Sense organs and the structure of the eye

The central nervous system receives information about changes in the external and internal environment through sense organs. Each sense organ receives its own kind of stimulus: the eye – light, ear – sound, nose – smell, tongue – taste, skin – touch, pressure, temperature and pain. Receptors in sense organs convert a stimulus into a nerve impulse. The impulses travel by nerve to the matching centre in the cortex, where a sensation is created. The receptors, the nerve path linking them to the centre and the cortical centre together are called an analyser (sensory system); Pavlov named it so. An analyser has three parts: peripheral (receptors), conducting (nerves) and central (cortical zone). The vision centre lies in the occipital lobe, hearing in the temporal and skin sense in the parietal lobe. Analysers work together: seeing a cloud, feeling wind and hearing thunder before rain, we take shelter. If one analyser does not work, the others become more sensitive (for example, hearing and touch are strong in a person who is blind). Protecting sense organs is important for safe vision and hearing.