THE SENSES Information Input There are five types

THE SENSES

Information Input There are five types of sensory receptors that receive stimuli and send information to the CNS: 1. Mechanoreceptors • Detect mechanical energy • Example: auditory receptors in the ears 2. Photoreceptors • Detect light energy • Example: photoreceptors in the retina of the eye

3. Chemoreceptors • Detect molecules or chemical conditions, such as acidity. • Example: Taste buds 4. Thermoreceptors • Detect flow of thermal energy • Example: receptors on the skin 5. Nociceptors (pain receptors) • Detect tissue damage or noxious (harmful) chemicals • Example: nociceptors in the skin

The Traditional Senses Vision • Most complex of the five senses • Light is detected at the photoreceptors found in the retina • Two types of photoreceptors: 1. Rods detect light at low intensities 2. Cones detect light at different wavelengths (colours) • Retina contains 120 million rods and 6 million cones • Information transmitted from the optic nerve occipital lobe of the CNS where light is interpreted

Major structures of the human eye: Blind spot

Hearing • Sound waves/signals transmitted from the auditory nerve (vestibularcoclear nerve) temporal lobe of the CNS where the sounds are interpreted equalizes pressure on both sides of the eardrum

Taste • Involve chemoreceptors • Taste receptors form part of the taste bud there about 10, 000 taste buds on the tongue • Taste receptors respond to five basic tastes: sweet, sour, salty, bitter, and umami (savoury) • Signals transmitted from taste receptors cerebral cortex and interpreted as different tastes

Diagram of taste buds

Smell • Involves chemoreceptors • Olfactory receptors in the nose detect smells • Nerves transmit signals from olfactory bulbs cerebral cortex and interpret as pleasant or unpleasant odours.

Smell / Taste Connection

Touch • Mechanoreceptors that detect touch and pressure are in the • skin and other surface tissues • skeletal muscles • walls of blood vessels • internal organs • Touch receptors are concentrated in the • fingertips • lips • tip of the tongue • Touch receptors are more widely spaced in the • back • arms • legs