1 HEADING VOCABULARY IMPORTANT INFOTHE SPECIAL SENSES HEADING VOCABULARY IMPORTANT INFO
2 The Special Senses General Senses: Special Senses:Two Classes of Receptors: General Senses: Temperature, Pain, Touch, Stretch & Pressure Special Senses: Gustation (taste),Olfaction (Smell), Vision, Audition (hearing) & Equilibrium Vision Let’s see what RECEPTORS you know and remember…not in your notes… Photoreceptors Smell Hearing chemoreceptors Hair Cells (not on your head, in your ear) Taste Equilibrium Hair Cells
3 Housed in complex sensory organsOphthalmology is science of the eye Otolaryngology is science of the ear
4 Olfactory Epithelium 1 square inch of membrane holding million receptors Covers superior nasal cavity and cribriform plate 3 types of receptor cells…
5 Cells of the Olfactory Membrane1. Olfactory Receptors bipolar neurons with cilia or olfactory hairs 2. Supporting cells columnar epithelium 3. Basal cells = stem cells replace receptors monthly Olfactory glands produce mucus Both epithelium & glands innervated (supplied with nerves) by cranial nerve VII.
6 Olfaction: Sense of SmellOdorants bind to receptors Na+ channels open Depolarization occurs Nerve impulse is triggered
7 Olfactory Pathway Axons from olfactory receptors form the olfactory nerves (Cranial nerve I) that synapse in the olfactory bulb pass through 40 foramina in cribriform plate Second-order neurons within the olfactory bulb form the olfactory tract that synapses on primary olfactory area of temporal lobe conscious awareness of smell begins Other pathways lead to the frontal lobe (Brodmanns area 11) where identification of odor occurs
8 Gustatory Sensation: TasteTaste requires dissolving of substances Four classes of stimuli--sour, bitter, sweet, and salty A 5TH sense, “umami” tastes like a meaty flavor 10,000 taste buds found on tongue, soft palate & larynx Found on sides of circumvallate & fungiform papillae 3 cell types: supporting, receptor & basal cells
9 Anatomy of Taste Buds An oval body consisting of 50 Gustatory Receptor Cells surrounded by supporting cells A single gustatory hair projects upward through the taste pore Basal cells develop into new receptor cells every 10 days.
10 Physiology of Taste Complete adaptation in 1 to 5 minutesThresholds for tastes vary among the 4 primary tastes most sensitive to bitter (poisons) least sensitive to salty and sweet Mechanism dissolved substance contacts gustatory hairs receptor potential results in neurotransmitter release nerve impulse formed in 1st- order neuron
11 Gustatory Pathway First-order gustatory fibers found in cranial nervesVII (facial) serves anterior 2/3 of tongue IX (glossopharyngeal) serves posterior 1/3 of tongue X (vagus) serves palate & epiglottis Signals travel to thalamus or limbic system & hypothalamus Taste fibers extend from the thalamus to the primary gustatory area on Parietal Lobe of the cerebral cortex providing conscious perception of taste
12 Accessory Structures of EyeEyelids or palpebrae protect & lubricate epidermis, dermis, CT, orbicularis oculi m., tarsal plate, tarsal glands & conjunctiva Tarsal glands oily secretions keep lids from sticking together Conjunctiva Palpebral & Bulbar stops at corneal edge dilated BV--bloodshot
13 Eyelashes & Eyebrows Eyeball = 1 inch diameter 5/6 of Eyeball inside orbit & protected Eyelashes & eyebrows help protect from foreign objects, perspiration & sunlight Sebaceous glands are found at base of eyelashes (sty) Palpebral Fissure is gap between the eyelids
14 Lacrimal Apparatus About 1 ml of tears produced per day. Spread over eye by blinking. Contains bactericidal enzyme called Lysozyme.
