Cardiac cycle 5- Atrial diastole ventricular systole

Cardiac cycle 5- Atrial diastole ventricular systole


– OKAY.
HERE WE ARE. WE’VE GENERATED AN ACTION
POTENTIAL THAT’S SENDING THE MESSAGE TO THE VENTRICLE
MUSCLE CONTRACTILE CELLS, “DUDE, DO YOUR JOB,
CONTRACT.” THEY BEGIN TO CONTRACT. THE VOLUME IS DECREASING
AS THE PRESSURE IS INCREASING. EVENTUALLY THE PRESSURE
OVERCOMES THE SEMILUNAR VALVES. AND THE BLOOD POURS OUT, EITHER INTO THE AORTIC
ARCH OR INTO, THERE’S MY AORTIC ARCH, OR INTO THE PULMONARY TRUNK. EITHER WAY, THE BLOOD IS NOT
BEING PUSHED OUT OF THE HEART BY THE CARDIAC MUSCLE TISSUE. THERE ARE SOME REALLY
INTERESTING THINGS ABOUT THE WAY CARDIAC
MUSCLE TISSUE IS ORGANIZED INSIDE THE HEART. IT’S ACTUALLY KIND OF SPIRAL. SO THAT IT’S ALMOST
LIKE WRINGING OUT THE HEART. THE CONTRACTION IS SUCH
THAT IT WRINGS OUT THE HEART AND PUSHES ALL THAT BLOOD UP
AND OUT THOSE ARTERIES. THIS PROCESS OF SQUEEZING
OUT THE BLOOD, YOU DON’T SQUEEZE IT ALL OUT. YOU ACTUALLY LEAVE
SOME IN THERE. AND THAT IS, WHAT DO YOU THINK?, END SYSTOLIC VOLUME. SO THE END SYSTOLIC
VALUE IS A SMALL NUMBER THAT IS ESSENTIALLY
THE AMOUNT OF BLOOD THAT’S LEFT AFTER VENTRICULAR
CONTRACTION HAS COMPLETED. THIS IS STILL
VENTRICULAR CONTRACTION. WE STILL ARE SUMMING UP
THIS ELECTRICAL ACTIVITY IN THE FORM OF THE QRS COMPLEX. THE QRS COMPLEX.
LOOK AT THE SIZE OF THAT THING. SERIOUSLY, IT’S HUGE COMPARED
TO THE P-WAVE AND THE T-WAVE, AND THAT’S
BECAUSE THE VENTRICLES ARE HUGE. IF YOU’VE TAKEN ANATOMY, YOU KNOW THAT IF YOU
GRAB YOURSELF A COW HEART OR A SHEEP HEART,
PRETTY MUCH OF IT IS VENTRICLE. AND IT MAKES SENSE. BECAUSE THE VENTRICLES,
THIS MOMENT, VENTRICULAR EJECTION, IS THE MOMENT
WHERE YOU’RE PUMPING EVERYTHING. THAT’S THAT PUSH THAT SENDS
THE WHOLE BLOODSTREAM, LIKE, ALL YOUR BLOOD,
ALL WHATEVER, 10 LITERS, PINTS,
10 PINTS, NOT LITERS, 10 PINTS OF BLOOD
THROUGH YOUR SYSTEM. LIKE, IT’S ALL BECAUSE OF
THIS MOMENT OF VENTRICLES CONTRACTING. AND IT’S KIND OF WILD,
IF YOU THINK ABOUT IT. THAT’S A STRONG
MUSCLE CONTRACTING A HUNDRED THOUSAND TIMES EVERY SINGLE DAY. WHAT?
THAT’S CRAZY TALK. OKAY, WE SQUEEZED OUT
ALL OF OUR BLOOD. WE’VE COMPLETED OUR CONTRACTION. LOOK WHERE WE’RE HEADED NEXT.