Chapter 16- Special Senses Flashcards
Sense of Taste
Gustation
Utilize taste receptors on surface of the tongue
Basic Qualities of Taste
Sweet
Salty
Bitter
Sour
Umami
Taste Buds
Collection of 50-100 epithelial receptor cells
Found in tongue papillae
Gustation Pathway
Facial nerve- Anterior 2/3 of tongue
Glossopharyngeal nerve- Post. 1/3
Vagus nerve- Epiglottis and lower pharynx
Pathway:
Solitary nucleus in medulla
Thalamus (Ventral posteromedial nucleus)
Parietal cortex
Sense of Smell
Olfaction
Bipolar receptor cells bind to chemicals to illicit response and synapse with olfactory bulb
Travel through cribriform plate of ethmoid bone
Olfactory Pathway
Bipolar receptor cell
Olfactory bulb
Mitral cell
Olfactory tract
Functions of the Eye
Protect and support photoreceptors
Gather, focus, and process light
Fibrous tunic
Most external layer of the eye
Cornea and Sclera
Cornea
Fibrous tunic anterior 1/6th of eye
Transparent layer that bends light
Avascular and very sensitive
Conjunctiva
Anterior end of cornea
Sclera
Fibrous tunic posterior 5/6th of eye
White, opaque region
Provides shape and attachment point for muscles
Vascular tunic
Middle layer of the eye
Choroid, ciliary body, and iris
Choroid
Vascular tunic posterior 5/6th of eye
Vascular, darkly pigmented membrane
Reduce scattering light
Provides support
Ciliary body
Vascular tunic anterior 1/6th
Thickened ring of tissue surrounding lens
Contains ciliary muscles
Produce Aqueous humor
Ciliary Muscles
Manipulate the shape of the lens to focus light on the retina
Contracting muscles relaxes lens
Iris
Visible colored part of the eye
Attached to ciliary body
Composed of smooth muscles that control pupil size
Iris muscles
Sphincter pupillae muscle- Limit light
Dilator pupillae muscle- Increase light
Sensory Tunic
Deepest layer of the eye
Retina
Retina
Sensory tunic
Houses photoreceptors
Notable locations:
Macula lutea and fovea centralis- High photoreceptor density
Anterior Segment of Eye
Anterior 1/6th
Anterior and Posterior Chambers:
In front of and behind iris
Filled with aqueous humor
Path of aqueous humor
Produced by ciliary bodies in posterior chamber
Circulate through anterior segment
Return to blood by scleral venous sinus in anterior chamber
Aqueous humor
Blood filtrate that supplies nutrients to lens and cornea
Posterior segment
Posterior 5/6th of eye
Filled wit vitreous humor- Thick substance that transmits light and maintains intraocular pressure
Rods
Photoreceptors more sensitive to light
Provides black and white vision in dim light
Cones
Photoreceptors that work best in bright light
Provide clear, color vision
3 types- red, blue, and green
Lens
Biconcave disc that changes shape to focus light on retina
Cataracts
Clouding of lens due to inadequate nutrition
Myopia
Nearsightedness
Caused by eyeball being too long
Hyperopia
Farsightedness
Caused by eyeball being too short
Optic nerve
Connects eye to optic chiasm
Optic chiasm
Site of crossing over of visual pathways
Optic tract
Connects optic chiasm to thalamus
Lateral Geniculate Nucleus
Nucleus in thalamus responsible for transmitting visual information
Optic radiation
Fibers that transmit information from thalamus to visual cortex
External ear
Auricle
External acoustic meatus
Tympanic membrane
Middle Ear
Tympanic cavity
Ossicles
Pharyngotympanic tube
Inner ear
Semicircular canals
Vestibule
Cochlea
Auricle (pinna)
Visible, external portion of the ear that directs sound
Tympanic membrane
Membrane that forms the border between the external and middle ears
Transmits sound to ossicles
Tympanic cavity
Hollow space in petrous portion of temporal bone
Ossicles
Bones in middle ear that amplify sound waves
Malleus (hammer)
Incus (anvil)
Stapes (Stirrup)
Pharyngotympanic tube
“Eustachian” or “Auditory” tube
Connect middle ear and pharynx to regulate pressure
Semicircular canals
Contain semicircular ducts
Responsible for detecting rotational acceleration
Vestibule
Contain utricle and saccule
Responsible for detecting head position and linear acceleration
Perilymph
Fluid continuous with cerebrospinal fluid that fills the bony labyrinth in inner ear
Endolymph
Fluid in membranous labyrinth that assists detection of hearing or equilibrium
Macula
Site of sensory epithelium within the utricle and saccule
Contains hair cells
Covered with otolithic membrane and otoliths that move with the force of gravity and bend hair cells
Crista ampullaris
Site of sensory reception within semicircular canals
Contain cupula surrounding hair cells
When rotating, endolymph flows and distorts cupula, stimulating hair cells
Parts of the Cochlea
Scala vestibuli- Connected to oval window
Cochlear duct (scala media)
Scala tympani- Connected to round window
Cochlear duct
Houses organ of corti- Site of hair cells
Basement membrane under organ of corti moves with vibration and pushes hair cells into tectorial membrane
Pathway of sound through ear
Tympanic membrane
Ossicles
Oval window
Scala vestibuli
Cochlear duct
Scala tympani
Round window
Equilibrium pathway
Vestibular branch of Cranial Nerve VIII
Transmits information of head position and movement
Goes to lower brain centers and reflex centers
Ascending Auditory Pathway
Cochlear Branch of Cranial Nerve VIII
Bipolar neurons
-Superior olivary nucleus in medulla
-Lateral lemniscus to inferior colliculi
-Medial geniculate nucleus in thalamus
-Primary Auditory Cortex (temporal lobe)
