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Conduction: Microanatomy and Physiology

The functional layers of the heart Endocardium (inner lining of heart), Epicardium (Outer lining of the heart), Myocardium (heart muscle)
Endocardium In contact with blood, simple squamous (endothelium), Valves and Ct are outgrowths of endocardium
Epicardium Contains blood vessels, simple squamous (mesothelium), also the same thing as visceral pericardium
Myocardium Cardiac muscle
Intercalated Discs allow for Coordinated heart contractions, connect cytoplasm of each cell to the cytoplasm of neighbors
Cardiac nuclei are located centrally
SA node is located in the Right atria
AV node is located in Septal wall of the right atrium
Purkinje cells appear as slightly transparent, large diameter cardiac myocytes in the endocardium
Mesothelial lining A serious layer that releases fluid to keep the heart from adhering to parietal pericardium
Annulus fibrosis A fibrous skeleton of connective tissue that insulates ventricles from the atria. Only depolarization from the AV node penetrates
___initiate the contraction of the heart Action potentials
Three areas of the heart that have automaticity (spontaneous depolarization) SA node, AV node, (some)Purkinje fibers
"Phase 4" is also known as the Slow diastolic depolarization
Outflow of potassium (Ik) is involved in Repolarization
"Funny channel" (If) is a inward sodium current when SA node cells have gone down to -60mV (resting minimum potential)
"Phase 4" is due to which ion current If or funny channel which is an influx of sodium
Calcium channels opening cause An influx of calcium which cause a rapid depolarization
Norepinephrine binding to Beta1 on the SA node causes Increase the function of If (funny channel) which increases rate of diastolic depolarization (Sympathetics)
M receptors binding with Acetylcholine in the SA node causes Increase in the potassium channel which decreases rate of diastolic depolarization (Parasympathetics)
Conduction rate in SA node .05 m/s
Conduction rate in atria 1 m/s
Conduction rate in AV node .01-.05 m/s
AV nodal conduction is dependent on on voltage-gated _____ channels Ltype-Calcium
Speed of conduction in Purkinje fibers 4-5 m/s
Created by: mcasto