Download to read offline
More Related Content
Similar to lecture 6 special senses.ppt
![(_nut)LECTURE_SAM[2].pptx](https://cdn.slidesharecdn.com/ss_thumbnails/nutlecturesam2-230922203647-8a3d0335-thumbnail.jpg?width=640&height=640&fit=bounds)
![HEALTH SYSTEMS MANAGEMENT II UNIT TWO [Autosaved].pptx](https://cdn.slidesharecdn.com/ss_thumbnails/healthsystemsmanagementiiunittwoautosaved-240218181923-21e24621-thumbnail.jpg?width=640&height=640&fit=bounds)
lecture 6 special senses.ppt
- 1. 1 KAAF UNIVERSITY COLLEGE PhysicianAssistance studies. The special senses Dr Joseph Somuah Akuamoah Senior lecturer
- 2. 2 The Special Senses Contents •Pain • Eye vision • Ear: hearing and equilibrium • Chemical senses:- taste and smell
- 3. 3 1. PAIN • Painis primarily a protective mechanism meant to bring to conscious awareness the fact that tissue damage is occurring or about to occur. • Furthermore, storage of painful experiences in memory helps us avoid potentially harmful events in the future. • There are 3 categories of pain receptors or nociceptors Mechanical nociceptors:- cutting, crushing, pinching Thermal nociceptors:- temperature extremes e.g heat Polymodal nociceptors:- all kinds of damaging stimuli
- 4. 4 2. EYE: VISION •Eyes capture the patterns of illumination in the environment as an “optical picture” on a layer of light sensitive cells, the retina (camera captures an image on a film) • The image on the retina is transmitted through a series of steps until it is finally perceived as a visual likeness of the original image.
- 5. 5 EYE: Protective mechanisms..1 •The eyeball, except for the anterior (front) part is sheltered by the bony socket in which it is positioned • The eyelids act like shutters to protect the anterior portion of the eye from insults. • The eyelids close reflexly to cover the eye under threatening circumstances such as dazzling light or rapidly approaching objects or instances when the surface of the eye is touched • Frequent spontaneous blinking of eyelids helps disperse the lubricating, cleansing, bactericidal tears.
- 6. 6 EYE: Protective mechanisms(2) • Tears are produced continuously by the lacrimal glands in the upper lateral corner under the eyelid. • This fluid flows across the anterior surface of the eye and drains into tiny canals in the corner of each eye eventually emptying into the back of the nasal passageway. • The eyes are also equipped with protective eyelashes, which trap fine, airborne debris such as dust before it can fall into the eye.
- 7. 7 EYE: fluid filledsphere • Each eye is a spherical, fluid filled structure enclosed by three layers. From outermost to innermost these are:- 1.The scleral cornea 2. The choroid/ciliary body/iris and 3. The retina. • Most of the eyeball is covered by a tough outer layer of connective tissue, the sclera, which forms the visible white part of the eye. • Anteriorly, the outer layer consists of the transparent cornea, through which light rays pass into the interior of the eye. Cornea and lens has no blood supply.
- 8. 8 EYE: fluid filledsphere…2 • The middle layer underneath the sclera is the highly pigmented choroid, which contains many blood vessels that nourish the retina. • The choroid layer becomes specialized anteriorly to form the ciliary body and iris. • The innermost coat under the choroid is the retina, which consists of an outer pigmented layer and an inner nervous-tissue layer. • The inner nervous tissue layer contains the rods and cones, the photoreceptors that convert light energy into nerve impulses.
- 9. 9 EYE: fluid filledsphere…3 • The interior of the eye consists of two fluid filled cavities separated by an elliptical lens. • The larger, posterior cavity between the lens and retina is a semifluid jellylike substance, the vitreous humor. Maintains the spherical shape of the eyeball. • The anterior cavity between the cornea and lens contains a clear, watery fluid, the aqueous humor. • The fluid, produced by the ciliary body at 5ml/day, carries nutrients for the cornea and lens and drains into a canal at the edge of the cornea into the blood. • Glaucoma (blockage of drainage canal) leads to accumulation of aqueous fluid which causes increased pressure on the eye.
- 10. 10 EYE: amount oflight entering the eye • Not all light passing through the cornea reaches the light sensitive photoreceptors, because of the presence of the iris. • The pigment in the iris is responsible for eye color. • The varied flecks, lines and others makes the iris unique for each individual, hence the basis for identification (instead of finger printing or DNA) • The center of the iris through which light enters the eye is the pupil. Contraction of the iris muscles controls amount of light entering the eye
- 11. 11 EYE: diseases • Withadvancing age the cells of the lens die and become stiff. With loss of elasticity, the lens can no longer assume the spherical shape required to accommodate for near vision…Presbyopia, affect most people by age 45 to 50 requiring them to use corrective lenses for near vision (reading) • The elastic fibers in the lens are transparent. These fibers occasionally become opaque so that light rays cannot pass through...Cataract • Myopia, near sightedness (short sighted or lens is too strong) or far sightedness…hyperopia are other vision disorders (long sighted or lens is too weak).
- 12. 12 3. EAR: HEARINGAND EQUILIBRIUM • The ear consists of 3 parts; the external, middle and inner ear. • The external and middle ear transmit airborne sound waves to the fluid -filled inner ear, amplifying the sound energy in the process. • The inner ear houses two different sensory systems: the cochlea, which contains the receptors for conversion of sound waves into nerve impulses, making hearing possible, and the vestibular apparatus, which is necessary for the sense of equilibrium.
