cardiac physiology Flashcards
is the resting membrane potential negative or positive
negative
what functional response does an action potential cause
nerve impulse or muscle contraction
what is an action potential generated by
rapid changes in electrochemical gradients across the cell membrane like movement of ions
what is the movement of ions in and out of the cell controlled by
specific ion channels embedded in the membrane
name the 3 ions involved in membrane potential
K+, Na+, Ca2+
what is depolarisation
membrane potential gets less negative
what is depolarisation in muscles
membrane potential goes positive
what is repolarisation
potential returns to negative resting potential
what is hyperpolarisation
membrane potential becomes more negative than resting potential
how to detect and monitor action potentials generated by myocytes
electrocardiogram (ECG)
what is excitation-contraction coupling and how is it achieved
-process which an electrical action potential leads to cardiac muscle cells contracting
-achieved by converting a chemical signal into mechanical energy via contractile proteins
what is contraction of actin and myosin filaments dependent on
calcium signalling
what do gap junctions do
link cytoplasm of neighbouring cells and enable rapid passage of ions/small molecules
structural features of myocardium that help membrane potential changes
intercalated discs- tight interactions, electrical coupling, branched to extend interconnections, single nucleus, lots of mitochondria
synchronised contractions- ensures cardiomyocytes work together, syncytium cardiac muscle
gap junctions- enable rapid passage of ions/small molecules
how do intercalated discs facilitate membrane potential changes
enable tight interactions and help electrical coupling, branched fibres to extend interconnections, single nucleus, abundance of mitochondria
describe the pathway of intrinsic waves of excitation
SA node to AV node to myocytes to bundle of His and purkinje fibres
which node is also called the cardiac pacemaker
sinoatrial node
what does the AV node do after receiving signals from the SA node
passes signals to bundle of His, depolarises both ventricles, branches out
how does the sinoatrial node cause an action potential
excites the right atrium then the left atrium then the atrioventricular node
autorhythmic cells are also called
pacemaker cells
what controls sinoatrial activity
autonomic nervous system signals
what does the influx of K+ cause
repolarisation
what does the influx of CA2+ cause
depolarisation of SAN
what does the influx of Na+ cause
depolarisation of cardiomyocytes
describe the action potential in autorhythmic/pacemaker cells
-no external stimulation to initiate action potential, undergoes spontaneous depolarisation when threshold is met
1.slow depolarisation caused by Na+ leaving cell faster than K+ through If channels
2.CA2+ channels open as membrane approaches threshold, causes more rapid depolarisation
3.K+ channels open causing efflux of K+ and membrane repolarises
describe the general shape of the graph of action potential of pacemaker cells and list the stages
slow depolarisation, action potential, repolarisation
graph-see notes
what does efflux mean
movement out of cell
describe the action potential of cardiomyocytes (contractile system)
resting phase- resting potential (-90mV) due to constant leak of K+, sodium and calcium channels closed
depolarisation- NA+ channels open and ions enter, depolarises inside cell (cell gets more positive inside), causes action potential
early repolarisation- cell is slightly positive, outward flow of K+ returns transmembrane potential to 0
plateau phase- K+ leave cell via delayed rectifier K+ channels, CA2+ go in cell, electrically balanced, tmp maintained at a plateau below 0 mV (refractory period)
repolarisation- CA2+ channels inactivated (no more going in cell), more K+ leaving cell so cell gets more negative
describe the general shape of the graph of action potential of cardiomyocytes and list the stages
resting, depolarisation, early repolarisation, plateau, repolarisation
graph- see notes
