CARDIAC CYCLE : The Rhythm of Life

CARDIAC CYCLE : The Rhythm of Life


Did you ever feel the lub dub sound our heart makes? Did it ever intrigue you to know the process that really goes behind that? It may seem just a sound but when we pull up the curtains there is a very interesting process known as cardiac cycle which results in the superficial lub dub sound that we all are aware of.. Hey, I am Deepika. let’s talk about cardiac cycle in this video. so this right here is our heart. we can see there are four chambers. the upper ones are auricles while the lower ones are ventricles. all these four chambers are connected through an opening which is guarded by valve. Kind of like adjacent rooms in your house. the opening between right article and right ventricle is guarded by tricuspid wall and that between left auricle and left ventricle is by the bicuspid valve. similarly, the valve between right ventricle and pulmonary artery and that between left ventricle and aorta is collectively guarded by a semilunar valves. the reason i did so much blabbing on valves is to make you realize that these valves play an important role in the cardiac cycle. their function basically is to regulate the flow of blood. can you stop your heart or make it beat faster with your mere thought. i hope the answer is no. it’s no, right? aren’t you amazed how your heart continues beating till the very death and that too without any assistance from the brain well that right there is called being independent. our heart manages to work by itself as it has its very own electrical system which carries electrical impulse throughout the heart so,let’s talk about this electrical system there is a specialized cardiac muscle called nodal tissue which is distributed in the heart we can see the patch of this tissue in the upper right corner of right auricle called SA node while one more mass in the lower left corner of right auricle called AVN. oh,oh wait right there what’s the thing coming out from AVN you ask? well these are the nodall fibers which arise from the AVN from the atrio-ventricularl junction upto the interventricular septum which then decides to separate their path, thus becoming right and left branches these branches then give rise to the minute fibers known as purkinje fibers (i hope i pronounced it right) throughout the ventricle musculature of their respective sides these right and left branches along the purkinje fibers are collectively known as bundle of His this whole arrangement ensures the grip on the whole heart. amazing nature! right? what makes these nodal tissue so special is that these fellas have the ability to generate action potentials on its own that means they are auto excitable and that’s how our heart take care of its own beating. you might be wondering that we are halfway through the video and the cardiac cycle has not even started yet well my dear fellas it will all add up as we are very near to the climax. to begin with all the four chambers are in relaxed state that means they are in Joint Diastole at this stage the bicuspid and tricuspid valve are open while the semilunar valves are closed which leads to the flinging of ventricles by blood from pulomanry veins and vena cava .r midst of all this SA node generates action potential which results in the atrial contraction or Atrial Systole. this contraction results in the increased blood flow in the ventricles by 30% meanwhile electrical impulse is conducted to the ventricles through AVN and bundle of his which results in their contraction AKA Ventricular Systole which by the way coincide with the atrial diastole. since ventricles are being filled by the blood hus increasing the pressure there and to prevent the backflow of blood to the auricles the bicuspid and tricuspid valves closes thus leading to the first ever sound LUB! with further increase in the pressure the semilunar valves shuus open the resulting the blood flow in the pulmonary artery and aorta and then right away to the circulatory pathway w until then the action potential ceases thus causing the ventricles to relax and to prevent backflow of the blood to the ventricles the semilunar valves closes thus resulting in the second sound DUB!. believe me, we are almost done .now the ventricular pressure starts declining further and simulataneously atrial pressure starts increasing due to blood flow from veins resulting in the opening of the bicuspid and tricuspid valve. from here we can see we reach back right where we started from. the blood once again moves into the ventricles and there comes the Joint Diastole stage again and the cycle continues. These sequential events which are cyclically repeated is known as cardiac cycle. our heart beats 72 times per minute that means that many cardiac cycle in a minute means that one cycle lasts for eight seconds and people say medical students suck at math so with this we are done with the cardiac cycle. Oh, wait wait the two prominent lub dub sound have a clinical diagnostic significance so when doctor put his stethoscope thing on your chest, he is looking exactly for this sound or any deviations in that yeah we’re done now. oh, wait wait! Just kidding. This is Deepika! Signing off. thank you for watching.