Electrical activity in the heart Flashcards
define automaticity
cells that can spontaneously generate action potentials
what is AVN
route where action potential can pass from atrium to ventricles
- electricity can only pass through here (insulation)
what is SAN
most excitable cells in the heart
- cells become depolarised
- they have the least negative RMP
- have the largest pacemaker current
- threshold is the most negative (-30mV)
what is the pacemaker current
time it takes to go from resting potential to action potential
what do all excitable cells have
all excitable cells have a refractory period
what is a refractory period
period during which cell can’t be excited again
describe how fast electrical events are in comparison to mechanical events
electrical events are faster than mechanical events
why are action potentials different
because there are different ion channels in the membranes of these cells
give an example of a pacemaker and what it is targeted by
- cyclic nucleotide gated channel
- targeted by Ivabradine (used for treatment of angina)
- allows Na+ ions into cell
what is the role of verapamil and diltiazem
- block L type ca2+ current
2. verapamil reduces cardiac output
what is the range of intracellular and extracellular Na
Extracellular= 135-145mM intracellular= 5mM
what is the range of intracellular and extracellular Ca2+
extracellular= 2mM Intracellular= 1um
what is the range of intracellular and extracellular K+
Extracellular= 3.5-5mM Intracellular= 140mM
what do gap junctions allow and what are the proteins involved
gap junctions allow electricity/action potential to pass through
- connexins are the proteins that form gap junctions
what is an electrocardiogram
measures changes in the membrane potential of cells in the heart
- doesn’t measure mechanical changes
