Special Senses PDF

TOPIC OUTLINE FOR CHAPTER 8 : SPECIAL SENSES (OUTLINED BY ALGERICO F. BAIñO, JR., RN ) PART 1 : THE EYE AND VISION 8.1 ANATOMY OF THE EYE 8.1.A. EXTERNAL AND ACCESSORY STRUCTURES 8.1.B. INTERNAL STUCTURES : THE EYEBALL 8.2. PHYSIOLOGY OF VISION 8.2.A. PATHWAY OF LIGHT THROUGH...

TOPIC OUTLINE FOR CHAPTER 8 : SPECIAL SENSES (OUTLINED BY ALGERICO F. BAIñO, JR., RN ) PART 1 : THE EYE AND VISION 8.1 ANATOMY OF THE EYE 8.1.A. EXTERNAL AND ACCESSORY STRUCTURES 8.1.B. INTERNAL STUCTURES : THE EYEBALL 8.2. PHYSIOLOGY OF VISION 8.2.A. PATHWAY OF LIGHT THROUGH THE EYE AND LIGHT REFRACTION 8.2.B. VISUAL FIELDS AND VISUAL PATHWAYS TO THE BRAIN ( IN SEQUENCE ) 8.2.C. EYE REFLEXES PART II : THE EAR : HEARING AND BALANCE 8.3. ANATOMY OF THE EAR 8.3.A. OUTER EAR 8.3.B. MIDDLE EAR 8.3.C. INNER EAR 8.4. HEARING ( IN SEQUENCE ) 8.5. HEARING ( IN SEQUENCE ) 8.5.A STATIC EQUILIBRIUM 8.5.C. DYNAMIC EQUILIBRIUM 8.5.C. HEARING AND EQUILIBRIUM DEFICITS PART III : CHEMICAL SENSES : SMELL AND TASTE 8.6. OLFACTORY RECEPTORS AND THE SENSE OF SMELL 8.7. TASTE BUDS AND SENSE OF TASTE PART IV : DEVELOPMENTAL ASPECTS OF THE SPECIAL SENSES  CHAPTER 8 SPECIAL SENSES ( outlined by Algerico F. Baiño, Jr., RN ) PART 1 : THE EYE AND VISION 8.1 ANATOMY OF THE EYE 8.1.A. EXTERNAL AND ACCESSORY STRUCTURES  ADULT EYE IS A SPHERE THAT MEASURES 1 INCH IN DIAMETER  ANTERIOR 1/6 OF THE EYE’S SURFACE IS NORMALY SEEN, THE REST IS ENCLOSED AND PROTECTED BY A CUSHION OF FAT AND WALLS OF THE BONY ORBIT  ACCESSORY STRUCTURES INCLUDES YOUR – EYELIDS, CONJUCTIVA,LACRIMAL APPARATUS AND EXTRINSIC EYE MUSCLES ACCESSORY STRUCTURES SUB – PARTS CHARACTERISTIC AND FUNCTION EYELIDS – protects the anterior of Medial Commissure ( Canthus ) and Median and lateral corners of the the eyes Lateral commissure ( canthus ) eye where eyelids meet Palpebral Fissure The Space between the eyelids in an open eye Eyelashes It Projects from the border of each eyelid Tarsal Glands Modified sebaceous glands associated with the eyelid edges and produces an oily secretion that lubricates the eye Ciliary Glands Modified sweat glands that lies between the eyelashes and their ducts open at the eyelash follicles Lacrimal Caruncle A raised area containing sebaceous and sweat glands that produce an oily, whitish secretion that also lubricates the eye CONJUCTIVA A delicate membrane that lines the eyelids and covers part of the outer surface of the eyeball Also secretes mucus, which helps to lubricate the eyeball and keep it moist LACRIMAL APPARATUS Lacrimal Glands Are located above the lateral end Protects , moistens and lubricates of each eye and continually the eye release a dilute salt solution ( tears ) onto the anterior surface Empties into the nasal cavity of the eyeball through several small ducts Lacrimal Canaliculi These 3 are the small ducts wherein Lacrimal Sac Tears passes through Nasolacrimal Ducts EXTRINSIC EYE MUSCLES Lateral Rectus ( VI Abducens ) Moves Eye Laterally ( External Eye Muscles ) – Medial Rectus ( III oculomotor ) Moves Eye Medially produce gross eye movements and Superior Rectus ( III oculomotor ) Elevates eye and turns it medially make it possible for the eyes to Inferior Rectus ( III oculomotor ) Depresses eye and turns it medially follow a moving object Inferior Oblique ( III oculomotor ) Elevates eye and turns it laterally Superior Oblique ( IV trochlear ) Depresses eye and turns it laterally  8.1.B. INTERNAL STUCTURES : THE EYEBALL  Eye / Eyeball : a hollow sphere composed of three tunics or layers and its interior is filled fluid called humors that help maintains its shape LAYERS THAT FORMS THE WALL OF THE EYEBALL LAYER SUB – PARTS FUNCTION FIBROUS Protective Sclera  Seen anteriorly as the “white of the eye” LAYER – Transparent Cornea  Through which the light enters Outermost  Well supplied with nerve endings (mostly pain fibers ) Layer  Blinking and increased tear production if cornea is touched  Exposed part of the eye, vulnerable to damage  Can repair itself  Has no blood vessels, thus can be transplanted without rejection VESICULAR Choroid  Posterior Region LAYER –  Blood rich tunic that contains the dark pigment, which prevents Middle / light from scattering inside