Covers how muscle tissue makes ATP, through the phosphocreatine system, glycolysis and oxidative phosphorylation, and the functional differences between skeletal, cardiac and smooth muscle plus myoepithelial cells. It then walks through contraction mechanisms in each muscle type, the main muscular dystrophies (Duchenne, Becker and myotonic) with their causes and symptoms, the dystrophin-associated protein complex, diagnosis and management, and finishes with four multiple-choice questions and answers.
Topic 68 of 70 in the MU Sofia syllabus for Biochemistry (Medicine, Year 2). The free AceMed note covers it in 6 sections, about 601 words (4 min of reading), with 10 flashcards.
In this note
MUSCLE TISSUE: METABOLISM AND FUNCTION
MOLECULAR MECHANISMS OF MUSCLE CONTRACTION
MUSCULAR DYSTROPHIES
DIAGNOSIS AND MANAGEMENT:
MCQS
ANSWERS
MUSCLE TISSUE: METABOLISM AND FUNCTION
Metabolism:
Energy Sources: Muscle cells use ATP as the immediate source of energy. ATP is regenerated via:
Phosphocreatine System: Provides rapid ATP replenishment by transferring a phosphate group from phosphocreatine to ADP.
Glycolysis: Breaks down glucose to produce ATP, with lactate as a by-product in anaerobic conditions.
Oxidative Phosphorylation: Utilizes glucose, fatty acids, and amino acids in the mitochondria to produce ATP efficiently under aerobic conditions.
MUSCLE TISSUE: METABOLISM AND FUNCTION
Function:
Skeletal Muscle: Voluntary muscles responsible for movement, posture, and heat production.
Cardiac Muscle: Involuntary muscle found in the heart, responsible for pumping blood.
Smooth Muscle: Involuntary muscle found in the walls of internal organs, responsible for regulating organ dimensions.
Myoepithelial Cells: Specialized cells that contract to expel secretions from glandular structures.
MOLECULAR MECHANISMS OF MUSCLE CONTRACTION
Skeletal Muscle:
Excitation-Contraction Coupling:
Action Potential: An action potential travels along the sarcolemma and down T-tubules.
Calcium Release: Triggers the release of Ca²⁺ from the sarcoplasmic reticulum.
Troponin and Tropomyosin: Ca²⁺ binds to troponin, causing a conformational change that moves tropomyosin away from the actin binding sites.
Cross-Bridge Cycling: Myosin heads bind to actin, perform a power stroke using ATP, and then detach to repeat the cycle.
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