15 Fibrous Tunic -- Description of CorneaTransparent Helps focus light (refraction) Astigmatism (irregular curvature of the cornea or lens) 3 layers Non-keratinized stratified squamous collagen fibers & fibroblasts simple squamous epithelium Transplants common & successful no blood vessels so no antibodies to cause rejection Nourished by tears & aqueous humor LASIK:
16 Fibrous Tunic -- Description of Sclera“White” of the eye Dense irregular connective tissue layer -- collagen & fibroblasts Provides shape & support At the junction of the sclera and cornea is an opening (scleral venous sinus) Posteriorly pierced by Optic Nerve (II)
17 Vascular Tunic -- Choroid & Ciliary Bodypigmented epithilial cells (melanocytes) & blood vessels provides nutrients to retina black pigment in melanocytes absorb scattered light Ciliary body ciliary processes folds on ciliary body secrete aqueous humor ciliary muscle smooth muscle that alters shape of lens
18 Vascular Tunic -- Iris & PupilColored portion of eye Shape of flat donut suspended between cornea & lens Hole in center is Pupil Function is to regulate amount of light entering eye Autonomic reflexes circular muscle fibers contract in bright light to shrink pupil radial muscle fibers contract in dim light to enlarge pupil
19 Vascular Tunic -- Muscles of the IrisConstrictor Pupillae (circular) are innervated by parasympathetic fibers while Dilator Pupillae (radial) innervated by sympathetic fibers. Response varies with different levels of light
20 Vascular Tunic -- Description of LensAvascular Crystalline proteins arranged like layers in onion Clear capsule & perfectly transparent Lens held in place by suspensory ligaments Focuses light on fovea
22 Layers of Retina Pigmented epitheliumnonvisual portion absorbs stray light & helps keep image clear 3 layers of neurons (outgrowth of brain) photoreceptor layer bipolar neuron layer ganglion neuron layer 2 other cell types (modify the signal) Horizontal cells Amacrine cells Label on your notes
23 Rods & Cones--PhotoreceptorsRods----rod shaped shades of gray in dim light 120 million rod cells discriminates shapes & movements distributed along periphery Cones----cone shaped sharp, color vision 6 million Fovea of Macula Lutea densely packed region at exact visual axis of eye 2nd cells do not cover cones sharpest resolution or acuity
24 Pathway of Nerve Signal in RetinaLight penetrates retina Rods & cones transduce light into action potentials Rods & cones excite bipolar cells Bipolars excite ganglion cells Axons of ganglion cells form optic nerve leaving the eyeball (blind spot) To thalamus & then the primary visual cortex
25 Cavities of the Interior of EyeballAnterior cavity (anterior to lens) filled with Aqueous Humor produced by ciliary body continually drained replaced every 90 minutes 2 chambers anterior chamber between cornea and iris posterior chamber between iris and lens Posterior cavity (posterior to lens) filled with Vitreous Body (jellylike) formed once during embryonic life floaters are debris in vitreous of older individuals
26 Aqueous Humor Continuously produced by Ciliary BodyFlows from posterior chamber into anterior through the pupil Scleral venous sinus Canal of Schlemm opening in white of eye at junction of cornea & sclera drainage of aqueous humor from eye to bloodstream Glaucoma increased intraocular pressure that could produce blindness problem with drainage of aqueous humor
27 Definition of RefractionBending of light as it passes from one substance (air) into a 2nd substance with a different density(cornea) In the eye, light is refracted by the anterior & posterior surfaces of the cornea and the lens
28 Refraction by the Cornea & LensImage focused on retina is inverted & reversed from left to right Brain learns to work with that information 75% of Refraction is done by cornea -- rest is done by the lens Light rays from > 20’ are nearly parallel and only need to be bent enough to focus on retina Light rays from < 6’ are more divergent & need more refraction extra process needed to get additional bending of light is called Accommodation
29 Accommodation & the LensConvex lens refract light rays towards each other Lens of eye is convex on both surfaces View a distant object lens is nearly flat by pulling of suspensory ligaments View a close object ciliary muscle is contracted & decreases the pull of the suspensory ligaments on the lens elastic lens thickens as tension is removed increase in curvature of lens is called Accommodation
30 Near Point of Vision and PresbyopiaNear point is the closest distance from the eye an object can be & still be in clear focus 4 inches in a young adult 8 inches in a 40 year old lens has become less elastic 31 inches in a 60 to 80 year old Reading glasses may be needed by age 40 Presbyopia glasses replace refraction previously provided by increased curvature of the relaxed, youthful lens
31 Correction for Refraction ProblemsEmmetropic Eye (normal) can refract light from 20 ft away Myopia (nearsighted) eyeball is too long from front to back glasses concave Hypermetropic (farsighted) eyeball is too short glasses convex (coke-bottle) Astigmatism corneal surface wavy parts of image out of focus How Lasik fixes Cornea to Correct Refraction Problems:
32 Photoreceptors Specialized neurons in the eye; named for shape of outer segment Transduction of light energy into a receptor potential in outer segment Photopigment membrane folded into “discs” & replaced at a very rapid rate Photoreceptor protein opsin contains a pigment molecule called retinal (derivative of vitamin A) In rod cells, these together are called rhodopsin Cone photopigments contain 3 different opsin proteins permitting the absorption of 3 different wavelengths (colors) of light Red Green Blue
