A&P Chapter 15 Flashcards
Olfaction
- sense of smell
- olfactory region
- superior region of the nasal cavity
- lined with olfactory epithelium
- olfactory epithelium is constantly replaced
- olfactory neurons are replaced every 2 months
Olfactory epithelium and bulb
- contains 10 million olfactory neurons
- olfactory neurons are bipolar
- axons project to olfactory bulb and synapse with 2nd neuron
- olfactory tracts project to cerebral cortex
- dendrites extend to olfactory vesicles
Neuronal pathways for olfaction
- olfactory relayed to cerebral cortex without thalamus
- axons enter olfactory bulbs and synapse with mitral cells or tufted cells
- olfactory tracts: terminate in olfactory cortex or secondary olfactory areas
Olfactory cortex
- temporal lobe
- conscious perception of smell
Secondary olfactory
- frontal lobe
- medial olfactory area:visceral and emotional
- intermediate olfactory area: inhibitory to facilitate rapid adaption
Taste(gustatory)
- taste buds: receptors; located in papillae
- filiform papillae
- vallate papillae
- foliate papillae
- fungiform papillae
Histology of taste buds
- oval in shape
- embedded in tongue and mouth epithelium
- 3 types of epitheleal cells: taste cells, basal cells, supporting cells.
- taste cells: replaced constantly, microvilli called taste hairs, opening called taste pore.
Function of taste
- substances dissolve in saliva
- enter the taste pores
- taste cells depolarize
- taste cells release neurotransmitters
- action potential stimulated in sensory neurons
Five major tastants
- Salt: sodium channels
- sour: hydrogen gated channels
- Sweet: potassium channels
- Bitter: calcium release
- Unami (glutamate or savory): calcium channel
Factors affecting taste perceptions
- temperature: warmth enhances sense of taste; cold inhibits
- structure: specificity not perfect; artificial sweeteners have a higher affinity for receptor binding sites.
neuronal pathways for taste
- 3 cranial nerves involved
- extend from taste buds to medulla oblongata
- facial nerve(VII): anterior 2/3 of the tongue
- glossopharyngeal nerve(IX): posterior 1/3 of tongue
- vagus nerve(X): epiglottis
Visual system
- can detect most distant stimuli of all sense
- eye: eyeball and lens; responds to light
- accessory structures
- optic nerve (II)
Accessory structures
- eyebrows, eyelids(palpebrae), conjunctiva (thin transparent mucous membrane), lacrimal apparatus( tear production)
Lacrimal gland
produces tears to moisten, lubricate, and wash. Pass through ducts then to eye
Lacrimal canaliculi
collect excess tears through openings called puncta
Lacrimal sac leads to nasolacrimal duct
opens into nasal cavity beneath the inferior nasal conchae
nasolacrimal duct
opens into nasal cavity
extrinsic eye muscles
- responsible for eyeball movement
- superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, inferior oblique
- innervated by trochlear(IV), Abducens(VI) and oculomotor(III)
Tunics of the eye
- fibrous tunic(sclera)
- white layer, gives shape and muscle attachment
- light and oxygen enter via cornea
- vascular tunic(choroid)
- middle colored layer
- iris regulates amount of light
- nervous tunic (retina)
- neural layer responds to light
- contains rods and cones
Aqueous humor
- front of eye
- fills anterior portion
- maintain occular pressure and eyeball shape
- provides nutrition
Vitreous humor
- back of eye
- fills posterior portion
- maintains pressure and shape
- holds lens and retina in place
Lens
- transparent and biconvex
- anterior surface is cuboidal epithelial cells
- posterior surface is columnar epithelial cells
- ligaments suspend lens between posterior and vitreous chambers( ability to stretch
Eye functions
- iris allows light to enter the eye
- light reaches retina is converted to action potential
- visible light: portion of spectrum that is visible
- focal point: convergence of light rays
- eye project clear image on retina
- adjustment occurs by changing shape of lens
Structures and function of retina
- consists of neural and pigmented layer
- neural layer
- photoreceptors, bipolar cells, and ganglionic cells
- synapses for adjacent neurons
- pigmented layer
- single kayer of malanin filled cells
- isolates photoreceptors and reduces light scattering
Rods
- non color vision and reduced light
- contains rhodopsin( consists of retinal and dopsin)
- continuously release inhibitory neurotransmitter glutamate
- glutamate release inhibited by hyperpolarization
cones
color vision and sharpness
- contains pigment iodopsin
- retinal combined with color- sensitive opsin
- each moiety of iodopsin is sensitive to narrow spectrum
- light hits the retina
- cones specific for wavelength generate action potential
Neuronal pathways for vision
- light enters the retina
- action potential travel optic nerve
- optic nerves connect to optic chiasm
- route of axons called optic tract
- optic tract can terminate in
- lateral geniculate nucleus
- superior colliculi
Hearing and balance
- divided into 3 parts
- ## external ear: auricle and external auditory canal,part you can touch and receives sound
external ear
- auricle and external auditory canal
- part you can touch and receiver of sound
middle ear
- air filled space containing 3 ossicles
- incus, malleus, stapes
inner ear
houses sensory organs for hearing and balance (eardrum)
Auricle
- fleshy visible portion of outer ear
- directs sound waves
ceruminious gland
- produces ear wax
Tympanic membrane
- thin transparent membrane
- conducts vibration
middle ear
- air filled space
- eustachian tube: opens into pharynx to equalize pressure
- ear ossicles: malleus, incus, stapes; transmit vibrations to oval window
bony labyrinth
chambers within the temporal lobe
Inner ear contains 3 regions
- cochlea: hearing
- vestibule: balance
- semicircular canals:balance
Inner ear
- membranous labyrinth: smaller tunnels within bony labyrinth
- filled wit endolymph and paralymph (fluid)
- spiral organs contain sensory hair cells
- hair cells have tip links that open potassium channels
external ear
- auricle collects sound waves
- sound waves travel auditory canal to tympanic membrane
middle ear
- soundwaves strike tympanic membrane
- tympanic membrane vibrates
- ear ossicle vibrate
Tensor tympani
inserts on malleus; innervated by cranial; nerve V
Stapedius
inserts on stapes and innervated by cranial nerve VII
Attenuation reflex
muscles contract during loud noises and prevent damaging vibrations
Balance
- static labyrinth: position of head relative to gravity; acceleration and deceleration
- dynamic labyrinth: evaluating head movement
Dynamic labyrinth
- allows direction perception
- 3 semicircular canals
- canals expanded into ampulla
- ampulla contains crista ampullaris
- crista ampullaris have a gelatinous cupula
- endolymph moves cupula and causes hair cells to bend
