BIO 241 1st Edition Lecture 6 Outline of Last Lecture I Coronary circulation the arteries II Coronary circulation the veins III Conduction system and pacemakers IV Conduction system components V Timing of conduction events VI Electrocardiogram ECG or EKG Outline of Current Lecture II Cardiac cycle 1 III Cardiac cycle 2 IV Ventricular filling V Isovolumetric contraction VI Ventricular ejection VII Isovolumetric relaxation VIII Overview of volume changes IX Timing of cardiac cycle Current Lecture II In cardiac cycle 1 two phenomena control blood flow through the heart The first are the contraction relaxation sequences of chambers The second is the opening closing of the AV and SL valves Blood always travels from an area of higher pressure to an area of lower pressure The pressure developed within a heart chamber is related to the volume of blood within that chamber and the size of the chamber There are a few pressures to keep in mind venous atrial ventricular and arterial pressures Venous return is the amount of blood flowing in the atrium per a set time period This is always happening III In cardiac cycle 2 the two atria contract while the two ventricles relax the two ventricles contract while the two atria relax and then all the chambers relax until the next P wave Ultimately systole means relaxation and diastole means contraction There are four phases of the cardiac cycle ventricular filling isovolumetric contraction ventricular ejection and isovolumetric relaxation IV During ventricular filling diastole is occurring The ventricles expand and pressure decreases causing the AV valves to open The AV valves open whenever atrial pressure is greater than These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute ventricular pressure There are three phases to ventricular filling The first is rapid ventricular filling which is exactly what it says blood flows in rapidly to the ventricles The second is diastasis which is slower because blood is only trickling out of the atrium These two steps together equal about 70 of the entire ventricular filling process The last step is atrial systole atrial relaxation which takes up 30 of the phase A term you need to know is end diastolic volume EDV which is measured right before the QRS complex contraction The EDV is both ventricles are on average 130 mL All of the blood from the atrium makes it to the ventricle V Isovolumetric contraction occurs when atrial diastole and then ventricular systole begin causing the AV valves to close Whenever ventricular pressure is greater than atrial pressure the AV valves will be shut No blood is ejected during this phase because arterial pressure is greater than ventricular pressure VI Ventricular ejection is when the blood leaves the ventricles because ventricular pressure is greater than arterial pressure The SL valves open when this is the pressure gradient There is rapid ejection first and then reduced ejection just like there was in ventricular filling A term to know is stroke volume SV which is the amount of blood the ventricle ejects from one cycle The average SV is around 70 mL The ejection fraction is the percentage of blood that ejects out of the total volume It can be found with this equation SV EDV x 100 It averages about 54 Another term is called end systolic volume ESV which is the built in reserve pile for exercise It averages 60 mL VII Isovolumetric relaxation is early ventricular diastole The ventricles expand and pressure decreases The SL valves close when arterial pressure is greater than ventricular pressure It is called isovolumetric because both ventricles contain the same amount of blood as each other at all times VIII EDV equals 130 mL The stroke volume is 70 mL Therefore the ESV the blood left from the previous heartbeat is 60 mL EDV SV ESV IX The average resting heart rate is around 75 beats minute One cardiac cycle requires 0 8 seconds The atrial and ventricular systoles require 0 4 seconds The quiescent period is around 0 4 seconds However it can shorten to increase heart rate On an EKG which you will look more into in lab the lubb is the first heart sound when ventricular pressure is greater than atrial pressure AV valves closing The dupp sound is when the SL valves snap shut
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