33 Color Blindness & Night Blindnessinability to distinguish between certain colors absence of certain cone photopigments red-green color blind person can not tell red from green Night blindness (Nyctalopia) difficulty seeing in low light inability to make normal amount of rhodopsin possibly due to deficiency of vitamin A
34 Light and Dark AdaptationLight adaptation adjustments when emerge from the dark into the light Dark adaptation adjustments when enter the dark from a bright situation light sensitivity increases as photopigments regenerate during first 8 minutes of dark adaptation, only cone pigments are regenerated, so threshold burst of light is seen as color after sufficient time, sensitivity will increase so that a flash of a single photon of light will be seen as gray-white
35 Visual Fields Left occipital lobe receives visual images from right side of an object through impulses from nasal 1/2 of the right eye and temporal 1/2 of the left eye Left occipital lobe sees right 1/2 of the world Fibers from nasal 1/2 of each retina cross in optic chiasm
36 Anatomy of the Ear Region
37 External Ear Function = collect sounds StructuresAuricle or Pinna elastic cartilage covered with skin External Auditory Canal curved 1” tube of cartilage & bone leading into temporal bone ceruminous glands produce cerumen = ear wax Tympanic Membrane or Eardrum epidermis, collagen & elastic fibers, simple cuboidal epith. Perforated eardrum (hole is present) at time of injury (pain, ringing, hearing loss, dizziness) caused by explosion, scuba diving, or ear infection
38 Middle Ear Cavity Air filled cavity in the temporal boneSeparated from external ear by eardrum and from internal ear by oval & round window 3 ear ossicles connected by synovial joints malleus attached to eardrum, incus & stapes attached by foot plate to membrane of oval window stapedius and tensor tympani muscles attach to ossicles Auditory tube (Eustachian Tube) leads to Nasopharynx helps to equalize pressure on both sides of eardrum Connection to mastoid bone=mastoiditis
39 Inner Ear---Bony LabyrinthVestibule canals ampulla Bony Labyrinth = set of tubelike cavities in temporal bone semicircular canals, vestibule & cochlea lined with periosteum & filled with perilymph (fluid) surrounds & protects Membranous Labyrinth
40 Cochlear Anatomy 3 fluid filled channels found within the cochleaScala Vestibuli, Scala Tympani & Cochlear Duct Vibration of the stapes upon the oval window sends vibrations into the fluid of the scala vestibuli
41 Tubular Structures of the CochleaStapes pushes on fluid of scala vestibuli at oval window At helicotrema, vibration moves into scala tympani Fluid vibration dissipated at round window which bulges The central structure is vibrated (cochlear duct)
42 Anatomy of the Organ of Corti16,000 hair cells have stereocilia (microvilli) Microvilli make contact with tectorial membrane gelatinous membrane that overlaps the Spiral Organ of Corti
43 Overview of Physiology of Hearing
44 Sound Waves http://www. nlm. nihVibrating object causes compression of air around it = sound waves audible range is 20 to 20,000 Hz hear best within 500 to cycles/sec or Hz speech is 100 to 3000 Hz Frequency of a sound vibration is pitch higher frequency is higher pitch Greater intensity (size) of vibration, the louder the sound measured in decibels (dB) Conversation is 60 dB; pain above 140dB OSA requires ear protection above 90dB
45 Deafness Nerve Deafness Conduction Deafnessdamage to hair cells from antibiotics, high pitched sounds, anticancer drugs the louder the sound the quicker the hearing loss fail to notice until difficulty with speech Conduction Deafness perforated eardrum otosclerosis
46 Physiology of Hearing Auricle collects sound waves Eardrum vibratesslow vibration in response to low-pitched sounds rapid vibration in response to high-pitched sounds Ossicles vibrate since malleus attached to eardrum Stapes pushes on oval window producing fluid pressure waves in scala vestibuli & tympani oval window vibration 20X more vigorous than eardrum Pressure fluctuations inside cochlear duct move the hair cells against the tectorial membrane Microvilli are bent producing receptor potentials
47 Cochlear Implants If deafness is due to destruction of hair cellsMicrophone, microprocessor & electrodes translate sounds into electric stimulation of the vestibulocochlear nerve artificially induced nerve signals follow normal pathways to brain Provides only a crude representation of sounds
48 Physiology of Equilibrium (Balance)Static Equilibrium maintain the position of the body (head) relative to the force of gravity macula receptors within saccule & utricle Dynamic Equilibrium maintain body position (head) during sudden movement of any type— --rotation, deceleration or acceleration crista receptors within ampulla of semicircular ducts
49 Detection of Position of HeadMovement of stereocilia or kinocilium results in the release of neurotransmitter onto the vestibular branches of the vestibulocochler nerve
50 Crista: Ampulla of Semicircular DuctsSmall elevation within each of three semicircular ducts anterior, posterior & horizontal ducts detect different movements Hair cells covered with cupula of gelatinous material When you move, fluid in canal bends cupula stimulating hair cells that release neurotransmitter
51 Detection of Rotational MovementWhen head moves, the attached semicircular ducts and hair cells move with it endolymph fluid does not but does bends the cupula and enclosed hair cells Nerve signals to the brain (Cerebellum) are generated indicating which direction the head has been rotated