Shivering

As Shivering Medicine knows a process of thermoregulation that tries to compensate for heat losses through automatic muscle activity in the event of a sharp drop in temperature. Shivering cold is triggered by the hypothalamus via the tremors. Disturbances in thermoregulation occur in diseases such as Sudeck's disease.

What is the shivering?

Shivering in the cold is a thermoregulatory process that is intended to ensure that the human body is at a good working temperature despite cold temperatures. Humans belong to the group of living beings that are at the same temperature and depend on the independence of their body temperature from outside temperatures, since processes such as the human metabolism depend on constant body temperatures. The greatest possible independence is made possible by thermoregulation.

In hot temperatures, for example, the human body automatically induces sweating. In cold temperatures, it gains warmth through processes such as shivering and the associated muscle activity. The net heat yield from shivering is low as long as the body has poor insulation. For example, the muscles need to be supplied with more blood, which means that when you start to shiver, heat is lost in particular.

The core temperature of the body only rises when the muscles involved are already warm. The involuntary tonic muscle activity of shivering therefore only sets in when there is a sharp drop in temperature and is only used by the body when there seems to be no other way out.

In warm-blooded animals such as humans, the central tremor line runs from the higher-level switching points of the thermoregulation to the main areas of the motor system. The shivering cold is triggered and maintained via this tremor line.

Function & task

Shivering cold should let people gain warmth. If the human body temperature falls due to high heat losses due to a low outside temperature, the main thermoregulatory switching point in the hypothalamus reacts to this phenomenon by stimulating the anterior pituitary gland. As a result of this stimulation, the anterior pituitary lobe releases TRH, i.e. the thyrotropin-releasing hormones. This process causes the sympathetic tone to increase involuntarily.

The increased sympathetic tone is evident in various effector organs. The peripheral blood vessels react to the increased tone, for example with vasoconstriction (vascular constriction), which throttles the loss of heat through body surfaces. The hair on the arrectores pilorum muscles stand up so that the pores of the skin close and heat loss caused by secretion is reduced.

The brown adipose tissue reacts to the increased tone of the sympathetic nervous system by producing heat in the form of increased lipolysis and in the muscles, extrapyramidal efferents generate an increase in skeletal muscle tone, which triggers the shivering and thus increases the release of heat.

The simultaneous release of TRH is also essential for heat production. The hormone corresponds to a tripeptide with different effects. As a neurotransmitter and neuromodulator, the hormone acts particularly internally in the hypothalamus and at the same time stimulates the increased secretion of TSH within the pituitary gland. The TSH in turn stimulates thyroxine secretion in the thyroid.

This hormone is converted into triiodothyronine in peripheral tissues, such as brown adipose tissue and the skeletal muscles, which is beneficial for heat generation in four different ways: In the metabolism, the basal metabolic rate increases, in the muscles the energy supply is increased through increased gluconeogenesis in the liver, In the brown adipose tissue, tremor-free heat build-up takes place on the basis of oxidative phosphorylation and the heart rate is increased by triiodothyronine.

Compared to the other processes of thermoregulation, shivering is rather uneconomical and has a correspondingly poorer heat balance than the tremor-free heat generation in brown adipose tissue.

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Illnesses & ailments

The thermoregulation and thus the shivering can be disturbed for various reasons. One of the most common reasons is iron deficiency, which particularly affects women and is often caused by high iron losses during menstruation or increased iron requirements during pregnancy.

In addition to disturbed thermoregulation, iron deficiency is associated with unspecific symptoms such as reduced endurance, general susceptibility to infections, increased fatigue or weakness. Increasing fatigue, increased irritability, headaches and a lack of concentration are common symptoms of iron deficiency. The same goes for hair loss.

With iron deficiency anemia and the associated anemia, the hemoglobin, hematocrit and the number of red blood cells decrease. Pronounced paleness, low blood pressure, unconsciousness and sleep disorders can be just as symptomatic of iron deficiency anemia as faster breathing, increased heart rate, changes in the nails, tongue papilla atrophy, swallowing disorders or even eating disorders such as Pica syndrome.

The thermoregulation and the shivering are not only disturbed by iron deficiency. Any disorders can just as well be related to diseases such as Sudeck's disease. In this disease, despite cold outside temperatures, there is, for example, an increased secretion of sweat and a widening of the blood vessels, as is actually done in the context of heat dissipation at hot outside temperatures. For heat dissipation, the processes described are typical functions of heat regulation that affect the entire body. In this way they ensure that the body temperature is maintained despite the heat. Since these processes occur independently of heat in Sudeck's disease, this activity pattern leads to a spontaneous one-sided reflex pattern, which significantly disrupts central thermoregulation.