the eye Vascular Ciliary Body  Anterior to the Choroid Layer and  Composed of Smooth Muscle has 3  Is attached to the lens by a suspensory ligament called the regions ciliary zonule Iris  Is pigmented and has a rounded opening called the pupil through which light passes  Fibers from the Iris arranged radially and circularly acts like a diaphragm of a camera  Iris also regulates the amount of light entering the eye so that we can see as clearly as possible in the available light  Close vision and bright light – circular muscles contract and pupil constricts / gets smaller  Distant vision and Dim light – Radial Fibers contract to enlarge / dilate the pupil which allows more light to enter the eye  Cranial Nerve III ( Occulomotor ) Controls the muscles of the Iris SENSORY Retina  Is two layered : LAYER – 1. Outer pigmented Layer – composed of pigmented cells Innermost that absorb light and prevent light from scattering Sensory inside the eye. Also acts as phagocytes to remove dead Layer or damaged receptor cells and store vitamin A needed for vision 2. Transparent Neural Layer – has millions f receptor cells, RODS and CONS, which are called photoreceptors because they respond to light LENS  A Flexible biconvex crystal-like structure  Is held uptight in the eye by the ciliary zonule to the ciliary body  It focuses the light entering the eye CHAMBERS / LOCATION FUNCTION SEGMENTS ANTERIOR / Anterior to the lens  Contains a clear watery fluid called Aqueous humor AQUEOUS  It helps maintain intraocular pressure (pressure inside SEGMENT the eye )  Provides nutrients for the avascular lens and cornea  Is reabsorbed into the venous blood through the scleral venous sinus or canal of Schlemm POSTERIOR / Posterior to the lens  Has a gel like substance called vitreous humor, which VITREOUS SEGMENT helps prevent the eyeball from collapsing inward and by reinforcing it internally  GLAUCOMA Causes Result Signs and Symptoms Management Caused by Pressure within the eye  No symptoms at first  Commonly treated blocked increases to dangerous levels  Halos around lights with eyedrops to drainage of and compresses the delicate  Headaches and blurred increase the rate of Aqueous retina and optic nerve can vision aqueous humor Humor lead to blindness unless drainage detected early  Laser or surgical enlargement of the drainage  Tonometer is used to measure the intraocular pressure 8.2. PHYSIOLOGY OF VISION 8.2.A. PATHWAY OF LIGHT THROUGH THE EYE AND LIGHT REFRACTION  Light rays are bent in the eye as they encounter the cornea, aqueous humor, lens and vitreous humor  Refractive / Bending power of the cornea and humors are Constant  Refractive / Bending power of the lens can be changed by changing its shape by making it more or less convex, so that the light can be properly focused on the retina The greater the lens convexity / bulge /thicker - the more it bends the light The flatter / thinner the lens - less it bends the light  A light from 20 feet away approaches the eye as parallel rays, and those that light that came from a close object tends to scatter and diverge / bulge, thus, the lens must bulge to make close vision possible  ACCOMODATION : Is the ability of the eye to focus specifically for close objects  REAL IMAGE : Is the image formed on the retina as a result of the light bending activity of the lens that is Reversed Left to right and upside down VISION PROBLEMS TYPE OF DESCRIPTION CAUSE CORRECTION VISION EMMETROPIA  Normal Vision  NONE  No Correction Needed or “harmonious Vision” Myopia  Nearsightedness  Occurs when the parallel light  Requires Concave corrective / short vision rays from distant objects are lenses that diverge the light  Can see near focused in front of the retina rays before they enter the objects but need  Nearby objects are in focus eye allowing the rays to corrective lenses because the lens converge farther back on the to see distant “accommodates” ( bulges) to retinal surface objects focus the image properly on the retina Hyperopia  Farsightedness  Occurs when parallel light rays  Requires Convex corrective  Can see distant from distant objects are lenses that converge the light objects clearly focused behind the retina rays