April 15th – I recently started training for my first ever 5K, and using my heart muscle more intensely then usual got me thinking. The heart is made of muscle cells which pump the body’s blood throughout our lives from dawn to dusk and then from dusk to dawn. They function on their own and beat a steady rhythm by contracting and relaxing, though this automatic rhythm can be altered by the parasympathetic and the sympathetic nerves which can quicken the pace or slow it down again. The cells are specially made to pump without a rest: abundant mitochondria and myoglobins help the cells to breathe, and coronary arteries bring lots of blood to feed the cells themselves (veins carry off the cells’ digested waste) – unless, of course, the arteries are blocked and then the cells can die! (A heart attack, or myocardial infarction, then results.) But in a normal healthy beating heart the cells are active once a second or a hundred thousand times a day, two billion times a life or more – the blood that’s pumped could make a river red. It’s said the night sky has a thousand eyes, the day but one; but that the light of the world dies with the dying sun. It’s said the mind has a thousand eyes, the heart a single one; but that the light of living dies if ever loving’s done. So guard your heart, with diligence, life’s well-spring from it flows. And give your heart to Truth alone, there shall your soul repose. #365DaysOfMicroscopy
