Fundamentals of Physiology - Muscles are Excitable Cells | BMS 360, Study notes of Biology

Download Fundamentals of Physiology - Muscles are Excitable Cells | BMS 360 and more Study notes Biology in PDF only on Docsity! 14 February Muscles are excitable cells Can generate action potentials Figure 9.1A Muscle fiber has multiple nuclei Myoblasts fuse → one fiber Striations on skeletal muscle Figure 9.2 Fiber contains myofibrils – contracting unit Fiber connected to tendon on each end Basic unit Between 2 Z lines (discs) H zone in center Titin filaments bind to Z line and myosin Thick filament – myosin Thin filament – actin (w/ troponin, tropomyosin) Figure 9.6 Actin anchored at one end on Z line Myosin has arms that grab actin Actin strands pulled toward center Figure 9.9 Relaxed state Low levels of Ca++ Myosin heads energized but cannot bind Tropomyosin blocking, held by troponin Activated state High levels of Ca++ Binds to troponin, tropomyosin moves out of the way Myosin binds Figure 9.8 Energized myosin head – ADP bound Myosin binds → ADP release → arm moves ATP binds to myosin head → release from actin Death – no ATP production Crossbridges stuck Rigor mortis Figure 9.11 Pores on fiber membrane allow access into transverse tubules Sarcoplasmic reticulum has swellings – lateral sacs Figure 9.12 Depolarizing signal travels into transverse tubules