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L18 NPB 101 - Lecture 18 •  SmartSite: – ...

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Unformatted text preview: Lecture 18 •  SmartSite: –  Lecture 18 Notes –  Midterm 1 (Wed 10/20): •  Reading (Recommended): –  Relevant por?ons Chapter 8 •  Announcements: –  Exam Room (based on Last Name) –  CAF Office Hrs (197 Briggs) •  T 9 ­10 and 5 ­6 •  30 MC ques?ons •  Covers lectures through Monday •  Star?ng Tuesday, lectures on Midterm 2) •  Requires students to bring and use SCANTRON 2000 (blue) •  Review •  Muscle –  Review Skeletal muscle –  Smooth muscle –  Cardiac muscle •  A ­D in 1322 Storer •  E ­Z in 123 Sci Lec Hall (regular room) –  EL Office Hrs (2041A SLB) •  M 5 ­7 •  Tu/Th 1 ­3 (Regular) 1 REV: Muscle •  Power stroke & cross bridge cycle •  Excita?on ­contrac?on coupling –  Force ­Velocity curve –  Length ­Tension rela?onship –  NMJ, T ­Tubule, SR, Ca2+, Relaxa?on •  Mechanics of contrac?on (number of cross bridges) •  Regula?on of contrac?on force •  Types of skeletal muscle fibers –  Fast vs. Slow –  Summa?on –  Motor unit size & number of motor units 2 Excita?on ­ Contrac?on Coupling AP from motorneuron Ach! End Plate Poten?al (EPSP) " AP on muscle fiber cell membrane (sarcolema) " AP conducted over sarcolema/T ­tubule " Excita?on of Sarcoplasmic Re?culum (SR) (increase PCa)! Diffusion of Ca2+ out of SR and into myofibril " Ca2+ binds with Troponin and shids Tropomysin " Ac?n ac?vated " Ac?n ­Myosin cross bridge " Myosin power stroke " FORCE" 3 Deac?vate Ach " RELAXATION" Diffusion of Ca2+ into Myofibril " Ac?vates Ca2+ SR reuptake pump " Pump Ca2+ back into SR " Decrease Ca2+ and deac?vate Ac?n" Smooth Muscle 4 Smooth Muscle •  Found in walls of hollow organs and tubes •  No stria?ons –  Filaments do not form myofibrils –  Not arranged in sarcomere paeern found in skeletal muscle •  Spindle ­shaped cells with single nucleus •  Cells usually arranged in sheets within muscle •  Have dense bodies containing same protein found in Z lines 5 Smooth Muscle •  Cell has three types of filaments –  Thick myosin filaments •  Longer than those in skeletal muscle –  Thin ac?n filaments •  Contain tropomyosin but lack troponin –  Filaments of intermediate size •  Do not directly par?cipate in contrac?on •  Form part of cytoskeletal framework that supports cell shape 6 Smooth Muscle Myosin & Ac?n •  Schema?c Representa?on of the arrangement of Thick and Thin Filaments in a Smooth Muscle Cell In Relaxed State Fig. 8 ­28, pg. 293 7 Smooth Muscle Myosin & Ac?n •  Schema?c Representa?on of the arrangement of Thick and Thin Filaments in a Smooth Muscle Cell In Contracted State Fig. 8 ­28, pg. 293 8 Ca2+ Ac?va?on of Myosin Cross Bridge Fig. 8 ­29, pg. 293 Note: No Troponin 9 Smooth muscle contrac?on •  Twitch is slower –  Cross bridges slower –  Ca2+ removal slower Fig. 8 ­27, pg. 292 10 Skeletal vs. Smooth Comparison of Role of Calcium In Bringing About Contrac?on in Smooth Muscle and Skeletal Muscle Fig. 8 ­30, pg. 294 11 Smooth Muscle •  Two major types –  Mul?unit smooth muscle –  Single ­unit smooth muscle 12 Mul?unit Smooth Muscle •  Each cell receives input •  Very few gap junc?ons between cells •  Each cell may contract independently of its neighbor 13 Mul?unit Smooth Muscle •  Neurogenic (ANS) •  Consists of discrete units that func?on independently of one another •  Units must be separately s?mulated by nerves to contract •  Found –  In walls of large blood vessels –  In small airways to lungs –  In muscle of eye that adjusts lens for near or far vision –  In iris of eye –  At base of hair follicles 14 Single ­Unit Smooth Muscle •  •  •  •  Motor neuronal input to a few cells Many gap junc?ons allow communica?on The cells contract as a group Func?onal syncy?um 15 Single ­unit Smooth Muscle •  Self ­excitable –  does not require nervous s?mula?on for contrac?on •  Also called visceral smooth muscle •  Fibers become excited and contract as single unit –  Cells electrically linked by gap junc?ons –  Can also be described as a func?onal syncy?um •  Contrac?on is slow and energy ­efficient –  Well suited for forming walls of distensible, hollow organs (diges?ve, reproduc?ve and urinary tracts) 16 Pacemaker Poten?al Fig. 8 ­31a, pg. 295 17 Slow Wave Poten?al Fig. 8 ­31b, pg. 295 18 ANS Postganglionic Innerva?on Fig. 8 ­32, pg. 297 Synapse “en passant” 19 Cardiac Muscle •  Found only in walls of the heart •  Striated •  Cells are connected by gap junc?ons –  Intercalated disks •  Innervated by ANS •  Involuntary 20 ...
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