When it is winter outside, why do some animals hibernate, while others go dormant? This has to do with different mechanisms of body temperature regulation! Our bodies regulate our body temperature to ensure we don’t suffer damage from cold or hot weather. They maintain a constant temperature by adjusting to the surrounding environment.
Let's delve a bit deeper into how we do this.
- First, we will review the definition of homeostasis.
- Then, we will define thermoregulation in the human body.
- Next, we will look into the different mechanisms of thermoregulation in humans and in other animals.
- Finally, we will go through the different disorders associated with thermoregulation and their underlying causes.
What is thermoregulation?
Before we look at how we regulate our body temperature, you need to know that our bodies try to maintain the equilibrium of our body mechanisms while adjusting to external stimuli. This is called homeostasis.
Homeostasis refers to the ability of an organism to maintain constant internal conditions regardless of changes in its external environment.
As an example, let's look at the regulation of blood glucose.
When your blood glucose level increases, the pancreas releases insulin to bring down these levels. Conversely, when blood glucose levels decrease, the body releases glucagon to raise blood sugar levels. This is done to maintain a constant glucose level to prevent a fluctuation that, if prolonged, can cause diabetes.
Now that you know how our body maintains equilibrium, we can talk about what thermoregulation is.
Thermoregulation is the ability of an organism to maintain and control the core internal temperature of its body, regardless of the external temperature.
Thermoregulation mechanisms bring our bodies back to homeostasis. Not all organisms can regulate their body temperature to the degree that humans can, but all organisms have to maintain it to some extent, if only to prevent internal damage.
Autoimmune Body Temperature Regulation
The human body's temperature ranges between 36.67 °C (98 °F) and 37.78 °C (100 °F). A common way our bodies regulate temperature is by sweating or shivering when it gets too hot or cold. An organism needs to maintain homeostasis because fluctuations in the internal temperature for a prolonged period can cause fatal damage.
Now, you may be wondering: what controls body temperature? And the answer to this is the hypothalamus in the brain region!
The brain's hypothalamus acts as a thermostat and regulates the body temperature.
For instance, if your body starts to heat up and deviates from the normal temperature range, the hypothalamus sends signals to the sweat glands, which help in heat loss and cool down your body via evaporation. Thus, the hypothalamus responds to external stimuli by initiating heat loss or heat promotion.
Types of thermoregulatory systems
There are two types of thermoregulatory systems: endotherms and ectotherms. Have you ever heard of "warm-blooded" and "cold-blooded" animals? If so, you might be familiar with the concept of endotherms and ectotherms, although you know them by their common names. You should know that the colloquial terms aren’t scientifically accurate, though, and are often avoided in scientific communication.
Endotherms
Fig. 2. Horses, like all mammals, are endotherms. Source: Unsplash.
Endotherms are mostly birds, humans and other mammals. They survive by generating heat through metabolic reactions. Such animals are usually called warm-blooded and produce a rapid amount of heat because of their very high metabolic rate.
Endotherms are organisms that are capable of generating sufficient metabolic heat to raise their body temperature above their surroundings.
In a cold environment, endotherms will generate heat to keep their bodies warm, while in a warm environment, the body will use sweating or other thermoregulation mechanisms to bring down the body temperature.
Ectotherms
Fig. 3. Lizards, like all reptiles, are ectotherms. Source: Unsplash.
Ectotherms, on the other hand, are typically called cold-blooded animals. No, it does not mean that these animals have cold blood, but rather that these animals depend on external heat sources to stabilize their body temperature. Ectotherms generally have a very low metabolic rate, meaning they don’t require a lot of nutrition or food. This is especially advantageous if food is scarce.
The body temperature of an ectotherm is largely determined by the external environment in which the organism resides.
Ectotherms do regulate their body temperature, but only for behavioural strategies such as basking in the sun or hiding in the shade to adjust their body temperature according to the surrounding environment.
Mechanism of thermoregulation
You now have an idea of the different thermoregulatory systems. Let's now look at the different mechanisms of thermoregulation and see how different organisms generate or lose heat to keep their body temperature stable.
There are a few more ways in which our body cools or raises our body temperature. It can simply be from sweating or a decrease in blood flow. Let’s explore how this works.
Heat generation
If an animal’s body needs to increase body temperature, it can do so in the following ways:
Vasoconstriction: When the receptors on your skin are subjected to cold stimuli, the hypothalamus sends signals to the blood vessels under your skin, causing them to become narrow. As a result, the blood flow decreases and retains heat in your body.
Heat loss
Conversely, if an animal observes an increase in body temperature greater than the normal range, it can cool down in the following ways:
- Vasodilation: When the body starts to overheat, the hypothalamus will send a signal to the blood vessels under the skin to widen. This is done to send the blood flow to the skin where it is cooler, thus releasing heat by radiation.
