So, what’s the endocrine system? You may have heard of adrenal glands and of people who are hypoglycemic or diabetic. The endocrine system is the collection of the body’s glands along with their hormones, and other hormone-producing organs. The endocrine system is extremely important as it regulates and controls an extraordinary number of functions in our bodies. Just as the nervous system uses electricity to send and receive messages, the endocrine system uses chemicals called hormones to accomplish even more amazing things. The endocrine system may not work as fast as the nervous system, but its effects last longer. The endocrine system is extremely complex, and scientists are continually discovering new functions and interactions of hormones throughout the body. We’ll discuss just a very small portion of the endocrine system in this article.
Glands are organs whose function is to manufacture hormones. Glands are found all over the body. For example, in our heads we have the hypothalamus, pituitary and pineal glands. In our neck and chest are the thyroid, parathyroid, and thymus glands. Some endocrine organs are also part of other systems, such as the pancreas which produces hormones but is also part of the digestive system, ovaries and testes which are glands but are also part of the reproductive system, and kidneys which produce hormones but are also part of the urinary system.
Hormones are chemical messengers that are produced and released in a gland and are transported, via the circulatory system, to other cells. In fact, each hormone has its target cells, which means that there are specific cells that will respond to it. Think of the hormone as a package and the bloodstream as the postal service. Only the cell with the correct “address” will accept the package. Other “packages” or hormones will be ignored. This use of hormones to coordinate cellular activities in distant parts of the body is called endocrine communication.
Let’s take a look at one organ in particular. The pancreas is situated just behind the stomach. As previously noted, it is part of both the endocrine system and the digestive system. In its role as a digestive organ, the pancreas releases certain pancreatic digestive juices through a tube and into the small intestine. The endocrine function of the pancreas involves controlling your blood sugar or glucose. Pancreatic endocrine cells produce hormones called glucagon and insulin. These two hormones work as a check and balance system. Glucagon raises blood glucose by affecting the liver, which can break down other substances and turn them into glucose and send it into the bloodstream. Insulin lowers blood glucose by increasing the glucose uptake of the body’s cells. Without insulin, glucose would circulate without being taken in by the cells, which need it for energy production. Think of insulin as the big brother that holds the little brother’s (glucose) hand, making it “ok” to go into the cell.
You have certainly heard of the disease called diabetes. Diabetes can be caused by several things but is generally characterized by glucose concentrations that are high enough to spill into the urine, making urine production excessive. In Type I diabetes, the pancreas fails to produce enough insulin. Type II diabetes is caused by the body’s inability to respond to insulin normally. In each case, the “big brother” isn’t available to help glucose into the cell. Without glucose, the body cannot produce energy necessary for life. Left untreated, diabetes can kill. When this system is working normally, the body is kept in balance, or homeostasis, which is how God planned it to work.
Homeostasis is another major function of the endocrine system. The following is an illustration of one of the processes of homeostasis, thermoregulation.
A frog, a rock, and you are sitting in the shade on your porch for a little while. It is late afternoon and the outside temperature is 102.0 degrees F. After a while, the temperature of the frog and the rock are approximately 102.0 degrees F; your temperature is 98.6 degrees F. As night falls, the temperature plummets to freezing. The temperature of the frog and the rock are now about 32.0 degrees F. Your temperature is 98.6 degrees F.
This illustrates the fact that man, unlike the frog or the rock, is homeothermic, which means that we maintain a constant temperature regardless of our surroundings. How is this possible? The process of this temperature regulation is called thermoregulation and it is quite complex. Heat is produced as a byproduct of metabolism. That is not a problem, but the body must remove heat, or we will get too hot. We lose heat through our skin, especially through evaporation when we sweat. You will have noticed that your skin gets red when you are hot. This occurs because blood vessels in your skin dilate which allow more blood flow to the surface and therefore more heat can be radiated off the skin. Conversely, when you are cold, your skin turns pale as the skin blood vessels constrict so that less heat is lost to the air. Your extremities get cold first because the body shunts blood to the head and trunk to protect the vital organs. Shivering is the body’s way to increase metabolism, which increases heat production. This occurs when you are too cold or during an infection when the body needs to increase its temperature.
The part of the brain called the diencephalon is the heat-regulating center. Neural messages pass to and from the heat center, keeping the body in constant temperature balance. If any portion of this process is not functioning, the entire process can fail. In other words, Adam must have been fully formed when God breathed life into him; he could not have gradually developed over time or his thermoregulatory system, and other body systems that are so intricately linked, would have failed, and he would not have lived.
Though we have touched on just a miniscule portion of the endocrine system, it is clear that God’s plan incorporates a wondrous balance within our intricate inner workings. “He shall feed his flock like a shepherd: he shall gather the lambs with his arm, and carry [them] in his bosom, [and] shall gently lead those that are with young. Who hath measured the waters in the hollow of his hand, and meted out heaven with the span, and comprehended the dust of the earth in a measure, and weighed the mountains in scales, and the hills in a balance?” Isaiah 40:11, 12.