Lesson 2 Part 1 - Special Senses Flashcards
five special senses
- olfaction
- gustation
- vision
- equilibrium
- hearing
special senses that use chemoreceptors (2)
olfaction and gustation
special senses that use mechanoreceptors (2)
equilibrium and hearing
gustation
sensory perception of molecules dissolved in water
tastants
chemical stimulus
gustatory receptor cells
sensory cells that perceive molecules dissolved in water
where are taste buds found?
found mainly on tongue, but also (especially in children) inside the cheeks, on the soft palate, pharynx, and epiglottis
lingual papillae
visible bumps on the tongue
four types of lingual papillae
- filiform
- foliate
- fungiform
- vallate
filiform papillae
small spikes with no taste buds that help sense food texture and provides friction
foliate papillae
form parallel ridges along sides of the posterior two thirds of the tongue, these have taste buds that degenerate by age 3
fungiform papillae
shaped like mushrooms, at the tips and sides of the tongue; each has three taste buds at the apex
vallate papillae
large papillae arranged in a V at the rear of the tongue and contain up to one-half of all taste buds
taste buds
clusters of 50-100 teste cells, supporting cells, and basal cells in a garlic bulb shape
taste cells/gustatory receptor cells
specialized epithelial cells that are NOT neurons
taste hairs
tufts of apical microvilli that act as receptor surfaces into a pit that is exposed to the oral cavity
taste pore
pit that exposes taste hairs to the oral cavity
taste cells synapse with and release neurotransmitters onto _____ neurons at their base
sensory
basal cells (mouth)
stem cells that replace taste cells every 7 to 10 days
supporting cells
taste
resembles taste cells but not synaptic vesicles or sensory role
five primary sensations of the tongue
salty, sour, sweet, bitter, umami
salty
produced by metal ions like sodium and potassium
sour
acids such as in citrus fruits
sweet
associated with carbohydrates and other foods of high caloric value
bitter
associated with spoiled foods and alkaloids such as nicotine, caffeine, and quinene
umami
meaty or savory taste of amino acids in chicken, beef broth; receptors sensitive to amino acids, small peptides, and nucleotides
oleogustus
proposed name for the taste of fats; receptors detect long chain fatty acids
two mechanisms of taste cell stimulation
sweet/bitter/umami and salty/sour
sweet/bitter/umami taste cell stimulation
sugars, alkaloids, and glutamate activate G protein (Gustucins) on taste cell membranes which activate second messenger systems
salty/sour taste cell stimulation
sodium and acids enter taste cells directly, depolarizing them
three cranial nerves carry taste information
facial nerve VII
glossopharyngeal nerve IX
vagus nerve X
the facial nerve VII carries taste info from what section of the tongue?
anterior two-thirds of the tongue
the glossopharyngeal nerve IX carries taste info from what section of the tongue?
posterior third of the tongue
the vagus nerve X carries taste info from what where? (3)
palate, pharynx, and epiglottis
fibers from the cranial nerves that carry taste info all synapse onto neurons located where?
medulla oblongata
second-order neurons from the medulla oblongata (for taste info) relay to…(3)
- hypothalamus and amygdala to activate reflexes like salivation/gagging/vomiting
- thalamus relays to the primary gustatory cortex in the insula for perception
- thalamus also relays info to orbitofrontal cortex for the overall impression of flavor
olfaction
sense of smell, response to airborne chemicals
oderants
airborne chemicals that our nose responds to for scent
olfactory mucosa
path of epithelium in the roof of the nasal cavity that houses receptor cells
what does the olfactory mucosa cover? (3)
- most of the superior nasal concha
- cribriform plate
- nasal septum of each nasal fossa
olfactory cells
neuons
olfactory hairs
immobile cilia on olfactory cells
where does the olfactory nerve CN I exit the nasal cavity?
cribriform foramina
axons of olfactory cells collect as _____
fascicles
lamina propria
superior to the mucosa, contains areolar connective tissue, blood vessels, nerves, and olfactory glands that produce mucus to coat the olfactory organs
each olfactory cell has receptors for _____ chemical odorant(s)
one
how are different odors detected?
due to the combination of olfactory cells being activated
olfactory transduction (3)
what is the process?
