A&P Exam 2

Skeletal System

  1. Macro and Micro-Organization of Muscle Tissue:

    • Macro: Muscle tissue is organized from the largest to smallest structure:

      • Muscle → Fascicle → Muscle Fiber → Myofibrils → Sarcomeres.

    • Micro: Muscle fibers (cells) contain myofibrils, which are made of repeating structural units called sarcomeres. Sarcomeres are composed of thin (actin) and thick (myosin) myofilaments.

  2. Functions of the Skeletal System:

    • Support: Provides a framework that supports the body.

    • Protection: Protects vital organs (e.g., brain, heart).

    • Movement: Serves as levers for muscles.

    • Mineral storage: Stores minerals like calcium and phosphorus.

    • Blood cell production: Red and white blood cells are produced in bone marrow.

    • Fat storage: Yellow marrow stores fat.

  3. Components of the Connective Tissue Matrix:

    • Collagen: A protein that provides tensile strength to bone and cartilage.

    • Calcium: Provides rigidity and strength in bone.

    • Phosphate: Works with calcium to form hydroxyapatite crystals, which harden bones.

    • Ground substance: A gel-like material containing proteoglycans that help with flexibility.

  4. Structure of Compact and Cancellous Bone:

    • Compact Bone: Dense, forms the outer layer of bones. Its structure includes osteons (Haversian systems) consisting of concentric rings of bone tissue called lamellae.

    • Cancellous Bone: Also called spongy bone, it has a porous structure with trabeculae, which provide strength without adding weight. Found in the epiphyses of long bones and inside flat bones.

  5. Bone Ossification:

    • Intramembranous Ossification: Bone develops directly from mesenchymal tissue. This process is responsible for forming flat bones like the skull.

    • Endochondral Ossification: Bone replaces a hyaline cartilage model. This is the process by which long bones develop.

  6. Bone Growth, Remodeling, and Repair:

    • Growth: Occurs at the epiphyseal plate (growth plate) in children, where cartilage is replaced by bone.

    • Remodeling: Continuous process involving osteoblasts (bone-forming cells) and osteoclasts (bone-resorbing cells), helping bones respond to stress and repair microfractures.

    • Repair: Involves the formation of a hematoma (blood clot), followed by fibrocartilage callus formation, and then conversion to bone (hard callus formation) which is later remodeled.

  7. Major Features of a Bone:

    • Epiphysis: The ends of long bones, where growth occurs.

    • Diaphysis: The shaft or central part of a long bone.

    • Metaphysis: The area between the epiphysis and diaphysis where bone growth occurs.

    • Medullary Cavity: Hollow space within the diaphysis, contains marrow.

    • Periosteum: Membrane covering the bone, except at joints.

    • Endosteum: Lining of the medullary cavity.

    • Articular Cartilage: Smooth cartilage at the ends of bones that reduces friction.

  8. Types of Joints:

    • Fibrous Joints: No movement (e.g., sutures in the skull).

    • Cartilaginous Joints: Limited movement (e.g., intervertebral discs).

    • Synovial Joints: Freely movable (e.g., knee, elbow).

  9. Types of Joint Movement:

    • Flexion: Decreasing the angle between bones.

    • Extension: Increasing the angle between bones.

    • Abduction: Moving a limb away from the body.

    • Adduction: Moving a limb toward the body.

    • Rotation: Turning a body part on its axis.

    • Circumduction: Circular movement (e.g., arm circles).

  10. Effects of Aging on Bones and Joints:

    • Bone mass decreases with age, leading to conditions like osteoporosis.

    • Joints may lose cartilage, leading to arthritis and reduced flexibility.

    • Tendons and ligaments become less elastic, limiting movement.

Skeletal Muscle

  1. Functions of the Muscular System:

    • Movement: Muscles contract to move body parts.

    • Posture: Muscles help maintain body posture.

    • Joint Stabilization: Muscles stabilize joints to prevent injury.

