Autoregulation is a biological term used to describe processes through which some biological systems are capable of regulating themselves. Autoregulation is most clearly exemplified by the distribution of blood and oxygen throughout the bodies of many different animals. Changes in external conditions and stimuli cause the systems governing blood flow to focus the flow of blood, and therefore oxygen, where it is needed the most. When necessary, blood vessels can constrict or dilate and heart rate can increase or decrease to moderate blood pressure throughout the body. This is of particular importance in the brain, where blood pressure must remain within a relatively small range to avoid damage.
In order to fully understand the importance of autoregulation, one must first understand the concept of homeostasis. Homeostasis, as applied to biological systems, is a natural, stable balance in which the system is able to maintain stable regulation regardless of external conditions. Processes such as the consumption of nutrients, formation of energy, and formation and distribution of proteins all contribute to homeostasis. Wild changes in energy consumption, nutrient distribution, or even temperature regulation can cause significant harm to an organism, so regulatory mechanisms are necessary to ensure the necessary balance is maintained. Autoregulation is one such mechanism through which particular biological systems are able to regulate themselves.
Autoregulation in the brain, referred to as cerebral autoregulation, is extremely critical because of the brain's importance and fragile nature. It requires a steady and constant flow of oxygen to remain functional and even brief periods of significant variance can be quite harmful. The specific purpose of this regulation is to maintain an unchanging flow of blood to the brain even when blood pressure fluctuates. Factors such as resistance, flow, and pressure are all important factors in determining the rate of blood flow in the brain. When one changes, others can generally adjust to compensate for the change without the need for external factors, such as hormones or neural signals.
The brain is not the only organ that contains autoregulatory mechanisms. The heart and kidneys are also capable of regulation without the need for chemical or neural triggers. The particular mechanisms of autoregulation tend to be quite similar and are generally closely linked to blood pressure, flow, and resistance. These autoregulation systems are highly important, if not absolutely necessary, in sensitive organs that need to maintain a precise, constant flow of blood to avoid damage. The organ itself is capable of regulation based on immediate factors without needing to depend on chemical or electrical intermediates that could be misdirected by other processes in the body.