receptors

detects change in internal and external environment (osmo,thermo,chemo, touch and pain)

hot OR cold in the skin: sensitive nerve ending, messages hypothalamus and cerebrum internally: blood temperature monitored

Hypothalamus osmotic pressure: concentration of substances dissolved in water blood plasma Stimulate hypothalamus to maintain water content

stimulated by particular chemical nose: sensitive to odours mouth: sensitive to taste Internal composition of body fluids (pH, concentration of O2 and CO2, heartbeat and breathing)

skin -> surface sensitive to light touch, greater concentration are more sensitive areas Hair follicle ->nerve endings at base of each follicle, responds to light touch Adapts rapidly

Stimulated by damage to tissues takes evasive action or seek medical attention Pain continues until stimulus is gone *highly concentrated in skin and mucous membranes, close to surface for increased speed of reaction and greater protection