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How heat affects our neurons

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Summer has many benefits for our body. Also for our brain.

The more hours of sunshine, the greater the production of serotonin, which positively affects our mood. Sunlight stimulates the production of the so-called “sunshine vitamin”, vitamin D, which has multiple health benefits. But not everything is happy: there is a heat limit from which our brain does not work properly: 40℃.

Human beings are homeotherms.

In other words, thanks to our hypothalamus – the region of the brain that regulates temperature – we are able to maintain a constant temperature of about 37 ℃, regardless of the ambient temperature. But when our body reaches temperatures above 40℃, the hypothalamus stops working properly and does not control our natural cooling system, perspiration (sweat).

That is when we can suffer a heat stroke.

Attention, balance, or sleep

In this situation, the nervous system is especially vulnerable. As the hypothalamus has to work excessively to maintain a suitable body temperature, other vital functions such as attention are left in the background, which is slowed down.

Something similar happens with the brain communication system. Nerve impulses take longer to spread and therefore our response capacity is much slower. We are, therefore, more tired and apathetic. All of this affects our mood, causing irritability and confusion. With heat, proteins denature – they lose their structure, they melt – which greatly affects neurons. This entire process also triggers an inflammatory response that modifies the homeostasis (balance) of the nervous tissue.

The reason is that high temperatures affect the blood-brain barrier that protects our central nervous system, altering that balance.

Specifically, there is a specific type of neuron that is especially sensitive to damage: Purkinje cells. These neurons are located in the cerebellum, and are responsible for motor function. Hence, one of the characteristic symptoms of heat stroke is motor weakness with severe impairment of coordination and balance.

High temperatures also make us rest worse.

Another function of the hypothalamus is to regulate sleep-wake cycles. To do this, it is guided by information that comes from the outside, such as the amount of light or temperature, which tell the brain when sleep should be induced. High temperatures confuse the hypothalamus , and hyperexcitation of the brain occurs, making it harder for us to fall asleep. Let’s not forget that our nervous system takes advantage of the hours of sleep to carry out maintenance functions necessary for its proper functioning. It is what we call “a restful sleep”.

Another problem associated with high temperatures is dehydration.

When it is above 2% of body weight it can lead to serious disturbances such as short-term memory loss , drowsiness or muscle fatigue. In addition, it favors that toxins are not eliminated correctly and accumulate in our body.

Does the brain freeze with cold drinks?

If at this point you are thinking that a possible solution to the heat would be to have a very cold drink, be careful! because our brain does not like sudden changes in temperature at all.

When drinking it, you can get a cold stimulus headache or, in other words, a strong feeling of headache when drinking something cold.

Our brain freezes. The answer to this effect is simple. We are confusing the circulatory system, which in turn is driving the brain crazy. And the brain responds with a wake-up call in the form of pain. We have already seen that our body is capable of regulating our body temperature. When it is cold our peripheral blood vessels constrict (shrink). This is what we call vasoconstriction. Thus the blood circulates away from the skin and body heat can be better maintained.

In hot weather, the peripheral vessels dilate (expand).

This is vasodilation

Thus, by expanding and being closer to the skin , heat transfer outside the body is favored. We sweat! and thus we control our body temperature. In summer the capillaries tend to be dilated to expel heat from the body. But if we suddenly drink something cold, the blood vessels quickly go from their normal dilation to remove heat, to contraction due to the cold of what we are drinking. The end result is that the circulatory system does not know how to act with so much heat and cold.

These changes in blood flow are detected by pain receptors in the palate and throat, which communicate with the brain through the trigeminal nerve , which sends sensory information about what is happening in the head. A portion of the trigeminal extends through the middle of the face and forehead, so the brain interprets that there is a problem and that sensation of stabbing pain occurs.

It is what we call a “referred pain”: it occurs in the palate or the throat but you feel it in the brain.

But do not spread panic

The brain doesn’t really feel pain, it’s just a feeling that goes away right away. To avoid this, you have to eat or drink slowly to get your palate used to this change in temperature. Although everyone has a trigeminal nerve, not everyone experiences brain freeze. Some people ‘s nerves may be more sensitive than others’. In fact, those who experience brain freeze may also be more prone to migraines. In conclusion, protect your brain from the heat, but be careful with the method you use. Although a cold drink or ice cream is well worth a few seconds of pain.


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