- Perspiration: We have already discussed how sweating, or perspiration, causes the body to cool down by the evaporation of sweat from the sweat glands on your skin. This is how humans cool their body temperatures most effectively, as the heat gathered by water evaporates and cools the body.
Below is a table highlighting the key differences between heat generation and heat loss:
HEAT GENERATION | HEAT LOSS |
Vasoconstriction | Vasodilation |
Thermogenesis | Perspiration |
Increased metabolism | Decreased metabolism |
Table
1. The table above shows the difference between heat generation and loss summary. Hormones Involved in Body Temperature Regulation
External conditions such as weather, and internal conditions such as illnesses, central nervous system (CNS) disorders, etc. can affect your body temperature. To counter this, the hypothalamus will take the necessary precautions to bring homeostasis to the body’s temperature. There are, in some cases, hormones involved that either increase or decrease the body temperature.
Estradiol
Estradiol is a form of estrogen, a hormone mainly synthesized by the ovaries in the female sex. It is a hormone that is used to bring the body’s temperature back to homeostasis by reducing the body temperature. The release of estradiol triggers vasodilation and promotes heat dissipation through radiation by making blood vessels broader. Low estradiol levels in the body can cause hot flashes or night sweats, which are usually seen during menopause in women.
Progesterone
Progesterone is another sex hormone produced in our bodies, although, the levels of progesterone are higher in females than males. Progesterone acts on the hypothalamus and acts as a trigger for increasing the body temperature. It increases metabolism and, as a result, increases body temperature. Progesterone levels elevate during the menstrual cycle and in turn also elevate the body temperature.
Body temperature regulation problems
If the body fails to maintain the internal temperature within the normal range, it can cause life-threatening disorders. There are two types of thermoregulatory issues called hyperthermia and hypothermia. Let's see how they get triggered and what happens as a consequence.
Disorders of Body Temperature Regulation
There are several disorders that are caused by external circumstances like weather, infection, and other factors.
Hyperthermia
When a person’s body temperature increases abnormally, they experience hyperthermia, which means that their body absorbs more heat than it can release.
In such cases, the person may experience dizziness, dehydration, cramps, low blood pressure, and high fever, among other dangerous symptoms. Such a case requires emergency medical treatment.
Hyperthermia is caused when a person is exposed to extreme heat and suffers overexertion. As a result, the body temperature may increase by more than 104 °F (40 °C), which can cause brain damage in extreme cases.
Hypothermia
Hypothermia is the opposite of hyperthermia, when a person is exposed to extremely cold temperatures, and the body can’t generate enough heat to maintain homeostasis.
Hypothermia is even more dangerous as it affects your ability to think clearly and can affect your decisions. Symptoms include shivering, memory loss, confusion, exhaustion, etc. A person exhibiting symptoms of hypothermia must receive medical assistance as it can be fatal. A hypothermic person's body temperature may drop below 95 °F (35 °C)
Causes of inability to regulate body temperature
What renders the body unable to regulate its body temperature? We have discussed so far how extreme weather can act as a trigger for a body temperature disorder. However, other factors can cause a body temperature disorder as well.
Age
Old people and infants have low immunity coupled with a decreased shiver reflex, which can reduce their ability to thermoregulate.
Infection
Many times, a person suffering from an infection may have a high fever. This is the body's defence mechanism to kill pathogens. However, if the person’s temperature is higher than 105 °F (40.5 °C), they may require medications to bring down their body temperature.
Disorders of the central nervous system (CNS)
A CNS disorder can impair the hypothalamus’ ability to thermoregulate. Disorders or injuries like brain damage, spinal injury, neurological diseases, etc.
Drug and alcohol use
People under the influence of drugs and alcohol can have impaired judgement about the cold weather and may lose consciousness, leaving them in a vulnerable state. This may lead to hypothermia in some cases.
Great! You are now familiar with thermoregulation, the body’s mechanism to regulate temperature, its importance, and the disorders that can happen if proper care isn’t taken.
Body Temperature Regulation - Key takeaways
- Thermoregulation is the ability of an organism to regulate and maintain a constant internal temperature.
- The human body's temperature ranges between 98 °F (36.67 °C) and 100 °F (37.78 °C).
- Endotherms generate heat through rapid metabolism to maintain homeostasis, while Ectotherms rely on external heat sources to regulate body temperature.
- Hyperthermia occurs when a person's body temperature exceeds 104 °F (40 °C).
- Hypothermia occurs when a person's body temperature falls below 95 °F (35 °C).
References
- Zia Sherrell, What is thermoregulation, and how does it work?, MedicalNewsToday, 2021
- Kimberly Holland, Thermoregulation, Healthline, 17 Oct 2022.
- Energy flow through ecosystems, Khan Academy.
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