Special Senses .pdf

Special Senses ' I Vision A Eyes : 1. Accessory Structures A. Eyebrows-short coarse hairs that overlie the supraorbital margin of skull; help shade eyes from sunlight a prevent perspiration going down forehead from reaching eyes B. Palpebrae (eyelids) 1)function: -protects eyes from foreign obj...

Special Senses ' I Vision A Eyes : 1. Accessory Structures A. Eyebrows-short coarse hairs that overlie the supraorbital margin of skull; help shade eyes from sunlight a prevent perspiration going down forehead from reaching eyes B. Palpebrae (eyelids) 1)function: -protects eyes from foreign objects, excessive light & injuries -contributes to overall lubrication of eye -allows blinking to distribute tears across eye to prevent dryness 2)Palpebral fissure (eyelid slit) 3)Medial& lateral Commissure 4)Lacrimal Caruncle-contains oil & sweat glands; produces "Sandman's” eye sand 5)tarsal plates -supports connective tissue, obicularis oculi & levator palpebrae superioris 6)Tarsal gland (meibomian gland): large sebaceous glands that produce meibum which help tears from evaporating too quickly 7)ciliary gland: ala accessory lacrimal glands which are modified sweat glands that are are located in the conjunctiva of the eye; produces tears which aid in lubricating& protecting eye's surface 8)Eyelash: short fine hairs that grow along the eyelid's edge; they serve to protect the eye from debris, dust& excessive light; triggers reflex blinking when touched C. Conjunctiva: thin, transparent layer covering the sclera of the inner surface of the eyelids; helps protects eye a keep it moist by producing mucous& tears; very sensitive to pain 1) Palpebral Conjuntiva2) Bulbar conjughtna - covers white of eye not including Cornea 3) Conjunctival sac -contact lens go here D. Lacrimal Appuratus 1) Lacrimal glands - secretes lacrimal secretion called tears which produce antibodies and antibacterial (lysozyme) 2 Lacrimal canaliculi 3) Lacrimal sac- where tears drain and go into nasal canal E. Extrinsic Eye Muscle - enable eye movement and help maintain shape of eye • rectus muscles - 4 in total • oblique muscles - 2 in total 2. Clinical Applications A. Chalazion: obstructed tarsal gland B. Stye C. Conjunctivitis (pink eye) D. Cold or nasal inflammation: inflammation of lacrimal ducts E. Diplopia (double vision) F. Strabismus (cross eyes): has to be treated early to prevent blindness 3. Structure of Eyeball A. Fibrous layer - dense & avascular- made of sclera and cornea 1) Sclera • protects & shapes eye • Anchors extrinsic muscles • Posterior at optic nerve and continuous with dura mater 2) Cornea B. Vascular layer (uvea) 1) choroid region - posterior portion • Supplies to blood to eye • brown pigment 2) Ciliary Body • surrounds lens and holds lens in place • ciliary muscles • capillaries - secretes fluid • ciliary zonule - connects ciliary body to lens • secretes aqueous humor (epithelial tissue) 3) Iris (lens between cornea and lens) • pupils: regulates amount of light that enters eye • Sphincter pupilae: causes constriction of pupils under parasympathetic control • dilator pupilae: dilates pupils which allow more light to come in under sympathetic control 4. Retina: Inner Layer of the Eye; Neural Region • attaches anteriorly to oral serrata and posteriorly at optic disc A. Embryonically from optic disc B. Photoreceptor cells C. Delicate 2 layer membrane 1) Pigmented layer - next to choroid; clings to eye absorbs light and prevents scattering of light; also know as the outer layer 2) Neural layer - inner transparent layer that is anteriorly to the margin of the ciliary body A. 3 types of neurons • 3 Photoreceptors (rods and cones) • Ganglion cells • Bipolar cells B. Ganglion cell axons C. Optic disc - where the optic nerve leaves eyes also know as the blind spot due to its lack of photoreceptors D. Photoreceptors • Rods - deals with high intensity; dim-light; no color vision. There are numerous rods around the the periphery of the eye • Cones - deals with color; bright light and high resolution color vision; most of the cones are in the macula lutea Fovea Centralis - this is where have our best vision acuity; also helps out fovea 5. Internal Chambers and Fluids A. Posterior segment 1) vitreous humor: fluid that transmits light; develops in embryo 2) supports posterior of lens 3) hold neural layer of retina against pigmented layer B) Anterior segment (contains aqueous humor) I) anterior chamber - located between cornea and iris 2) posterior chamber - located between iris and lens 3) supplies nutrients and water oxygen to cornea and lens 6. Lense: Biconvex, transparent, flexible avascular organ A. Less epithelium; cuboidal cells B. Lens fiber • filled with protein called crystalline • Constantly