1 / 26

Muscle: Anatomy Physiology

Leo
Download Presentation

Muscle: Anatomy Physiology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

    1. Muscle: Anatomy & Physiology Lecture 20

    3. Motor Pool all a motor neurons that innervate a single muscle An a motor neuron and all the muscle fibers that it innervates 1:3 to 1:100 fewer muscle fibers ---> finer control 3 types based on speed of contraction & fatigue ~ Motor Pools & Motor Units

    4. Type 1 Fibers Slow fibers dark red slow, sustained contraction slow to fatigue Aerobic metabolism many capillaries & mitochondria oxygen required for ATP synthesis myoglobin gives dark red appearance ~

    5. Type 2b Fibers Fast fatigable fibers white fibers rapid, brief contraction fast to fatigue produce about 10x force of Type 1 Anaerobic metabolism fewer capillaries & mitochondria ATP generated by glycolysis lactic acid buildup ~

    6. Type 2a Fibers Fast fatigue-resistant fibers pale red properties intermediate to types 1 & 2b rapid, brief contraction slow to fatigue produce least force Aerobic & Anaerobic metabolism many capillaries & mitochondria ~

    7. Types of Motor Units Most muscle contain both slow- & fast-twitch fibers ratio depends on function e.g. ankle extensors Soleus active during standing hi ratio of slow fibers Medial Gastrocnemius: active during running & jumping hi ratio of fast fibers ~

    8. Neuromuscular Junction Synapse between neuron & effector Cholinergic (ACh) nicotinic receptors Motor end-plate postsynaptic membrane folds packed with receptors increased surface area ~

    9. Motor end-plate

    10. Graded Control of Muscle Contraction Highly reliable synapse 1 presynaptic AP ---> 1 postsynaptic AP ---> 1 twitch (contract/relax) temporal summation ­ tension & sustained contraction Recruitment ­ # motor units ---> ­ tension order: smallest ---> largest ~

    11. Muscle Contraction AP generated in muscle fiber (cell) Ca++ released from internal stores Muscle fiber contracts continues while Ca++ & ATP available Relaxation Ca++ sequestered by active transport ~

    12. Muscle Fiber Structure Multinucleated fusion of multiple precursor cells Sarcolemma Excitable membrane Myofibrils: contractile units Sarcopasmic reticulum (SR) sequesters Ca++ T tubules AP from sarcolemma to SR like inside-out axons ~

    14. Myofibril: structure & function Sarcomeres repeating sections Z lines dividers between sarcomeres thin filaments anchored to Z lines actin & troponin Thick filaments between thin filaments myosin Contraction:filaments slide by each other ~

    17. Contraction Excitation-contraction coupling Myosin “heads” crossbridges w/ actin Ca++ dependent binds to troponin, reveals binding site Myosin head rotates “ratchets” actin inward ~

    18. Contraction ATP binds to myosin ---> detachment cocks myosin ---> binds again rigor mortis: no ATP fibers remain crosslinked Repeats as long as Ca++ present sequestered via active transport ~

    23. Movement Disorders of Muscle

    24. Duchenne’s Muscular Dystrophy Muscular Dystrophies wasting away of muscles metabolic / structural abnormalities Duchenne’s best understood young boys ~

    25. Duchenne’s Muscular Dystrophy Cause hereditary - maternal X chromosome single gene ---> protein dystrophin maybe involved in Ca++ regulation Treatment Inject dystrophin or mRNA Gene therapy promising for muscles ~

    26. Myasthenia Gravis Severe muscle weakness rapid fatigue following exercise Develops in people of all ages Most common: women in 30s Risk of respiratory paralysis Autoimmune disorder body develops antibodies for ACh-R reduces synaptic transmission ~

    27. Myasthenia Gravis: Treatment AChE inhibitors Ż degradation of ACh narrow therapeutic window too much ACh ---> paralysis Reduce immune response remove thymus filtering antibodies from blood temporary ~

More Related