Muscle Physiology 2 Pre-lecture Notes PDF

Summary

These are pre-lecture notes on muscle physiology for an applied science course at London Metropolitan University. The notes cover the structure and function of different muscle types (skeletal, smooth, cardiac), mechanism of muscle contraction, and energy production pathways involved. They also include detailed diagrams and key concepts.

Full Transcript

Applied Sciences PT4050 and PT7001 Muscle Physiology Part 2 Chris Chamberlin and Dr Ben Hunter [email protected] Learning Outcomes Smooth muscle Structure and innervation Three muscle types Skeletal, smooth, cardiac Contraction regulation i...

Applied Sciences PT4050 and PT7001 Muscle Physiology Part 2 Chris Chamberlin and Dr Ben Hunter [email protected] Learning Outcomes Smooth muscle Structure and innervation Three muscle types Skeletal, smooth, cardiac Contraction regulation in smooth and skeletal muscle Energy supply Types of Muscle Types of Muscle Skeletal Muscle · Striation (sarcomeres) · Effector of somatic nerve system · Voluntary contraction · Neuromuscular junction-specific · Multi-nuclei (fusion) Smooth Muscle · No striation (filaments not form sarcomeres) · Effector of autonomic nerve system · Involuntary contraction · Varicosites-diffuse · Gap junctions Cardiac Muscle · Striation (sarcomeres) · Effector of autonomic nerve system · Involuntary contraction · Gap junctions · Intercalated disks ”On-off switch” – Skeletal and Cardiac · Interaction of actin and myosin depends on regulatory proteins on the thin filament: · Tropomyosin – blocks myosin binding sides on actin · Troponin C – binding site for Ca2+ · Troponin T – binds to tropomyosin · Troponin I – binds to actin · Ca2+ binds to troponin-C then a conformational change occurs which moves tropomyosin · This then revelas the myosin binding site and a cross-bridge can form ”On-off switch” – Smooth · Smooth muscle doesn’t contain troponin, therefore Ca2+ triggers contraction via different mechanism · Ca2+ binds to protein called calmodulin · Binds to myosin light chain kinase (MLCK) · Myosin light chains are then phosphorylated · This permits the binding of myosin to actin Depolarisation in different muscle · Skeletal – AP triggers release of calcium from SR · Cardiac and smooth – the AP and source of calcium differ Twitch contraction Contraction produced in response to a single action potential All or nothing for a given muscle fibre Can be induced for a muscle fibre, a motor unit or a whole muscle Latency: time delay between stimulation (nerve AP or direct electrical) – E-C coupling Contraction phase – cross-bridge cycling Relaxation phase – Ca2+ uptake Twitch contraction Frequency and Summation Action potential: 2 ms Contraction: 10–200 ms, possible to summate Tension (force) depends on [Ca2+]i Freq. of stim., Ca2+ release>uptake, [Ca2+]i When the system is saturated (all troponin bind with Ca2+ and cross-bridge cycling maxed out) – tetanus (long lasting contraction) Frequency and Summation Energy Production - ATP Energy Production - ATP How does ATP provide energy? Reaction (catabolic) - ATP  ADP + P + Energy + Heat Stores of ATP in body are sufficient for few seconds of maximal work. Energy Production – PCr System PCr used as follows: PCr  P + Cr + Energy Facilitated by the enzyme creatine kinase Energy released from catabolic PCr reaction ADP + P + Energy  ATP Anabolic reaction – phosphate and energy reform ATP Energy Production – Glycolysis 10 enzyme-controlled reactions Glycolysis  breakdown of 6-carbon molecule - Glucose (C6H12O6)  two 3-carbon molecule of pyruvic acid (C3H6O3) Net gain of 2 ATP All reactions are reversible Energy Production – Glycolysis “CHO” 10 Enzyme ATP Synthesised Controlled Reactions Pyruvate No oxygen Oxygen Lactic acid Krebs cycle Just to get this right… Energy Production – Glycolysis “CHO” 10 Enzyme ATP Synthesised Controlled Reactions Pyruvate No oxygen Oxygen Lactic acid Krebs cycle Energy Production – Aerobic Pathways Energy Production – Aerobic Pathways Krebs cycle (or citric acid cycle) consists of a series of reactions that result in a net production of (per molecule of glucose): 2 x ATP ( = 2 ATP from glycolysis) = 4 ATP 6 x NADH (+ 4 NADH from glycolysis) = 10 NADHs ≈ 30 ATP 2 x FADH2 ≈ 4 ATP 38 ATPs produced from complete oxidation of glucose (Krebs and Electron Transport Chain) Triglyceride Energy Production – Aerobic Pathways Glycerol Glycerol 3x Fatty acid Enters glycolysis Moved into Kreb’s cycle H+ taken to electron transfer chain Glycolysis Acetyl Co-A Total energy production 15-19 ATP Krebs cycle Krebs cycle Fatty acids H+ ions H+ ions When not attached to glycerol called free fatty acids Broken down by beta-oxidation ETC ETC Acetyl coenzyme A is taken to Kreb's cycle H+ taken to electron transfer chain Each Fatty acid, 129 ATP 129 (x3) = 19 ATP 387 ATP Energy Production – Systems Summary See learning outcomes.

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