being added to; more lens fiber lens flexible B. Overview of light 1. Photons 2. Wavelengths of Light 3. Visible spectrum (only part that is visible A) Red is the longest wavelength and violet is the shortest. Black is an absorption of all the colors and white is the reflect of all the colors C. Optics 1. Refraction - bent at an oblique angle 2. Lenses - can also reflect light due to its biconvex lenses A. Convex B. Concave * majority of the refracting power is in cornea at fixed emmetropic (normal vision) 3. Focusing on Retina A. Pathway B. Light refractions (3 steps) 1) Light enter cornea 2) Light enters lens 3) Light leaves lens C. Focusing on distant vision D. Focusing for close vision 1) accommodation of lenses - increases refractory power • near point of vision • Presbyopia (old people’s vision) 2) constriction of pupils D. Photopigments 1. Retinal (made from Vitamin A 2. Opsins (4 kinds) - retinal binds with this; each rod has its own opsin 1) Photopsins (found in cones) 2) Rhodopsins (found in rods) 3) Melanopsins (found in ganglion cells) 4) Rhodopsin like opsin (found in various organism and tissues 3. Isomers of Retinal 4. Rhodopsin formation and breakdown 1) rhodopsin (deep purple pigments) 2) produced in dark 3) pigment bleaching (light hitting rhodopsin) 4) pigment regeneration 5. Photo transduction (enzyme cascade of light transduction reactions) 1) in dark, cation channels open 2) light initiates enzyme cascade which close cation channels 3) light then activate rhodopsin which activates G-protein, transducin which activates phosphodiesterase to break down cGMP to GMP 4) as cGMP levels fall, cation channels close which result in hyperpolarization to -70mv E. Visual Information 1. Visual Pathway A) optic nerves B) Optic chiasm (place where optic nerves cross C) Optic tract D) primary visual cortex (part of brain that perceives vision 2. Depth Perception 3. Visual Processing (direction/speed of movement F. Diseases 1. Glaucoma 2. Macula Degeneration (physical deterioration of macula lutea; can lead to blindness, HTN A) tend to lose vision in middle B) can’t see color well 3. Detached Retina A) flashes of light B) possible blindness · II Olfaction A. Olfactory Receptors 1.Found in the olfactory epithelium A) olfactory neurons are bipolar 2. Specificity of Olfactory Receptors A) can detect just a few molecules and can send signals back to the brain B) Physiology of Smell • volatile (lighter molecular weight) - able to reach know • Receptor Proteins : odorant bind to receptor protein which starts process of smell transduction III TASTE A. Tastebuds 1. Gustatory epithelial cells 2. Basal Epithelial Cells B. Taste Sensation • sweet • Sour • Umami C. Physiology of Taste IV Hearing A. Regions of Ear 1.External Ear A) Pinna/Auricle - captures and directs sound into ear canal B) helical - same job as Pinna C) Lobule (earlobe) D) external auditory (ear canal) • Ceruminous gland (helps produce cerumen) • Cerumen (aka earwax helps prevent dust/debris and insects from coming into the ear) 2. Middle Ear A) Ossicles • Stapes (stirrup) • Incus (anvil) - incurs receives sound vibrations from malleus and amplifies them and sends them to the stapes • Malleus (hammer)- helps transmits sound vibrations from ear drum to inner ear B) pharyngotympanic tube (Eustachian tube) - The pharyngotympanic tube, also known as the Eustachian tube, connects the middle ear to the nasopharynx, the part of the throat located behind the nose. This tube plays a crucial role in regulating air pressure in the middle ear. It opens and closes to equalize air pressure between the middle ear and the external atmosphere. This function is essential for maintaining optimal conditions in the middle ear, preventing discomfort, and ensuring the proper functioning of the ear. 3. Inner Ear A. Cochlea - Responsible for hearing. - Coiled, snail-shaped structure. - Converts sound vibrations into electrical signals that are sent to the brain. B. Vestibular System - Contributes to balance and spatial orientation. - Includes the semicircular canals and otolithic organs (utricle and saccule). - Detects head movements and provides information about the body's position in space. C. Semicircular Canals - Three fluid-filled canals oriented in different planes. - Detect rotational movements of the head. D. Utricle and Saccule - Part of the otolithic organs in the vestibular system. - Detect linear acceleration and the position of the head concerning gravity. E. Auditory Nerve - Transmits electrical signals from the cochlea to the brain. - Integrates auditory information for perception. These components work together to facilitate both hearing and balance, making the inner ear a crucial part of the auditory and vestibular systems.