What Controls Body Temperature?
The body temperature is controlled by a small area of the brain known as the hypothalamus which maintains the body’s temperature through thermoregulation.
The hypothalamus works like a thermostat for the body and maintains the temperature in the range of 97.7-99.5 °F (36.5-37.5 °C) .
- What Is Hypothermia?
Hypothermia is when the body temperature is lower than 95 °F (35.5 °C).
- What Is Fever?
Hyperthermia is when the body temperature is higher than 99.5 °F (37.5 °C).
- What Is Hyperpyrexia?
Hyperpyrexia is when the temperature is higher than 104 °F (40 °C).
1. How Does the Hypothalamus Regulate Body Temperature?
The Hypothalamus regulates body temperature (Thermoregulation) through 3 mechanisms: Afferent sensing, central sensing, and efferent responses .
- Afferent Sensing
Afferent sensing is associated with temperature sensors known as thermoreceptors that are distributed throughout the body.
Thermoreceptors are sensory nerve endings that are part of the nervous system. They are categorized into receptors for warmth detection and receptors for cold detection .
Receptors for warmth detection are known as C fibers, while receptors for cold are known as Aδ fibers.
- Central Control
This part is controlled by the hypothalamus which receives information about the body temperature from the thermoreceptors.
- Efferent Responses
Efferent responses are automatic responses to changes in the temperature such as sweating, vasoconstriction (narrowing of the vessels), vasodilatation (dilatation of the vessels), and shivering .
2. What Hormone Controls Body Temperature?
The hypothalamus is the part of the brain that controls body temperature; however, heat is internally generated by the metabolisms (energy production) of the different organs of the body where thyroid hormones such as thyroxine (T4), and triiodothyronine (T3) play an essential role.
3. Does Low Body Temperature Indicate Thyroid Problems?
A low body temperature is not necessarily due to problems with the thyroid; however, increased sensitivity to cold is one of the symptoms of hypothyroidism .
4. What Time of Day Is Body Temperature the Highest?
The highest body temperature was reported to be an early evening at 6 pm .
5. What Factors Affect Body Temperature?
Temperature fluctuations can be associated with the following factors:
Older individuals (more than 60 years old) have a lower temperature mean (average) compared to those individuals less than 60 years old  .
Women have a slightly lower temperature than men . However, during pregnancy and ovulation, this temperature increases, while it is lower at the start of the menstrual cycle.
- Circadian Rhythms
The body temperature is highest at 6 pm in the evening and lowest at 3 am in the morning .
- Physical activity
During physical activity and exercise the body generates a significant amount of heat due to the intense energy consumption.
There is an increase in the body s metabolism meals which leads to an increase in the temperature of the body.
Fever is due to infections such as a virus or bacteria, heat exhaustion, and inflammation (e.g., rheumatoid arthritis).
Antibiotics and blood pressure or seizures can increase the body temperature.
6. What Vitamins Help with Body Temperature?
Vitamins B1, B2, B3, B5, and B7 (Biotin) are directly involved in the metabolic conversion of food into energy necessary for the maintenance of body temperature.
7. Can Mental Stress Cause Fever?
Some individuals, especially young women, develop a high fever when they are exposed to emotional events which cause stress. This type of fever is known as psychogenic fever .
8. What Are the Disorders of Body Temperature?
Disorders of the body temperature include any disorders that can cause a fever or hypothermia.
8.1. What Causes Fever?
Fever is mainly caused by sepsis, however, inflammation, and medications can also contribute to fever.
8.1.1. What is Sepsis?
During sepsis, fever is caused by exogenous pyrogens (e.g., pathogens) or endogenous pyrogens such as cytokines that interact with an area of the brain known as the organum vasculosum of the lamina terminalis (OVLT) or supraoptic crest.
The activation of the OVLT results in the increase in the synthesis of molecules known as prostanoids which are involved in inflammation (e.g., prostaglandins and prostacyclins) and in vasoconstriction (thromboxanes).
Prostanoids act by slowing down the activity of the warm sensitive neurons of the hypothalamus leading to an increase in the temperature .
8.1.2. Is Fever Associated with Inflammation?
Inflammation is a natural event that occurs following tissue damage or infections that results in swelling, redness, heat, and pain.
During inflammation, several inflammatory mediators are released by the cells involved in wound healing or in fighting infections.
These mediators are also pyrogenic (causing fever) and may act in a similar way to that of the sepsis pyrogenic mediators.
In some cancer patients fever also appears to be mediated by the same mechanism as that of sepsis .
8.1.3. Which Drugs Induce fever?
Some pharmacological drugs can cause heat loss from the peripheries, directly damage tissues, interfere with the hypothalamus central temperature regulation, stimulate an immune response, or have pyrogenic properties .
- Antimicrobial agents such as beta-lactam antibodies and sulphonamides.
- Volatile anesthesic agents
- Anti-depressants such as SSRI
- Opioids such as fentanyl
- Central nervous system stimulants such as amphetamines and cocaine
- Psychedelics such as lysergide
- Anticholinergic agents such as bronchodilators and ephedrine
- Anti-emetics such as cyclizine
- Synthetic cathinones such as bupropion
8.1.4. What Is Endocrine fever?
Hyperthyroidism is associated with the increase in body temperature due to the increase in the secretion of the thyroid hormones, thyroxine (T4), and triiodothyronine (T3) that play an essential role in the metabolisms (energy production) of the different organs of the body .
8.2. What Causes Hypothermia?
There are several disorders and medications that cause hypothermia:
8.2.1. What Disorders Cause Hypothermia?
Some disorders can affect the body capacity to regulate core temperature:
- Anorexia Nervosa
- Poor Nutrition
- Spinal Cord Injuries
- Severe Arthritis
- Parkinson Disease
8.2.2. What Medications Cause Hypothermia?
Changes in body temperature can be caused by the following drugs:
- Narcotic Pain Medications
8.3. Heart-Related Illness
In chronic heart failure, there is an alteration in the balance between heat production and heat loss but also an increased risk of ischemia or stroke that can damage the brain and also affect the metabolism .
The body temperature is controlled by the hypothalamus through mechanisms that involve afferent sensing, central control, and efferent responses. Any factors that disturb the normal functioning of these mechanisms lead to a change in the body’s temperature.