鶹Լostasis and temperature regulation
The conditions inside our body must be carefully controlled if it is to function effectively. The maintenance of steady conditions. The ability of the body to maintain a constant internal environment, eg temperature and blood glucose concentration. is the maintenance of a constant internal environment in the body. The Body system that includes the brain, spinal cord and nerves. and the The glands that release hormones into the bloodstream to regulate factors including metabolism, growth, development and reproduction. - which produces Chemical messenger produced in glands and carried by the blood to specific organs in the body. - are involved in homeostasis.
The body control systems have three basic parts:
- 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 or a gland (eg the pancreas). These receive information from the receptors, process the information and initiate a response.
- The organ, tissue or cell that produces a response., such as muscles or glands produce the response. Muscles would A muscle tenses as fibres shorten or create tension. while glands would 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 at which A protein which catalyses or speeds up a chemical reaction. work best, which is around 37°C. This process is controlled by the thermoregulatory centre, which is contained in the The part of the brain that detects changes in blood temperature and water concentration. 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 thermoregulatory centre.
Too cold
When we get too cold:
- Skeletal muscles contract 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.
- Blood vessels, which lead to the skin capillaries, become narrower - they constrict - which allows less blood to flow through the skin and conserve the core body temperature. This is called Narrowing of aterioles supplying the skin's blood capillaries, causing less blood to flow..
Too hot
When we get too hot:
- Sweat glands in the skin release more sweat. The sweat evaporates, transferring heat energy from the skin to the environment.
- Blood vessels leading to the skin capillaries become wider - they dilate - allowing more blood to flow through the skin, and more heat to be lost to the environment. This is called The increase in diameter of the skin arterioles to increase blood flow and increase heat loss by radiation..
The hairs on the skin also help to control body temperature. The hairs lie flat when we are warm, and rise when we are cold.
If we are too cold, nerve impulses are sent to the hair erector muscles 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)
- blood flowing in the skin capillaries
Vasoconstriction and vasodilation
The amount of blood flowing through the skin capillaries is altered by vasoconstriction and vasodilation.
| 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.
Generally, when the body temperature is too low, a variety of processes happen - vasoconstriction, sweating stops and shivering starts.
When the temperature is too high, different processes happen - vasodilation and sweat production, which both transfer energy from skin to the environment, resulting in a cooling effect.