Page 240 - Biology_F5

Coordination and Irritability

Thermoreceptors Examples of thermoreceptors are bulbs of
Thermoreceptors are specialised nerve cells Krauze, which sense coldness and organ
or receptors that can detect differences of Ruffin, which detects heat. These cells
in temperature. They can detect hotness are connected to heat gain and heat loss
(heat) and coldness (cold). They are of centres of the hypothalamus.
two types, namely heat and cold receptors.
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They are found through out the skin Nociceptors (pain receptors)
to allow sensory reception throughout These are receptors that can detect pain
the body. The location and number of and they are found in the skin, muscles,
thermoreceptors determine the sensitivity bones, blood vessels, and some organs
of the skin to temperature changes. (Figure 4.23).

Heat Light Pain Cold
receptor touch receptor receptor Hair

Epidermis

Dermis

Nerve Connective Hair Strong

tissue movement pressure

Figure 4.23: Sensory receptors of the skin

Chemoreceptors impulses from these receptors travel to the
These are receptors that detect chemical olfactory bulb (Figure 4.24). When odour
stimuli such as smell, taste, and humidity. molecules enter the nose, they stimulate
They have the ability to respond to a diverse the olfactory cilia (tiny hairs) attached to
range of chemical substances in food, receptor cells, causing nerve impulses to
nasal passage, and blood. For example, pass to the olfactory bulb and then to the
olfactory receptors in the roof of the nasal brain.
cavity can be stimulated by odours. Nerve

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