chasing the heart beat

Early in the morning, I am sitting down outside in my veranda all alone with a blank mind. It is drizzling in the court yard in front. The atmosphere is gloomy. The lawn grass is all wet and the drenched orchids are drooping heavy. And I can see that the newspaper bundle lying on the iron gate is damp.
I don’t know why my hands are trembling. Must be the weakness of the nerves due to lack of proper sleep at night. I can hear my heart beat as if it is hammering off far away in a mill. I can even see the rhythm in the tremble of my hands. I counted the number of beats per breath. Seven beats of heart per every inhalation and two per exhalation.
What prompts my breathing? As soon as inhaling is completed, the urge to exhale presses making the breath collapse with no choice. The exhalation is fast. It is a sort of haste to come to rest. But only for a second, and then it is time to inhale again. The inhalation is a craving to drink in as much fresh air as possible from outside. The process, the urges and cravings, come from nowhere in particular, or it comes from everywhere. It is the very existence, my life!
But nothing like that is felt about the beating of my heart. No urge, no craving. It just goes on beating with no conscious control or power on my part. Wherefrom does the prompt for the heart to beat come? And wherefrom does the urge to think like this come? Thoughts come from memory of course. Memory is the storehouse of words, images, relationships, feelings. But the prompt or trigger for the outflow of thoughts is somewhere else. A continuous urge from an unknown source seem to pop them up.
Very difficult to grasp the entity that make the heart beat, the mind think. It looks futile to chase it, to find it.