1.04 UTF-8 0 0 0 the thick filament of muscle is called what? 2 myosin 1 the thin filament of muscle is called.... 2 actin (+ troponin and tropomyosin) 1 what bundles the myosin units together 2 myomesin 1 what aligns the filaments attaching them to the Z line. This is a rigid protein. 2 nebulin 1 what stabilizes the sarcomeres by attaching the myosin to the z line. This is an elastic protein. 2 titin 1 what helps to anchor the thin filament to the Z line? 2 alph-actinin 1 what are the steps in the myosin cross-bridge cycle? 2 1) binding of actin to ADP and Pi release 2) Release of ADP=power stroke 3) ATP binding to Actin (release of Z line) 4) ATP hydrolysis (recovering stroke=actine and myosin bound with ADP+Pi) 1 what is the rate limiting step of the myosin cross-bridge cycle 2 in the heart hydrolysis is slow hydrolysis of ATP 1 what is the large storage pool of phosphate that can be used to regenerate ATP 2 creatine phosphate (a high energy phosphate) 1 what are the two sources of ATP? 2 Glycolysis (anaerobic with products of pyruvate and lactate) Citric Acid Cycle (aerobic with CO2 and H2O as products) 1 at rest Calcium concentrations are _________, but during activity they are ___________ 2 low high 1 what regulates contraction 2 calcium 1 what are the 3 domains of Troponin and what do they bind? 2 TnC--binds Calcium TnI--binds actin TnT--binds tropomyosin 1 when TnC binds Calcium it has ____________ affinity for the _____________ and the __________ releases actin 2 the effect is to move tropomyosin out of the way and maybe change actin conformation higher TnI TnI 1 contration contiues until.... 2 there is a drop in the free calcium concentrations 1 what is the name of the channel that releases Ca from the SR to the cytosol 2 Ryanodine receptor 1 what is the name of the channel that allows Ca into the cell 2 DHP sensitive Ca channels 1 what are three structures invovled in the regulation of Calcium 2 the membrane T tubules (invaginations of the membrane) sacroplasmic reticulum 1 the SR is composed of what two components? 2 longitudinal elements that form a network of tubes longitudinal elements end in the terminal cisternae 1 what is the sequence of events following an AP in the sarcolemma 2 invades T tubule activates DHPR Ca channel causes ST ca relase through RyR using CICR Ca binds Tn cross-bridge and contraction 1 what is the sequence of events in activation 2 depolarization increase in Ca increase in CaTn change in tropomiosin increase in cross bridges force 1 what are the passive forces in contraction 2 elastic elements such as titin keeping the structure of the sarcomere from lengthening. As well as CT and collagen which are external components. 1