How do the complex activities in the various parts of the brain, the simple all-or-nothing rings of billions of interconnected neurons, and the various chemical systems within the body, work together to allow the body to engage in everyday behaviours? The answer lies in a remarkable combination of electrical and chemical processes controlling the nervous and endocrine systems.

The nervous system, the electrical information highway of the body, is made up of bundles of interconnected neurons that fire in harmony to carry messages throughout the body. For example, when we get out of bed in the morning, we would experience a sharp drop in blood pressure if it were not for the action of the sympathetic system, which automatically increases blood flow through the body. Similarly, after we eat a big meal, the parasympathetic system automatically sends more blood to the stomach and intestines, allowing us to efficiently digest the food. The two systems work together to maintain vital bodily functions, resulting in homeostasis, the natural balance in the body’s systems.

Another highly complex system that sends messages through the body is known as the endocrine system. It consists of three main components: endocrine glands, hormones and target cells. In humans there are eight main glands in the endocrine system: adrenal gland, pituitary gland, hypothalamus, pancreas, thyroid, pineal gland, parathyroid gland and the reproductive glands.

How does the system work? With nerve impulses, the reaction is usually quick; for example, if you put your hand near a flame, the nerves in your fingers will react immediately and you will withdraw your hand. But with hormone signals released by the endocrine system, the effects are not as instantaneous, but they can be long lasting.

Endocrine glands are found scattered all over the body and are structurally and functionally very different from each another. When a hormone reaches its target organ, it triggers a response in the organ, making its functions speed up or slow down. For instance, consider the factors that lead up to feeling thirsty. If you exercise and sweat, your body loses water. If you lose enough water that it begins to affect homeostasis, your brain senses it. It triggers your pituitary gland to secrete antidiuretic hormone (ADH – also called vasopressin), which tells your kidneys to retain water. The kidneys go to work re-absorbing water within your renal system. This will result in less urination. If your system needs still more water, your brain will then trigger a conscious order for you to drink – you will feel thirsty. Once you’ve drunk enough water, your brain will tell the pituitary gland to stop secreting ADH. Your thirst will feel quenched. Your endocrine system, working in conjunction with your nervous system, has maintained your body’s homeostasis.

But the complexities and dependencies keep on increasing. There are some glands that release hormones to trigger other glands to release hormones! Then you find some organs interfacing between different systems. For example, the hypothalamus (a small, specialised extended segment of brain located in the mid-central region) links the nervous and endocrine systems and uses both systems to achieve homeostasis.

So here are the questions science has no answer for. How did the body determine what is the right balance of chemicals and responses that is required to support life (homeostasis)? How did it know that it needed a particular chemical message to alter a particular part of the body to correct an abnormal state the body was experiencing? How did one complex gland evolve independently of the other seven and yet seem to work in perfect accord with every other gland? How could a lock and key approach work for just the right tissues to be affected by just the right hormone? And when the hormones and receptors are developing the right connectors how can the body possibly function?

The answer, of course, is that evolution could not possibly build such intricate systems over any length of time. All the evidence points to a body which was created as a complete functioning unit from the very first day it was made. The Creator of life has declared that He made all things through wisdom (Psa 104:24). How straight forward it is to marvel at the evidence and simply believe.