answers for Chapters 5, 6, and 7 based on your study guide: ⸻ ✅ Chapter 5 – Skeletal System 1. Functions of the Skeletal System • Support • Protection • Movement (with muscles) • Mineral storage (calcium, phosphorus) • Blood cell production (hematopoiesis) • Fat storage (yellow marrow) ⸻ 2. Axial vs Appendicular Skeleton Axial (80 bones) • Skull • Vertebral column • Ribs • Sternum • Hyoid Appendicular (126 bones) • Pectoral girdle (clavicle, scapula) • Upper limbs • Pelvic girdle • Lower limbs ⸻ 3. Bone Components • Compact (cortical) bone • Spongy (trabecular) bone • Periosteum • Endosteum • Bone marrow (red & yellow) • Articular cartilage ⸻ 4. Cortical vs Trabecular Bone • Cortical (compact): Dense, outer layer, strength • Trabecular (spongy): Porous, inside bone, reduces weight, houses marrow ⸻ 5. Bone Classification by Shape • Long (femur) • Short (carpals) • Flat (sternum) • Irregular (vertebrae) • Sesamoid (patella) ⸻ 6. Structure of a Long Bone • Diaphysis (shaft) • Epiphysis (ends) • Medullary cavity • Periosteum • Compact bone • Spongy bone ⸻ 7. Microscopic Bone Structure • Osteon (Haversian system) • Central canal • Lacunae (contain osteocytes) • Canaliculi (nutrient pathways) ⸻ 8. Osteoblast vs Osteoclast • Osteoblast: Builds bone • Osteoclast: Breaks down bone ⸻ 9. Three Types of Joints • Fibrous: Immovable (skull sutures) • Cartilaginous: Slight movement (intervertebral discs) • Synovial: Freely movable (knee) ⸻ 10. Osteoporosis & Arthritis • Osteoporosis: Bone thinning • Arthritis: Joint inflammation ⸻ ✅ Chapter 6 – Muscular System 1. Three Muscle Types • Skeletal: Voluntary, striated, attached to bones • Cardiac: Involuntary, heart only • Smooth: Involuntary, organs ⸻ 2. Connective Tissue Coverings • Endomysium → around muscle fiber • Perimysium → around fascicle • Epimysium → around whole muscle ⸻ 3. Fascicle Bundle of muscle fibers (covered by perimysium) ⸻ 4. Sarcomere Functional unit of muscle Boundaries: Z discs ⸻ 5. Bands • I band → thin only • A band → thick (and overlap) ⸻ 6. Filaments • Thick → Myosin • Thin → Actin, Troponin, Tropomyosin ⸻ 7. During Contraction • Sarcomere shortens • Z discs move closer • I band shortens • A band stays same ⸻ 8. Role of Calcium & ATP • Calcium: Exposes binding sites • ATP: Powers contraction & releases myosin ⸻ 9. Cross Bridge Myosin head binding to actin ⸻ 10. Neuromuscular Junction • Nerve releases acetylcholine (ACh) • ACh binds receptors • Muscle action potential starts ⸻ 11. Steps of Skeletal Muscle Contraction 1. Nerve impulse 2. ACh release 3. Muscle action potential 4. Ca²⁺ released from SR 5. Cross bridge formation 6. Power stroke 7. ATP binds & detaches 8. Relaxation when Ca²⁺ removed ⸻ 12. Three Ways Muscles Produce ATP • Direct phosphorylation (creatine phosphate) • Anaerobic glycolysis • Aerobic respiration ⸻ 13. Oxygen & Lactic Acid • Aerobic: Requires oxygen • Anaerobic glycolysis: Produces lactic acid ⸻ 14. Fastest Energy System Direct phosphorylation ⸻ 15. Isotonic vs Isometric • Isotonic: Muscle shortens (lifting weight) • Isometric: Tension, no movement (holding weight) ⸻ ✅ Chapter 7 – Nervous System 1. CNS Brain + spinal cord Function: control center ⸻ 2. PNS Cranial nerves + spinal nerves ⸻ 3. Afferent vs Efferent • Afferent: Sensory → to CNS • Efferent: Motor → from CNS ⸻ 4. Three Parts of Neuron • Dendrites (receive) • Cell body • Axon (send signal) ⸻ 5. Synapse Junction between neurons Synaptic cleft = gap between them ⸻ 6. Neurotransmitters Chemical messengers between neurons ⸻ 7. Three Neuron Types • Sensory • Motor • Interneurons ⸻ 8. CNS Neuroglia • Astrocytes • Oligodendrocytes • Microglia • Ependymal cells ⸻ 9. Action Potential Phases • Resting (-70mV) • Depolarization (Na⁺ in) • Repolarization (K⁺ out) • Hyperpolarization ⸻ 10. Myelinated Axons Faster Because Saltatory conduction (jumps between nodes) ⸻ 11. Reflex & Components Automatic response 5 parts: 1. Receptor 2. Sensory neuron 3. Integration center 4. Motor neuron 5. Effector ⸻ 12. Four Lobes of Cerebrum • Frontal → movement • Parietal → sensation • Temporal → hearing • Occipital → vision ⸻ 13. Thalamus, Hypothalamus, Epithalamus • Thalamus → sensory relay • Hypothalamus → homeostasis • Epithalamus → melatonin ⸻ 14. Brainstem Parts • Midbrain → reflexes • Pons → breathing control • Medulla → heart rate ⸻ 15. Cerebellum Balance & coordination ⸻ 16. Meninges • Dura mater • Arachnoid mater • Pia mater Protect CNS ⸻ 17. CSF Cerebrospinal fluid Found in ventricles & around brain/spinal cord ⸻ 18. Spinal Cord Structure: gray center, white outside Function: reflexes & signal pathway ⸻ 19. Sympathetic vs Parasympathetic • Sympathetic → fight or flight • Parasympathetic → rest and digest ⸻ 20. Effects on Organs Sympathetic: • ↑ heart rate • Dilates pupils • Stops digestion Parasympathetic: • ↓ heart rate • Constricts pupils • Stimulates digestion ⸻ 21