Thermoregulation physiology

What is the Thermoregulation physiology: Let us know about Thermoregulation physiology. Temperature is the process that allows organisms to regulate their body temperature, modulating heat loss and gain. The animal kingdom has different mechanisms of temperature regulation, both physical and moral. (Thermoregulation physiology)

Regulating body temperature is a basic activity for any living being, since the parameter is important for the homeostasis of the body and affects the functionality of enzymes and other proteins, membrane fluidity, ion flow, and others.

In their simplest form, thermoregulation networks are activated through a circuit that integrates the inputs of thermoreceptors located in the skin, in the viscera, in the brain, among others.

The main mechanisms in the face of these cold or heat stimuli include cutaneous vasoconstriction, vasodilation, heat production (thermogenesis) and sweating. Other mechanisms include behaviors to promote or reduce heat loss.

Thermoregulation physiology
Thermoregulation physiology

Basic Concepts: Heat and Temperature

In order to talk about thermoregulation in animals, it is necessary to know the exact definitions of words that are often confused among students.

Understanding the difference between heat and temperature is essential to understand the thermal regulation of animals. We’ll use inanimate bodies to tell the difference: Think of two metal cubes, one 10 times bigger than the other.

Each of these cubes is in a room at a temperature of 25 °C. If we measure the temperature of each block, both will be at 25 °C, although one is larger and the other is smaller.

Now, if we measure the amount of heat in each block, the result will be different between the two. To do this we must move the blocks to a room with absolute zero temperature and determine the amount of heat they give off. In this case, the amount of heat in the larger metal cube would be 10 times greater.


Thanks to the previous example, we can conclude that the temperature is the same for both and is independent of the volume of each block. Temperature is measured as the speed or intensity of movement of molecules. (Thermoregulation physiology)

In the biological literature, when authors refer to “body temperature”, they refer to the temperature of the central regions of the body and the peripheral regions. The temperature of the central regions reflects the temperature of the “deep” tissues of the body – the brain, heart and liver.

On the other hand, the temperature of the peripheral regions is affected by the passage of blood to the skin and is measured in the skin of the hands and feet.


Conversely – and returning to the example of blocks – heat is different in both inert bodies and is directly proportional to the amount of matter. It is a form of energy and depends on the number of atoms and molecules of the substance in question.

Type: Thermal Bonding Between Animals

In animal physiology, there are a range of terms and categories used to describe thermal relationships between organisms. Each of these animal groups has special adaptations – anatomical, physiological or physiological – that help them maintain their body temperature within an adequate range.

In everyday life, we call endothermic and homeothermic animals”warm-blooded”, and poikilothermic and ectothermal animals”cold-blooded”.

endotherm and ectotherm

The first term is endothermy, it is used when the animal manages to warm up with the metabolic production of heat. The opposite concept is exothermic, where the temperature of the animal is imposed by the surrounding environment.

Some animals are unable to be endothermic, because although they produce heat, they do not fast enough to hold it.

Poikilotherm and Hometherm

Another way to classify them is according to the animal’s thermoregulation. The term poikilothermic is used to refer to animals with variable body temperatures. In these cases, the body temperature is higher in the hot environment and it is lower in the cold environment.

A Poikilotherm animal can self-regulate its temperature through behavior. That is, hiding it from the said radiation by detecting it in areas of high solar radiation to raise the temperature, or to reduce it.

The terms poikilotherm and ectotherm basically refer to the same phenomenon. However, poikilotherm emphasizes the variability of body temperature, while in ectotherm it refers to the importance of ambient temperature to determine body temperature.

The opposite term of poikilotherm is homeotherm: thermoregulation by physical means – and not just thanks to the deployment of behaviour. Most endothermic animals are able to regulate their temperature. (Thermoregulation physiology)



Fish are the perfect example of ectothermic and poikilothermic animals. In the case of these vertebrate swimmers, their tissues do not generate heat through metabolic pathways and, in addition, the temperature of the fish is determined by the body temperature of the water where they swim.


Reptiles display very marked behaviors that allow them to (morally) regulate their temperature. These animals seek out warm areas – such as perching on a hot stone – to raise the temperature. Otherwise, where they want to reduce it, they will try to hide from the radiation.

birds and mammals

Mammals and birds are examples of endothermic and homeothermic animals. These metabolically produce their body temperature and regulate it physiologically. Some insects also exhibit this physiological pattern.

Its ability to regulate temperature gave these two lineage animals an advantage over their poikilothermic counterparts, as they could establish a thermal equilibrium in their cells and their organs. This made the processes of nutrition, metabolism and excretion more robust and efficient.

For example, humans maintain their temperature at 37 °C, within a fairly narrow range – between 33.2 and 38.2 °C. Maintaining this parameter is absolutely vital for the survival of the species and mediates a range of physiological processes in the body.

Spatial and temporal endothermy and alternation of ectothermia

The distinction between these four categories often becomes confusing when we examine the cases of animals that alternate between categories either spatially or temporally.

