1 / 13

Skeletal Muscle Physiology cont.

Skeletal Muscle Physiology cont. . Diagram the chemical and mechanical steps in the cross-bridge cycle and explain the effect on the muscle fiber length. Describe the end of contraction mechanisms. Muscle excitation and energy sources. Three roles of ATP in muscle function.

mariel
Download Presentation

Skeletal Muscle Physiology cont.

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. Skeletal Muscle Physiology cont. • Diagram the chemical and mechanical steps in the cross-bridge cycle and explain the effect on the muscle fiber length. Describe the end of contraction mechanisms. Muscle excitation and energy sources. • Three roles of ATP in muscle function. • Three sources of ATP for muscle function.

  2. Sliding myofilaments shorten sarcomeres

  3. Excitation -contraction coupling • ACh binds to, opens nicotinic Na+/K+channels • Muscle depolarizes • Ca2+ released from sarcoplasmic reticulum • Ca2+ binds to troponin, cross-bridge cycling between actin & myosin begins, filaments slide

  4. http://www.sci.sdsu.edu/movies/actin_myosin_gif.html

  5. Draw and label a diagram to show the following stage of the cross-bridge cycle: At rest, when the muscle is not stimulated.

  6. Skeletal Muscle Physiology cont. • Diagram the chemical and mechanical steps in the cross-bridge cycle and explain the effect on the muscle fiber length. Describe the end of contraction mechanisms. Muscle excitation and energy sources. • Three roles of ATP in muscle function. • Three sources of ATP for muscle function.

  7. End of contraction • ACh destroyed by ACh-esterase in synapse • Muscle repolarizes • Ca2+ returned to SR by Ca2+ active transporter • ATP hydrolysis (+Mg) reextends myosin head • Muscle elastic elements recoil, muscle returns to resting length. Titin is the largest polypeptide known (34,350 amino acids in length). It spans from the M to Z lines.

  8. Draw and label a diagram to show the following stage of the cross-bridge cycle: 2. At death when the muscle has depleted ATP. (rigor)

  9. Genetic mutationturns tot into superboy4-year-old is first documentedhuman case, scientists sayA German boy, seen here at seven-months old, has a genetic mutation that boosts muscle growth.

  10. Excitation-Contraction Coupling • action potentials, generated at neuromuscular junction travel around sarcolemma and through T-tubules • T-tubules signal SR to release Ca2+ into sarcoplasm (cytosol) • Ca2+ saturates troponin (in non-fatigued state) • troponin undergoes conformational change that lifts tropomyosin away from actin filament

  11. E-C Coupling (cont.) • myosin head attaches to active site on actin filament forming cross-bridge • after forming cross-bridge, myosin head moves actin-myosin complex forward and ADP and Pi are released • ATP binds with myosin head, which releases actin, and returns to original position • in resting state, myosin head contains partially hydrolyzed ATP (ADP and Pi)

  12. E-C Coupling (cont.) • entire cycle takes ~50 ms although myosin heads are attached for ~2 ms • a single cross-bridge shortens 10 nm • as long as action potentials continue, Ca2+ will continue to be released • when action potentials cease, SR Ca2+ pumps return Ca2+ ceasing contractions • skeletal motor units follow “all or nothing” principle

More Related