Home Chapter 9 – Skeletal Muscles 1. Connective Tissue Surrounding a Skeletal Muscle: • Epimysium: Surrounds the entire muscle. • Perimysium: Surrounds bundles of muscle fibers (fascicles). • Endomysium: Surrounds individual muscle fibers. 2. Histology and Function of Sarcomeres: • Histology: Sarcomeres are the structural and functional units of skeletal muscles, composed of repeating units between two Z-lines. • Function: They enable muscle contraction through the sliding filament mechanism. 3. Main Components: • Thin Filaments: Actin, tropomyosin, and troponin. • Thick Filaments: Myosin. 4. Function of Transverse Tubules and Sarcoplasmic Reticulum: • Transverse Tubules (T-tubules): Transmit action potentials deep into the muscle fiber. • Sarcoplasmic Reticulum: Stores and releases calcium ions for muscle contraction. 5. Motor Unit: A motor neuron and all the muscle fibers it innervates. 6. Neuromuscular Junction: The synapse where a motor neuron meets a muscle fiber, allowing for signal transmission. 7. Synapse: A junction between two neurons or a neuron and a muscle cell where communication occurs. 8. Actions of Acetylcholine (ACh): • Initiates muscle contraction by binding to receptors on the sarcolemma. • Degraded by: Acetylcholinesterase. 9. Neurotransmitter Released at Motor Axon Terminals: Acetylcholine. 10. Steps in Excitation-Contraction Coupling: • Action potential travels along sarcolemma. • Calcium is released from the sarcoplasmic reticulum. • Calcium binds to troponin, causing tropomyosin to move, exposing binding sites on actin. • Myosin heads form cross-bridges and initiate contraction. 11. Order of Muscle Fiber Contraction: • Action potential → Calcium release → Cross-bridge formation → Power stroke → ATP binding → Cross-bridge detachment. 12. Mechanism of Muscle Contraction: • Sliding filament theory: Actin and myosin filaments slide past each other. 13. Interaction of Actin, Myosin, and Calcium: • Calcium binds to troponin, shifting tropomyosin to expose myosin-binding sites on actin, enabling cross-bridge cycling. 14. Cross-Bridges: Myosin heads that bind to actin during contraction. 15. Contraction Types: • Isotonic: Muscle length changes. • Eccentric: Muscle lengthens under tension. • Isometric: Muscle tension without length change. • Concentric: Muscle shortens under tension. 16. Force of Muscle Contraction: • Controlled by motor unit recruitment. • Partial Tetany: Incomplete relaxation. • Fused Tetany: Sustained contraction without relaxation. 17. Bones and Muscles as Levers: • Fulcrum: Pivot point of the lever. 18. Synergist and Antagonist: • Synergist: Assists the primary mover. • Antagonist: Opposes the primary mover. 19. Muscle Atrophy: Wasting of muscle due to disuse or disease. 20. Myasthenia Gravis: Autoimmune disorder causing muscle weakness by targeting ACh receptors. 21. Linea Alba: A fibrous structure running down the midline of the abdomen. 22. Origin, Insertion, and Actions of Specific Muscles: (Let me know which specific ones you’d like to focus on.) Chapter 17 – Digestive System 1. Alimentary Canal: A continuous muscular tube extending from the mouth to the anus. 2. Functions of the Digestive System: • Ingestion, digestion, absorption, and elimination. 3. Breakdown and Absorption: • Carbohydrates: Begin in the mouth (amylase). • Proteins: Start in the stomach (pepsin). • Fats: Start in the small intestine (lipase, bile). 4. Layers of Alimentary Canal Walls: • Mucosa, submucosa, muscularis, serosa. 5. Accessory Organs: • Liver, pancreas, gallbladder. 6. Sympathetic vs. Parasympathetic Effects: • Sympathetic: Decreases digestion. • Parasympathetic: Enhances digestion. 7. Hormones: • Gastrin: Stimulates gastric juice secretion. • Cholecystokinin (CCK): Stimulates bile and pancreatic juice. • Secretin: Stimulates bicarbonate secretion. 8. Peristalsis vs. Segmentation: • Peristalsis: Wave-like contractions. • Segmentation: Mixing movements. 9. Epiglottis Function: Prevents food from entering the trachea. 10. Heartburn: Caused by stomach acid reflux into the esophagus. 11. Stomach Parts: Fundus, body, pylorus. 12. Secretions: • Parietal Cells: Hydrochloric acid, intrinsic factor. • Chief Cells: Pepsinogen. 13. Digestive Enzymes and Substances: • Amylase: Breaks down starch. • Pepsin: Digests proteins. • Trypsin: Protein digestion. • Lipase: Fat digestion. • Bile Salts: Emulsify fats. 14. Liver, Gallbladder, Pancreas Functions: • Liver: Produces bile. • Gallbladder: Stores bile. • Pancreas: Produces enzymes and bicarbonate. 15. Anatomy of Bile Ducts: • Common hepatic, cystic, and pancreatic ducts form the common bile duct. 16. Functions of Large Intestine: • Absorption of water, vitamin production, and feces formation. 17. Defecation Reflex: Triggered by rectal wall distension. Chapter 18 – Nutrition 1. Excess Glucose Storage: As glycogen in the liver and muscles. 2. Tissue Requiring Glucose: Nervous tissue (brain). 3. Triglyceride Components: Glycerol and three fatty acids. 4. Essential Amino Acids: Cannot be synthesized by the body