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CSU - ANEQ 305 - ANEQ305 Week 5 Class Notes - Class Notes

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CSU - ANEQ 305 - ANEQ305 Week 5 Class Notes - Class Notes

School: Colorado State University
Department: Science
Course: Functional Large Animal Anatomy/Physiology
Professor: Hyungchul Han
Term: Fall 2016
Tags: Animal physiology, animalscience, Animal Science, ANEQ305, anatomy, Physiology, and Colorado State University
Name: ANEQ305 Week 5 Class Notes
Description: These notes cover Chapter 8- Muscle Physiology
Uploaded: 02/19/2018
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background image ANEQ 305 
 
Chapter 8: Muscle Physiology 
8.1: Introduction 
● Muscle cells  ○ Produce  ​force/work  ○ Utilize  ​microfilament​ system  ○ Can  ​shorten/develop tension  ○ Chemical energy ​ of ATP → turn into ​mechanical energy  ○ 3 types  ■ Skeletal 
■ Cardiac 
■ Smooth  
● Muscle contraction  ○ For locomotive movement 
○ Propulsion of contents 
○ Manipulation of external objects 
○ Emptying body contents 
○ Production of heat/sound 
8.2: Skeletal Muscle  ● Makes up muscular system 
● Skeletal muscle cells (muscle fibers) are large (10-100μm diameter), 
elongated/cylindrical  ○ Formed by fusion of many  ​myoblasts​ during embryonic development → multiple  nuclei  ○ Parallel ​ to each other, ​bundled​ together by ​connective tissue  ○ Extend  ​full length  ● Myofibrils  ○ Specialized  ​contractile elements  ○ 90% muscle volume 
○ Cylindrical intracellular organelles → run full length of muscle fiber 
○ Greater density=greater force generated 
background image ○ Smaller % myofibrils → can’t generate much tension but can contract at a higher  frequency for prolonged periods of time  ● Myofibrils have regular arrangement of thick/thin filaments  ○ Thick filaments  ■ 12-18nm in diameter, 1.6μm in length 
■ Composed of 
​myosin  ● Tails ​ intertwined with ​globular heads​ projecting at one end  ● Each head has an  ​acting binding site​ and an ​ATPase  ○ Thin filaments  ■ 5-8nm in diameter, 1.0μm in length 
■ Composed of 
​actin   ■ Can attach to  ​myosin  ■ Tropomyosin ​ forms strands covering the actin binding sites in relaxed  muscle  ■ Troponin ​: protein complex with 3 subunits  ● One subunit binds to tropomyosin, one to actin, and one to Ca2+ 
● When not bound to Ca2+, troponin stabilizes tropomyosin in its 
blocking position  ● Basis of striations of skeletal muscle   ○ Alternating dark bands ( ​A bands​) and light bands (​I bands​)  ■ A-band ​: consists of a stacked set of ​thick filaments​ and portions of thin  filaments overlap them  ■ I-band ​: consists of the portions of the thin filaments that are not  overlapping thick filaments  ■ H-zone ​: (lighter area in the middle of the dark band) has only thick  filaments  ■ M-line ​: (in center of A band) holds thick filaments together  ■ Z-line ​: (in center of I band) is a flat, cytoskeletal disk where thin filaments  connect  ● Sarcomere ​: area between 2 Z-lines, functional unit of skeletal  muscle  8.3: Molecular Basis of Muscle Contraction  ● Sliding filament mechanism 
background image ○ Thin filaments  ​slide​ toward center of A band → ​sarcomere​ shortens  ○ Neither thick or thin filaments change in length 
○ Mechanism applies to both vertebrate and non-vertebrate striated muscle 
● Cross bridge cycling  ○ Ca2+ binds with troponin → troponin changes shape → binding sites on actin are  uncovered  ○ Myosin globular heads (cross-bridges)  ​bind to actin  ○ Cross bridge bends  ​45 degrees inward​, pulling thin filament with it (​power stroke​)  ○ Myosin  ​detaches​ from actin and returns to its original conformation, attaching to a  new site ​ on actin  ○ Complete shortening is accomplished by  ​repeated cross bridge cycles  ● Ca2+ = link between excitation and contraction  ○ Contraction stimulated by the release of acetylcholine (ACh)  at neuromuscular  junctions   ■ Action potential results  ○ Surface membrane dips into muscle fiber →  ​transverse tubule​ (T-tubule)   ■ Action potentials enter through T-tubule 
■ Induces permeability changes in adjacent 
​sarcoplasmic reticulum  ○ Ca2+ stored in  ​lateral sacs​ in sarcoplasmic reticulum  ○ Action potential in T-tubule triggers  ​release of Ca2+ from sarcoplasmic reticulum  to cytosol  ○ Elevated cytosolic Ca2+ ​ results in an ​increased binding of Ca2+ to troponin​ →  initiating contraction  ○ During relaxation, Ca2+ is pumped back into the sarcoplasmic reticulum via  Ca2+ -ATPase pumps ​ → reducing cytosolic Ca2+ levels  ● ATP powers cross-bridge cycling  ○ Myosin ATPase on thick filaments  ​splits ATP​  to form ADP (adenosine  diphosphate) and inorganic phosphate (Pi)  ○ During and after subsequent power stroke, Pi/ADP  ​released  ○ Myosin ATPase site attaches new ATP  ■ This permits detachment of cross-bridge to set up for another power stroke  ● Contraction activity outlasts action potential that created it  ○ Action potential 1-2sec 

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School: Colorado State University
Department: Science
Course: Functional Large Animal Anatomy/Physiology
Professor: Hyungchul Han
Term: Fall 2016
Tags: Animal physiology, animalscience, Animal Science, ANEQ305, anatomy, Physiology, and Colorado State University
Name: ANEQ305 Week 5 Class Notes
Description: These notes cover Chapter 8- Muscle Physiology
Uploaded: 02/19/2018
8 Pages 50 Views 40 Unlocks
  • Better Grades Guarantee
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  • Notes, Study Guides, Flashcards + More!
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