Thermoregulatory disorder

Physiology

• Thermoregulation is a vital function of the autonomic nervous system in response to cold and heat stress.
• Thermoregulatory physiology sustains health by keeping body core temperature within a degree or two of 37°C, which enables normal cellular function.
• Heat production and dissipation are dependent on a coordinated set of autonomic responses.
• The clinical detection of thermoregulatory impairment provides important diagnostic and localizing information in the evaluation of disorders that impair thermoregulatory pathways, including autonomic neuropathies and ganglionopathies.

Thermostat

• The physiological control of the body's core temperature takes place primarily through the hypothalamus, which assumes the role as the body's "thermostat".
• This organ possesses control mechanisms as well as key temperature sensors, which are connected to nerve cells called thermoreceptors.
• Thermoreceptors come in two subcategories; ones that respond to cold temperatures and ones that respond to warm temperatures.
• Scattered throughout the body in both peripheral and central nervous systems, these nerve cells are sensitive to changes in temperature and are able to provide useful information to the hypothalamus through the process of negative feedback, thus maintaining a constant core temperature.

Related diseases

Menopausal hot flashes

• Menopausal hot flashes are thought to be a disorder of thermoregulation initiated centrally within the medial preoptic area of the hypothalamus.
• These heat-loss mechanisms appear to be activated in the presence of normal core body temperature.
• Studies have demonstrated that thermal stimuli have the potential to alter sleep stages. The central thermoregulatory mechanism underlying hot flashes may affect hypnogenic pathways inducing sleep and heat loss in the absence of a thermal load.

Hyperthermia

Hyperthermia occurs when the body’s heat-regulating mechanisms fail, and the body temperature becomes too high.

Hypothermia

Hypothermia occurs when the body loses heat faster than it can produce it. Prolonged exposure to cold temperatures can cause hypothermia.

Infections

When a person has an infection, harmful microorganisms invade the body and multiply. These pathogens can thrive at typical body temperatures, but an increased temperature makes it more difficult for some of them to survive.

Endocrine disorders

The endocrine system comprises glands and organs that produce hormones, such as the pancreas, thyroid, pituitary gland, and adrenal glands. If something interferes with hormone production, it can affect body temperature.

Hypothyroidism, can lead to a lower body temperature, while an overactive thyroid, called hyperthyroidism, can cause a higher body temperature.

CNS disorders

• Brain injuries / tumors
• Spinal cord injuries
• Parkinson’s or MS

Sleep and Thermoregulation

• Sleep and body temperature are tightly interconnected in mammals
• Warming up our body helps to fall asleep and the body temperature in turn drops while falling asleep.
• Preoptic area of the hypothalamus (POA) serves as an essential brain region to coordinate sleep and body temperature
• In the 1920s, lesions in the POA were found to be associated with insomnia in human patients affected by encephalitis lethargica (von Economo, 1930)

• Studies suggest a critical role of the POA in integrating temperature information and triggering behavioral and autonomic responses through their central and peripheral downstream targets to adjust the body temperature
• Different types of sleep disorders, especially those associated with aging, may be influenced by altered body temperature rhythms or dysregulation of vasodilation resulting in an impairment to prepare the body for sleep
• Dysfunctions in sensing and transferring temperature information to the neurons controlling sleep within the POA may contribute to attenuate the sleep onset in the elderly. Elucidating how POA neurons receiving peripheral temperature signals interact with the sleep-promoting neurons and integrate circadian rhythms, and how these circuits become dysfunctional with aging will greatly improve our current therapeutics for sleep disorders.