Endocrine Reflexes: Types & Functions

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson we'll be learning about the different types of endocrine reflexes, simple and complex. We'll go over what these two types of reflexes are and look at multiple examples of each in the human body.

What Are Endocrine Reflexes?

When winter strikes, many of us turn on the space heater or crank up the heat. Some of us even have a thermostat that regulates the temperature for us. You set the thermostat to a comfortable temperature and when the room temperature drops too low, the thermostat triggers the heater to turn on. Heat pours into the room and it gets warmer. When the temperature reaches the set point, the thermostat triggers the heater to turn off.

Our bodies have functions like thermostats

Just like our homes, our bodies also want to stay in perfect balance, called homeostasis. And just like we have a theromstat to regulate our homes, our bodies also have ways of regulating themselves to maintain homeostasis. Our bodies need to control many aspects of our physiology, not just temperature. Our internal thermostats regulate blood sugar levels, pH, blood pressure, sleep, hunger and much more. These internal thermostats are called endocrine reflexes.

Our endocrine system is a network of cells, tissue and organs that secrete chemicals called hormones. Hormones are chemicals that travel through the blood to control body functions. The pathways that regulate how much of which hormones are released at any particular time are called endocrine reflexes.

Simple Endocrine Reflexes

The most basic type of an endocrine reflex is called a simple endocrine reflex. This involves just one type of hormone. In a simple endocrine reflex, a cell senses a change in the environment and then secretes a hormone in response. This simple pathway is like having a heater in your house that automatically turns on and off. When the temperature rises above a certain point, the space heater senses it and automatically shuts off. If it gets too cold, the heater senses it and automatically turns back on. Let's look at an example in the body next.

Parathyroid Hormone

Many of us know that it's important to get adequate calcium in our diet. Calcium is known for its importance in healthy bones, but it also plays a crucial role in heart and brain function. The body monitors the concentration of blood calcium very closely using cells in the parathyroid glands.

The parathyroid glands have a large blood supply and detect changes in blood calcium levels. If blood calcium drops too low the parathyroid glands secrete parathyroid hormone, which travels through the blood to various locations in the body to increase blood calcium.

Homeostasis of blood calcium levels is mediated by the simple endocrine reflex of parathyroid hormone
calcium regulation

If the blood calcium runs too high, the parathyroid glands stop making parathyroid hormone, which prevents secretion of calcium into the blood, thus lowering blood calcium. The processes is continuously adjusted based on blood calcium levels in the body to maintain homeostasis.


Many of us have heard of insulin in the context of diabetes. This important hormone is responsible in part for controlling blood glucose levels and becomes disregulated during diabetes. Normally, in response to high blood glucose levels, such as after a meal, beta cells inside the pancreas are stimulated to produce insulin. Insulin travels through the blood and signals body cells to take in glucose, which lowers blood glucose concentrations. When blood glucose levels drop, the beta cells stop producing insulin and blood glucose levels rise again.

Complex Endocrine Reflexes

Complex endocrine reflexes are, well, as you might imagine, a little more complex than simple endocrine reflexes. Complex endocrine reflexes involves two or more hormones and has intermediate steps to regulation. In complex endocrine reflexes one organ typically releases hormones that control the release of additional hormones from another part of the body. Let's look at a common example: the hypothalamus and pituitary gland.

Hypothalamic-Pituitary Axis

The hypothalamus is like a mediator between the nervous and endocrine system. It sits anterior to the brain stem and secretes hormones that regulate the main endocrine organ in the body, the pituitary gland. The pituitary gland can be divided into two sections, the anterior and posterior pituitary. The hypothalamus secretes hormones into the blood that control hormone production and secretion by the anterior side.

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