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The Special Senses

Remember the five senses you learned in elementary school? Seeing, smelling, hearing, touching, tasting? That's what this chapter is about.

Dr. Candace Smith

on 10 December 2012

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Transcript of The Special Senses

Sight: How the body turns light energy into brainwaves Touch: How the skin sends signals about the world around you Smell: It isn't real...it's just chemicals Sound: How the ear turns vibration into a symphony Taste: Why you love ice cream http://movies.netflix.com/WiMovie/Nova_scienceNOW_How_Does_the_Brain_Work/70170267?trkid=2361637 The tongue is a mass of muscle tissue with structures called papillae
Taste buds cover the papilla, which are stimulated by sweet, sour, salty, and bitter tastes THE TONGUE Partial or complete loss of smell
May result from a variety of factors including inflammation of the nasal cavity lining due to respiratory infection, tobacco smoke, or using certain drugs such as cocaine Anosmia Humans smell using 12 million olfactory receptor cells
Bloodhounds have 4 billion olfactory receptor cells
Much better sense of smell.
Specially trained for search and rescue The human nose can detect about 10,000 different smells
A dog can detect about 10 times that many THE NOSE The outer ear
collects sound waves and directs them into auditory canal
The middle ear
equalizes air pressure
The inner ear
fluid-filled duct vibrates with sound waves THE EAR PATHWAY OF VISION THE EYE Sclera - outer layer or white of eye
Cornea - center and front of sclera
Choroid coat - middle of the eye
Iris - colored, muscular part
Pupil - circular opening in iris
Lens - behind iris and pupil
Retina - innermost (third) coat THE EYE Chemoreceptors
Thermoreceptors Somatic senses SPECIAL SENSES Sensory impulses from taste receptors in the tongue
Fibers of the facial, glossopharyngeal, and vagus nerves
Medulla oblongata
Impulses ascend to the thalamus
Then are directed to the gustatory cortex in the parietal lobe of the cerebrum Taste Nerve Pathway Locations of the four primary taste sensations. Sense of Taste Rhinitis
Nasal polyps
Deviated nasal septum DISORDERS OF THE NOSE Stimulated olfactory receptor cells send nerve impulses along their axons which form the first cranial nerves and synapse with neurons located in enlargements called olfactory bulbs.
Impulses are analyzed in the olfactory bulbs and travel along olfactory tracts to the limbic system
Major interpreting areas (olfactory cortex) for these impulses are located within the temporal lobes and at the bases of the frontal lobes Olfactory Nerve Pathways Hearing loss
Conductive hearing loss
Sensorineural damage Otitis media
Meniere’s disease EAR DISORDERS 8th Cranial Nerve or “Auditory Nerve” carries signals from cochlea to brain
Fibers of the auditory nerve are present in the hair cells of the inner ear
Auditory Cortex: Temporal lobe of the brain where sound is perceived and analyzed Central Auditory System The Cochlea Connects the stapes to the middle ear wall
Contracts in response to loud sounds; known as the Acoustic Reflex Stapedius Muscle Lined with mucous membrane; connects middle ear to back of the throat (nasopharynx)
Equalizes air pressure Eustachian Tube THE EAR THE EYE Consists of three semi-circular canals
Shares fluid with the cochlea
Controls balance Vestibular System Cochlea - Snail-shaped organ with a series of fluid-filled tunnels; converts mechanical energy into electrical energy Structures of the Inner Ear (From Merck Manual) Thin membrane
Forms boundary between outer and middle ear
Vibrates in response to sound waves
Changes acoustical energy into mechanical energy Tympanic Membrane Auricle (Pinna)
Collects sound
Helps in sound localization
Most efficient in directing high frequency sounds to the eardrum Structures of the Outer Ear Vision defects
Strabismus Conjunctivitis
Macular degeneration
Detached retina
Eye injuries EYE DISORDERS THE EYE A: Malleus
B: Incus
C: Stapes
Ossicles are smallest bones in the body
Transmit sound waves to inner ear The Ossicular Chain How do you know?
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