Temperature control is very important in living things. In this article I will talk about temperature and the mechanisms we can carry out to regulate body temperature. Last week there have been unique temperature events, such as the Valley of Death that have reached the temperature of 54.4º.
Not all animals have equal temperature control. You can create a classification like the following depending on how they perform that control:
Body temperature control is not identical in all organisms. In homeotherms two types of temperature are distinguished:
The mechanisms of heat genesis (generation) occur in the central compartment. Losses occur in the surface compartment. Body temperature is going to be a weighted sum of the 2 factors.
En el control de la temperatura vamos a tener un centro termorregulador que es el hipotálamo. Llegan aferencias cutáneas que informan cual es la temperatura de la piel. Al hipotálamo llega información del compartimento central, en función de esta información el hipotálamo regula la termogénesis (generación de calor) y la termolisis (el calor corporal es eliminado).
To remove heat the body can perform several actions:
Thermogenesis are mechanisms of heat generation. Among them we find:
Heat is generated in the central compartment and removed in the surface compartment. From the central compartment to the surface compartment is heat is moved by:
In addition, there are thermal responses that will allow the body to cool or warm up. The most important thermal responses are:
At the level of the skin there is a fairly thick capillary plexus. Deeper there are arteriovenous anastomosis, small vessels that connect the arterial circuíto with the venous circuíto.
We can avoid cooling if we prevent them from passing near the skin, which is the area where heat is lost in such a way that according to the needs of the organism can occur entry and exit to the subcutaneous circle. This glass motility mechanism is the main mechanism for adjusting heat losses.
When a drop in temperature occurs our body has mechanisms to counteract that drop. The general action is called hypothermia. It is a body temperature of less than 35 °C. It occurs when the ambient temperature is very low and we are poorly sheltered and there are also air currents and heat dissipation in considerable ways. A wind of 20 ºC is as if we had an ambient temperature of 4 ºC. The wind complicates the situation.
If we are in contact with water, the body loses large amounts of heat by conduction. Snow is low heat conductive. Heat losses are minimized.
Thermogenic failure can occur. It does not occur in normal people but in the elderly, or children. The elderly have less muscle activity, worse overall temperature control, less fat and deficiencies in the hypothalamus. In children the mass-surface ratio is reduced with size. The ratio of surface area to volume is greater the smaller the radius. A pigeon has a higher volume surface ratio than we do. In children it also occurs and they have worse thermal control. There may also be hypothalamic lesions. Therefore, the thermal control is poor.
They’re pretty consistent. The most common are:
Continued exposure to cold leads to acclimatization to the cold. Man has colonized climates as aggressive as polar areas and deserts. It involves an increase in metabolic rate at the expense of an increase in thyroid production.
Hypothermia occurs in three phases:
In this case there are large temperature drops and they affect the surface compartment, especially the extremities. Maybe:
The most important is the freezing that affects the aerial parts, protruding parts of the corportal structure, the extremities. They are further away from the central compartment, losing heat more easily. The effect of freezing is due to different processes, the water of the cells crystallizes and prevents the transfer of information and normal operation. Crystals facilitate the denaturation of proteins and organelles of the cytoplasm.
Rupture coupled with vasoconstriction produces ischemia in the distal parts (lack of blood supply, associated with anoxia). An ischemia is infarctions, deaths of cells due to lack of blood supply. It will also facilitate the aggregation of lymphocytes which is an embolism, foreign particles inside a vessel or contents. The problem appears when embolisms clog small vessels producing ischemia. This occurs especially in arteriosclerosis.
Frostbite trigger the inflammatory reaction. According to the severity of the freeze they are classified into three groups:
There are also freezes like trench foot. It occurs because the foot cools in a humid and unhygienic environment, produces ischemia in the feet and the humid environment facilitates infection and infected yagas are formed, but without pain.
There is also the appearance of chilblains. Lesions with a bluish-red appearance and itching are due to small varicose veins in the superficial veins.
The cold starts pathophysiological processes are not frequent but they are not due to the drop in temperature. Redness effect, Raynoud phenomenon, if we put the hand in cold water and a progressive vascular process occurs, vasoconstriction and vasodilation after, white, blue and red hand edemas occur.
When there is an increase in heat we have three fundamental mechanisms:
In addition, people who live in warm climates, suffer acclimatization processes that are optimizations of individuals. It is based on lowering the temperature threshold to produce sweating. They are refrigerated before. It also increases sweating, it has a risk which is dehydration.
Ambient humidity can be an adjuvant factor to heat. The air is saturated at a certain temperature. The lower that temperature, the sooner the air becomes saturated. The best mechanisms to remove heat is sweating that depends on ambient humidity. The sweating ability is greatly reduced.
Heat can have a direct general action called heat stroke which is due to the inability of the body to cool to certain temperatures. It happens to marathon runners. The temperature was not very high but the atmosphere completely saturated and could not be properly cooled. Also inappropriate discharges in a humid and warm atmosphere. It affects athletes, welders and soldiers.
It is due to the inability to cool and if the temperature greater than 41 °C the proteins are denatured. When an egg is fried there is a change in appearance, the proteins are functional, they stop performing their function.
There is an increase in metabolism as well as increased heat production. Metabolism is the main generator of heat. You get into a vicious circle and that makes the situation worse. This will affect the organs that make up the body, the most sensitive are the central nervous system, muscle, liver, pancreas and kidney.
In addition another alteration is that by effect of heat this releases large amounts of coagulation proteins. Under normal conditions the blood does not coagulate since the anticoagulant factors if the balance is broken there are disseminated intravascular coagulations, in such a way that in any situation the coagulation that produces the disseminated vascular intravascular coagulation occurs. It produces generalized embolisms and will affect the function of the organs. One situation that occurs is in certain children suffering from meningitis. It can lead to death in a very short time.
There are 2 phases:
The most common is syncope due to heat. It is produced by a physiological conflict between 2 different stimuli. It happens in people who are standing. Heat produces vasodilation. The bipedal position involves vasoconstriction of the arteries of the upper mids.
Sometimes vasodilation predominates, displacement of the volume of fluid to the legs, blood pressure drops, the individual becomes dizzy.
There is also exhaustion. They are due to electrolyte disorders. Sweat is composed of water and is salty. Due to this salt loss disorders occur in the membrane potentials in the cells. Vasodilation on the descent instead of recovering the volume with salty liquid since the water needs water and salts. If they drink water, they suffer from cramps and exhaustion due to lack of electrolytes.
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