Student Special Senses PDF

SPECIAL SENSES DR. JACQUELINE MOBLEY AHS 2202 TODAY WE WILL LEARN ABOUT The 4 major special senses The anatomical The transmission of Taste, Smell, Hearing, Vision structures associated the nerve impulse for...

SPECIAL SENSES DR. JACQUELINE MOBLEY AHS 2202 TODAY WE WILL LEARN ABOUT The 4 major special senses The anatomical The transmission of Taste, Smell, Hearing, Vision structures associated the nerve impulse for with the special senses the special senses What are the names What components of for the neurons in each the ear are for hearing, Extraocular structures special sense & where and which are for anatomy and function they are located balance  Taste Smell SPECIAL SENSES Hearing Vision  TASTE Gustatory sense Chemical taste receptors are called taste buds Majority are located on the sides of papillae on the tongue A few on mouth & pharynx Anatomy of the taste bud Small rounded structures Composed of gustatory cells and supporting cells Taste pore (opening) is present on the top of each taste bud Gustatory cells have tiny hair-like processes (dendrites) to receive stimulus  Humans Sweet TYPES OF Sour Salty TASTE Bitter Animals may be different in perception of taste Cats do not respond to sweet, lack receptors SMELL Olfactory sense Also a chemical sense Animal perception of smell is likely wildly more vivid than humans 2 patches of olfactory epithelium live deep in the nasal passages Sensory olfactory cells (neurons) mixed with supporting cells Hair-like processes (modified dendrites) project up into the mucus layer of epithelium VOMERONASAL ORGAN Vomeronasal organ Present in multiple species Located in the rostroventral portion of the nasal cavity Pheromones are chemical substances for communication Flehmen response Facial expression of when pheromones are detected HEARING Auditory sense Hair cells are the receptors for hearing Components of the auditory system: External ear Funnel to collect sound wave vibrations and transfer to ear drum (tympanum) Middle ear Amplifies and transmits vibrations to the inner ear Inner ear Location of the actual sensory receptors to generate nerve impulse for hearing Receptors for equilibrium are here too HEARING Most hearing structure are located within the temporal bone ✓ External ear canal ✓ Middle ear cavity ✓ Inner ear structures Membranes cover the bony cavities Thi s Photo by Unknown Author i s l icensed under CC BY EXTERNAL EAR Pinna Elastic cartilage and skin Can often move toward direction of sound External auditory canal (external acoustic meatus) Soft membrane-lined tube at the base of the pinna to the tympanum L-shaped in many domestic species Outer vertical, inner horizontal Tympanic membrane (eardrum) Paper-thin membrane separating external auditory canal from the middle ear  Hollowed-out area of the temporal bone Lined with soft tissues Filled with air MIDDLE EAR Contains ossicles & opening of the eustachian tube Separated from the inner ear by the membranes that cover the oval and round windows of the cochlea  OSSICLES Malleus (hammer) Connects to tympanum Connects to incus via synovial joint Incus (anvil) Connects to malleus and stapes Stapes (stirrup) Connects to incus and membrane that covers the oval window of the cochlea Thi s Photo by Unknown Author i s l icensed under CC BY FUNCTION OF OSSICLES They act as levers to transmit sound waves Sound travels from tympanum to the cochlea via ossicles Decrease amplitude of vibrations but increase the force Tensor tympani Tiny muscle Attaches to the malleus Stapedius Tiny muscle Attaches to the stapes EUSTACHIAN TUBE Auditory tube Connects middle ear cavity to the pharynx Function Equalizes air pressure on the 2 sides of the tympanum  INNER EAR – THE COCHLEA Cochlea Complex structure for HEARING Snail shell-shaped spiral cavity in temporal bone Contains the organ of Corti → the organ of hearing Organ of Corti The organ of corti is made of hair cells and supporting cells Runs the length of the cochlea in a long tube called the cochlear duct Filled with fluid called endolymph Thi s Photo by Unknown Author i s l icensed under CC BY U-shaped tube runs on