Medicine knows as cold shivering a process of thermoregulation that attempts to compensate for heat loss by automatic muscle activity when the temperature drops sharply. Cold shivering is triggered by the hypothalamus via the tremor pathways. Disturbances in thermoregulation occur in diseases such as Sudeck’s disease.
What is cold shivering?
Medicine knows as cold shivering a process of thermoregulation that attempts to compensate for heat loss by automatic muscle activity when the temperature drops sharply. Cold shivering is a thermoregulatory process designed to maintain a good working temperature of the human body despite cold temperatures. Humans belong to the group of equi-warm organisms and depend on the independence of their body temperature from external temperatures, since processes such as human metabolism depend on constant body temperatures. The most extensive independence is made possible by thermoregulation. At hot temperatures, for example, the human body automatically initiates sweating. At cold temperatures, it gains heat through processes such as cold shivering and related muscle activity. However, the net heat gain from cold shivering is low as long as the body has poor insulation. For example, the muscles must be supplied with more blood, which means that heat is initially the main thing lost during shivering. The core temperature of the body only rises when the muscles involved are already warm. The involuntary tonic muscle activity of cold shivering therefore only sets in when the temperature drops sharply and is thus only used by the body when there seems to be no other way out. In warm-blooded animals, such as humans, the central tremor pathway extends from the higher-level switching points of thermoregulation to the main areas of the motor system. It is through this tremor pathway that cold shivering is initiated and maintained.
Function and task
Cold shivering is supposed to make people gain warmth. When the human body temperature, due to high heat loss from a low outside temperature drops, the main thermoregulatory circuit in the hypothalamus responds to this phenomenon by stimulating the anterior pituitary. This stimulation causes the anterior pituitary to secrete TRH, or thyrotropin-releasing hormone. This process causes the sympathetic tone to increase involuntarily. The increased sympathetic tone is manifested in various effector organs. Peripheral blood vessels, for example, respond to the increased tone with vasoconstriction (vasoconstriction), which throttles heat loss across body surfaces. At the musculi arrectores pilorum, the hairs stand up so that the skin pores close and secretion-induced heat loss is shut down. Brown adipose tissue responds to increased sympathetic tone by producing heat in the form of increased lipolysis, and in the muscles, extrapyramidal efferents produce an increase in skeletal muscle tone that triggers cold shivering, resulting in increased heat release. The simultaneous release of TRH is equally essential to 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. TSH in turn stimulates thyroxine secretion in the thyroid gland. This hormone is converted in peripheral tissues, such as brown adipose tissue and skeletal muscle, to triiodothyronine, which promotes heat production in four different ways: In metabolism, basal metabolic rate increases; in muscle, energy provision is increased by increased gluconeogenesis in the liver; in brown adipose tissue, shiver-free heat formation occurs based on oxidative phosphorylation; and heart rate is increased by triiodothyronine. Cold shivering, compared with the other processes of thermoregulation, is rather uneconomic and has a correspondingly worse heat balance than shiver-free heat generation in brown adipose tissue.
Diseases and ailments
Thermoregulation, and therefore cold shivering, can be disturbed for a variety of reasons. One of the most common reasons is iron deficiency, which affects women in particular and is often caused by high iron losses during menstruation or increased iron requirements due to pregnancy.In addition to impaired thermoregulation, iron deficiency is associated with non-specific symptoms such as a reduction in stamina, a general susceptibility to infections, increased fatigue or weakness. Increased fatigue, increased irritability, headaches and lack of concentration are also common accompanying symptoms of iron deficiency. The same is true for hair loss. In iron deficiency anemia and associated anemia, hemoglobin, hematocrit, and red blood cell count decrease. Pronounced pallor, low blood pressure, unconsciousness, and sleep disturbances may be as well symptomatic of iron deficiency anemia as accelerated breathing, increased heart rate, changes in the nails, tongue papillae atrophies, dysphagia, or even eating disorders such as pica syndrome. Thermoregulation and cold shivering are not exclusive to iron deficiency. Any disturbances may just as well be related to diseases such as Sudeck’s disease. In this disease, despite cold outside temperatures, for example, there is increased sweat secretion and widening of the blood vessels, which actually occurs as part of heat reduction in hot outside temperatures. For heat dissipation, the processes described are typical functions of heat regulation that affect the entire body. They thus ensure the maintenance of body temperature despite heat. However, because these processes occur independently of heat in Sudeck’s disease, this pattern of activity leads to a spontaneously unilateral reflex pattern that significantly disrupts central thermoregulation.