Human Physiology Laboratory
Human Physiology Laboratory BIO 378
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This 7 page Class Notes was uploaded by Dessie Botsford on Sunday October 11, 2015. The Class Notes belongs to BIO 378 at Eastern Kentucky University taught by Gary Ritchison in Fall. Since its upload, it has received 7 views. For similar materials see /class/221462/bio-378-eastern-kentucky-university in Biology at Eastern Kentucky University.
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Date Created: 10/11/15
B10 378 Lecture 7 Skeletal Muscle A Structure of Muscle Fiber and Myo laments 1 attached to Bones by Tendons connective tissue 2 muscle is made up ofmuscle bers Perimysium Bone Blood Vessels Endomysium Muscle Fiber Cell Tendon EPimEi m Fassicle Endom ysium 3 each muscle ber is composed of myo brils myo laments H c 11quot Ending 4 There are two types of myo laments lt V Sarcomere Myosin Lattice mm g Immest SW Networks a Thick myofilaments are made of MYOSIN have myosin heads which have ATP binding sites b Thin myo laments are made of three proteins 1 Actin have binding sites for Myosin heads 2 Troponin 3 Tropomyosin 5 These myo brils myo laments have distinct banding patterns Sarcomere a A band Dark dense portion where thick and thin laments overlap b H zone Central area where there are only thick laments c I band Light area between A band and Z line where there are only thin laments d Z line Dark line separating sarcomeres 6 Skeletal muscles have a Sarcoplasmic Reticulum SR Sarcoplasmic Reticulum Saroolomma Myo brils Terminal cisternae Transverse lu Dule Sarcoplasmic reticulum Mitochondria 4 a similar to ER of other cells b SR is c stores Calcium Ions d The SR has calcium gates that pump calcium via active transport into the SR from the cytoplasm of the muscle cell B In a relaxed muscle 1 Calcium gates are closed therefore calcium stays in the SR 2 there is a very high concentration of calcium in the SR and very low concentration of Ca in the cytoplasm 3 the binding sites for the myosin heads on the actin laments are covered by Tropomyosin C Muscle contraction l A nervous impulse depolarizes the SR and causes calcium gates to open 2 Calcium ions diffuse rapidly out of the SR into the cytoplasm 3 The calcium binds to a binding site on the Troponin molecules 4 When a calcium ion lls this site it causes a change in the shape amp position of the Troponin When the Troponin shifts if pulls the Tropomyosin to which it is attached 5 Movement of the Tropomyosin permits the Myosin head to contact the Actin 6 Contact of Myosin head with Actin causes the ATP molecules to break down to ADP THIS RELEASES ENERGY 7 The release of energy causes the myosin head to swivel forward During the swivel the Myosin head is rmly attached to Actin When the head swivels it pulls the Actin and the entire thing myofilament forward Many Myosin heads are swivelling simultaneouslytheir collective efforts are enought to pull the entire thin myofilament 8 At the end of the swivel the ATP has completely broken down to ADP a Thus the Myosin head ATP sites are empty and the Myosin head cannot maintain its attachment to Actin b Therefore the Myosin head swivels back into the starting position c however lots more ATP are starting to fill the ATP binding sites because 9 By the time the Myosin head has swivelled back the ATP binding sites have been refilled As a result the Myosin head can once again bind firmly to the Actin MymiN mmphx Ammllrh39x Tlml39mna m ATP 5 I 12 1 1119mm A3 my 10 M Eancmsshxdge 3D Ammauan 11 When the hmnusimpulse stops than the calmum gates close 12 on the Tropomn molecules W1thoutCaTropomn retums tons ongmal shape and head and hem and therefore the muse1e stops contracting relaxes 11 As A 1 1h Am and swwel ef nently Thxs deehne m ATP levels m a musele causes So dunng contraction 1 z lmes eome closer 2 deth ofA bands decreases 3 deth ofH zones decreases 4 Therexsno change m the wxdth ofthe I bands Useful links Human Physiology Muscle Muscles Back to B10 378 Syllabus
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