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2.28- cardiovascular physiology 21.Since cardiac muscle is a hybrid between skeletal and smooth muscle, the actual mechanism ofcontraction is a hybrid between skeletal and smooth muscle2.on the 1stslide of the PPT, exchange the order of 7 and 8 because it takes the removal of calcium fromthe cytoplasm in order for relaxation to occura.FROM THE SLIDE- CONTRACTION &RELAXATION INTHE RIGHT ORDERi.1. Action potential enters from adjacent cellii.2. Voltage gated calcium channels open.Calcium enters the celliii.3. Calcium induces calcium release through ryanodine receptor channelsiv.4. Local release causes calcium spark(s)v.5. Summed calcium sparks create a calcium signalvi.6. Calcium ions bind to troponin to initiate a contractionvii.7. Calcium is pumped back into the SR for storageviii.8. Relaxation occurs when calcium unbinds from troponinix.9. Calcium is exchanged with sodiumx.10. Sodium gradient is maintained by the sodium potassium ATPase3.1stthing that happens is the action potentialtravels to the muscle membrane and then it hitsthe t tubule which then opens up a voltage gatedcalcium channela.So then you get an inward calcium currenti.Remember that an inwarddirected calcium current helpsmaintain the plateau ofdepolarizationthat makes theaction potential have this longextended refractory period. Soelectrically calcium helps toprolong the state ofdepolarization.b.It ALSO initiates the contraction similar tohow it does it in smooth muscle:CICR:calcium interacts with ryanodine receptoron the SR membrane, activates and opens the Ryr and induces calcium release from the SRc.The calcium from the extracellular and the calcium from the SR are individually called theCALCIUM SPARKS but when they are ADDED TOGETHER they are calledthe CALCIUM SIGNALi.This signal is strong enough to initiate a contraction that is very similar to whathappens in skeletal muscleii.Ca binds to troponin, unmasks the binding sites on the actin, allowing actin and myosinto form cross bridges. iT also activates the myosin ATPase and allows for the powerstroked.Relaxation occurs when calcium is cleared from the cytoplasmi.It is done in 2 ways1.Traditional way= SERCA= calcium pump that pumps calcium back up into the SR2.and by the calcium sodium exchanger in the cardiac muscle membranes whichexchanges 1 calcium out of the sarcomere for 3 sodium in=ANTIPORTERii.these 2 mechanisms reduce the level of calcium inside the cardiac __ cytoplasm, causingthe cross bridges to break and relaxation to occur
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/Human-Physiology-From-Cells-to-Systems-9th-Edition-9781285866932-627/
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Chapter 14 / Exercise 17
Human Physiology: From Cells to Systems
Sherwood
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iii.the sodium is cleared bySodium-Potassium ATPase1.at this point the muscle is ready to contract again4.AP PROPAGATION across the hearta.The pacemaker is theSA node= sinoatrial nodei.It generates AP spontaneously because of this funny sodium current that slowlydepolarizes the membrane to threshold.

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Term
Fall
Professor
Wit
Tags
Physiology, AP, i, cross sectional area
We have textbook solutions for you!
The document you are viewing contains questions related to this textbook.
Human Physiology: From Cells to Systems
The document you are viewing contains questions related to this textbook.
Chapter 14 / Exercise 17
Human Physiology: From Cells to Systems
Sherwood
Expert Verified

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