Chp 15: Special Senses Flashcards
What are the 5 special senses that aid humans in interpreting their environment?
Gustatory, olfactory, vision, auditory, equilibrium
How do special senses differ from general senses?
Special senses: more complex neuron structure, greater area of cerebral cortex, organs are located in the head, involve mainly cranial nerves
Taste bud location
Mostly in papillae (peglike projections of tongue mucosa) but some scattered on soft palate, inner surface of cheeks, pharynx, and epiglottis
Gustatory epithelial cells
Receptor cells for taste Long microvilli (gustatory hairs) project from tips of all gustatory epithelial cells and extend through taste pore to surface of epithelium where they are bathed in saliva
Basal epithelial cells
Act as stem cells, dividing and differentiating into new gustatory epithelial cells
Fungiform papillae
Scattered over tongue surface, taste buds aree located mainly on tops of these mushroom-shaped fungiform papillae
Foliate papillae
Taste buds are found in the side walls of the foliate papillae
Vallate papillae
Largest, least numerous papillae
Inverted V shape at back of tongue
5 Primary Tastes (and mechanism of taste differentiation)
Sweet: OH+ Sour: H+ Salty: ions Bitter: alkaloids Umami: glutamate and aspartate
The gustatory pathway
Branch of the facial nerve (VII) transmits impulses from taste receptors in the anterior two-thirds of the tongue
Lingual branch of glossopharyngeal nerve (IX) serves the posterior third and the pharynx
Taste impulses from the few taste buds in the epiglottis and the lower pharynx are conducted by the vagus nerve (X)
These afferent fibers synapse in the solitary nucleus of the medulla, steam to thalamus, then to gustatory cortex in the insula.
Olfactory apparatus
Olfactory epithelium: located in roof of nasal cavity
Olfactory sensory neurons are cushioned by supporting cells
Olfactory stem cells lie at base of epithelium
Olfactory cilia increase receptive surface area
Role of thin mucus lining of olfactory epithelium
Solvent that captures and dissolves airborne odorants
Olfactory pathway
Olfactory sense neurons form olfactory nerves that synapse in overlying olfactory bulbs
Filaments of olfactory nerves synapse with mitral cells in glomeruli
When mitral cells are activated, impulses flow from olfactory bulbs via olfactory tracts to piriform lobe of the olfactory cortex
Accessory eye structures
Eyebrows: shade eyes from sunlight, prevent perspiration from reaching eyes Eyelids Eyelashes Conjunctiva Lacrimal apparatus Extrinsic eye muscles
Blood shot eyes are
Dilation of blood vessels in conjunctiva
Lacrimal apparatus
Lacrimal gland lies in orbit above lateral end of eye, releases tears
Blinking spreads tears downward, across eyeball, to lacrimal canliculi
Drain into lacrimal sac then into nasolacrimal duct, which empties into nasal cavity
Sclera
Forms posterior portion of fibrous layer, protects and shapes eyeball, provides anchoring site for extrinsic eye muscles
Cornea
Anterior portion of fibrous layer
Clear, forms window that lets light into eye
Choroid
part of vascular layer (middle of the eyeball)
Blood vessel rich, dark brown membrane, its blood vessels nourish all eye layers
Ciliary body
Anterior part of choroid
Part of vascular layer
Thickened ring of tissue that encircles the lens , controls lens shape
Extrinsic eye muscles
Straplike muscles, 4 rectus, 2 oblique
Control movements of each eyeball
Lateral rectus
moves eye laterally
VI
Medial rectus
moves eye medially
III
Superior rectus
Elevates eye and turns it medially
III
Inferior rectus
Depresses eye and turns it medially
III
Inferior oblique
Elevates eye and turns it laterally
III
Superior oblique
Depresses eye and turns it laterally
IV
Retina
Innermost layer of eyeball
Contains millions of photoreceptors that transduce (convert) light energy
Rods
Dim light and peripheral vision receptors
More numerous and more sensitive to light than cones
Cones
Vision receptors for bright light and color vision
Fovea centralis
Pit in center of macula lutea, lateral to blind spot
Contains only cones
Visual pathway to brain
Axons of retinal ganglion cells exit eye in optic nerves
At optic chiasma, fibers cross over to opposite side and continue via optic tracts which send most of their axons to synapse with neurons in the thalamus, fibers project to the primary visual cortex in the occipital lobes
Cataract
“waterfall” clouding of the lens
Glaucoma
Damage to the retina and optic nerve due to increased pressure within eye (if drainage of aqueous humor is blocked)
Ear gross anatomy
External: auricle/pinna funnels sound waves into the external acoustic meatus
Middle: tympanic cavity; small air-filled, mucosa-lined cavity, contains auditory ossicles
Internal: “labyrinth” bony and membranous portions, provides secure site for delicate receptor machinery
Tympanic membrane
eardrum, boundary btwn outer and middle ears
Sound waves make the eardrum vibrate, transfers sound energy to tiny bones of middle ear and makes them vibrate
Pharyngotympanic/Auditory/Eustachian Tube
Links middle ear cavity with nasopharynx
Usually flat and closed but can be opened briefly to equalize pressure
Mucus drainage
Semicircular canals
Region of bony labyrinth Lie posterior and lateral to the vestibule
Anterior, posterior, and lateral semicircular canals in each internal ear
Vestibule
Central egg-shaped cavity of bony labyrinth
Cochlea
Spiral, conical, bony chamber of the bony labyrinth
Organ of Corti
aka spiral organ, the receptor organ of hearing
Housed in cochlear duct
Auditory pathway
Sound vibrations are collected by outer ear, travel into ear canal, ear drum vibrates and moves auditory ossicles in middle ear, which carry the vibrations the cochlea in the inner ear
Fluid vibrates cilia, which are attached to auditory nerves, send signals to brain
Sensorineural deafness
Results from damage to neural structures (including hair cells) Single explosively loud noise or prolonged exposure to high-intensity sounds, degeneration of cochlear nerve, strokes, tumors in auditory cortex
Conduction deafness
Occurs when something hampers sound conduction to the fluids of the internal ear
ex// compacted earwax, ruptured eardrum, middle ear inflammations
