Sense Organs: Organ of Sight

SENSE ORGANS

Information about the mechanical, thermal, chemical and electromagnetic changes in the internal and external environment are perceived by sensory receptors in our bodies. These process the information and make us aware of changes.

There are four main groups of sensory receptors namely;

(i) Mechanoreceptors: these detect mechanical stimuli such as sound, gravity, pressure, vibrations, etc.

(ii) Thermo receptors: These detect thermal stimuli such as heat and cold.

(iii) Chemo receptors: These detect chemical stimuli such as odour and taste.

(iv) Photo receptors: These detect electromagnetic visual stimuli such as light intensities and colour.

The sensory receptors transform the stimulus received into a nerve impulse which is transmitted to the central nervous system for interpretation and appropriate response.

FORMS OF SENSORY RECEPTORS 

There are different types of sensory receptors;

(i) The primary sense cells: these exist as free nerve endings of nerve fibres e.g. the touch receptors in the mammalian skin.

(ii) Secondary Sense cells: these consist of groups of cells that are not neurones but are specialized to detect stimuli.