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47 Cards in this Set
- Front
- Back
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General senses versus special senses |
General senses : large group of different types of touch receptors Special seneses : taste , smell , sight , hearing and balance |
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Special sensory receptors |
Localized - confined to the head region Receptors are not free ending of sensory neurons Special receptor cells : neuron- like epithelial cells or small peripheral neurons |
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Taste |
Taste - gustation Receptors - classified as chemoreceptors that respond to food dissolved in saliva fluid |
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The superior surface of tongue |
Stratified squamous epithelium Filliform papillae Fungiform papillae Foliate papillae Vallate papillae Sulucs terminals : mark border between mouth and pharynx Lingual tonsil : covers posterior 1/3rd of tongue that lies in oropharynx |
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Filliform papillae on tongue |
The most numerous papillae on tongue Small and conical pointed in shape Line up in parallel rows which enable tongue to grasp and manipulate food do not contain taste buds |
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Tongue papillae with taste buds |
Fungiform , foliate and vallate papillae contain taste buds Fungiform papillae : mushroom shaped and scattered over tongue surface ; taste buds on apical surface Foliate papillae : on the posteriorlateral surface ; taste buds on side wall of tongue Vallate papillae : inverted V-shaped row bordering the posterior third of the tongue dorsum and directly anterior to the terminal sulcus , taste buds on side walls |
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Taste buds |
Present on fungiform , folliate and vallate papillae on the tongue surface Contain taste receptors Collection of 50-100 epithelial cells Contain two major cell types Gustatory epithelial cells Basal epithelial cells Long microvilli ( gustatory hairs) project from gustatory epithelial cells and extend through a taste pore to the surface of the stratified squamous epithelium Cells in taste buds replaced every 7-10 days |
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Taste sensation and the gustatory pathway |
Five basic qualities of taste - sweet , sour , salty , bitter and umami - umami is elicted by glutamate and means 'pleasant savory taste' in japanese The taste map is a myth All taste modalities can be elicted from all areas of tongue containing taste buds |
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Gustatory pathway |
Taste information reaches the cerebral cortex primarily through facial (CNVII) , glossopharyngeal (CN IX) and vagus nerve (CN ,X) Bitter taste receptors are found in stomach Gustatory sensory neuron synapse in the solitary nuclues of the medulla from which impulses are transmitted to the thalamus where they synapse and then travel to the gustatory area of the cerebral cortex in the insula |
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Smell |
Smell : olfaction Receptors : classified as chemoreceptors which respond to airborne chemicas that dissolve in fluids of the nasal mucosa |
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Smell (olfaction) |
Olfactory receptors are part of the olfactory epithelium Olfactory epithelium is pseudostratified simple columnar and contains three main cell types - olfactory sensory neurons ( bipolar) - supporting epithelial cells - Basal epithelial cells |
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Smell : cell body to epithelium |
Cell bodies of olfactory sensory neurons are bipolar and are located in olfactory epithelium Have a apical dendrite that projects to the epithelial surface and ends in a knob from which olfactory cilia radiate Olfactory cilia act as receptive structures for smell Mucus captures and dissolves odor molecules |
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Smell : cell body to brain |
Gather in bundles of axon filaments of the olfactory neurons Pass through the cribriform plate of ethmoid bone Enter into the olfactory bulbs and synapse with mitral cells ( output cells ) in complex synaptic clusters called glomeruli Mitral cell trasmit impulses along the olfactory tract to 1. limbic system 2. Piriform lobe of the cerebral cortex which includes the hooklike uncus and is the primary olfactory cortex |
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Disorder of smell sense |
Anosmia : absence of the sense of smell Due to injury , colds , allergies or zinc deficiency Uncinate fits - distortions of smells or olfactory hallucinations Often result from irritation of olfactory pathways After brain surgery or head trauma |
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Olfactory receptors outside of nose |
