Thermoregulation is the biological mechanism responsible for maintaining a steady internal body temperature. The three mechanisms of thermoregulation are efferent responses, afferent sensing, and central control.
The thermoregulation system includes the hypothalamus, sweat glands, circulatory system, and skin.
The human body maintains a temperature of about 98.6°F (37°C) using various physical processes. These include sweating to lower the body temperature, shivering to raise it, and narrowing or relaxing blood vessels to alter blood flow.
If an individual is unable to regulate their temperature, they could overheat, leading to hyperthermia. The opposite is also true: If the core temperature falls below a safe level, it will cause hypothermia. Both conditions can potentially be life threatening.
This article explores thermoregulation and how this essential process works. It also covers thermoregulation disorders and their possible causes.
Thermoregulation is how mammals maintain a steady body temperature. Unlike reptiles, which have a body temperature that changes with their environment, mammals need to keep a consistent body temperature all of the time. In humans, the healthy range is within a degree or two of 98.6°F (37°C).
When thermoregulation works as it should, the body performs at its optimum level. A temperature that is too high or too low
- heart
- circulatory system
- brain
- gastrointestinal tract
- lungs
- kidneys
- liver
The human body uses
- efferent responses
- afferent sensing
- central control
Efferent responses are the behaviors that humans can engage in to regulate their own body temperature. Examples of efferent responses include putting on a coat before going outside on cold days and moving into the shade on hot days.
Afferent sensing involves a system of temperature receptors around the body to identify whether the core temperature is too hot or cold. The receptors relay the information to the hypothalamus, which is part of the brain.
The hypothalamus acts as the central control, using the information it receives from afferent sensing to produce hormones that alter body temperature. These hormones send signals to various parts of the body so that it can respond to heat or cold in the following ways:
| Response to heat | Response to cold |
|---|---|
| sweating | shivering, or thermogenesis |
| dilated blood vessels, known as vasodilation | constricted blood vessels, known as vasoconstriction |
| decrease in metabolism | increase in metabolism |
The healthy temperature range for the human body is very narrow. If the body cannot maintain a temperature within this range, thermoregulation disorders can develop.
Hyperthermia
Hyperthermia occurs when the body’s heat-regulating mechanisms fail, and the body temperature becomes too high. There are
- heat cramps, which present as heavy sweating and muscle cramps during exercise
- heat exhaustion, which is more serious and causes a range of symptoms
- heatstroke, which is a medical emergency
The symptoms of heat exhaustion are:
- sweating
- pale, clammy, or cold skin
- fast or weak pulse
- tiredness
- weakness
- dizziness
- nausea or vomiting
- headaches
- fainting
Heatstroke causes similar symptoms, but with some important differences, including:
- flushed or hot skin, which may be dry or damp
- a fast, strong pulse
- a body temperature of 103°F (39.4°C) or higher
Learn more about the differences between heat exhaustion and heatstroke.
Hypothermia
Hypothermia occurs when the body loses heat faster than it can produce it. Prolonged exposure to cold temperatures can cause hypothermia. The symptoms
- shivering
- confusion
- exhaustion or feeling very tired
- fumbling hands
- slurred speech
- drowsiness
- memory loss
In young children and babies, hypothermia causes cold skin, which may be bright red in those with light skin tones.
Several factors can affect thermoregulation, including environmental conditions, diseases, and certain medications.
Extreme weather
Extreme weather can significantly affect the body’s ability to regulate temperature.
Hypothermia occurs when a person has exposure to extremely cold temperatures for an extended period. In these instances, the body loses heat quickly, and heat production cannot keep up, causing a dip in body temperature.
In addition to freezing temperatures, hypothermia can also occur in cool temperatures if sweat, rain, or submersion in cold water chills someone.
On the opposite end of the spectrum, hot weather and extended exposure to the sun can cause the body to overheat. Instead of losing more heat than it can produce, the body heats up faster than it can cool itself down.
Someone may
- drinking insufficient fluids
- wearing heavy, insulating clothing
- visiting overcrowded places
- exerting themself physically, especially outside
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.
For this reason, part of the immune response to infections is often a fever. This occurs when the body raises its own temperature in an effort to kill infection-causing organisms. Many doctors recommend letting a fever run its course so that the body can adequately protect itself.
However, problems can arise if the body temperature becomes too high, hindering necessary functions. If someone has a fever above
Age
Infants and older adults have a
Older adults tend to have a lower body temperature and may not develop fevers when they contract a viral or bacterial illness. Sometimes, they can develop hypothermia instead.
Other diseases
Other diseases can also affect thermoregulation. These include:
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.
For example, an underactive thyroid, or hypothyroidism, can lead to a lower body temperature, while an overactive thyroid, called hyperthyroidism, can cause a higher body temperature.
Central nervous system (CNS) disorders
The CNS includes the brain, spinal cord, and nerves. Conditions that affect the CNS can interfere with thermoregulation by impairing afferent sensing and central control. Some examples of these conditions
- brain injuries
- spinal cord injuries
- neurological diseases, such as Parkinson’s or multiple sclerosis
- tumors
Medications
Certain medications can disrupt thermoregulation as a side effect, causing a temporary rise in body temperature. Some people refer to this as “drug fever.” Examples of medications that can have this effect include:
- antimicrobials, such as antibiotics
- nonsteroidal anti-inflammatory drugs (NSAIDs)
- first generation anticonvulsants
- antidepressants
Usually, thermoregulation quickly returns to normal when a person stops taking the drug. People should always speak with a doctor before changing the dosage of their medication.
Mammals use thermoregulation to keep the body within a tight temperature range. This is essential for health, as it allows organs and bodily processes to work effectively.
If a person’s body temperature strays too far from 98.6°F (37°C), they can develop hyperthermia or hypothermia. Various factors can contribute to this, including infections, extreme weather, medications, and other health conditions.
Thermoregulation disorders can be a medical emergency. If a person has symptoms of hypo- or hyperthermia, it is important to dial 911 or the number of the nearest emergency department.