Special Senses

General Senses Widely distributed throughout the body Examples Touch Pain Proprioception (provides information about the position of the body)

Special Senses Produced by highly localized sensory organs Examples Smell Taste Sight Hearing Model of the human nose

The Inner Ear

Structures of the outer and middle ear Outer ear Pinna- collects and focuses sound waves External auditory canal- passage way that leads to the ear drum Ear drum- also called tympanic membrane. It vibrates with sound waves. Middle ear hammer, anvil, and stirrup- bones that transmit vibrations Oval and round windows- two openings that connect the middle ear to inner ear Auditory tube- angles air pressure to be equalized

How We Hear Sound waves are collected by the auricle and conducted through external auditory meatus toward the tympanic membrane which causes vibrations The vibrations of the stirrup produce waves in the perilymph of the cochlea. This makes the perilymph move and this pushes against the membrane of the round window This causes the vestibular membrane to vibrate. It creates waves in the indolymph and the basilar membrane Cochlear nerves (located in the cochlar ganglion), send axons to the cochlar nueculas in the brain stream Neurons project to other areas of the brain stream to inferior collicuculus thalamus auditory cortex of the cererum. rt

Olfactory - nose

Smell- Olfactory Molecules in the air enter the nasal cavity and dissolve in the mucus lining of the uppermost shelf of the nose (chemoreceptors – cilia) The olfactory neurons of the molecules contact the olfactory receptors who send impulses to the axons. The olfactory bulbs send this to the brain which interprets each scent.

Taste - tongue *

Taste Saliva breaks down the food into fluid. The chemicals in the fluid attach to the taste cells. Nerve fibers send impulses to the facial nerves, which send impulses to taste cortex of parietal lobe for interpretation.

Structures of the eye pictures

Accessory structures of the eye Eyebrows-protect eyes by preventing perspiration from running down the forehead. Eyelids- protect the eyes from foreign objects Conjunctiva- covers inner surface of the eyelids Lacrimal Apparatus- produces tears Extrinsic Eye Muscles- help movement of the eye

Eye structures Sclera – outermost, white, hard, layer Cornea – transparent part of sclera, light in Choroid – 2nd layer, black, absorbs light Retina – innermost layer, bipolar cells: rods- night vision and cones- color vision Ciliary body – holds the lens in place Iris – colored part of eye, regulates light Fovea Centralis – area producing sharpest vision

Chambers of the eye Anterior compartment- between the lens and cornea, divided into anterior chamber and posterior chamber Filled with aqueous humor Helps maintain pressure in the eye Bends light Provides nutrients to inner eye Circulates around the cornea Posterior compartment Filled with a transparent jellylike substance called the vitreous humor Holds the retina in place Has many similar functions to the aqueous humor Unlike aqueous humor, it does not circulate

Path of sight input The rods / cones synapse bipolar sensory cells to the optic nerve reaches the thalamus of brain Visual cortex of occipital lobe of cerebrum

Eye Disorders Conjunctivitis- also called pink eye, an infection of the conjunctiva Chalazion- a small lump in the eyelid caused by obstruction of an oil producing gland Cataract- clouding of the natural lens Glaucoma- malformation or malfunction of the eye’s drainage structures Myopia- nearsightedness Presbyopia- an eye in which the natural lens can no longer accommodate Stye- same as chalazion