L.O. Students will describe the ways the body maintains homeostasis. Do Now: On your paper. Notes are in yellow. 1

What do the experts say about homeostasis?

Words to know… Maintain – keep up. Constant – the same. Internal – inside the body. Environment – surroundings of the body. 3

What is Homeostasis? Body cells work best if they have the correct Temperature Water levels Glucose concentration Your body has mechanisms to keep the cells in a constant environment. 4

The maintenance of a constant environment in the body What is Homeostasis? The maintenance of a constant environment in the body 5

In Other Words... The weather report from inside your body is ALWAYS THE SAME. 6

Controlling body temperature All mammals and birds maintain a constant body temperature. Human beings have a body temperature of about 98.6 ºF. If your body is in a hot environment your body temperature is 98.6 ºF If your body is in a cold environment your body temperature is still 98.6 ºF 7

What mechanisms are there to cool the body down? 1. Sweating 8

Sweating The skin 9

What mechanisms are there to cool the body down? 2. Enlargement of the blood vessels There are capillaries underneath your skin that expand if hot. This brings the blood closer to the surface of the skin so more heat can be lost. This is why you look red when you are hot! 10

This means more heat is lost from the surface of the skin If the temperature rises, the blood vessel dilates (gets bigger). 11

What mechanisms are there to cool the body down? 3. Panting Similar to sweating 12

Panting

What mechanisms are there to warm the body up? Shrinking of the blood vessels The capillaries underneath your skin get constricted (smaller). This takes the blood away from the surface of the skin so less heat can be lost. 14 14

This means less heat is lost from the surface of the skin If the temperature falls, the blood vessel constricts (gets shut off). 15

What mechanisms are there to warm the body up? Goosebumps The hairs trap a layer of air next to the skin which is then warmed by the body heat Does NOT work in humans. Why? 16

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