The endocrine system's hormones form a messaging system is in addition to the nervous system we are more familiar with. We all know that our brain is where we do our concept processing. In fact, the central nervous system controls many functions of the body, weather we think about it or not, such as eating, or with activities we don’t even realize we do, like blinking. To say the brain isn’t used to control our 10 organ systems would be wrong, but it is not the only thing. The brain can also use the endocrine system besides the typical nervous system.
Think of the nervous system (auto and not) to be an electrical system. Messages from the brain quickly travel through the nerves to our body’s organs almost instantaneously. These messages, cause changes to the body to help us react to environmental conditions quickly. Other conditions within the body may not need messaging so quick. For these situations the body uses the endocrine system, in conjunction with signaling from the brain. From the endocrine system, messages are sent chemically through biochemical mechanisms or actions to other parts of the body.
These messages can take hours, days, weeks, months, and even years to impact the other organ systems. Typically, the endocrine system participates in responses to long-term conditions, requiring long-term adjustments to inter-organ relationships.
Signaling and control operations are performed by the endocrine system to regulate core body temperature as an example. A favorite scenario often told in a Systems Thinking course is the one of a home thermostat, where the thermostat signals the heater when the room becomes too cold. The heater responds by producing heat. When the room reaches a defined temperature, the thermostat, signals the heater, and the heater turns off. We see this as a “Heating System”.
This scenario provides an example of the signaling within a system, much like that found in our body. A system, as we speak of a system, is more than the sum of its parts. It may exhibit adaptive, dynamic, goal-seeking, self-preserving, and sometimes evolutionary behavior.
Think about this. How do you know whether you are looking at a system or just a bunch of stuff? Can you identify different parts of that collect of stuff? Do the parts affect each other? Do the parts together produce an effect that is different from the effect of each part on its own? Does the effect, the behavior over time, persist in a variety of circumstances?
Many of the interconnections in our organ systems operate through the flow of information, actual or symbolic. Information holds systems together and plays an important role in determining how the systems operate. The least obvious part of a system, its purpose, is often the most crucial determinant of the system’s behavior.
A stock is the foundation of any system. Stocks are the elements of the system that you can see, feel, count, or measure at any given time. Stocks change over time through the actions of time. Flows are filling and draining, births and deaths, purchases and sales, growth and decay, deposits and withdrawals, success and failures. A stock, then, is the present memory of the history of changing flows within a system.
Our blood sugar level is a measure of system stock, sugar. Blood pressure is a stock. Our white blood count is similarly a measure of stock, white blood cells. Systems can have many different stocks. Stocks change over time through the actions of a flow. When stock levels affecting system behavior change, detrimentally effecting the system’s behavior and purpose, we seek to modify it. When we like the change, and see it as beneficial to the system behavior, we seek to sustain the stock level.
Electrical potential and hormones are the flows between our body’s systems. As the levels of stock change, behavior changes. Endocrine glands produce hormones, for example, the protein hormone leptin, which regulates appetite and energy expenditure, is formed in adipocytes, providing a specific signal reflecting the nutritional state of the body to the central nervous system.
This is an example of our hormone’s long-term monitoring the nutritional state, signaling to the central nervous system when a stock hits a threshold, and then leveraging electrical potential for a short-term response. In this case, the nervous system and the endocrine system are forming a larger system with a larger purpose. Systems can be hierarchical with various purposes at the different levels.
Likewise, our stock of insulin synthesis is regulated by the concentration levels of glucose. Many times, blood flow is used to transport hormones such as these within the circulatory system, forming a different system for a different purpose.
Our organ systems are complex systems with multiple levels of hierarchy, interconnections, stocks, and flows invoking multiple purposes and behavior. As a Health Guardian, monitoring stock levels used in hormonal signaling and resulting in system behavior can be an important tool in pathology prevention efforts.