can lead to extreme muscle development.

Hydrostatic Skeleton

Fluid-filled chamber(s) that muscles push against (ex: earthworm).

Exoskeleton

Hard external skeleton that muscles attach to (ex: insects).

Endoskeleton

Internal framework of hardened elements where muscles attach (ex: vertebrates).

Vertebrate

Animal with a vertebral column (backbone).

Axial Skeleton

Skull, vertebral column, rib cage.

Appendicular Skeleton

Shoulder girdle, hip girdle, and limbs (or fins).

Vertebrae

Individual bones of the vertebral column separated by discs.

Spinal Cord

Runs through vertebral column; connects body to brain.

Bone

Collagen-rich, mineralized organ wrapped in connective tissue; stores minerals, supports organs, produces blood cells.

Compact Bone

Dense, outer, weight-bearing layer.

Spongy Bone

Lightweight bone with internal spaces filled with marrow.

Red Marrow

Produces blood cells; located in spongy bone.

Yellow Marrow

Stores fat; fills long bone cavities.

Osteoporosis

Condition where bones lose calcium and become weak and likely to break.

Joint

Where two bones meet.

Fibrous Joint

Bones held tightly by dense connective tissue (ex: skull bones).

Cartilaginous Joint

Bones connected by cartilage (ex: between vertebrae).

Synovial Joint

Most movable; bones held by ligaments; lubricated with synovial fluid.

Ball-and-Socket Joint

Allows rotation (shoulder, hip).

Gliding Joint

Bones slide over each other (wrist, ankle).

Hinge Joint

Movement in one plane (elbow, knee).

Arthritis

Chronic joint inflammation.

Osteoarthritis

Degenerative joint disease; common in older adults.

Rheumatoid Arthritis

Autoimmune disorder where immune system attacks synovial membrane.

Tendon

Dense connective tissue strap that connects muscle to bone.

Opposing Muscle Pairs

Muscles that reverse each other's actions (e.g., biceps vs. triceps).

Sphincter

Ring-shaped muscle controlling passage through openings.

Skeletal Muscle Fiber

Long, cylindrical, multinucleated cell containing myofibrils.

Myofibrils

Threadlike bundles inside muscle fibers containing contractile units.

Sarcomeres

Contractile units within myofibrils composed of actin and myosin.

Actin

Thin filament; interacts with myosin during contraction.

Myosin

Thick filament; motor protein that binds and pulls on actin.

Sliding-Filament Model

Explains how muscles contract by sliding actin and myosin past each other.

Creatine Phosphate Pathway

Quick ATP source; lasts 5-10 seconds.

Aerobic Respiration

Produces ATP using oxygen; supports long-duration activity.

Lactate Fermentation

Generates ATP without oxygen; used when oxygen is limited.

Red Muscle Fibers

Have myoglobin, many mitochondria; good for endurance.

White Muscle Fibers

Low myoglobin and few mitochondria; good for quick, strong bursts.

Muscle Fatigue

Decline in ability to generate force during continued activity.

Aerobic Exercise

Increases blood supply & mitochondria; improves endurance.

Strength Training

Builds more actin and myosin; increases power.

Lipoprotein Lipase (LPL)

Enzyme that helps muscles take up fatty acids and triglycerides.

Effects of Inactivity

Reduced LPL, higher blood glucose, increased risk of cardiovascular disease and diabetes; sitting too long is harmful even if you exercise.