Feedback Loops

Positive and negative feedback loops are essential for homeostasis in the human body. They provide the controls needed to keep the effects of hormones and hormone chain reactions from spiraling out of control.

Negative feedback loops act to reverse changes in the        body’s physiological condition. For example, cells in the pancreas detect a rise in blood glucose levels. This stimulus causes beta cells in the pancreas to release insulin which causes muscles, fat cells, and liver cells to take in the glucose. The negative feedback begins when blood glucose decreases. Alpha cells in the pancreas then inhibit the release of insulin from beta cells. This is a dynamic process that goes on all the time to maintain homeostasis of blood glucose levels.

 A positive feedback loop like full-term childbirth intensifies the change in the body’s physiological condition and is considered normal as long as there is an endpoint. In childbirth, the cervix stretches as the baby moves down the birth canal. Stretch receptors in the cervical tissue send messages to the brain which triggers the release of oxytocin. Oxytocin makes the mother’s contractions stronger, stretching the cervix more and pushing the baby farther down the birth canal. This cycle continues until the baby is born and stimulation of the stretch receptors in the cervix stops sending signals to the mother’s brain.

Nervous System

The nervous system is intricately involved in visual perception which also helps maintain homeostasis.

Within the process of homeostasis the nervous system detects and responds to adaptions within the body's internal and external environments by sending fast electrical impulses through nerves to the brain which instructs an effector and enables them to react quickly and return the body to a state of equilibrium

Endocrine System

The endocrine system consists of ductless glands that secrete hormones into the blood stream. These hormones drive the homeostatic feedback loops that keep the body healthy and in equilibrium. The endocrine system is intimately integrated into physiological processes in order for it to carry out its functions.

Excretory System

The urinary/excretory system influences homeostasis by regulating the amount (volume) and the makeup (composition) of blood.

The makeup of blood is regulated in a couple ways. The kidneys act to filter out metabolic wastes, like urea, that are picked up by the bloodstream. The kidneys prevent the buildup of this waste by removing it from the body. The kidneys also help keep the pH of the blood right where it's supposed to be, which is about 7.4. They do this by controlling the rate of removal of hydrogen ions (H+), which are responsible for the acidity of fluids.