The Heart Flashcards
what is an echocardiogram?
an ultrasound of the heart
what is the right AV valve called?
tricuspid
what is the left AV valve called?
mitral valve
what are the stages of the cardiac cycle?
atrial systole
atrial diastole
ventricular systole - first phase
ventricular systole - second phase
ventricular diastole - early
ventricular diastole - late
what happens during atrial systole
atria are full of blood
atrial contraction forces blood into ventricles
what happens during ventricular systole?
muscle of ventricle starts to contract, shuts AV valves, pressure still building in the ventricle. when contraction is advanced enough to high pressure then the valves will open and ventricles eject blood
what happens during ventricular diastole?
ventricular cells stop contracting and relax, pressure in ventricles decrease and blood starts to flow back which catches in SL valves and forces them closed. blood flows into relaxed atria
what happens during the late phase of ventricular diastole?
all chambers are relaxed. ventricles fill passively. return to atrial systole and filling of atrium.
what is inotropy?
contractile capability of the heart muscle itself, conditions can affect it
how can blood pressure be calculated?
cardiac output x peripheral vascular resistance
what is peripheral vascular resistance?
how distesible arterial circulation is
what are cardiac muscle cells like?
large long thin cells, act with striations and packed with contractile units and lots of mitochondria, joined by intercalated discs
what are the powerhouse of the cardiac muscle cells?
contractile filaments
myosin and actin
how are the myocardial cells arranged within the heart?
fibres of myocytes are lined up in one direction, sheets then wrapped around the heart so that when it contracts there is an efficient movement
what is the action potential?
the dynamic signal that is sent between cardiac myocyte cells to signal for contraction
what is membrane potential?
determined by ion conc inside vs outside the cell
generally about -80mV
what is it called when positive molecules make their way inside the cell?
depolarisation
what is it called when positive molecules travel back outside of the cell?
repolarization
where are potassium ion conc higher?
intracellularly
where are Ca ions higher?
extracellularly
where are Na conc higher?
extracellularly
what are potassium currents?
repolarizing
what are sodium and Ca currents?
depolarising
what happens during an action potential?
sequential activation and inactivation of inward (Na+ and Ca2+) and outwards (K+) currents
what are the phases of a cardiac action potential?
upstroke
notch
plateau
repolairsation
resting
what happens during upstroke?
1st stage, opening of voltage gated Na+ channels allows inwards flow
what happens during notch phase ?
rapid voltage dependent inactivation of sodium current, activation of depolarising outwards K current
what happens during the plate phase?
activation of further K currents
inwards Ca current
plateau of action potential
what happens during depolarisation stage?
calcium current switches off as Ca conc inside cell rise
outward K currents predominate and cell returns to resting potential
where in the heart is there never a resting potential?
SA node, constant cycle of depolarisation and depolarisation
sometimes AV node which is constantly active
what is the hierarchy of pacemakers?
SAN - 70bpm
AVN - 50 bpm
purkinje cell - 30bpm
what is the activity of the myofilaments deoendent on?
Ca concentrations intracellularly
what happens during excitation contraction coupling?
membrane depolarisation
activation of L type Ca channels
inwards movement of Ca
Ca induced Ca release
Ca binds to myofilaments initiating contraction
relaxation
return to resting Ca levels
what are the grooves within the membrane of the cell called?
T tubules,
what are inside the T tubules?
packed with L type calcium channels
what is the sarcoplasmic reticulum?
intracellular store of Ca
packed full of calcium
release is mediated by reanidane receptor
opens and pours calcium inside the cell
what happens during calcium induced calcium release?
calcium released into the cell from the L type current which is picked up by ranodeine receptor, opens up and pours calcium into the cell.
calcium entry into the cell from L type calcium channels produces a massive amount of calcium release form intracellular stores.
what happens during relaxation stage of excitation-contraction coupling?
after depolarisation of action potential
pump of sarcoplasmic reticulum pumps Ca back into the stores
extrusion of Ca on pump and exchanger so that calcium that entered cell from the L channel leaves
what does the route of the left coronary artery look like?
splits into two main branches
anterior descending comes down the front of the heart and wraps over round the apex of the left ventricle
circumflex artery circles around the base of the heart at the AV margin and travels round that margin and wraps round the back of the heart to share supply of the posterior surface with the right coronary artery territory
where do the coronary arteries arise from?
the base of the aorta, just above the SL valve cusps
main origins are form the right and the left
what does the route of the right coronary artery look like?
comes down towards inferior surface if heart and supplies branches around the inferior posterior surface
how do the coronary veins generally run?
with the coronary arteries
where do all the coronary veins drain into?
coronary sinus
where does the coronary sinus drain into?
right atrium
when is the window for coronary arterial flow?
during the diastolic phase
allows perfusion of the ventricular muscle
when could coronary flow to the heart be limited?
when diastolic pressure is low
ventricular end diastolic pressure is high
where does the right side of the heart lie?
underneath the sternum
what is the inferior border of the heart largely made up of?
the right ventricle
where do we listen for the aortic valve?
right sternal edge
2nd - 3rd left interspace
where do we listen to the pulmonary valve?
similar level on the sternal edge
2nd - 3rd level
where do we listen to the tricuspid valve?
left sternal border down towards apical level of heart
4th - 5th interspace
where do we listen to the mitral valve?
apical impulse of the heart
in the midclavicular line
what does blood pressure measure?
difference in systolic and diastolic pressure in the aorta and arterial circulation
what is the JVP?
what atrial pressure is
what does cardio myopathy?
disease of the heart muscle
which pair of ribs are the false ribs?
8-10
what causes the initial depolarisation of the Sino-atrial node?
calcium entry into the cells via voltage gated calcium channels
In which phase of the cardiac cycle do the aortic and pulmonary valves open?
ventricular ejection
in which part of the cardiac cycle are all of the heart valves closed?
early ventricular systole
What type of cell junction allows the electrical signal to pass between cells in cardiac muscle?
gap junctions
What is the physiological reason for splitting of the 2nd heart sound?
During inspiration the pulmonary valve closes later and the aortic valve closes earlier
Which vein can act as an alternative route for blood to the heart if either superior vena cava or inferior vena cava are occluded?
azygous
