Physiology Flashcards
how does digoxin affect heart contractility
inhibits Na/K pump which increases intracellular Na – > decreasing Na/Ca pump = increase intracellular Ca
Laplace law
wall tension = pressure x radius
wall stress = pressure x radius / 2x wall thickness
mid-late diastolic murmur
mitral stenosis
early disatolic murmur
aortic regurgitation
continuous machinery murmur
patent ductus arteriosus
ejection systolic murmur
aortic stenosis
holoystolic high pitched ‘blowing’ murmur
mitral/tricuspid regurgitation
late crescendo murmur with midsystolic click
mitral valve prolapse
holosystolic, harsh sounding murmur
Ventricular septal defect
Phase 0 of cardiac cell cycle
phase - rapid depolarisation as voltage gated Na channels open
phase 1 of cardiac action potential
initial replarisation - inactivation of voltage gated Na channels. voltage gated K channels begin to open
phase 2 of cardiac action potential
plateau due to influx of Ca which balances K efflux. Ca influx triggers Ca release from sarcoplasmic reticulum and myocyte contraction
phase 3 of cardiac action potential
rapid repolarisation - massive k efflux through opening of voltage gated slow delayed-rectifier K channels and closure of voltage gated ca channels
phase 4 of cardiac action potential
resting potential, high K permeability through K channels
main differences in pacemaker action potential to myocardial action potential
pacemaker action potential occurs in SA and AV node
phases 1 and 2 are absent
phase 0 - due to opening of voltage gated Ca channels as K channels permenantly inactivated
phase 3 due to inactivation of Ca channels and activation of K channels
phase 4 due to slow spontaneous depoarisation of If funny current channels.