Lec 22 - Heart 2 Flashcards
Which component of the conduction system is known as the “pacemaker” of the heart?
SA node [sinoatrial node]
where is the SA node located? what is its purpose?
located in the posterior wall of right atrium
initiates heartbeat
where is the AV node located and what is its function?
medial of inferior atrium
receives message from SA node located in right atrium. sends message to AV bundle.
where is the atrioventricular bundle His found, and what is its function.
“tract” or collection of conduction fibers located in the interventricular septum
transmits message to Purkinje fibers
where are the purkinje fibers found and what is its function?
located in walls of ventricles
conduct impulse to myocardium
results in ventricular contraction (excites ventricles)
what is the purpose of the conduction system?
To stimulate cardiac muscle fibers to contract without the need for direct stimulus from the nervous system.
which node does sympathetic stimulation act on?
SA node.
what hormone does sympathetic stimulation release?
norepinephrine
what hormone does parasympathetic stimulation release?
acetylcholine
what does a cardiac cycle refer to?
a complete heartbeat.
which node initiates each cardiac cycle?
SA node
as the atria contracts, what occurs?
they simultaneously force blood into both ventricles
what is the systole?
"lubb" ventricles CONTRACT AV VALVES close Blood is ejected from the heart. Blood in right ventricle exits through the pulmonary arteries while that in the left ventricle leaves through the aorta.
what is the diastole?
"dubb" the ventricles RELAX SEMILUNAR VALVES close av valves OPEN Blood has filled the atria which are awaiting the signal from the SA node to begin the next cardiac cycle
appx how many times per minute does the cardiac cycle occur?
70 times per min