before they enter the but need  Can see distant objects clearly eye corrective lenses  Nearby Objects appear blurry to see nearby  Subjected to eyestrain objects Astigmatism  Multiple focal  Presence of uneven curvatures  Special cylindrically ground points on the in the cornea or lens lenses or contacts Retina and  Blurry images occur because blurry vision points of light are focused not as points on the retina but as lines  8.2.B. VISUAL FIELDS AND VISUAL PATHWAYS TO THE BRAIN ( IN SEQUENCE ) 1. AXONS CARRYING IMPULSES FROM THE RETINA 2. OPTIC NERVE 3. OPTIC CHIASMA - Where the fibers from the medial side of each eye cross over to the opposite side of the brain 4. OPTIC TRACTS - The resulting Fiber tracts from the optic chiasma. Each optic tract contains fibers from the lateral side of the eye on the same side and the medial side of the opposite eye 5. OPTIC RADIATION - these are the axons that are formed when the optic tract fibers synapse with the neurons in the thalamus 8.2.C. EYE REFLEXES EYES MUSCLES NECESSARY FOR PROPER EYE FUNCTION EYE MUSCLES STIMULATION EXAMPLES INTERNAL EYE MUSCLES  Autonomic Nervous  Ciliary Body - alters lens curvature System  Radial and Circular muscles of the Iris - controls pupil size EXTERNAL EYE MUSCLES  Somatic Fibers of the  Rectus and Oblique muscles which control eye ( EXTRINSIC ) cranial nerves III, IV and movements and make it possible to follow VI moving objects REFLEXES TYPE OF REFLEX ACTION MUSCLES INVOLVED CONVERGENCE  Reflexive Movement of the eyes medially  External Eye Muscles when we view close objects  Both eyes are aimed toward the near object being viewed PHOTOPUPILLARY  When the eyes are suddenly exposed to  Internal Eye Muscles REFLEX bright light, the pupils constrict  Is Also a protective reflex that prevents excessively bright light from damaging the delicate photoreceptors ACCOMODATION  When pupils constrict reflexively when we  Internal Eye Muscles PUPILLARY REFLEX view close objects and provides more acute vision  PART II : THE EAR : HEARING AND BALANCE  MECHANORECEPTORS - THE RECEPTORS THAT RESPONDS TO SOUND VIBRATIONS AND GROSS MOVEMENTS OF THE HEAD 8.3. ANATOMY OF THE EAR - THERE ARE 3 MAJOR AREAS OF THE EAR AREAS SUB - PARTS DESCRIPTION EXTERNAL Auricle / Pinna Shell Shaped structure surrounding the auditory canal opening ( OUTER ) EAR External Auditory Short, Narrow chamber carved into the temporal bone of the skull - Involved with Meatus / Auditory Has ceruminous glands in its skin lined walls which secrete waxy hearing Canal yellow cerumen Tympanic membrane / Where sound waves hits and vibrate eardrum MIDDLE EAR - Middle ear cavity / Is a small, air filled, mucosa lined cavity within the temporal bone Involved with Typanic cavity hearing Oval Window and 2 openings Round Window Pharyngotympanic Tube It is normally flattened and closed however, it opens during / Auditory Tube swallowing and yawning to equalize the pressure in the middle ear cavity with the external , or atmospheric pressure Ossicles Are the Collective term of the 3 smallest bones which are 1. Hammer / Malleus 2. Anvil / Incus 3. Stirrup /Stapes Transmit and amplify the vibratory motion of the eardrum to the fluids of the inner ear like dominoes INTERNAL EAR Bony Labyrinth / Osseus Are the Bony chambers located deep within the temporal bones - Involved with Labyrinth behind the eye socket equilibrium 3 subdivisions and hearing 1. Cochlea - Spiraling , Pea sized 2. Vestibule 3. Semicircular Canals 8.4. HEARING ( IN SEQUENCE ) 1. SOUND WAVES ( ANY ) 2.PASSES IN THE EXTERNAL EAR 3.PASSES IN THE MIDDLE EAR - SOUND WAVES AMPLIFIED 4. REACHES THE TINY OVAL WINDOW , SETS THE FLUIDS OF THE INNER EAR INTO MOTION, PRESSURE WAVES SET UP VIBRATIONS IN THE BASILAR MEMBRANE 5. RECEPTOR CELLS IN THE BASILAR MEMBRANE ARE STIMULATED BY VIBRATING MOVEMENT OF THE BASILAR MEMBRANE 6. THE HAIRS OF THE RECEPTOR CELLS BENDS 7. HAIR CELLS TRANSMITS IMPULSES ALONG THE COCHLEAR NERVE ( DIVISION OF CRANIAL NERVE VIII / VESTIBULOCOCHLEAR NERVE ) TO THE AUDITY CORTEX IN THE TEMPORAL LOBE, WHERE INTERPRETATION OF THE SOUND, OR HEARING, OCCURS 8.5. EQUILIBRIUM  it responds to various head movements  The vestibular apparatus is the equilibrium receptor of the inner ear  2 branches : STATIC EQUILIBRIUM AND DYNAMIC EQUILIBRIUM BRANCH FUNCTION SEQUENCE OF EVENTS to ACHIEVE EQUILIBRIUM 8.5.A  It reports on changes in the position of the 1. The Vestibule consists of 2 fluid filled cavities, STATIC head in space with respect to the pull of the utricle and saccule EQUILIBRIUM gravity when the body is not moving 2. The utricle and the saccule contain hair cells  Helps keep our head erect with overlapping gelatinuous material.  