what does the intrinsic conduction system consist of
autorythmic cardiac cells
what do autorythmic cardiac cells do
initiate and distribute impulses throughout the heart
mass of autorythmic cells located in the right atrial wall near the entrance of the superior vena cava
SA node
mass of autorhythmic cells located in the inferior portion of the internal septum abouve the tricuspid valve
AV node
autorhythmic cells located in the inferior part of the interatrial septum the only electrical connection between atria and ventricles
AV bundle
Two branches resulting from a splitting of the AV bundle conveys impulses down the interventricular septum
Bundle Branches
Fibers that run through the interventricular septum, penetrate the heart apex, turn superiorly and ramify in the ventricular walls
Purkinje fibers
what does the P wave represent
atrial depolorization
what does the QRS complex represent
ventricular polorization
the doe the T wave represent
ventricular repolorization
tracing on an ECG that results from the movement of the depolorization wave from SA node through Atria. it lasts about 0.08 Secs. atrial contraction follows
P wave
Tracing on an ECG that results from the ventricular depolorization. Atrial repolorization also occurs during this time. Lasts about 0.08 sec ventricular contraction follows
QRS complex
Tracing on an ECG caused by ventricular repolorization. It lasts about 0.10 secs ventricular relaxation follows
T wave
what does the cardiac cycle include
all the events related to the flow of blood through the heart during one complete beat
what do heart valves do in response to differences in pressure on thier two sides
open and close
what are the 3 phases of the cardiac cycle
ventricular filing
ventricular systole
isoventricular relaxation
describe the flow of blood into the atria at the start of ventricullar filling
are the valves open or closed at this point
blood flows passivly into the atria through open AV valves
open
where does the blood go after it passes the AV valve
at this point is the pressure higher or lower in the ventricles
ventricles
lower
what happens when the atria contract
force remaining blood into ventricles
what happens to interventricular pressure when the ventricles contract
intraventricular pressure rises
what happens to the AV valves when the ventricles contract
they close
what does rising ventricular pressure open
semi-lunar valves
what happens when semi lunar valves are forced open
blood is ejected from the heart
what happens during isovolumetric relaxation
ventricles relax and ventricular pressure drops
what does blood do during isovolumetric relaxation
backflows
what happens to the semilunar valves during isovolumetric relaxation
they close
describe the ventricles after the semilunar valves close during isovolumetric relaxation
totally closed off
what have the atria been doing while the ventricles have been contracting and relaxing during isovolumetric relaxation
filling with blood
what happens to the AV valves when atrial pressure exceeds ventricular pressure
open
describe the contraction of the atria
both contract at the same time
describe the contraction of the ventricles
both contract at the same time
what do pressure changes reflect
alternating contraction and relaxationof the heart
what does blood move along
pressure gradient
describe the pressure gradient blood moves along
higher to lower gradient through any available opening
what do pressure changes cause
valves to open and close
what does the opening and closing of the heart valves result in
keeps blood flowing in forward direction
what is cardiac output
the amount of blood pumped out by each ventricle in one minute
what 2 variable is cardiac output related to
heart rate
stroke volume
what si the equation for cardiac output
CO=HR X SV
what is heart rate
number of times heart beats in one minute
what is the average heart rate
75BPM
what is stroke volume
amount of blood pumped by each ventricle w each heart beat
what is the average stroke volume
70 ml per beat
what is stroke volume
represents the difference between end diastolic volume and systolic volume
what is the equation for stroke volume
SV = EDV - ESV
what is the equation for stroke volume using average values
70 ml/beat = 120 ml/beat - 50 ml/beat
what is end diastolic volume (EDV)
amount of blood remaining in each ventricle at the end of diastolic relaxation
what is end systolic volume (ESV)
amount of blood remaining in each ventricle at the end of systole