Muscle Physiology Mini-Lesson 1 PDF

Muscle Physiology Mini-Lesson 1 Muscle General Overview Structure of Skeletal Muscle Guiding Question: What structures allow muscles to contract?  Muscle General Overview  Muscle Comes in Three Type...

Muscle Physiology Mini-Lesson 1 Muscle General Overview Structure of Skeletal Muscle Guiding Question: What structures allow muscles to contract?  Muscle General Overview  Muscle Comes in Three Types Skeletal Cardiac Smooth  Quick Comparison Between Muscle Types Use chemical energy Contraction (ATP) to generate requires force/do work/allow Somatic Autonomic elevation of Type: movement: Striated: voluntary*: involuntary: [Ca2+]i: Skeletal X X X X Cardiac X X X X Smooth X X X  Skeletal Muscle Basics Role of skeletal muscle in maintaining homeostasis: 1. Acquisition of nutrients/fuel 2. Processing food (chewing, swallowing) 3. Breathing 4. Escape from harm 5. Generation of heat for temperature control 6. Source of amino acids for times of famine Skeletal muscle is big and expensive! - 30% (in women) to 40% (in men) of total body mass - #1 consumer of nutrients, O2 (uses LOTS of ATP!) - High metabolism produces abundant wastes that tend to disrupt ECF homeostasis Skeletal Muscle Structure Whole Skeletal Muscle (an organ = several tissue types) Muscle Fiber (one cell) Myofibrils (cylinders of intracellular contractile filaments arranged in repeating units) Thick and Thin Filaments Myosin and Actin Molecules  A Closer Look at Thick Filament Structure - Each myosin molecule contains a long, rod-like, heavy chain segment that forms the core of the filament and 2 globular cross-bridge heads that extend out towards the overlying actin - Each cross-bridge head has two binding sites – one for actin and one for ATP; the ATP binding site serves as an enzyme that hydrolyzes ATP, called myosin-ATPase  A Closer Look at Thin Filament Structure G-Actin Binding site for attachment with (Globular) myosin cross-bridge Actin molecules Actin F-Actin helix Like a 2-strand pearl necklace + (Filamentous) Spans 7 G-actins 1 per Tropomyosin Tropomyosin Troponin Sarcomere Structure - One unit of the repeating thin and thick filament pattern within the myofibril is called a sarcomere. - The sarcomere is the functional unit of muscle. Be sure to identify: Sarcomere (2 µm) Z line (disk) A band I band H zone M line (disk) Titin  Sarcomere Structure Cross-section of the thick and thin filaments:  Other Myofibril Structures Sarcolemma ≈ Plasma Membrane … T-tubules (transverse-tubules) Sarcoplasmic Reticulum ≈ Smooth ER … Terminal Cisternae Excitation-Contraction (EC) Coupling in Skeletal Muscle (occurs during the latent period) (Stores Ca2+) Thin Filament Regulation of Skeletal Muscle Contraction (100 nM) (100 nM) (1-10 µM) ↑Ca2+ The myosin cross-bridge and actin can physically interact allowing the muscle to contract. Contraction: Activation of myosin cross-bridges to exert force on the thin filaments Contraction = Active Force = Tension Generation Development