heart pt.4 Flashcards
The period of one heartbeat and the beginning of the next. The heart consists of four pumps working in pairs. The atria pump together followed by the ventricles pumping together
cardiac cycle
all four chambers are relaxed (diastole; ventricles are passively refilling)
cardiac cycle begins. 1st
atria contract; finish filling ventricles
atrial systole. 2nd
continues until start of next cardiac cycle (through ventricular systole)
atrial diastole. 3rd
Contracting ventricles push AV valves closed but not enough pressure to open semilunar valves
ventricular systole first phase. 4th
no volume change and all valves closed. during first phase of ventricular systole
isovolumetric contraction
Increasing pressure opens semilunar valves; blood leaves ventricle. aka Ventricular ejection
ventricular systole second phase. 5th
Ventricles relax and their pressure drops; blood in aorta and pulmonary trunk backflows, closes semilunar valves
early ventricular diastole. 6th
All valves closed; no volume change; blood passively filling atria
isovolumetric relaxation. 7th
ventricles passively fill to 70%. all chambers relaxed. AV valves are open
late ventricular diastole. 8th (last step)
a prominent and distinctive feature of the pressure waveform in the central arteries (aortic elastic walls recoil)
dicrotic notch
first heart sound in cardiac cycle. occurs when ____ valves close. marks start of ventricular contraction
Lubb. AV
second heart sound in cardiac cycle. occurs when ______ close.
Dupp. semilunar
sound 3 is blood flowing into _____ and sound 4 is _____ contraction. these are very faint sounds. Rarely heard in adults
ventricles, atrial
The heart is controlled indirectly by signals from the brain and by hormones, mostly in form of adjusting
heart rate
each heartbeat begins with an action potential from this node. This is also known as the “pacemaker.”
sinoatrial (SA) node
Node located In posterior wall of right atrium, near superior vena cava
SA node aka pacemaker
conduct APs to atria as it continues toward the ventricles. transmits from SA node to AV node
internodal pathways
contains pacemaker cells, but does not generally affect heart rate. Can take over for SA if it fails, though it only generates beats at 40-60 a second.
atrioventricular (AV) node
Conducting cells transmit signal from AV node down through interventricular septum. Usually only electrical connection between atria & ventricles
AV bundle
stems off AV bundle. has right and left. ___ side is larger because left ventricle needs more. Conducting cells transmit signal to apex of heart, then spreading out in ventricular walls
bundle branches, left
ascends off bundle branches into ventricle wall. important role in cardiac conduction
purkinje fibers
This node stimulates the depolarization of atria immediately and contraction quickly follows. Impulse moves to AV node, where it delays the action potential for 100ms, allowing ventricles to fill. During the delay, atrial systole is occurring.
SA node
after AP reaches AV bundle, signal travels quickly through left and right bundle branches in the interventricular septum, reaching the Purkinje fibers located the ventricular wall. Causes depolarization and contraction of both ventricles almost simultaneously. Ventricular systole begins in the ____ of the heart and moves toward _____
apex, atria
Cardiac pacemaker cells have ______ resting membrane potentials. Slow ___ channels are open and __ channels are closed which causes gradual depolarization.
unstable, Na+, K+
