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Musculoskeletal System - Coggle Diagram
Musculoskeletal System
ORGANIZATION OF THE SKELETAL SYSTEM
Axial Skeleton (80 bones)
Function: Forms the central axis of the body; primarily protects internal organs.
Bones: Skull, Auditory ossicles, Hyoid bone, Vertebral column (spine), and Thoracic cage (ribs and sternum).
Appendicular Skeleton (126 bones)
Function: Forms the limbs and the girdles that attach the limbs to the axial skeleton; primarily used for movement.
Bones: Pectoral girdles (scapulae and clavicles), Upper limbs (arms, forearms, hands), Pelvic girdle (hips), and Lower limbs (thighs, legs, feet).
FUNCTIONS OF THE SKELETAL SYSTEM
Support: Provides a rigid framework that supports the soft tissues of the body.
Protection: Guards vital internal organs (e.g., the skull protects the brain; the rib cage protects the heart and lungs).
Movement: Serves as levers for skeletal muscles, allowing locomotion and manipulation.
Mineral Storage: Acts as a reservoir for essential minerals, particularly calcium and phosphate.
Hematopoiesis (Blood Cell Formation): Red bone marrow is the primary site of blood cell production.
Fat Storage: Yellow bone marrow stores triglycerides (fat), which serve as an energy reserve.
MUSCLE CONTRACTION & ATP (ENERGY)
Primary Energy Source: Adenosine Triphosphate (ATP) is the direct energy source for muscle contraction.
Role of ATP in the Sliding Filament Mechanism:
ATP binds to myosin heads, allowing them to detach from the actin filament after a power stroke.
Hydrolysis of ATP into ADP and inorganic phosphate energizes the myosin heads, preparing them for the next attachment and power stroke.
ATP is also essential for actively pumping calcium ions ($Ca^{2+}$) back into the sarcoplasmic reticulum, which is required for muscle relaxation.
ATP REGENERATION PATHWAYS
Because muscle ATP stores are limited, ATP must be rapidly regenerated via three main pathways:
Phosphocreatine System
Mechanism: Creatine phosphate donates a phosphate group to ADP.
Duration: Supports very short bursts of intense activity (first 6-10 seconds).
Anaerobic Glycolysis:
Mechanism: Breakdown of muscle glycogen into pyruvate (no oxygen required).
Duration: Supports moderate-duration activity (up to about 1 minute).
Byproduct: Produces lactic acid, leading to muscle fatigue.
Aerobic Metabolism (Oxidative Phosphorylation):
Mechanism: Uses oxygen ($O_2$) to break down carbohydrates, fats, and proteins in the mitochondria.
Duration: Produces the bulk of ATP during prolonged, lower-intensity exercise.
Efficiency: Highly efficient and produces minimal waste.