At any given time, your body should be around 98.6 degrees Fahrenheit, or 37 degrees Celsius. This doesn't happen "automatically." Even though we usually don't consciously think about it, our bodies work hard to maintain the same temperature. Bodily functions carry out this work, but our brains are critical in this process.
Temperature regulation is only one way that the body aims to maintain homeostasis. Homeostasis is another word for "balance." When our temperature is at 96.8 degrees Fahrenheit, we are balanced. Any other time, the brain and body work together to restore that balance.
Let's learn how that happens and how our brains are involved in that process.
What Part of the Brain Regulates Body Temperature?
The hypothalamus is in charge of regulating body temperature and maintaining homeostasis. This part of the brain is constantly gathering information about temperature and sending signals to cool or warm the body. When we sweat, shiver, or get goosebumps, we can thank the hypothalamus!
What is the Hypothalamus?
The hypothalamus is a small gland deep in the center of the brain. Temperature regulation is one piece of what the hypothalamus does. The role of the hypothalamus is to control the release of hormones throughout the body.
Other functions that the hypothalamus controls to maintain homeostasis include:
- Heart rate
- Blood pressure
- Sex drive
- Mood
- Sleep
- Hunger and appetite
- Thirst
One small part of the brain, the hypothalamus makes a big difference in how we feel and our overall health!
So what happens when our temperature does increase or decrease beyond "balanced" levels? The hypothalamus gets to work.
What Happens When It Gets Too Hot?
Let's say you step outside and it's 100 degrees. What do you expect to happen? You might sweat. You might feel thirsty. All this is the result of the hypothalamus attempting to cool your body down.
The hypothalamus receives sensory information that we gather from our senses of touch, taste, smell, sight, and sound. Of course, the sight of a thermometer is not going to tell the hypothalamus to cool the body down. But if the skin starts to feel hot, the hypothalamus must respond.
Sweating
One way that the hypothalamus responds to heat is sweating. Signals are sent from the hypothalamus to the sweat glands to release water throughout the skin. This water is meant to cool the body down. (Physical exertion or even stress can also trigger this same response.)
Vasodilation
You could probably guess that sweating is the result of excessive heat, but what about vasodilation? Vasodilation is the widening of blood vessels throughout the body. Again, this is done from the direction of the hypothalamus. When the blood vessels dilate, blood can more easily flow throughout the skin and release heat. Heat loss eventually brings the temperature of the body down until it is back to 96.8 degrees Fahrenheit.
Another way that the hypothalamus cools down the skin is by relaxing the muscles of the hair on the skin. With these muscles relaxed, heat can escape.
What Happens When It Gets Too Cold?
When you step out into a cold winter's day, what can you expect? Without even thinking consciously, you might start shivering. The hair on your arms stands up. You might even get goosebumps. This is all the result of the hypothalamus at work.
Shivering
Why do we shiver? Shivering creates energy, which heats up the body. Even if you're not running a marathon or lifting weights in the cold, a bit of shivering can create heat and raise your temperature.
Goosebumps
Shivering and goosebumps are actually the result of directive from your hypothalamus. The hypothalamus orders the body to release adrenaline to create heat. When this happen, the hairs of your body stand on end and you get goosebumps!
Vasocontractions
So far, you have learned about vasodilation, which occurs when the body is too hot. But what about when it's too cold? Blood vessels do the opposite. Vasoconstriction occurs when blood vessels constrict to keep blood close to vital organs. In the event that our bodies are stuck in freezing cold temperatures, our hearts, lungs, and other organs are most at risk. Vasoconstriction keeps warm blood around them, even if that means keeping blood from flowing. Have you ever wondered why the tips of your fingers and toes get cold first? Now you know why!
Brain Freeze
Knowing all this, I want you to think about a pretty common phenomenon: brain freeze. The body's attempts to create homeostasis may just be the reason we experience brain freeze!
Scientists are not exactly sure why we experience brain freeze, but many believe it has to do with vasoconstriction in the brain. Once those blood vessels dilate, they may rub up against a pain nerve. As a result, we feel pain at the front of our brains.
What Happens When You Have a Fever?
If you have ever had a cold, infection, or virus, you know that the body doesn't always stay at 98.6 degrees. People experiencing a fever have an internal temperature between 98.6 and 102.2 degrees Fahrenheit. The body does not immediately break out into a sweat when you experience a fever...why?
The hypothalamus isn't slacking or sick when you have a fever. In fact, it's simply following orders. When an infection is present in the body, the immune system sends out a message to the hypothalamus. In response, the hypothalamus allows the body's internal temperature to rise. Of course, it doesn't rise too much - having an internal temperature higher than around 102 degrees puts organs at risk. But the blood vessels constrict and you may shiver in order to increase your temperature.
This also explains why you sweat at the moment that your fever breaks. Once the hypothalamus knows it's okay to lower the body temperature again, it sends out a signal and you sweat. All this time, our fevers are actually a way that we can protect ourselves!
What Happens In The Brain During Hot Flashes?
There is one last phenomenon I want to discuss as it relates to core temperature. If you have ever watched a mother, grandmother, or aunt go through menopause, you probably know something about “hot flashes.” During a hot flash, a person feels very sensitive to the temperature. They sweat, shiver, and feel an intense warmness throughout their body.
Why does this happen? To understand why, it’s important to know that menstrual cycles affect our core temperature. Small fluctuations in temperature take place before and after ovulation. The neurons that provide data to the hypothalamus about the outside weather are very closely linked to the neurons that trigger puberty and menopause.
Neuroscientists are close to pinning down whether that neuron can definitely be named as the trigger for hot flashes, but we still have a few lingering questions about that phenomenon. What we do know is that during a hot flash, the hypothalamus becomes much more sensitive to heat. Normally, the body doesn’t trigger sweat or shivering until the temperature reaches beyond a certain threshold of a few tenths of a degree. During menopause, that threshold is much smaller. Shivering and sweating are much more likely.
Temperature regulation is just one way that our brains are constantly working to keep us alive and healthy. If your temperature is “normal,” you can thank your hypothalamus!
