Physiology of Muscle Contraction PDF

C o ll e g e N a m e – ‫ا‬ Physiology of Skeletal Muscle ‫س‬ ‫م‬ Contraction ‫ا‬ ‫ل‬ Dr. Mohammed Moizuddin Khan ‫ك‬ ‫ل‬ ‫ية‬ Reference Read-Guyton and Hall 14th Edition, -Chapters 6 and 7 Pa...

C o ll e g e N a m e – ‫ا‬ Physiology of Skeletal Muscle ‫س‬ ‫م‬ Contraction ‫ا‬ ‫ل‬ Dr. Mohammed Moizuddin Khan ‫ك‬ ‫ل‬ ‫ية‬ Reference Read-Guyton and Hall 14th Edition, -Chapters 6 and 7 Page Number 79 to 100 Watch https://www.youtube.com/watch?v=BVcgO4p88AA ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar C o ll e g Learning objectives e N a At the end of the lecture the students should able to know m e The physiologic anatomy of the skeletal muscle. – ‫ا‬ ‫س‬ The general mechanism of skeletal muscle contraction. ‫م‬ ‫ا‬ The molecular mechanism of skeletal muscle ‫ل‬ ‫ك‬ contraction & relaxation. ‫ل‬ ‫ية‬ Sliding filament mechanism. ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar  The Muscle Action Potential ( AP ) Muscle RMP = -90 mV ( same as in nerves ). Duration of AP = 1-5 ms ( longer duration than nerve AP , me – ‫ الكلية‬which ‫اسم‬ is usually about 1 ms ). Loading… Conduction Velocity = 3-5 m/s ( slower than big nerves ). ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar C o ll e Each muscle cell g e (fibre) is covered N a m by a cell-membrane e – called Sarcolemma. ‫ا‬ ‫ س‬ Each cell contains ‫م‬ ‫ا‬ few hundreds to a ‫ل‬ ‫ك‬ few thousands ‫ل‬ ‫ية‬ Myofibrils. ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar  Each Myofibril contains Actin filaments (thin) & Myosin (thick) filaments. me – ‫اسم الكلية‬ Loading… Each myofibril is striated: consisting of Dark bands (called A-bands) ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar C o ll Sarcomere - Contractile unit of muscle, it is the zone between two e g Z lines ( discs)=2 micrometer in length in resting state. e N Z discs (lines) – Extend all the way across myofibrils a m 3-Bands- Inside each sarcomere, e – 1. I band (of actin only ) ‫ا‬ 2. ‫س‬ H band(of myosin only) 3.‫م‬ A band (of actin & myosin) ‫ا‬ ‫ل‬ ‫ك‬ ‫ل‬ When contraction takes place Actin & Myosin slide upon each ‫ية‬ other , & the distance between two z-discs decreases : This is called as Sliding Filament Mechanism ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar  EM Evidence for Sliding Filaments me – ‫اسم الكلية‬ ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar C o ll e g e Sarcoplasm: N a matrix inside muscle fiber in m e which myofilaments suspended – ‫ا‬ Sarcoplasmic reticulum: ‫س‬ ‫ م‬it is endoplasmic reticulum ‫ا‬ ‫ ل‬inside sarcoplasm full of Ca. ‫ك‬ ‫ ل‬T- tubules: ‫ية‬ extend from one side of muscle to other. ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar  Muscle Contraction Muscle proteins : Thick filament: Myosin Thin filament : 1. me – ‫اسم الكلية‬ Actin 2. Troponin 3. Tropomyosin Thick Myosin filament has head + tail, Cross bridges Head has ATP site ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar C o ll e Thin filament g e N a m e – ‫ا‬ Two F-Actin strands ‫س‬ ‫م‬ ‫ا‬ ‫ل‬ ‫ك‬ ‫ل‬ ‫ية‬ Groove between the 2 F- actin strands ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar  Actin & Myosin me – ‫اسم الكلية‬ Loading… ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar C o ll e g e N a MOLECULAR MECHANISM OF m e MUSCLE CONTRACTION – ‫ا‬ ‫س‬ ‫م‬ Excitation –contraction coupling ‫ا‬ ‫ل‬ ‫ك‬ ‫ل‬ https://www.youtube.com/watch?v=BVcgO4p88AA ‫ية‬ ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar  Events of muscle contraction: *** Acetylcholine released by motor nerve »»»»» EPP »»»»» depolarization muscle AP »»»»» Spread of AP into T tubule »»»»»release of Ca from sarcoplasmic reticulum into the cytoplasm »»»»» Ca me – ‫الكلية‬ ‫اسم‬combines with troponin »»»»» troponin pull tropomyosin sideway »»»»» exposing the active site on actin »»»»» myosin heads with ATP on them, attached to actin active site »»»»» the head of myosin cross bridges bend pulling actin toward center of sarcomere (Power stroke) using energy of ATP»»»»»ADP & P released »»»»» ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar C o ll e Events of muscle contraction: g e N Linkage between actin & myosin broken as new ATP binds to myosin cross bridge a m >>> ATP hydrolyzed and cross bridge go back to its original conformation. e – ‫ا‬ When a new ATP occupies the vacant site on the myosin head, this triggers ‫س‬ detachment of myosin from actin ‫م‬ ‫ا‬ ‫ل‬ The free myosin swings back to its original position, & attached to another actin, & ‫ك‬ ‫ل‬ the cycle repeat its self ‫ية‬ ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar  Events of muscle relaxation: When ca is pumped back into sarcoplasmic reticulum »»»»» ca detached from troponin »»»»» tropomyosin return to its original position me – ‫اسم الكلية‬ »»»»» covering active site on actin »»»»» prevent attachment between actin and myosin»»»»» relaxation ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar C o ll e g e N a m e – ‫ا‬ ‫س‬ ‫م‬ ‫ا‬ ‫ل‬ ‫ك‬ ‫ل‬ ‫ية‬ ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar me – ‫اسم الكلية‬ ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar C o ll e g e N a m e – ‫ا‬ ‫س‬ ‫م‬ ‫ا‬ ‫ل‬ ‫ك‬ ‫ل‬ ‫ية‬ ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar  ATP is needed for 3 things : what are they ? ATP is needed for 3 things : (1) Power stroke. (2) Detachment of myosin from actin active sites me – ‫اسم الكلية‬ (3) Pumping C++ back into the Sarcoplasmic reticulum. Is muscle relaxation a passive or active process ? A : it is active ; Why ? Because it needs ATP. ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar C o ll e Ca++ is needed in nerve & muscle : when and where g e N ? a m e A : In nerve needed for exocytosis ( & release of – ‫ا‬ Ach) ‫س‬ ‫م‬ In Muscle needed for contraction. ‫ا‬ ‫ل‬ ‫ك‬ ‫ل‬ ‫ية‬ ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar  THANK me – ‫اسم الكلية‬ YOU ‫حاضرة حسب التقويم‬0‫ رقم ا‬Class No. according to Calendar