Temporary alterations of thermal regulation can be discounted by mammals that experience periods of hibernation. These animals are usually homeothermic during the season of the year when they are not hibernating and are not able to regulate their body temperature during hibernation.

Spatial variation occurs when the animal regulates the temperature in areas of the body regularly. Bumblebees and other insects can regulate the temperature of their thoracic segments and are unable to regulate the rest of the areas. This state of differential regulation is called heterothermy. (Thermoregulation physiology)

physiology of thermoregulation

Like any system, the physiological regulation of body temperature requires the presence of an afferent system, a control center and an effective system.

The first system, the afferent one, is in charge of capturing information through dermal receptors. After this, the information is transmitted through the nerve to the thermoregulatory center through the blood.

Under normal circumstances, the body’s organs that generate heat are the heart and liver. When the body is performing physical work (exercise), skeletal muscle is also a heat generating structure.

The hypothalamus is the thermoregulatory center and functions are divided into heat loss and gain. The functional region mediating heat maintenance is located in the posterior region of the hypothalamus, whereas the loss is mediated by the anterior region. This organ acts like a thermostat.

The control of the system is dual: positive and negative, mediated by the cerebral cortex. Affective responses are of the behavioral type or are mediated by the autonomic nervous system. Both these mechanisms will be studied later.

thermoregulation mechanism

body system

The mechanisms for regulating the temperature differ between the types of temperatures achieved, i.e. whether it is an increase or decrease in temperature. So we will use this parameter to establish the classification of the mechanism:

high temperature regulation

In order to achieve regulation of body temperature against heat stimuli, the body must promote its loss. There are several mechanisms:


In humans, one of the most important features of skin circulation is the wide range of blood vessels. Blood circulation through the skin varies greatly depending on environmental conditions and changes from high to low blood flow.

The ability of vasodilatation is important in the thermoregulation of individuals. The high blood flow during periods of increased temperature allows the body to increase the transmission of heat, from the core of the body to the surface of the skin, eventually dissipating. (Thermoregulation physiology)

When blood flow increases, blood volume increases in turn. Thus, a large amount of blood is transferred from the core of the body to the surface of the skin, where heat transfer takes place. The blood, now cooler, is transferred back to the nucleus or center of the body.


Along with vasodilatation, sweat production is important for thermoregulation as it helps with the dissipation of excessive heat. In fact, sweat production and subsequent evaporation are the body’s main mechanisms for losing heat. They also function during physical activity.

Sweat is the fluid produced by the sweat glands, called eccrine, distributed throughout the body in a significant density. The evaporation of sweat manages to transfer body heat to the environment in the form of water vapor.

low temperature regulation

In contrast to the mechanisms outlined in the previous section, in conditions of a drop in temperature, the body must promote the conservation and production of heat by:


This system follows the opposite logic described in vasodilatation, so we will not go into much detail in the explanation. Cold stimulates the contraction of the dermal vessels, thus prevents heat dissipation.  


Have you ever wondered why “goose bumps” appear when we are facing low temperatures? This is a mechanism to avoid heat loss called pilgrimage. However, as humans have relatively little hair in our body, it is considered a poorly rudimentary system.

When each hair regrows, the layer of air that comes into contact with the skin increases, reducing air convection. This reduces heat.

heat generation

The most intuitive way to combat low temperatures is through the production of heat. This can happen in two ways: by shivering and non-shivering thermogenesis.

In the first case, the body produces rapid and involuntary muscle contractions (which is why you shiver when you are cold) that produce heat. Shivering production is expensive – energetically speaking – so the body will resort to it if the above systems fail.

The second mechanism is led by a tissue called brown fat (or brown adipose tissue), in English literature it is usually summarized under the abbreviation. brown adipose tissue ).

This system is responsible for reducing the production of energy in metabolism: instead of creating ATP, it leads to the production of heat. This is a particularly important mechanism in children and small mammals, although the most recent evidence has noted that it is also relevant in adults.

moral system

Moral apparatus includes all the behaviors exhibited by animals to regulate their temperature. As we have mentioned in the example of reptiles, organisms can be placed in the environment of the future to promote or avoid heat loss.

Different parts of the brain are involved in the processing of this response. These behaviors are effective in humans, although they are not physically correct.

changes in thermoregulation

The body experiences small and delicate changes in temperature throughout the day, which depend on certain variables, such as circadian rhythms, hormonal cycles, among other physiological aspects.

As mentioned, body temperature orchestrates a vast range of physiological processes and the loss of its regulation can lead to disastrous conditions within the affected organism.

Both thermal extremes – both high and low – negatively affect organisms. Very high temperatures, above 42 °C in humans, affect the proteins, promoting their denaturation. In addition, DNA synthesis is affected. Organs and neurons are also damaged.

Similarly, temperatures below 27 °C cause severe hypothermia. Changes in neuromuscular, cardiac and respiratory activity have fatal consequences.

When thermoregulation does not work properly, many organs are affected. Among them, the heart, brain, gastrointestinal tract, lungs, kidneys and liver.