Electrical activity of the heart Flashcards
how is the action potential generated?
initiated through the movement of ions across a cell membrane.
how are cells normally charged?
cells are polarised, negative on outside, positive exterior
how does potassium move across the cell?
the cell membrane is permeable to potassium. it can diffuse into the cell [passive] or be removed via voltage gated ion pumps that require energy.
What is the role of catecholamines?
open the HCN channels faster
what is the role of acetylcholine?
to open the HCN channels slower
how is the generator potential created?
sodium diffuses into the cell via diffusion changing the cell from -60mV to -40mV. This causes the voltage gated channels to open.
what is the need for the plateau phase?
to prevent tetany in cases of recurrent stimuli and allow the heart to fill with blood.
What is the role of t tubules?
to allow the rapid movement of calcium into the cell.
what is the role of the AV node?
transmit the electrical impulse between the atrium and the ventricles. It delays this to allow the ventricles to fill by having small fibres and fewer gap junctions.
what is meant by automaticity?
the ability of the cell to spontaneously generate an action potential.
what is the effect of sympathetic stimulation?
increased heart rate,
increased force of contraction, increase cardiac output
what is the effect of parasympathetic stimulation?
decreases heart rate, decreases force of contraction, decreases cardiac output.
What is the main stimulant of sympathetic stimulation?
noradrenaline, which binds to Beta 1 adrenoreceptors.
How does noradrenaline increase cardiac output?
it binds with the type 1 beta adrenoreceptors which increase the enzyme adenyl cyclase which increase the amount of cAMP.
what is the main stimulant of parasympathetic stimulisation?
acetylcholine which bind to M2 receptors.
