BMS 300 1st edition Lecture 30 Outline of Last Lecture I. Coronary vasculature and cardio myocytes -coronary arteries -capillaries -cardial sinus-right atrium II. Source of cardial circulation -coronary arteries at the base of aorta -source of pressure 1. Aortic pressure during diastole 2. why not systoleIII. Cardiomyoctes -generic cardiomyocte 1. uninucleate2. intercalated disks >desmosomes>gap junctions -types 1. contractile These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.2. conductile IV. Contractile Structure -sarcomeres -EC couplings Outline of Current Lecture V. Cardiomyocyte structure and function -cardiomyocyte type 1. conductile >deliver electric signal to contractile cells >set rate and rhythm 2. contractile >generate force >sarcomere shorteningVI. Structure of cardiomyocytes -intercalated disks -gap junctions VII. Electrical signaling -conductile1. HCN channels (generator potential) 2. v-gated Ca2+ channels 3. v-gated K+ channels -contractile1. v-gated Na+ 2. v-gated Ca2+3. v-gated K+-membrane structure of contractile cells 1. T-SR junction 2. Ca2+ induced Ca2+ releaseCurrent LectureCardiomyocytes-contractile cardiomyocytes: comprise the myocardium of the atria and ventricles >generate force by sarcomere shortening >99% of cardiomyocytes-conductile cardiomyocytes: to carry/propagate electrical signals from sites of signal initiation to the contractile cells >without these you can’t generate a heartbeat or a contraction -your heart can’t function without both of them the two have to work in concert with each other -conductile cardiomyocytes largely lack contractile machinery >specialized ion channels -they both contain a single nucleus, they are fairly small, and fairly similar-the two are interdigitated with each other at the site known as the intercalated disk-the plasma membranes of the two never fuse, they are always separate but in the disks there are gap junctions -these gap junctions (as communicating junctions) provide electrical continuity-there are also desmosomes (anchoring junctions) not as important in the conductile cells-the conductile cardiomyocytes are not randomly distributed throughout Conductile system-using the same image that we have used for the past few lectures of the drawing of the heart -there’s a wall that separates the left and right ventricles from each other called the septum-the other piece is that the only connection between the atria and ventricles is through the atria ventricular valves-there’s a connective tissue layer that isolates the atrial myocardium from the ventricularmyocardium -all of them will be connected together but there are separate electrical pathways that are only connected by the conductile system -on the outside wall of the right atrium is a structure known as the sinoatrial node (SA node) >cluster of conductile cardiomyosins -we will find that reaching out from the cluster are pathways of connected conductile cells -if you look at the surface of the right atrium you will see clusters of the SA nodes and there’s a linkage that goes over to the left atrium -once we get down on the wall of the ventricular myocardium there is a structure knownas the atrial ventricular node -there is also a bundle of his which is a common bundle that comes out of the AV node which splits into two branches the left and the right bundle branch -these bundle branches then branches further and they are called purkinje fibers which play the role of delivering action potentials to contractile cardiomyocytes **the conductile cells on the atria will deliver an electrical signal to the contractile cells on the atriaChannel types of the conductile cardiomyocytes1. HCN channel >H: hyperpolarization cyclic nucleotide gated channel >channel opening requires hyperpolarization >it must bind cytoplasmic cyclic AMP (cAMP)>the HCN channel has a sodium ion channel that’s permeable to sodium and in addition it has a cAMP binding site
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