Control of Body Temperature

Homeostatic Control of Body Temperature

Thermoregulation requires coordination between the brain, a central nervous system (CNS) component, and effectors.

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!

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.

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.

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.

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):

• Sweating

• Vasodilation

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.

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.

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.

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.

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.