What Is the Preoptic Area?

S. Berger

Many automatic functions are handled by a part of the brain called the hypothalamus. Within this region, there is an oval-shaped group of cells called the preoptic area. Primarily, this area is responsible for thermoregulation, the process by which the body maintains a constant temperature by gaining or losing heat. Certain components of this area serve other functions, such as creating thirst, inducing sleep, and regulating male sexual behavior.

The preoptic area, located in the hypothalamus, regulates body temperature.
The preoptic area, located in the hypothalamus, regulates body temperature.

Keeping the body temperature constant is an important unconscious process for warm-blooded animals. Special sensory cells known as thermoreceptors located in the skin and certain membranes detect temperature changes, and relay this information to the preoptic area. After receiving this information, this region sends messages to appropriate parts of the hypothalamus responsible for temperature responses. In turn, these regions generate automatic responses to heat or cold, depending on the preoptic area's output.

The preoptic area is involved in inducing sleep.
The preoptic area is involved in inducing sleep.

This area of the hypothalamus actually contains several smaller nuclei, or groups of neurons, each with their own unique functions. Located in the center of this area, the median preoptic nucleus helps to regulate thirst. Sensory cells that detect a lack of water due to loss of their own volume send signals to the median preoptic nucleus. The nucleus then releases the chemical norepinephrine to higher processing centers that create the conscious feeling of thirst. Norepinephrine production stops after the individual consumes water, stopping the feeling of thirst.

Another important nucleus in the preoptic area is the lateral preoptic nucleus, located toward the edge of this area. Cells involved in thermoregulation are found here, but this nucleus serves another important function. It helps to signal non-rapid eye movement (REM) sleep through the release of molecules like galanin, which inhibits the activity of other neurons.

Between the lateral and median preoptic nuclei lies the medial preoptic nucleus. This region is sometimes called the sexually dimorphic nucleus because it shows a size difference between genders. Males have a larger medial preoptic nucleus, and it is more spherical in shape. Additionally, females tend to experience more cell death in this region due to a lack of activity.

Molecules like dopamine stimulate cells in this portion of the preoptic area, and when stimulated, these neurons regulate male sexual behavior. Animal studies have shown that stimulation results in copulation behavior and the release of compounds like gonadotropin-releasing hormone. Higher dopamine stimulation is seen in response to testosterone levels, as well as by sensory stimulation, such as the presence of a female.

The preoptic area has a role in regulating male sexual behavior.
The preoptic area has a role in regulating male sexual behavior.

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Discussion Comments

hamje32

@nony - Is love nothing more than a chemical release? This is what I wonder when I read about dopamine’s role in sexual behavior.

Some people have developed perfumes and stuff that supposedly contain love chemicals which are guaranteed to create sexual attraction between men and women.

Honestly, I hope we haven’t come to that. I would still like to believe that free will has a role to play in romantic relationships.

nony

@everetra - Just stick with water and you’ll be okay. Soft drinks are sugar and your body will never need that.

All you need is eight glasses of water per day and you should be okay. Speaking of appetites, however, there are products on the market that will supposedly suppress your appetite. They will make you feel full on less food.

I don’t know if they interfere with norepinephrine production or what, but they do something in the brain to make you feel that you’ve had your fill.

everetra

@miriam98 - I don’t think your thermoregulation system is failing. Its job is to keep your job at a normal body temperature, and I am sure you remained at the typical 98.6 degrees or thereabouts even in cold weather.

Some people are just more uncomfortable in the cold. What I wonder about is the role that it plays in triggering thirst impulses.

Does this mean that every time I grab a soft drink that my body is thirsty or is my body just craving it? How can you tell what is genuine thirst and what is indulgence?

miriam98

I am extremely sensitive to cold. I don’t know if that means that my preoptic area is not working properly or that I just don’t have enough body fat.

I mean it’s laughable the way I shake in extreme cold. I went to Denver one winter and the locals were marveling at how much I shuddered in the cold air while they stayed calm and collected, even though we were all bundled up the same way.

I think in the end it’s owing to the fact that I am from the Middle East, where we are just not used to cold temperatures.

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