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.

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