Body temperature and the thermoregulatory centre
Greg Foot explains the role of the hormone ADH on the permeability of the kidney tubules - regulating the water levels in the body
The conditions inside our body must be carefully controlled to allow it to function effectively. The maintenance of a constant internal environment in the body. is the maintenance of a constant internal environment in the body. The Body system that includes the brain, spinal cord and nerves. and Chemical messengers produced in glands and carried by the blood to specific organs in the body. are responsible for controlling this.
The body control systems are all automatic, and involve both nervous and chemical responses. It has many important parts, including:
- Organ, tissue or cell that detects a stimulus. detect a stimulus, which is a change in the environment, such as temperature change
- Coordination centres in the brain, spinal cord and pancreas. They receive information from the receptors, process the information and instigate a response.
- The organ, tissue or cell that produces a response., such as muscles or glands create the response. Glands often release a hormone, which would restore the optimum condition again.
Body temperature
Body temperature is one of the factors that is controlled during homeostasis. The human body maintains the temperature that A protein which catalyses or speeds up a chemical reaction. work best, which is around 37°C.
If body temperature increases over this temperature, enzymes will denature and become less effective at catalysing important reactions, such as respiration.
This process is controlled by the thermoregulatory centre, which is contained in the hypothalamus in the brain, and it contains receptors sensitive to the temperature of the blood. The skin also has temperature receptors and sends nervous impulses back to the hypothalamus.
The hypothalamus responds to this information by sending Electrical signals that travel along the nerve fibre from one end of the nerve cell to the other. to effectors in the skin to maintain body temperature.
The skin
The skin contains three layers: The epidermis, dermis and a layer of fatty tissue.
Structures within these layers are involved in thermoregulation.
Too hot
When we get too hot:
- Sweat glands in the dermis release more sweat onto the surface of the epidermis. The sweat evaporates, transferring heat energy from the skin to the environment.
Too cold
When we get too cold:
- Skeletal muscles A muscle tenses as fibres shorten or create tension. rapidly and we shiver. These contractions need energy from The chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration., and some of this is released as heat. Nerve impulses are sent to the hair erector muscles in the dermis, which contract. This raises the skin hairs and traps a layer of insulating air next to the skin.
The control of body temperature is an example of a negative feedback mechanism. It regulates the amount of:
- shivering (rapid muscle contractions release heat)
- sweating (evaporation of water in sweat causes cooling)
Vasoconstriction and vasodilation - Higher
The amount of blood flowing through the skin capillaries is altered by Narrowing of aterioles supplying the skin's blood capillaries, causing less blood to flow. and The increase in diameter of the skin arterioles to increase blood flow and increase heat loss by radiation..
| Too cold | Too hot | |
| Process | Vasoconstriction | Vasodilation |
| Arterioles | Get narrower | Get wider |
| Blood flow in skin capillaries | Decreases | Increases |
| Heat loss from skin | Decreases | Increases |
| Process | |
|---|---|
| Too cold | Vasoconstriction |
| Too hot | Vasodilation |
| Arterioles | |
|---|---|
| Too cold | Get narrower |
| Too hot | Get wider |
| Blood flow in skin capillaries | |
|---|---|
| Too cold | Decreases |
| Too hot | Increases |
| Heat loss from skin | |
|---|---|
| Too cold | Decreases |
| Too hot | Increases |
These diagrams show the processes that take place when vasoconstriction and vasodilation occur.
When the temperature is too high, different processes happen: Vasodilation, sweat production, which both transfer energy from skin to the environment, resulting in a cooling effect.