Control of Heart Rate and the Cardiac Cycle Flashcards
Tachycardia
increased heart rate
increased activity of sympathetic nerve
bradycardia
decreased heart rate
increased activity of parasympathetic nerve
chronotropic effect and how it works
changes in heart rate
changes the slope of pacemaker potential
what is cardiac output and how is it calculated
the volume of blood pumped by EACH ventricle per minute
CO = HR x SV
how is stroke volume calculated
typical values
end diastolic volume - end systolic volume = SV
135 - 65 = 70 ml
which nerve supplies parasympathetic action to the heart
Vagus
what effect does acetylcholine have at the heart
inhibitory
what effect does noradrenaline have at the heart
stimulatory
how does parasympathetic stimulation on the SA node decrease HR
causes hyperpolarisation (longer to reach AP threshold)
increases K+ permeability
effects of parasympathetic stimulation of the heart
decreased AV node excitability ( HR decreases)
shortened plateau phase of atrial contractile cells (time between atrial and ventricular contraction increased)
which chambers of the heart are effected by parasympathetic stimulation
atria only
how does sympathetic stimulation of the SA node increase HR
causes opening of funny channels and transient Ca2+ channels
effects of sympathetic stimulation of the heart
reduced AV delay
increased electrical conduction within the heart
speeds up relaxation
which chambers of the heart are effected by sympathetic stimulation
atria and ventricles
max heart rate calculation
220 - age
