We need to regulate our body temperature at all times using homeostatic mechanisms. When we get too warm, our body knows to initiate sweating, and when we get too cold, our bodies begin to shiver! This is part of our nervous and Endocrine System's Homeostasis role to ensure that reactions in the body can continue considering our cellular Proteins, such as Enzymes, are sensitive to temperature! Thermoregulation is the term given to the control of body temperature.
Homeostasis is the maintenance of steady-state conditions inside the body, regardless of external conditions, like environmental temperature! We've got a whole article on the topic!
Homeostatic Control of Body Temperature
Thermoregulation requires coordination between the brain, a central nervous system (CNS) component, and effectors.
Effectors are Cells or tissues that are responsible for bringing about the response to a stimulus. Examples include muscle Cells and sweat glands.
The Part of the Brain that Controls Body Temperature
The hypothalamus is an area of the brain responsible for the control of body temperature and many other critical homeostatic systems of the body. The hypothalamus plays a vital role in activating control systems when our body temperature gets too hot or too cold. When the hypothalamus senses that we are too hot, it sends messages to our sweat glands to make us sweat, which helps cool us down. On the flip side, when the hypothalamus senses that we are too cold, it sends signals to your muscles that make you shiver and generate heat!
To better understand the hypothalamus, look at our article on The Brain!
Glands that Control Body Temperature
Sweat glands are found in our skin but more predominately in areas like our axilla (under our arm), palms of the hand, soles of the feet and the groin. These glands play an essential role in controlling body temperature, especially when our body temperature rises above the set point.
The set point is the 'normal' point at which a particular function, reaction, or activity happens at its highest level in the body. This set point applies to the correct balance of multiple factors, including temperature, pH, and concentration, amongst other things.
For example, the general set point for our body temperature is around 37.1 C.
When the temperature of the body increases, the sweat glands secrete water. This cools the body as the water released by the sweat glands evaporates on the skin's surface, releasing heat. If the body temperature decreases to a value below the set point, sweating stops to prevent a further drop in body temperature.
Remember that most homeostatic mechanisms require Negative Feedback. When we make changes, we must stop the mechanisms causing the changes to prevent over-correction. For example, when we sweat, we need to stop sweating once our body temperature cools down again.
Individuals who exercise more often and are fitter tend to sweat more than those who do not. Sweating is a physiological response designed to keep our body running as efficiently as possible. When exercising, fitter people start sweating sooner than unfit people and produce more sweat. This is because their body is more adapted to Metabolic Rate changes. Cells respire at greater rates in healthier individuals causing a more significant and quicker increase in temperature through these exothermic reactions. This causes the body to release sweat sooner and to release more sweat than in unfit individuals.
Negative Feedback Control of Body Temperature
Negative Feedback systems allow for adjustments in our bodies when changes happen beyond a set point. Think about a negative feedback system as a dial that can be turned up or down.
Think about turning the water on before you get into the shower. If the water is too cold, you turn the dial up to increase the temperature. The opposite works as well. You can use the dial to turn the water temperature down if the water is too warm. The 'set point' is the water temperature you prefer. If the temperature goes above or below the 'set point', you adjust to correct it and bring it back to the temperature that suits you best.
Increase in Body Temperature
When temperature Receptors located in the hypothalamus detect a deviation in body temperature, it activates signals and cascades to effectors to correct this. When your body temperature increases above the set point, the following responses are triggered (among others):
The skin plays an essential role in controlling our body's temperature when we get too warm. One of the main ways our body loses heat is through our skin. Vasoconstriction and vasodilation are the processes of narrowing and widening the lumens of Blood vessels, respectively. When we get too hot, our Blood vessels close to the skin vasodilate, enabling more heat to escape the body through the skin. This helps to cool the body and decrease body temperature.
Sweating is another process activated when the hypothalamus detects a rise in body temperature. As previously mentioned, sweat glands all over our bodies release water onto the skin's surface. This water then evaporates from the skin's surface, allowing the body temperature to cool down.
These two processes, sweating and vasodilation, work together to bring the body temperature back to the set point. These mechanisms do not act in isolation.
Decrease in Body Temperature
When your body temperature decreases below the set point, Receptors in the hypothalamus detect this change and send signals to effectors. The following responses are triggered:
- Shivering
- Vasoconstriction
Shivering relies on the fact that Respiration is an exothermic reaction. This means that Respiration releases energy (heat). When we shiver, we contract muscles all over our body, increasing the Respiration rate in muscle cells. As the cells are respiring at a greater rate, they release more heat, keeping our bodies warmer.
Similarly, we can increase our body temperature by using large groups of muscles when we're cold. One of the best ways to help someone who may be suffering from hypothermia is to have them stand up and walk around. This engages the muscles in their legs, which are some of the biggest muscles in the body, and causes lots of exothermic reactions to happen in the body, allowing the body temperature to increase!
Vasoconstriction also helps to prevent heat loss in our bodies. When the Blood vessels near the skin vasoconstrict, it forces less Blood to travel through them. As less Blood travels through these vessels closer to the skin's surface, less heat is lost through the skin.
In summary, our blood vessels vasodilate when we get too hot, increasing blood flow near the skin. This allows more heat to be lost through the skin, decreasing body temperature. As well as this, we also sweat. This allows the body to lose water from these glands, with the water then evaporating off the skin's surface, cooling the body down. When we get too cold, the opposite response happens. The blood vessels vasoconstrict, decreasing blood flow around the skin and allowing less heat to be lost through the skin. On top of this, we start shivering. This involves muscles in the body repeatedly contracting to generate heat.
Neural control of body temperature
A large proportion of Body Temperature Regulation is under neural control. This means that it is controlled by signalling pathways between different neurons. Neurons are nervous system cells. They carry electrical messages, causing changes very quickly compared to hormonal signalling. The changes caused by the nervous system are much shorter-lasting when compared to those caused by hormones.
Check out our Endocrine and Nervous Systems articles to better understand these critical body systems!
We can take the concepts discussed above and apply them to control of body temperature. Imagine the body detects that our body temperature is above the set point. This message needs to be quickly relayed to effectors so that a quick change can happen (for example, sweating). This allows our body temperature to quickly move back to the set point. Once this happens, we don't continue to sweat. Sweating (and shivering) often don't last for long periods, showing us that these responses are not long-lasting.
Let's outline the exact mechanism of body temperature under neural control. First, let's recap the necessary components of a central control mechanism. We need;
- Detectors
- Control Centre
- Effectors
- Negative Feedback
We discussed negative feedback in a previous section, so let's focus on the other components now. The detectors for regulating body temperature are temperature-sensitive neurons in the anterior hypothalamus. The hypothalamus is an area of the brain which controls many different homeostatic mechanisms. Once this sensory input reaches the brain, it is relayed through a connector neuron in the brain and sent to an effector via a motor neuron.
You may see the connector neuron, also named the relay neuron or coordinator neuron. These all refer to the neuron found inside the CNS that passes information from the sensory neuron to the motor neuron!
In general, effectors can be either muscles or glands. In the case of sweating, our effectors are sweat glands. If we were shivering, our effectors are muscles all over the body that contract to release heat.
Control of body temperature - Key takeaways
- Temperature receptors in the hypothalamus detect changes in body temperature and send signals to effectors, such as sweat glands or muscle cells to correct this.
- Thermoregulation is a homeostatic mechanism that uses negative feedback.
- When your body temperature increases above the set point, mechanisms such as sweating and vasodilation are activated.
- When your body temperature decreases below the set point, mechanisms such as shivering and vasoconstriction are activated.
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