Odor receptors are present in the liver , kidney , hear lung colon and even sperm Receptors in kidney can influence blood pressure Olfactory receptors in the testes function as a chemical guidance system that helps the sperm find the unfertilized egg |
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Olfactory receptors outside of nose |
Humans have over 350 different types of olfactory receptors More than 15 olfactory receptors that exist in the nose are found in human skin cells Exposing one of these receptors to synthetic scandalwood odor ( scandalore ) sets off a cascade of molecular signals that appears to induce healing in injured tissue. In human studies , skin abrasions healed 30% faster in the presence of scandalore |
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Eye and vision |
70% of all sensory receptors in the body are in the eyes 40% of the cerebral cortex is involved in processing visual information Anterior one sixth of the eye surface is visible white the rest is positioned in boney eye socket |
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Accessory structures of the eye |
Eyebrows - coarse hair on the superciliary arches Eyelids ( palpebrae) - seperated by palpebral fissure - meet at the medial and lateral angles - lacrimal caruncle - reddish elevation at the medial canthus - Tarsal plates - connective tissue within the eyelids - Tarsal glands - modified sabeceous glands |
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Accessory structures of the eye |
Levator palpebrae superioris muscle - moves upper eyelid Conjuctiva - transparent mucous membrane - Palpebral ( tarsal) conjunctiva - Bulbar conjunctiva - Conjunctival sac |
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Accessory structures of the eye |
Lacrimal apparatus keeps the surface of the eye moist lacrimal gland - produces lacrimal fluid Excretory ducts of lacrimal glands Lacrimal punctum Lacrimal canaliculus Lacrimal sac - fluid empties into nasal cavity Nasolacrimal duct Inferior meatus |
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Types of tear production |
Continuous ( or basal ) tears are produced for basic eye function such as lubrication Reflex ( or irritant) tears occur when the eye is exposed to excessive light , cold , wind , a foreign body or irritating gas Psychogenic tears are shed for emotional reasons |
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Tears |
Produced by lacrimal gland and released through excretory ducts of lacrimal glands We produce 5- 10 ounces of continuous ( basal) tears a day even if we do not cry |
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Extrinsic eye muscles |
Six extrinsic eye muscle that control movment of eye Originate in the wall of the orbit Insert on outer surface of the eyball Annular ring - origin of the four rectus muscle The six extrinsic eye muscles are Lateral rectus and medial rectus Superior rectus and inferior rectus Superior oblique and inferior oblique |
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Extra ocular eye muscle action |
Medial rectus CIII : moves eye medially Superior rectus CN III : elevates eye and turns it medially Inferior rectus CN III : depresses eye and turns it medially Lateral rectus CN VI : elevate eyes and turns it laterally Superior oblique , CN IV : depresses eye and turns it laterally |
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Anatomy of the eyeball |
Componets of the eye Protect and support the photoreceptors Gather, focus and process light into precise images Anterior lobe : most anterior part of the eye Posterior pole : most posterior part of the eye External walls - composed of three tunics Internal cavity - contains fluid ( humors ) |
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Anterior and posterior segments of eyes |
The lens and cilliary zonules divide the eye into anterior and posterior segments |
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Posterior segment of eye |
Filled with vitreous humor Clear , jelly like substance Transmit light Support the posterior surface of the lens Helps maintain intraocular pressure |
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Anterior segment of eye contains both anterior and posterior chambers |
Anterior chamber : between the cornea and iris Posterior chamber : between the iris and lens Both chambers are filled with aqueous humor |
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Aqueous humor |
Formed from a filterate of the capillares in the cilliary processes Flows from the posterior chamber through the puil into the anterior chamber Reabsorbed into the venous blood by the scleral venous sinus Renewed continuously Provides nutrients to the lends and cornea |
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Gluacoma = increased intraocular pressure in the anterior segment |
Occurs when aqueous humor drains more slowly than it forms Cause compression on the retina and optic nerve which can lead to blindness |
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The lens |
