1 / 31

Muscle Anatomy and Physiology

Muscle Anatomy and Physiology The Neuromuscular Junction / Motor Unit Anatomy: Max=>Min Muscle, fasciculus, fiber, fibrils, filaments Epimysium, perimysium, endomysium “Bundles within bundles” Contractile units: SARCOMERES Thin: actin, troponin, tropomysim Thick : myosin

omer
Download Presentation

Muscle Anatomy and 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 and Physiology The Neuromuscular Junction / Motor Unit

  2. Anatomy: Max=>Min • Muscle, fasciculus, fiber, fibrils, filaments • Epimysium, perimysium, endomysium • “Bundles within bundles”

  3. Contractile units:SARCOMERES • Thin: actin, troponin, tropomysim • Thick: myosin • Z-lines, A-band, I-band, H-Zone

  4. Motor Units • Motor Neuron + Muscle fiber(s) • TERMS: • Twitch: Single contraction & relaxation of a motor unit • Tetanus: Sustained contraction by summing “twitches” • Recruitment: Smooth moves – How many units needed?

  5. How Many Units? • The number of Motor Units recruited for a task depends on: 1. Demand 2. Duration

  6. Excitation - Contraction Coupling • Pre-Synaptic Terminal (Nerve): Acetylcholine released • Post-Synaptic Terminal (Motor Endplate): Ach stimulates by binding =>Muscle fiber depolarization • Contraction!

  7. Excitation: • Resting Membrane Potential: Membranes separate charges: Polarized • Depolarization: Charge reversal across membrane

  8. Action Potential (AP) Depolarization travels along membrane AP travels along sarcolemma=> T-tubules => sarcoplasmic reticulum => Terminal Cisternae => Calcium released

  9. Sarcomeres Shorten HOW????

  10. Sliding Filament Theory • The Action Potential reaches the Terminal Cisternae • Calcium released binds to Troponin • Tropomysin “moves” out of the way • Myosin-Actin Crossbridges formed

  11. Contraction: • All-or-None “Twitch” • Sarcomere units shorten by thin and thick filaments “sliding” past each other

  12. The Physiology of Muscle Contraction and ATP

  13. Take “Five”: Draw and Label The Neuromuscular Junction: Page 158 *What is the chemical Neurotransmitter?

  14. One More Visit to that Neuromuscular Junction: • Acetylcholine released • Binds with Ach-Receptors – linked to Na+ Channels • Na+ influx – DEPOLARIZES Motor endplate • Causing an ACTION POTENTIAL • Etc. Etc. Etc.

  15. What Happens to the Acetylcholine? • Good Question Sherlock: • Homework: • Describe the fate of Acetylcholine • Think diabolically of poisons that could interfere with the normal function of the neuromuscular junction…

  16. Toxins: Neuromuscular Junction • Affecting Production, Release, Binding or degradation of Acetylcholine • Nerve Gas: Inhibit degradation • Black Widow Toxin: Massive release of Acetylcholine • Botulism: Inhibits Acetylcholine Release

  17. Death by Sarin: Acetylcholine accumulates in NMJ • Runny nose, eyes, drooling, sweating, • Difficulty breathing, tight chest • Nausea, vomiting, loss of “control” • Twitching, jerking, staggering • Headache, confusion, coma and convulsions

  18. Something Lighter Please • Check out this cool site for specific exercises! • http://www.exrx.net/Lists/Directory.html

  19. Muscle Energetics

  20. Where Does All That ATP Come From? • Energy for work is supplied by the breakdown of “FUELS” • FUELS: CHO, FAT, (PROT) • Glucose is preferred for intense work • Fats are the “slow burners” and use lots of Oxygen

  21. Energetics of Contraction - Continues • ATP-PC: fast, limited • Anaerobic Glycolysis: Cytosolic breakdown of Glucose without O2 – Forms Lactic Acid • Aerobic Oxidation: slow,but plentiful supply of ATP

  22. All Three Contribute APT at All times… • Supply Rate and Demand Rates • ATP-PC: Fastest Rate – 10 seconds max • Anaerobic Glycolysis: 2-5 minutes max • Aerobic (Oxidative Phosphorylation): Slowest rate, almost endless capacity

  23. The Marathon: • Hours of exercise possible • Uses ATP from aerobic (oxidative) sources • Oxygen Delivery!

  24. The Half-Mile…or: • More Intense • Bursts Lasting 2-5 minutes with rests • Using Anaerobic Glycolysis • Lactic Acid Buildup

  25. The Sprints and Jumps • Less than 10 seconds duration • Very Intense • Creatine Stores in Muscles contribute to CP-ATP production

  26. Creatine Phosphate: • Increase ATP-PC contribution of energy • Used in Maximum intensity-short term work • May extend work effort a few seconds…or repititions • Useless without training…

  27. One Last Crazy “Engebretsen Simulation” • 5 Volunteers to be the “Motor Neuron” • 1 Volunteer to be “Post-Synaptic Membrane” • 6 Sarcolemma-Triad volunteers • 2 Terminal Cisternae volunteers • The rest are sarcolemmas joining hands 

  28. Muscle Fatigue: • More Complicated than you think: • ATP depletion very rare: usually seen with max efforts - cramps • Lactic ACIDOSIS slows all functions • Psychological fatigue…Central perception of exhaustion

  29. II Myosin Fast, Force, Fatigue “White”: Glycogen Anaerobic Bigger I Myosin Slow, Endure “Red”: Myoglobin, mitochondria, Aerobic Smaller Muscle Fiber Types: Fast (II, IIa) vs Slow (I)

  30. We Made It!

More Related