Home1. Functions of Muscles: • Movement: Muscles contract to produce movement in the body, such as walking, running, or even facial expressions. • Posture and Stability: Muscles help maintain posture and stabilize joints, preventing falls or loss of balance. • Heat Production: Muscle contractions generate heat, which is vital for maintaining body temperature. • Protection of Internal Organs: Muscles, particularly in the abdominal region, protect internal organs from injury. • Circulation of Blood and Lymph: Cardiac and smooth muscles play roles in circulating blood and lymph throughout the body. 2. Characteristics of Muscles: • Excitability (Responsiveness): Muscles can respond to stimuli (like nerve signals). • Contractility: Muscles can contract or shorten when stimulated. • Extensibility: Muscles can be stretched without damage. • Elasticity: Muscles can return to their original shape after being stretched or contracted. 3. Locations of Smooth, Cardiac, and Skeletal Muscle: • Smooth Muscle: Found in walls of internal organs (e.g., stomach, intestines, blood vessels). • Cardiac Muscle: Found only in the heart. • Skeletal Muscle: Attached to bones and responsible for voluntary movements. 4. Events of Skeletal Muscle Contraction: 1. Nerve Impulse: A signal is sent from a motor neuron to the muscle. 2. Release of Acetylcholine: The neurotransmitter acetylcholine is released into the neuromuscular junction. 3. Muscle Fiber Activation: Acetylcholine stimulates muscle fibers, causing an action potential. 4. Calcium Release: The action potential triggers the release of calcium ions from the sarcoplasmic reticulum. 5. Cross-Bridge Formation: Calcium binds to troponin, moving tropomyosin, which allows myosin heads to attach to actin. 6. Power Stroke: Myosin heads pull actin filaments inward, causing the muscle to contract. 7. Relaxation: ATP breaks the cross-bridge, and the muscle relaxes when calcium is pumped back into the sarcoplasmic reticulum. 5. Isometric vs. Isotonic Contractions: • Isometric Contraction: The muscle generates tension without changing its length (e.g., holding a weight in a fixed position). • Isotonic Contraction: The muscle changes length while generating tension (e.g., lifting a weight). 6. Primary Functions of the Skeletal System: • Support: Provides structural support for the body. • Protection: Shields vital organs (e.g., brain, heart, lungs). • Movement: Works with muscles to allow movement. • Mineral Storage: Stores minerals like calcium and phosphorus. • Blood Cell Production: Bone marrow produces blood cells. • Energy Storage: Fat is stored in bone cavities. 7. Parts of a Long Bone: • Diaphysis: The shaft of the bone. • Epiphysis: The ends of the bone. • Metaphysis: Region between the diaphysis and epiphysis. • Medullary Cavity: Hollow cavity inside the diaphysis, containing bone marrow. • Periosteum: Outer membrane covering the bone. • Endosteum: Inner lining of the medullary cavity. 8. Inner and Outer Connective Tissue Linings of a Bone: • Outer: Periosteum. • Inner: Endosteum. 9. Structure of a Flat Bone: • Compact Bone: Dense bone found on the outside. • Spongy Bone: Lighter, less dense bone found inside, filled with red or yellow marrow. • No medullary cavity (unlike long bones). 10. Parts of the Osteon: • Central Canal (Haversian Canal): Contains blood vessels and nerves. • Lamellae: Concentric layers of bone matrix surrounding the central canal. • Lacunae: Small spaces containing osteocytes (bone cells). • Canaliculi: Small channels that connect lacunae and allow for nutrient exchange. 11. How Calcitonin, Calcitriol, and PTH Affect Blood Calcium: • Calcitonin: Lowers blood calcium levels by inhibiting osteoclast activity (bone resorption). • Calcitriol: Increases blood calcium by promoting calcium absorption in the intestines and bone resorption. • PTH (Parathyroid Hormone): Raises blood calcium by stimulating osteoclasts to break down bone and release calcium. 12. Two Forms of Ossification: • Intramembranous Ossification: Bone develops directly from mesenchymal tissue (e.g., flat bones of the skull). • Endochondral Ossification: Bone replaces a cartilage model (e.g., long bones). 13. Difference Between Appositional and Interstitial Growth: • Appositional Growth: Increase in bone diameter (growth at the surface). • Interstitial Growth: Increase in bone length (growth from within). 14. Different Joint Types: • Fibrous Joints: Connected by fibrous tissue (e.g., sutures of the skull). • Cartilaginous Joints: Connected by cartilage (e.g., intervertebral discs). • Synovial Joints: Have a fluid-filled joint cavity (e.g., knee, elbow). 15. Components of a Synovial Joint: • Articular Cartilage: Covers the ends of bones. • Synovial Membrane: Lines the joint capsule and produces synovial fluid. • Joint Capsule: Surrounds the joint, providing stability. • Ligaments: Connect bones to other bones. • Synovial Fluid: Lubricates the joint. 16. Hinge Joint Location: • Found in the elbow and knee. 17. Pivot Joint Location: • Found between the first and second cervical vertebrae (atlantoaxial joint). 18. Difference Between a Tendon and a Ligament: • Tendon: Connects muscle to bone. • Ligament: Connects bone to bone. 19. What is a Bursa? • A fluid-filled sac that reduces friction and cushions pressure points between the skin and bones or muscles and bones. 20. Three Types of Arthritis: • Osteoarthritis: Degeneration of joint cartilage and underlying bone, often due to wear and tear. • Rheumatoid Arthritis: Autoimmune disease causing inflammation in joints. • Gout: Caused by the accumulation of uric acid crystals in the joints. 21. Strain vs. Sprain: • A strain is damage to a muscle or tendon, whereas a sprain is damage to a ligament