Shivering (also called shuddering) is a bodily function in response to cold and extreme fear in warm-blooded animals. When the core body temperature drops, the shivering reflex is triggered to maintain homeostasis. Skeletal muscles begin to shake in small movements, creating warmth by expending energy. Shivering can also be a response to fever, as a person may feel cold. During fever, the hypothalamic set point for temperature is raised. The increased set point causes the body temperature to rise (pyrexia), but also makes the patient feel cold until the new set point is reached. Severe chills with violent shivering are called rigors. Rigors occur because the patient's body is shivering in a physiological attempt to increase body temperature to the new set point.
Biological basis
Located in the posterior hypothalamus near the wall of the third ventricle is an area called the primary motor center for shivering.[citation needed] This area is normally inhibited by signals from the heat center in the anterior hypothalamic-preoptic area but is excited by cold signals from the skin and spinal cord. Therefore, this center becomes activated when the body temperature falls even a fraction of a degree below a critical temperature level.[citation needed]
Increased muscular activity results in the generation of heat as a byproduct. Most often, when the purpose of the muscle activity is to produce motion, the heat is wasted energy. In shivering, the heat is the main intended product and is utilized for warmth.[citation needed]
The functional capacity of the thermoregulatory system alters with aging, reducing the resistance of elderly people to extreme external temperatures. The shiver response may be greatly diminished or even absent in the elderly, resulting in a significant drop in mean deep body temperature upon exposure to cold. Standard tests of thermoregulatory function show a markedly different rate of decline of thermoregulatory processes in different individuals with ageing.[4]
^Goldstein A. (1980). Thrills in response to music and other stimuli. Physiol. Psychol. 8, 126–129.
^Schoeller, F., Eskinazi, M., Garreau, D. (2018) Dynamics of the knowledge instinct: Effects of incoherence on the cognitive system. Cognitive Systems Research 47: 85-91.
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Oka, T. (2015). Psychogenic fever: how psychological stress affects body temperature in the clinical population. Temperature: Multidisciplinary Biomedical Journal, 2(3), 368–378. http://doi.org/10.1080/23328940.2015.1056907
^Ring, Francis J. and Phillips, Barbara, Recent Advances in Medical Thermology, pp. 31-33; Springer Publishing, 1984
External links
Look up shivering in Wiktionary, the free dictionary.