Extremely important to divers because it Embedded in the gelatinous material are enables them to tell which way is up to the granules of calcium carbonate called otoliths surface 3. When the head is tilted, otoliths in the  Our sense of Static equilibrium - position of gelatinous material slide “downhill”over the hair the head with respect to gravity - is due to cells stimulating them. Hair cells sends signals to the receptors of the vestibule the brain 4. The brain interprets the signal to know the position of the head 8.5.B.  Responds to angular or rotational 1. The three semicircular canals are oriented DYNAMIC movements of the head rather than to perpendicularly to one another. At the base of  EQUILIBRIUM straight line movements each canal is a gelatinuous mass called the  Our sense of Dynamic equilibrium - curpula in which the hair cells are embedded. equilibrium when the body or head is 2. The canals and the chambers are filled with a moving - is due to semicircular canals, fluid that moves when the head does. The which report rotational movements of the movement of fluid pushes the cupula and head, including those caused by stimulates hair cells that send messages to the acceleration or deceleration brain regarding body position and movement 3. The brain interprets the signal and maintains our balance 8.5.C. HEARING AND EQUILIBRIUM DEFICITS DEFICIT DESCRIPTION CAUSE SIGNS AND SYMPTOMS Conduction Results when  Build up of earwax  Will still be able to hear by bone Deafness something interferes  Fusion of the ossicles conduction although her ability to hear air with the conduction of ( otosclerosis ) conducted sounds ( normal conduction sound vibrations to  Ruptured eardrum route ) is decreased or lost the fluids of the inner  Otitis media -  Hearing aids are helpful ear and can be inflammation of the permanent or middle ear temporary  Thus, it results from Mechanical factors Sensorineural Occurs when there is  Extended listening to  Cannot hear better by either conduction Deafness degeneration or excessively loud sounds route damage to the  Thus, it results from a  Hearing aids are not helpful receptor cells in the problem with nervous spiral organ of corti, system structures to the cochlear nerve, or to the neurons of the auditory cortex Meniere’s A serious pathology  Exact cause is Unknown  Progressive deafness occurs Syndrome affecting the inner  Suspected Causes :  Affected individuals become nauseated , ear Arteriosclerosis, often have howling or ringing sounds in degeneration of the their ears and vertigo ( sensation of cranial nerve VIII, spinning ) which is so severe that they increased pressure of cannot stand up without extreme the inner ear fluids discomfort  PART III : CHEMICAL SENSES : SMELL AND TASTE  CHEMORECTORS : RECEPTORS FOR TASTE AND OLFACTION 8.6. OLFACTORY RECEPTORS AND THE SENSE OF SMELL PARTS OF THE OLFACTORY RECEPTORS  Are the receptors for the sense of Smell  It occupies a postage stamp- sized area in the roof of each nasal cavity  Are exquisitely sensitive and olfactory neurons tend to adapt rather quickly when they are exposed to an unchanging stimulus ( Odor )  The olfactory pathways are closely tied into the limbic system ( emotional - visceral part of the brain ) thus, it is long lasting and very much a part of our memories and emotions PARTS CHARACTERISTIC OLFACTORY RECEPTOR CELLS Sensory Neurons of the olfactory receptor equipped with olfactory hairs When Stimulated by chemicals dissolved in the mucus, they transmit impulses along the olfactory filaments OLFACTORY HAIRS Long cilia that protrudes from the nasal epithelium and are continuously bathed by a layer of mucus secreted by the underlying glands OLFACTORY