Thermoregulation

The Thermoregulation refers to all regulatory processes for maintaining body temperature. Warm-blooded animals maintain a constant temperature regardless of the outside temperature. The center of heat regulation is the hypothalamus.

What is thermoregulation?

Warm-blooded animals have to maintain their body temperature because the various systems and body processes in their organism are geared towards a certain ideal temperature. Humans have a body temperature of 37 degrees Celsius, relatively independent of the outside temperature. At these temperatures there is an ideal temperature environment for his body processes.

Like all other warm-blooded animals, humans are dependent on regulatory processes to maintain constant body temperatures. These processes are called thermoregulation or Thermoregulation summarized. Depending on the external temperatures, the organism initiates various processes within the framework of heat regulation, such as shivering cold, sweating, metabolic adjustments or fat burning.

The heat regulation eludes voluntary control and is completely automated. A physiological control loop is available for this purpose. Its first instance are the thermoreceptors. The detected temperature information is transmitted from the receptors to the thalamus in the central nervous system. The hypothalamus connected to it is the actual center of heat regulation. From this part of the central nervous system, commands are sent into the body that have a regulatory effect on body temperature.

Function & task

The human body is in permanent heat exchange with the environment through conduction, convection, radiation and evaporation. The individual exchange mechanisms initiate heat loss and passive heating at the same time. If both are no longer in balance, the organism must react with regulations to keep the body temperature constant.

The human body constantly produces heat in the thermogenesis of muscles and metabolism. It is relatively well insulated from the environment by subcutaneous adipose tissue. In addition, he has the ability to lower his temperature, which results as an imperative from the constant thermogenesis.

The thermal receptors bind permanently and involuntarily to temperature stimuli. The sense cells of the sense of touch are not only located on the superficial skin, but also in the tissues and especially the mucous membranes. They project the measured temperatures via the thalamus to the hypothalamus, where they are evaluated and, if necessary, answered with regulatory processes.

At low outside temperatures, the hypothalamus increases the tone of the sympathetic nervous system, which results in a wide variety of processes with the effect of saving heat and producing heat. For example, a temperature gradient is initiated. From the core of the body and the organs of the head, chest and abdominal cavity, the temperature in the peripheral tissues drops compared to the environment, especially in the muscles of the periphery.

The blood flow decreases within the outer layer of the body. This reduces the supply of heat with blood from metabolically active tissue. In this way, the periphery isolates the core of the body, so to speak. The peripheral blood vessels are less supplied with blood in order to minimize heat loss via the blood.

The skin pores contract for the same purpose. They also induce goose bumps. The straightened hair creates a small insulating layer of air through which the radiating body heat escapes more slowly. In extreme cold, muscle tremors are also induced. Muscle work creates heat. For this reason, the muscles are involuntarily stimulated to contractions. Shivering is only efficient in moderation. Therefore, it usually only starts when there is an acute risk of hypothermia.

The burning of brown adipose tissue initiated in the cold shows significantly more efficiency. Therefore, warm-blooded animals mainly serve combustion processes as regulatory measures in the cold.

The outside temperatures also have an effect on metabolic activity, which is mainly influenced by hormones by the hypothalamus. Metabolism is automatically increased in cold temperatures as increased metabolic rates produce heat. When it is hot, the hypothalamus reduces the tone of the sympathetic nervous system. The metabolism is then downregulated so as not to produce any additional heat. The vessels expand to stimulate heat loss through the blood.

The most important heat regulation for humans in hot outside temperatures, however, is the evaporation of sweat. When it is hot, the sweat glands are automatically stimulated to excrete more fluid and the evaporation of sweat has a cooling effect on the body.

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Illnesses & ailments

Thermal regulation can be affected by disorders due to medication and deficiency symptoms. Inadequate sweating in cold temperatures and shivering despite the heat can result. In addition, various diseases of the nervous system can disrupt the regulatory chain, especially in the case of injuries to the thalamus, the hypothalamus or their projection pathways. Lesions in the sympathetic area can also be responsible for dysregulations in the metabolism or in the muscles, which affect the processes of heat regulation.

Diseases of the sweat glands or metabolic diseases can also be responsible for dysregulation. The same applies to diseases of endocrine glands, such as the anterior pituitary lobe.

In the case of phenomena such as heat stroke, temperature regulation generally fails. The balance of heat regulation is thrown out of balance by heat damage to the cells and organelles. Heat strokes are often preceded by increased heat production, e.g. through extreme sports at hot temperatures. The enzyme system is damaged by heat stroke with core body temperatures of 40 degrees Celsius. The thermoregulatory mechanisms usually fail completely with this phenomenon. This often results in an uncontrolled increase in temperature, which in the end can even cause necrosis or multiple organ failure.

In general, abnormal temperature perception is not to be equated directly with disturbances in heat regulation. Perception of temperature is individual and depends on many factors that are not necessarily associated with the disease value.