either side of the cochlear duct Contains perilymph COCHLEA CONTINUED Oval window and round window are located at the base of the cochlea Stapes attaches to the oval window Round window attaches to nothing, helps with pressure Organ of corti & its membranes Organ of corti is made of hair cells (and their dendrites) & supporting cells Organ of corti is sandwiched between the basilar membrane & tectorial membrane Tectorial membrane lies on top of the hairs When it moves, it moves the hairs  Sound waves enter Tympanic membrane Ossicles vibrate pinna vibrates HOW SOUND IS Stapes pushes & Perilymph around the cochlear duct Round window acts pulls the oval as a pressure relief TRANSMITTED window as it vibrates vibrates back and forth mechanism Tectorial membrane and hair cells of the Nerve impulse is Cochlear duct moves Organ of corti rub generated together  Inner ear EQUILIBRIUM Equilibrium controls balance CONTROLS Receptors are located in the vestibule BALANCE and the semicircular canals Vestibule senses position of the head and linear motion Semicircular canals senses rotary motion of the head THE VESTIBULE Located between the cochlea and semicircular canals Utricle & saccule are 2 sac-like spaces that make up the vestibule Contain endolymph, surrounded by perilymph A macula is present in each utricle and saccule Macula: patch of sensory epithelium Macula consists of hair cells, supporting cells, gelatinous matrix, and otoliths Gravity causes gelatinous matrix and otoliths to put pressure on hair As the head moves, the hair is moved, generating nerve impulse THE SEMICIRCULAR CANALS Semicircular canals are located at right angles to each other At the end of each canal is an ampulla The crista ampullaris is located within the ampulla The crista is similar to the macula but does not have otoliths Cupula is a gelatinous area sitting on top of the crista As the head turns, the endolymph moves the cupula, which moves the hair on the crista  THE EYE Thi s Photo by Unknown Author i s l icensed under CC BY-NC-ND VISION Photoreceptors The neurons for vision Located in the retina Layers of the eye Fibrous layer (outer) Vascular layer (middle) Nervous layer (inner)  FIBROUS LAYER Allows light to enter the eye & provides structure Cornea: transparent window Orderly arrangement of collagen fibers No blood vessels! Rich supply of pain receptors Amount of water in the cornea must be regulated (excess = corneal edema) Sclera: the white of the eye Thi s Photo by Unknown Author i s l icensed under CC BY Collagen fibers Limbus: the junction of the sclera and cornea  VASCULAR LAYER: THE UVEA Iris Ciliary body Choroid Thi s Photo by Unknown Author i s l icensed under CC BY-NC-ND  VASCULAR LAYER: IRIS The colored part of the eye Pigmented smooth muscular diaphragm Radially arranged muscle fibers – open the pupil Circularly arranged muscle fibers – close the pupil Opens and closes to let more or less light in The pupil is the opening at the center of the iris Innervation to the iris comes from the autonomic nervous system Remember fight or flight? Pupils get bigger! Thi s Photo by Unknown Author i s l icensed under CC BY-SA VASCULAR LAYER: CILIARY BODY Ring of tissue immediately behind the iris Ciliary muscles adjust the shape of the lens to allow near & far vision Ciliary muscles are within the ciliary processes Ciliary processes attach to the periphery of the lens by tiny suspensory ligaments When relaxed, muscles pull the lens tight into a flat shape When contracted, muscles put less tension on the lens and it assumes a more round shape  VASCULAR LAYER: CHOROID Located between the sclera and the retina Houses melanin pigment & blood vessels to supply the retina Mostly we appreciate the choroid as the middle layer Thi s Photo by Unknown Author i s l icensed under CC BY-SA lining the inside of the back part of the eye Tapetum lucidum A highly reflective area of the eye Not present in pigs & humans Increases reflection to amplify light in low-light settings  NERVOUS LAYER: RETINA The retina lines the back of the eye (fundus) Photoreceptors are the neurons for vision 2 types of sensory receptors Rods & cones