A thick , transparent , biconvex disc Held in place by its ciliary zonule Lens epithelium - covers anterior surface of the lens Elongated lens fibers form the bulk of the lens New lens fibers are continuously added Lens enlarges throughout |
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The eye as an optic device |
Structures in the eye bend light rays Light rays converge on the retina at a single focal point Light bending structures are the lens , cornea and humors Accomodation : curvature of the lens is adjustable which allows for focusing on nearby objects |
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Three layers of wall of eye |
Fibrous layer (sclera and cornea) Vascular layer ( choroid , ciliary body and iris ) Sensory layer : ( pigmented layer , neural layer) |
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The fibrous layer |
Most external layer of the eyeball and is composed of dense connective tissue in two different regions: sclera and cornea Sclera : - posterior five-sixths of the tunic White , opague region Provides shape and an anchor for eye muscles Cornea anterior one sixth of the fibrous tunic Limbus Junction between sclera and cornea Scleral venous sinus - allows aqueous humor to drain |
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Cornea |
Epithelium ( outer layer) Thick layer of dense collagen - rich connective tissue Endothelium ( inner layer) Cornea is avascular , but gets O2 from air in front and nutrients from aqueous humor behind Cornea is richly supplied with sensory nerve endings , most of which are pain receptors |
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Vascular layer of eye |
Choroid Cilliary body iris |
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Choroid |
Vascular Darkly pigmented membrane Forms posterior five-sixth of the vascular tunic Brown color - from melanocytes Prevents scattering of light rays within the eye Choroid corresponds to the arachnoid and pia matter |
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Cilliary body |
Thickened ring of tissue , which encircles the lens Ciliary body consists chiefly of smooth muscle called the cillary muscle which acts to focus the lens Ciliary processes - posterior surface of the ciliary body Ciliary zonule ( suspensory ligament) is a halo of fine fibrils attached around entire circumference of the lens |
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The iris |
Visible colored part of the eye Attached to the ciliary body and positioned anterior to the ciliary body Composed of smooth muscle Pupil is the round , central opening Dilator pupillae muscle ( radially arranged ) dilates pupils Sphincter pupillae muscle ( circularly arranged ) constrict pupils Pupillary light reflex : protective response to pupil constriction when a bright light is flashed in the eye |
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Inner layer of eye |
Retina : thin outer pigmented layer and a thicker inner neural layer Optic nerve |
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Regional specialization of the retina |
Neural layer ends at the posterior margin of the ciliary body and this junction is called ora serrata retinae Macula lutea - contains mostly cones Fovea centralis - contains only cones and is region of highest visual acuity Optic disc - blind spot |
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The inner layer ( retina ) is composed of two layers |
Pigmented layer - single outer layer of melanocytes Neural layer - most inner layer with a sheet of nervous tissue |
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Neural layer of retina , types of neurons |
Photoreceptor cells ( rods and cones ) Bipolar cells Ganglion cells A 4th cell type is an interneuron ( amacrine and horizontal cells ) which process visual information |
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Two main types of photoreceptor " neurons |
Rod cells - more sensitive to light and allow vision in dim light Cone cells - operate best in bright light and enables high acuity , color vision |
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Photoreceptor |
Rods and cones have an inner and outer segment Outer segments are receptor regions that contain light absorbing pigments Light particles modify the visual pigment and generate a nerve impulse |
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The retina neural layer of the inner layer |
Photoreceptor cells signal bipolar cells Bipolar cells signal ganglion cells to generate nerve impulse Axons from ganglion cells run along internal surface of the retina and exit eye within the optic nerve |
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Visual pathways to cerebral cortex |
Axons of the ganglion cells exit the eye at the optic nerve Axons extending from the medial ( nasal) side of retina run contralaterally through optic chiasm into optic tract Axon extending from the lateral ( temporal side of retina run ipisilaterally into the optic tract Optic trac send axons to the lateral geniculate nuclues of thalamus and synpase with thalamic neurons Fibers of the optic radiation reach the primary visual cortex. |
