"I praise you,
so wonderfully you made me;
wonderful are your works."
The physical makeup of a human being is a wonder to behold and considering some aspects of human nature will help us to appreciate God's handiwork.
Take for example, the Circulatory system of man. It must be capable of reaching every single cell of the body in order to keep it alive and functioning . How many cells comprise the human body? A estimated 100,000,000,000,000 cells or much more than the number of stars of our galaxy. So, to reach every cell it it must branch out in ever smaller channels reaching a diameter of 5 microns (1,000 microns = 1 millimeter), that is to a point invisible to the human eye. This river of life is estimated to be 100,000 miles long. Now the earth's diameter is 24,902 miles; this means that the Circulatory system would stretch around the earth four times.
The pulsating heart drives the river or life. It pulses about 2 1/2 billion times in an average lifetime. Science tells us that it is a complex electrical system which drives it, but in the final analysis it originates from the life force which is the human soul kept in existence by God. Some may not see the life force of the soul involved in the pulsating heart because we may substitute a mechanical (AbioCor), with its own electrical system. How then, does the soul keep you alive? As we have observed previously, the life form of the soul is present in the whole body and each of its parts; it is that which keeps it alive. We have merely aided the life force of the soul but have not eliminated the substantial form of the body, the soul, from the overall functioning of the body.
Another wonder of man's body is his Nervous System with the brain as its primary center. The brain is made up of 100,000,000,000 nerve cells with a million billion dendrite connections, all sending information from nerve to target nerve by a process of electrochemical energy at a speed of 30 milliseconds. The number of connections is staggering. If you were to count one number per second it would take you 30 million years to reach the end. "On the neural level, we are actually witnessing a continual display of mind over matter. Or possibly more accurately stated, the consciousness of mind over the consciousness of matter." (Gerald L. Schroeder, The Hidden God, Simon & Schuster, NY, 2001, p.106) The brain is the physical interface between the soul and, directly or indirectly, with the body as a whole and the outer world. There are those who maintain that all consciousness is a product of the brain, there is no intellectual soul. "True, the conscious mind arises from the brain. Destroy the cortex and you destroy consciousness. Destroy the brain and the palpable mind goes into oblivion. But the physical organ of the brain may be the only circuitry that makes the mind humanly perceptible. In that case, a form of consciousness may remain." (Ibid., p.152) If you break a radio it will no longer receive the music but the waves are still our there, so it is with the brain/mind connection.
In the Middle ages the question was raised regarding memory in the intellectual soul. St. Thomas Aquinas points out that if matter (brain) can hold memory, so can the soul retain it even better but according to the nature of the recipient. The intellect remembers by abstraction while the brain, according to recent studies, remembers a " set of encoded neural connections". St. Thomas states, "If we take memory only for the power of retaining species, we must say that it is in the intellectual part. But if in the notion of memory we include its object as something past, then the memory is not in the intellectual, but only in the sensitive part, which apprehends individual things. For past, as past, since it signifies being under a condition of fixed time, is something individual." (Summa, Pat I, Q. 79, #6) In any event, for the memory of the intellectual soul to becomes useful it needs a corresponding brain function.