    • Heat Production: Muscles generate heat during contraction.

  2. Microscopic Structure of a Muscle:

    • Muscle Fiber: A single muscle cell.

    • Myofibrils: Bundles of myofilaments (actin and myosin).

    • Sarcomere: The basic unit of contraction; made up of actin (thin) and myosin (thick) filaments.

      • A Band: Length of the thick myosin filament.

      • I Band: Region with only actin (thin filaments).

      • H Zone: Area where only myosin is present.

      • Z Line: Marks the boundary of a sarcomere.

  3. Resting Membrane Potential and Action Potential:

    • Resting Membrane Potential: The electrical charge difference across a cell membrane when the cell is at rest, typically -70 mV.

    • Action Potential: A rapid change in membrane potential that propagates along the membrane, leading to muscle contraction.

  4. Neuromuscular Junction Events:

    • Neurotransmitter Release: Acetylcholine (ACh) is released from motor neurons and binds to receptors on the muscle cell membrane.

    • Depolarization: The muscle cell membrane depolarizes, leading to an action potential.

    • Calcium Release: Action potential travels to the sarcoplasmic reticulum, causing the release of calcium, which binds to troponin and moves tropomyosin, allowing myosin and actin to interact.

  5. Events in Muscle Contraction and Relaxation:

    • Contraction: Calcium binds to troponin, exposing binding sites on actin. Myosin heads attach to actin, pull, and release, leading to sarcomere shortening.

    • Relaxation: Calcium is pumped back into the sarcoplasmic reticulum, troponin and tropomyosin block actin sites, and the muscle relaxes.

  6. Muscle Twitch, Tetanus, Recruitment, and Summation:

    • Twitch: A single, brief contraction of a muscle fiber.

    • Tetanus: A sustained contraction due to rapid stimulation.

    • Recruitment: Increasing the number of active motor units to increase muscle strength.

    • Summation: Increased force from successive stimuli before the muscle has time to relax.

  7. Aerobic vs. Anaerobic Respiration:

    • Aerobic: Requires oxygen; produces more ATP (e.g., Krebs cycle, oxidative phosphorylation).

    • Anaerobic: Does not require oxygen; produces less ATP (e.g., glycolysis, leads to lactic acid).

  8. Isometric vs. Isotonic Contractions:

    • Isometric: Muscle tension increases but the muscle does not change length.

    • Isotonic: Muscle changes length to move a load (concentric and eccentric).

  9. Fast-Twitch vs. Slow-Twitch Muscles:

    • Fast-Twitch: Quick, powerful contractions but fatigues quickly (ideal for sprinting).

    • Slow-Twitch: Endurance-focused, slow to fatigue (ideal for long-distance activities).

  10. Excitation-Contraction Coupling:

    • The process by which an action potential leads to muscle contraction via calcium release and interaction between actin and myosin.

Metabolism

  1. ATP:

    • What it is: Adenosine triphosphate, the primary energy carrier in cells.

    • What it does: Provides energy for muscle contraction, active transport, and other cellular functions.

  2. ATP Synthesis:

    • Substrate-level phosphorylation: Direct transfer of a phosphate group from a substrate molecule to ADP (e.g., glycolysis).

    • Oxidative phosphorylation: Uses oxygen to produce ATP via the electron transport chain and chemiosmosis (occurs in mitochondria).

  3. Metabolism:

    • Glycolysis: Breakdown of glucose into pyruvate, producing 2 ATP (anaerobic).

    • Krebs Cycle: Processes pyruvate into ATP, NADH, and FADH2 (aerobic).

    • Electron Transport Chain: Uses NADH and FADH2 to create ATP via oxidative phosphorylation.

  4. Aerobic vs. Anaerobic Metabolism:

    • Aerobic: Oxygen required, produces more ATP.

    • Anaerobic: No oxygen required, less ATP, results in lactic acid