Chemo- receptors include those receptors related with smell and taste (Elaine & KatjaHoehn 455); they are found in the smell and taste organs, the nose and the tongue.

Mechano-receptors are the receptors related with hearing, touch, vibration and stretch; they are in the dermis. Thermo- receptors detect changes in temperatures, they are found in the dermis (Elaine & KatjaHoehn 455) Photo- receptors detect changes in the amount of visible and ultraviolet light received by the eyes; they are found in the eyes. Pain receptors detect changes in pressure, chemicals, and heat in tissues; they are found in all tissues. Osmo-receptors detect changes in the osmotic pressure of the blood (Elaine & KatjaHoehn 455).

Visual Pathway

Cornea acts as a protective cover for the outer part of the eye and focuses light to the retina. Aqueous humor of anterior segment nourishes the anterior structures of the eye and the shapes the eye by supporting the anterior structures (Inge & Isabel 97) Lens has refractive properties and focuses incoming light to the retina. Vitreous humor of posterior segment helps to shape the eye by supporting the internal parts. Retina contains receptor cells for light (photoreceptors) which send impulses to the optic nerve. Bipolar cells are neurons carrying visual nerve messages. Ganglion cells receive visual message from bipolar cells and transmit them to the thalamus for interpretation (Inge & Isabel 93). Optic nerve carries and controls vision nerve messages (Inge & Isabel 93). Thalamus is the visual integration center; occipital lobe processes basic visual images.

Auditory Pathway

Auditory tube maintains equal air pressure on tympanic membrane (Catherine & Gary 344). Meatus traps sound waves. Ossicles amplify vibrations from the eardrum and transmit them to the stapes (Catherine & Gary 342). The movements of stapes while in the oval window cause the transmission of vibrations to perilymph. Oval window is the entrance of vibrations from stapes (Catherine & Gary 342). Auditory hair cells provide the movement of the hair converts vibrations into nerve impulses (Catherine & Gary 340). Cochlear nerve carries nerve messages of sound. Inferior colliculus interprets nerve messages of sound (Inge & Isabel 97).

Thalamus is the auditory integration center (Inge & Isabel 97). Primary auditory cortex interprets impulses as sound.

Olfactory Pathway

Olfactory epithelium collects chemical signals. Olfactory receptor cells convert the signals into nerve impulses. Olfactory nerve carries olfactory nerve messages. Olfactory bulb sends the nerve messages to the brain; it has glomeruli which send the nerve messages to different regions in the brain thus eliciting a specific perception of the odor (Catherine & Gary 340). Olfactory cortex interprets and identifies smells (Catherine & Gary 340).

Limbic system stimulates emotional responses related to the odor.

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