- 13. 13 EXTERNAL EAR • Theexternal ear consists of the pinna (ear), external auditory meatus (ear canal) and tympanic membrane (eardrum). • The pinna (cartilaginous) collects sound waves and channels them down the external auditory meatus. Many species like dogs can cock their ears in the direction of the sound to collect more sound waves but human ears are immobile. • The entrance to the ear canal is guarded by fine hairs. The skin of the canal contains modified sweat glands that produce cerumen (ear wax). The hairs and earwax prevent particles from reaching the inner ear to accumulate or injure the tympanic membrane.
- 14. 14 Tympanic membrane • Thetympanic membrane vibrates when struck by sound waves. • The inside of the eardrum is exposed to atmospheric pressure via the eustachian tube, which connects the middle ear to the pharynx (back of the throat). • During rapid external pressure changes (e.g during airflight) the ear drum bulges painfully as pressure outside the ear changes whilst the pressure in the middle ear remains unchanged. • Opening the eustachian tube by yawning allows the pressure on both sides of the tympanic membrane to equalize, relieving the pressure distortion as the eardrum pops back into place.
- 15. 15 Fluid movements inthe inner ear • The middle ear transfers the tympanic membrane vibrations to the fluid of the inner ear..mechanoreceptors.. • This transfer is facilitated by the sensitive 3 small bones or ossicles (malleus, incus and stapes). Malleus is attached to the tympanic membrane and stapes attached to the oval window. • The ossicular system amplifies the pressure of the airborne sound waves. • Tiny muscles in the middle ear contract reflexly in response to loud sounds (over 70 dB), causing the tympanic membrane to tighten and limit movements of the ossicular chain.
- 16. 16 VESTIBULAR APPARATUS • Theinner ear has another specialized component, the vestibular apparatus, which provides information essential for the sense of equilibrium and for coordinating head movements with eye and postural movements. • The vestibular apparatus detects changes in position and motion of the head. • All components of the vestibular apparatus contain endolymph and are surrounded by perilymph. • Fluid imbalances within the inner ear lead to Meniere’s disease. It is characterized by severe vertigo accompanied by pronounced ringing in the ears (tinnitus) and some loss of hearing.
- 17. 17 DEAFNESS • Loss ofhearing (deafness) may be temporary or permanent, partial or complete. • Deafness can classified into two types – conductive deafness and sensorineural deafness. • Conductive deafness:- sound waves are not adequately conducted through the external and middle portions of the ear to set the fluids in the inner ear in motion. Possible causes are blockage by ear wax, rupture of ear drum, middle ear infections. • In Sensorineural deafness, sound waves are transmitted to the inner ear, but are not translated into nerve endings for the brain to interpret. Defect can lie with the auditory nerves or organ of corti.
- 18. 18 CHEMICAL SENSE: TASTEAND SMELL • Unlike the eyes’ photoreceptors and the ears’ mechanoreceptors the receptors for taste and smell are chemoreceptors. • The sensations of taste and smell in association with food intake influence the flow of digestive juices and affects appetite. • Furthermore, stimulation of taste or smell receptors induces pleasurable or objectionable sensations and signals the presence of something to seek (good- tasting food) or to avoid (a potentially toxic or bad tasting substance. • Thus the chemical senses provides a quality-control check point for substances available for ingestion.
- 19. 19 CHEMICAL SENSE: TASTEAND SMELL • In lower animals, smell plays a major role in finding direction, seeking prey or avoiding predators and in sexual attraction to a male. • The sense of smell is less sensitive in humans and much less important in influencing our behavior (although millions of dollars are spent on perfumes and deodorants to make us smell better and be more socially attractive)
- 20. 20 Mechanism of gustation(taste) • The chemoreceptors for taste sensation are packaged in taste buds, about 10,000 of which are present in the oral cavity and throat, with the majority on the upper surface of the tongue. • A taste bud consists of about 50 taste receptor cells, packaged like slices of an orange. • Each taste bud has a small opening, the taste pore through which fluids in the mouth touches the surface of its receptor cells, taste receptor cells. • We can discriminate among thousands of different taste sensations, yet all tastes are varying combinations of five primary tastes: salty, sour, sweet, bitter and umami (meaty or savory taste).
- 21. 21 Mechanism of Olfactory(smell) • The olfactory mucosa, a 3cm2 patch of mucosa in the ceiling of the nasal cavity contains 3 cell types:- olfactory receptor cells, supporting cells, basal cells. • The axons of the olfactory receptor cells collectively form the olfactory nerve. • The supporting cells secrete mucus, which coats the nasal passages. • The basal cells are precursors for new olfactory receptor cells which are replaced every 2 months.
- 22. 22 Questions 1. Explain whyyour sense of smell is reduced when you have a cold, even though the cold virus doesn’t directly adversely affect the olfactory receptor cells. 2. Kojo Mensah complained to his doctor of bouts of dizziness. The doctor asked whether by dizziness he meant a syncope or vertigo? a) What is syncope b) What is vertigo? c) Why is this distinction important in differential diagnosis of his condition d) What are some possible causes of each of these symptoms? 3. Patients with certain nerve disorders are unable to feel pain. Why is this disadvantageous?