Sweat is a great cooling system, but if you're sweating a lot on a hot day or after playing hard you could be losing too much water through your skin. Then you need to put liquid back in your body by drinking plenty of water so you won't get dehydrated say: dee-HI-drayt-ed.
Sweat isn't just wet — it can be kind of stinky, too. But the next time you get a whiff of yourself after running around outside and want to blame your sweat glands, hold on! Sweat by itself doesn't smell at all. It's the bacteria that live on your skin that mix with the sweat and give it a stinky smell. And when you reach puberty, special hormones affect the glands in your armpits — these glands make sweat that can really smell. But sweating is vitally important for body temperature regulation and your overall health.
A person's internal body temperature generally hangs around 98 degrees Fahrenheit. There's flexibility here, but if your body gets too hot, whether it's due to the temperature outside, being physically active or having a fever, bad things can happen — for instance, heat stroke.
Fortunately, your body has very sophisticated mechanisms for sensing and regulating body temperature. As soon as your body's internal temperature starts rising, your hypothalamus a small region in your brain tells eccrine sweat glands distributed all over your body that it's time to start cooling you down by producing sweat.
Cooling down, however, isn't as easy as this sweat just dripping off of you. Some of this sweat has to evaporate off of your skin for this process to actually work. That's because cooling your body via sweating relies on a principle of physics called "heat of vaporization.
It takes energy to evaporate sweat off of your skin, and that energy is heat. As your excess body heat is used to convert beads of sweat into vapor, you start to cool down. The other trade off here, though, is that you also lose water as you sweat — and water is critically important for just about every organ in your body.
This means that when you're sweating, you also need to make sure you're drinking plenty of water so you can replace the water you lose with water you can use. All this to say, releasing heat through beads of sweat that can easily evaporate off the skin is a very effective way of cooling your body down.
By contrast, your dog releases heat by panting — which isn't nearly as effective as sweating. It is called idiopathic because no cause can be found for it. It can develop during childhood or later in life and can affect any part of the body, but the palms and soles or the armpits are the most commonly affected areas. The excessive sweating may occur even during cool weather, but it is worse during warm weather and when a person is under emotional stress.
Some known causes include:. In most cases, no investigations are required to diagnose hyperhidrosis. Occasionally, a blood test for thyroid disease is recommended. Reduced sweating is called hypohidrosis if there is partial loss of sweating, or anhidrosis if there is complete lack of sweating. This can occur for a number of reasons, which include:. Lack of sweating may create problems of temperature control and lead to steep rises in body temperature during hot weather.
Occasionally, this can be life threatening. Heat stroke or sun stroke can occur in hot weather when not enough sweat is produced to keep the body cool. Symptoms can include:. Excessive loss of body salts and water can lead to a life-threatening complication known as heat exhaustion.
Heat stroke can be managed, and heat exhaustion prevented, by seeking a cool, shaded place, drinking plenty of fluids and sponging the body with water, if necessary. Then, when the hypothalamus of the brain notices a temperature above the normal threshold, it activates a process called negative feedback. So as temperature goes up, the human body fights back by dilating blood vessels to give off heat and by sweating.
When body temperature returns to normal, the brain inactivates these processes. Once the body has been alerted that it needs to cool off, its sweat glands become active. There are 4 million of these glands all over the body — everywhere but the lips. The eccrine glands on the foreheads, palms and soles of our feet are connected to emotional signals as well as temperature changes.
This is why we get sweaty palms before giving a speech. How does sweating actually cool us off? Water released from our pores evaporates, cooling our skin and releasing heat.
This requires understanding a bit of molecular chemistry. If the liquid water increases in temperature, the average kinetic energy — energy from the movement of the different water molecules — also increases. If it reaches a certain temperature, the fastest moving molecules will move so quickly they can jump out of the pool, taking their energy with them. This technical explanation is essentially another way of saying that as the wind blows, in addition to heat from our bodies being directly carried away by the air aka convective heat transfer , water evaporates more quickly.
Along with water, we release salt and nitrogenous wastes, like urea. While it may seem efficient to dump these unwanted materials out with our sweat, it actually reduces the efficiency of evaporative cooling.
This is due to a concept in chemistry called colligative properties. They are a property of solutions that depend on the number of dissolved particles in the solution.
0コメント