The skin and temperature control

Structure and functions in living organisms · Hormones and temperature control · note 4 of 4

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The skin and temperature controlSpec 2.93

The skin helps to keep the body temperature steady. It has two main layers, the epidermis (thin outer layer) and the dermis below it. The dermis contains sweat glands, blood vessels and temperature receptors.

Cross-section of skin showing the epidermis on top of the dermis, a coiled sweat gland in the dermis with a sweat duct leading to a pore at the surface, a blood vessel loop and a temperature receptor. — The structures in the skin involved in **temperature regulation**.

Skin responses to temperature change
	Body too hot	Body too cold
Sweating	Sweat glands release sweat onto the skin. Sweat evaporates and takes heat from the skin, cooling the body	Little or no sweat is produced
Blood vessels in the dermis	Vasodilation: vessels widen, more blood flows near the surface, more heat is lost	Vasoconstriction: vessels narrow, less blood flows near the surface, less heat is lost
Overall effect	More heat is lost, so body temperature falls back to normal	Less heat is lost, so body temperature rises back to normal

Two skin cross-sections: on the left, too hot, the blood vessel below the surface is wide (vasodilation) and many heat arrows leave the skin; on the right, too cold, the vessel is narrow (vasoconstriction) and little heat is lost. — **Vasodilation** brings more blood near the surface to lose heat; **vasoconstriction** reduces heat loss.

Common mistake:

Blood vessels do not move up or down in the skin. They get wider (vasodilation) or narrower (vasoconstriction).

Quick check

Name two differences between nervous and hormonal communication.
Show answer
Nervous is fast and short-lived using electrical impulses; hormonal is slower and longer-lasting using chemicals in the blood.
Which gland makes insulin?
Show answer
The pancreas.
Where is adrenaline produced?
Show answer
In the adrenal glands.
Biology only What does ADH change in the kidney?
Show answer
It makes the collecting ducts more permeable to water, so more water is reabsorbed.
What happens to skin blood vessels when you are too hot?
Show answer
They widen (vasodilation), so more heat is lost.

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