(I Thess. 5:8; Eph. 6:16-17)
The heart and the mind are often connected to the spiritual world in their functions as the life of the body (heart) and the controller of our thoughts (the brain). The Bible tells us to guard our heart above all things, because everything we do, flows from it (Prov. 4:23). The word heart is found more than 800 times in the Old Testament and 200 of these times, it is related to the soul of man: intellect, emotions, will. In the field of the physical, the heart and the brain are two organs that work together communicating in four ways:
Neurologically (through the transmission of nerve impulses
Biochemically (via hormones and neurotransmitters)
Biophysically (through pressure waves)
Energetically (through electromagnetic fields interactions).
The brain and the heart together comprise the soul of man. As a matter of fact, man is what his soul is. The soul, which is invisible, becomes visible in the ways we behave. Our actions reveal what is inside our heart and mind. The heart, the size of a fist, is a muscular organ serving as a pump carrying blood via the circulatory system, supplying oxygen, nutrients, and removing carbon dioxide from it. In an amazing way complete in divine wisdom, the heart is the life of man, as it controls the flow of blood, for life is in the blood.
The Bible says that everything we do flows from it. Imagine that, a muscular organ with such power, but in the physical, it does not do it alone. It just cannot do it. It takes the brain to work with it, for the brain, our three-pound organ, controls our thoughts, memory, speech, etc. The central nervous system consists of the brain and the spinal cord. It receives information through the five senses: smell, sight, touch, taste and hearing. The messages are meaningfully put together to serve us. In the Garden of Eden, Eve was tempted by the sight sense. And when the woman saw that the tree was good for food and that it was delightful to look at, and a tree to be desired in order to make one wise, she took of its fruit and ate; and she gave some also to her husband, and he ate (Gen. 3:6). So, here we have the lust of the eye. The connection between our hearts and our brain happens silently, in a subconscious dialog of emotion through signals between our heart and our brains. Our emotional estate when out of control, affects the body, and the soul. Anger, for example, is one of many reactions that takes a toll on our health, when not under control. The Bible warns us when angry, do not sin. There is nothing wrong in displaying anger, when kept under control. Do not let anger control you; let not the sun go down upon your wrath (Eph. 4:26); Psalm. 4:4 says: Be angry and sin not; commune with your own hearts upon your beds and be silent. Controlling anger is one way to guard the heart and the mind, and also the body. Diseases often happen to the body when we hold anger deeply in our hearts and minds -soul. From mental illnesses to heart diseases as in stroke, heart attack, hypertension, etc. The body is very much affected as a result of the heart’s and brain’s decision. It receives the injuries as the result. Protecting the heart and mind, the rest of our organs will be protected also. Solomon says, Keep your mouth free of perversity; keep your corrupt talk far from your lips; let your eyes look straight ahead; fix your gaze directly before God; give careful thought to the paths for your feet and steadfast in all you ways. Do not turn to the right or the left; keep your foot from evil (Prov. 4:24-27). Mouth, lips, eyes, feet will follow the heart and the thoughts of the mind. The Bible says, Out of the heart, the mouth speaks (Matt. 12:34). Paul advises us to control our thoughts directing them to whatever is true, whatever is worthy of reverence and is honorable and seemly, whatever is just, whatever is pure, whatever is lovely and lovable, whatever is kind and winsome and gracious. If there is any virtue and excellence, if there is anything worthy of praise, think on and weigh and take account of these things (Phil. 4:8).