Sympathetic Regulation of Cardiac Rate and Force Flashcards
What is a positive dromotropic effect?
increases AV nodal conduction velocity
What is a positive inotropic effect?
increases contractility
What is the benefit of decreasing the duration of systole?
heart has time to refill - incomplete relaxation decreases SV
What is a positive chronotropic effect?
increases HR
What is a positive lusitropic effect?
decreases duration of systole
How does the sympathetic stimulation increase cAMP?
noradrenaline activates beta 1 adrenoceptors - coupling through Gs protein - activates adenylyl cyclase - increases cAMP
How does sympathetic stimulation increase AV node conduction velocity?
increased funny current and Ca2+ influx
What are the effects of sympathetic stimulation?
positive chronotropic effect (increased HR), positive inotropic effect (increased contractility), positive dromotropic effect (increased AV nodal conduction velocity), increased automaticity, positive lusitropic action ( decreased duration of systole), increases activity of Na+/K+ ATPase, cardiac hypertrophy (long term)
How does sympathetic stimulation increase HR?
increases funny current and Ca2+ influx - increases slope of pacemaker potential, increase Ca2+ influx - decreases threshold
How does sympathetic stimulation increase contractility?
increases phase 2 - increases Ca2+ influx - increases Ca2+ release from the sarcoplasmic reticulum
What happens if the activity of Na+/K+ ATPase is increased?
increases the rate of repolarisation
What receptors does the sympathetic system stimulate in the heart?
beta 1 adrenoceptors
What is increased automaticity?
increased tendency for non-nodal regions to acquire spontaneous activity
