Temperature Regulation

1. Responses
2. Classifications of Body Temperature
3. Difficulty Managing Body Temperature
   
   • The Elderly
   • The Very Young
   • Those with Long Term Disease
4. Quiz

• Temperature is regulated in the body through a negative feedback loop and needs to be maintained within a normal range, so that the body can function properly.
• The ideal temperature is around 37°C.
• The body has many mechanisms to help keep the temperature ideal such as shivering, sweating, vasoconstriction, vasodilation and voluntary actions.
• The elderly, the very young and those with chronic disease can struggle to put these mechanisms into place, meaning they can sometimes struggle to regulate their own body temperature. 

Feedback

Temperature regulation (also called thermoregulation) is an important feature of human homeostasis. This is because, broadly, the body needs to balance; providing heat as activation energy for reactions in cells vs limiting heat so as not to denature any enzymes. This is done through a negative feedback loop, as shown in the diagram below. To learn more about feedback loops, see our article Introduction to Endocrinology in our Endocrinology series.

Diagram - Negative feedback shown diagrammatically, with regulation of body temperature used as an example

Creative commons source by OpenStax [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

The ideal body temperature is 37°C ± 1°C. This is the range at which the body can work most efficiently, and the temperature will oscillate within this range as the negative feedback loop circulates.

The sensors of temperature exist in the skin (measures external ambient temperature), and the hypothalamic preoptic area (detects core body temperature). The hypothalamic preoptic area measures the temperature of the blood directly and receives impulses from the thermoreceptors in skin and mucous membranes.

Responses

If the body is too hot, the following things occur to attempt to cool it:

• Reduced sympathetic vasoconstrictor tone and activation of cholinergic sympathetic fibres, leading to increased cutaneous vasodilation.
• Sweating - sweat glands activated all over the body.

If the body is too cold, the following things occur to attempt to warm it:

• Increased sympathetic noradrenergic activity leading to increased vasoconstriction.
• Shivering - Repeated muscle contraction requires more ATP, so more respiration, which releases heat as a by-product.

Humans can also employ voluntary mechanisms, like putting on a jumper or seeking shade.

Classifications of Body Temperature

• <28°C - Life threatening Hypothermia
• <35°C - Hypothermia
• 36.5-37.5°C - Typical normal adult core body temperature range
• >38°C - Hyperthermia
• >41°C - Severe Hyperpyrexia

It is important to know the definitions of hypo- and hyperthermia, because this will affect the management of a patient who presents at this temperature.

Preview the Temperature Regulation quiz