Special Senses Senses General Senses include temperature, pain, touch, pressure, vibration, and proprioception. Special Senses include olfaction, gustation, equilibrium, and hearing. Types of Receptors Mechanoreceptors?stretching, touch, pressure in autonomic NS structures (barorecpetors) and body position (proprioceptors) Chemoreceptors--chemical?gustation, olfaction, and autonomic NS chemicals Nociceptors--pain Thermoreceptors--temperature Photorecptors--light--70% of all receptors Taste (Gustation) closely associated with smell Gustatory Organs (Taste Buds) located along the surface in elevations called Papillae (10,000 or more) Taste Buds Respond to dissolved chemicals 6 types of taste sensations Sweet Sour Bitter Salty Umami Water Smell (Olfaction) Detect to 50 or more specific scents Olfactory Organs in the upper wall of the Nasal Cavity Bipolar neurons -- Receptor Cells --Olfactory Hair Cells Mucous membranes trap particles Smell (Olfaction) LowThreshold: amount needed for detection Adaptation: time for decrease in sensitivity First second or so about 50% gone FYI: Usually in one minute even strong scents are no longer smelled Sight (Vision) most complex of over 70% of the sensory receptors in the body are photoreceptors for sight Includes eye, and accessory structures Accessory structures of the eye Eyelid, eyelashes = protects Exocrine glands Conjunctiva=mucous membrane of the eyelid and eye Helps moisten and lubricate the eyeball Accessory Structures of the Eye Lacrimal apparatus Produces tears to keep eye moist Drains through the nasal cavity Accessory structures of the eye Extrinsic muscle of the eye 6 muscles that move eyes Tunics (layers) of the Eye Fibrous Tunic = outermost layer Sclera--forms most of the fibrous tunic--the white of the eye Fibrous layer of the Eye (cont) Cornea--transparent coat of iris--slightly bulged by aqueous humor Most common transplant Vascular Tunic Blood supply Choroid --thin posterior portion Ciliary Body-thick anterior portion, attaches to lens with ligaments Iris--colored portion Pupil dilation and constriction Iris = anterior, colored portion Pupil= hole in iris Vascular Tunic (cont) Lens--changes shape for close-up or long range?lens accommodation Ligaments attached to ciliary body Nervous Tunic the inner layer of the eye Retina = thin fragile layer of neurons Rods and Cones Rods = elongated dendrites--black and white and night vision Cones = dendrites with tapered ends color sensitive Sharpens vision Outer Ear direct sound waves toward the eardrum Auricle = the outer portion Auditory Canal = extends into temporal bone Middle Ear an air filled space Aka Tympanic Cavity Auditory Ossicles smallest bones in the body Malleus (hammer) Incus (anvil) Stapes (stirrup) Middle Ear (cont) Eustachian Tube = Middle Ear to the Pharynx (throat) for pressure equalization between the middle ear and the atmosphere Tympanic Membrane (Eardrum) = thin, semitransparent, barrier, separates outer and middle ear vibrates in response to sound waves striking it The Inner Ear hearing and equilibrium Cochlea (hearing) Vestibule (balance) Semicircular Canals (balance) Cochlea The Cochlea shape resembles a snail shell contains the Organs of Corti for hearing Cochlea (cont) winding passageways or canals Contains perilymph and endolymph separated by membranes Fluids aid in transmission of vibration Hearing Organs--Organs of Corti move in response to endolymph motion Release neurotransmitters Steps of Hearing 1. Sound waves into auditory canal 2. Tympanic membrane vibrates 3. Ossicles vibrate and magnify sound Steps of Hearing 4. Oval window vibrates causes movement of perilymph and endolymph Steps of Hearing 5. Endolymph causes hair cells of organs of Corti to vibrate 6. Vibration transferred by neurotransmitter to auditory nerve to brain for interpretation Equilibrium (Balance) detected by receptor cells in the Inner Ear Determines body position and movement of head Uses sight and neurotransmitters sent by semicircular canals and vestibule Semicircular canals The Semicircular Canals = three loops Ampulla at entrance of loops contain Cristae Hair cells in Cristae release neurotransmitters brain interprets these & responds appropriately Vestibule Vestibule: chamber between the cochlea and the semicircular canals contains perilymph and endolymph Vestibule cont Maculae =contain hair-like cells, Otoliths on surface, move Otoliths respond to gravity DISEASES AND DISORDERS OF THE SPECIAL SENSES Presbyopia Lens looses ability to change shape Usually caused by age Myopia (near sighted) Caused by eye shape being too long Causes light to focus in front of retina Corrected with glasses or contacts Hyperopia (far-sighted) Caused by eye shape being shorter than normal Causes light to focus behind the retina Corrected with glasses or contacts Cataracts Caused by clouding of the lens Can be replaced with artificial lens Conjunctivitis Caused by an infection of the conjuctiva More commonly called ?pink eye? Conjunctivitis Deafness Two types: Conductive: caused by blockages in the auditory canal Caused by middle ear infections Eardrum damage Sensorineural deafness Damage to auditory nerves Cochlear malformation or damaged by infection Brain damage in temporal lobe Glaucoma Aqueous humor build up puts pressure on the retina Can damage retina if not treated Macular Degeneration Section of the retina called the macula (large concentration of blood vessels) is damaged causing tunnel vision until vision is gone Middle Ear Infection Usually involves the eardrum being infection by bacteria or virus Bacterial treated with antibiotics Common in children Strabismus Caused by weak eye muscles Can be surgically corrected or by patching the good eye to encourage other eye to work properly Tinnitis Caused by improper discharge of electrical impulses of the Organs of Corti Hair cells Vertigo Caused by otoliths improperly aligning with membranes Causes dizziness and nausea
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