FILAMENTS Are bundled axons of olfactory neurons that collectively make up the olfactory nerve ( cranial nerve I ) OLFACTORY NERVE Conducts the impulses to the olfactory cortex of the brain where the odor is interpreted 8.7. TASTE BUDS AND SENSE OF TASTE PARTS CHARACTERISTIC TASTE BUDS These are the receptors for the sense of taste and are widely scattered in the oral cavity. Most are located in the tongue, few are scattered on the soft palate, superior part of the pharynx, inner surface of the cheeks Are subjected to huge amounts of friction and are burned by hot foods because of their location PAPILLAE These are small peg like projections Located on the dorsal tongue surface Vallate Papillae ( Circumvallate ) - large round papillae where taste buds are located Fungiform Papillae - Papillae that are found on the top of the tongue and are more numerous Foliate papillae - Papillae that are found at the sides of the tongue GUSTATORY CELLS Specific receptor cells ( Epithelial Cells ) that that responds to chemicals dissolved in the saliva GUSTATORY HAIRS Are long microvilli that protrude through the taste pore and when stimulated they depolarize and the impulse are transmitted to the brain CRANIAL NERVES CRANIAL NERVES VII ( facial ), IX( glossopharyngeal ) AND X ( vagus ) - all of these carry taste impulses from the various taste buds to the gustatory cortex BASAL CELLS Stem cells found in the deeper regions of the taste buds, they replace the taste bud cells every 7 to 10 days FIVE BASIC TASTE SENSATIONS RECEPTORS SUBSTANCES THAT RESPONDS SWEET RECEPTORS Sugars, sacharine, alcohols, amino acids and some lead salts SOUR RECEPTORS Hydrogen ions or the acidity of the solution BITTER RECEPTORS Alkaloids SALTY Metal ions in a solution UMAMI ( discovered by the Japanese ) Elicited by the amino acids Glutamate and Aspartate Responsible for the beef taste of steak  PART IV : DEVELOPMENTAL ASPECTS OF THE SPECIAL SENSES STAGE DESCRIPTION NEWBORN  Is the only special sense that is not fully functional when the baby is born  Eyeballs are fore shortened  All babies are born hyperopic ( farsighted )  Newborn sees only in gray tones  Makes uncoordinated eye movements  Often sees using only one eye at a time  Lacrimal glands are not fully developed until about 2 weeks after birth, so within 2 weeks the baby’s cry is tearless 5 MONTHS  Able to focus on articles within easy reach  Can follow moving objects  Visual acuity is till poor  Their vision is 20/200 - meaning that a mature individual clearly sees the object 200 feet away, and an infant can see the same object if it is moved 20 feet away from them. 5 YEARS OLD  Color vision is well developed  20/30 visual acuity  Depth perception is present, providing a readiness to begin reading SCHOOL AGE  Hyperopia replaced by Emmetropia ( normal vision ) which continues about age 40 AGE 8 - 9  Eyeballs continue to enlarge until this age, Lens grow throughout life Age 40  Presbyopia ( Farsightedness ) begins to set in due to decreased lens elasticity making it difficult to focus for close vision AGING OCCURS  Lacrimal glands are less active  Eyes tend to become dry and more vulnerable to bacterial infection and irritation  Lens loses its crystal clarity and becomes discolored , thus , it scatters light causing a distressing glare when the person drives at night  Pupils are somewhat constricted because dilator muscles of the iris becomes less efficient AGE 70  Decreased amount of light reaching the retina and visual acuity is lowered  HOMEOSTATIC IMBALANCES CONDITION DESCRIPTION CAUSE MANAGEMENT COMPLICATIONS STRABISMUS A Congenital Unequal pulls by the SURGERY Brain may stop recognizing eye problem external eye muscles signals from the deviating eye commonly called that prevents the causing the eye to become as “Crossed baby from functionally blind Eyes” coordinating movement of the two Unable to focus eyes both eyes simultaneously on the same object CONGENITAL Maternal Rubella ( Germal BLINDNESS OR Infection that Measles ) CATARACTS occur during early pregnancy OPTHALMIA Infection of the Gonorrhea Antibiotics Baby’s eyelids become red, NEONATURUM baby’s eye swollen and produces pus / conjuctivitis during delivery