Vasoconstriction, vasodilation, shivering and sweating
Vasoconstriction is a response to being too cold. The process involves the narrowing of blood vessels at the skin surface to reduce heat loss through the surface of the skin.
Vasodilation is a response to being too hot. The process includes the widening of blood vessels at the skin surface to increase heat loss through the surface of the skin.
This table summarises the two processes.
| 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 |
When you are cold you may start shivering. Shivering is caused by involuntary contractions of your muscles. Muscle contractions require energy from Chemical reaction that takes place inside living cells, which uses glucose and oxygen to release the energy organisms need to live. Carbon dioxide and water are by-products of respiration. which releases heat. This heat is used to warm the body up.
When you are too hot you will sweat. Sweat is produced by the sweat glands and travels up the sweat duct and out of the sweat pore onto the skin surface. Here it will evaporate, taking excess body heat with it. Your body uses this mechanism to cool down.
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