Thi s Photo by Unknown Author i s l icensed under CC BY-SA RETINA Layers of the retina Pigment layer (not sensory) Photoreceptor layer (deepest sensory layer, light passes through the other layers to reach this layer) Bipolar cell layer (integrate & relay impulses) Ganglion cell layer (integrate & relay impulses) Nerve fiber layer  PHOTORECEPTORS Photoreceptors are the neurons 2 types of special dendrites Rods Light-sensitive Create coarse, more gray colored images Cones Color & detail Many animals have less cones to perceive color Fovea centralis – accumulation of rods, present in primates for crisp vision Thi s Photo by Unknown Author i s l icensed under CC BY-SA THE RETINA CONTINUED The nerve fibers converge on the optic disc Nerve fibers A few vessels NO PHOTORECEPTOR CELLS ON THE OPTIC DISC (BLIND SPOT) Optic disc fibers form the optic nerve to the brain  Aqueous compartment Compartment in front of the lens Anterior chamber: in front of the iris ** this part we can see with the naked eye, just by looking at EYE someone** COMPARTMENTS: Posterior chamber: behind the iris AQUEOUS & Contains watery aqueous humor VITREOUS Vitreous compartment Compartment behind the lens Contains clear fluid like watery gelatin Provides support to the eye and facilitates transfer of light to the retina  AQUEOUS COMPARTMENT Aqueous humor is produced & drained constantly Passage of fluid Aqueous is produced in cells of the ciliary body Passes through the pupil into the anterior chamber Drains at the iridocorneal angle through the canal of Schlemm Thi s Photo by Unknown Author i s l icensed under CC BY-SA-NC CLINICAL DISEASE: GLAUCOMA Glaucoma: high intraocular pressure Causes: Lens luxation, genetic, uveitis, other What’s happening? Aqueous humor does not drain Pressure builds up in the globe Vision can be permanently lost Diagnosis: Tonometry Treatment: Eye drops, enucleation LENS Soft transparent structure biconvex disc Can be pulled flat or made more rounded by ciliary muscles Made of microscopic fibers in onion-like arrangement Accommodation Ciliary body muscles contract or relax to allow for near or far vision Contracted muscles: near vision Relaxed muscles: far vision Thi s Photo by Unknown Author i s l icensed under CC BY  HOW AN IMAGE IS FORMED Refraction Bending of light rays through a substance Refractions occurs through the cornea, aqueous, lens, vitreous Thi s Photo by Unknown Author i s l icensed under CC BY-SA Image is refracted onto the retina Original image is upside down! Brain turns the vision right-side up  EXTRAOCULAR STRUCTURES - CONJUNCTIVA Conjunctiva Mucus membrane lining inner eyelids & surface of eye Palpebral conjunctiva: eyelids Bulbar conjunctiva: surface of eyeball Conjunctival sac is where the 2 conjunctiva meet Where you place eye drops! Thi s Photo by Unknown Author i s l icensed under CC BY-NC-ND  EXTRAOCULAR STRUCTURES - EYELIDS Eyelids are folds of skin lined with conjunctiva Lateral and medial canthus: where upper & lower eyelids come together (corners of the eyes) Meibomian glands Little dots lining the waterline of the eye Produce waxy substance to prevent tears from spilling over eyelid Eyelashes Nictitating membrane: 3rd eyelid T-shaped plate of cartilage covered by conjunctiva Ocular surface: lymph nodes and accessory lacrimal gland No muscles attach to the 3rd eyelid, passive movement only Thi s Photo by Unknown Author i s l icensed under CC BY EXTRAOCULAR STRUCTURES: LACRIMAL APPARATUS Tears are produced by Lacrimal glands (dorsolateral to each eye) Accessory lacrimal glands (nictitating membrane) Tear drainage Lacrimal puncta on upper & lower lids Flow down ducts to lacrimal sacs Flow down single ducts called nasolacrimal ducts to the nasal cavity  Composition of tear film Inner mucus layer (antimicrobial) Produced by conjunctival cells Middle tear layer (moisture) TEAR FILM Lacrimal glands Outer oily layer (reduces evaporation) Meibomian glands EYE MUSCLES 6 extraocular muscles attach to sclera Skeletal muscle 4 Rectus muscles (straight muscles) Dorsal, ventral, lateral, medial 2 oblique muscles Dorsal & ventral oblique Bonus muscle: retractor bulbi THE END