- odorant binds G protein-coupled receptor on the olfactory cells
- activates cAMP second-messenger system which opens ion channels for Na+ and Ca2+
- depolarizes the membrane and triggers an action potential to the brain
some odorants act on _____ of the _____ nerve instead of olfactory cells
nociceptors, trigeminal
odorants that act on nociceptors (4)
ammonia, methol, chlorine, capsaicin
olfactory cell axons pass through the roof of the nose, and enter a pair of _____ _____
olfactory bulbs
olfactory cells synapse with _____ cells and _____ cells in the olfactory bulbs
mitral, tufted
olfactory glomeruli
synapses between olfactory nerves and mitral/tufted cells; each receives input from cells with the same receptor type; each is dedicated to a particular type of odor
what do the tufted and mitral cell axons leave the glomeruli as?
olfactory tracts; they bypass the thalamus to reach the primary olfactory cortex
how are memories/emotional responses formed with scents?
some scent signals are relayed to the amygdala, hippocampus, insula, and hypothalamus
where are basal stem cells located?
in the taste bud and olfactory epithelium
both gustatory cells and olfactory receptor cells have…
a high turn-over rate
death of receptor cells (gustatory/olfactory) are replaced by cellular division of what cells?
basal stem cells
hearing
response to vibrating air molecules (pressure waves in the air)
equilibrium
sense of motion, body orientation, and balance
hair cells (ear)
mechanoreceptors within the inner ear
sound
any audible vibration of molecules
what causes an eardrum to vibrate?
air molecules hitting the eardrum
pitch
whether a sound is high or low is determined by frequency of vibrations
loudness
perception of sound energy, intensity, or amplitude of vibrations
outer (external) ear
funner for conducting airborne vibrations to the eardrum
auricle (pinna)
what you generally think of as the “ear”
auditory canal (external acoustic meatus)
slightly curved passage leading through the temporal bone to the eardrum
guard hairs
hinders objects and organisms from entering the auditory canal
cerumen
earwax
middle ear
located in the tympanic cavity in the temporal bone, bounded by eardrum and the inner ear
tympanic membrane
the “eardrum”, a slightly conical membrane that vibrates in response to sound
what is the tympanic membrane innervated by? (2)
the vagus and trigeminal nerves
tympanic cavity
air-filled space between the outer and inner ears
pharyngotympanic tube
passageway to the nasopharynx, normally flattened and closed but opens when swallowing and yawning ; how air enters
auditory occicles
three smallest bones of the body; connect the tympanic membrane to the inner ear
malleus
has a long ‘handle’ attached to the inner surface of the tympanic membrane and a ‘head; that articulates with the incus
incus
has a triangular body that articulates with the malleus and a long limb that articulates with the stapes
stapes
shaped like a stirrup, the base is held in an opening called the oval window, where the inner ear beings
stapedius
muscles attached to the stapes
tensor tympani
muscle attached to the eardrum
tympanic relfex
the stapedius and tensor reflexively contract to protect the inner ear from loud noises
otitis media
middle ear infection; common in children
why are children more likely to get middle ear infections?
their auditory tube is shorter and more horizontal than adults
symptoms of a middle-ear infection
fluid accumulation in the tympanic cavity producing pressure, pain, and impaired hearing
tympanostomy
lancing the tympanic membrane and inserting a tube to drain fluid from the tympanic cavity
inner (internal) ear
portion of ear housed within a maze of temporal bone passages
inner ear: bony labyrinth
internal passages in the temporal bone
inner ear: membranous labyrinth
fleshy tubes suspended within the bony labyrinth
perilymph
fluid between bony and membranous labyrinths; similar in composition to cerebrospinal fluid
endolymph
fluid within the membranous labyrinth; similar in composition to intracellular fluid
vestibule
chamber where the labyrinths begin; contains the organs of equilibrium
cochlea
coiled organ used in hearing; contains three fluid-filled chambers separated by membranes
scala vestibuli
superior chamber filled with perilymph; begins near the oval window and spirals to the apex
scala tympani
inferior chamber filled with perilymph; extends from the apex of the round window
round window
window covered by the secondary tympanic membrane
cochlear duct (scala media)
middle chamber, filled with endolymph; bounded above by vestibular membrane and below by basilar membrane
spiral (acoustic) organ
structure that converts vibrations to nerve signals; located within the cochlear duct, resting upon the basilar membrane
stereocilia
long, stiff, microvilli on the apical surface of hair cells
tectorial membrane
a gelatinous membrane on top of the stereocilia, and attached to it
basilar membrane
the bottom layer of the spiral organ
ossicles and their muscles have a protective function
lessen the transfer of energy into the inner ear
tympanic reflex
loud noise causes the tensor tympani to contract, tensing the eardrum, and the stapedius contraction reduces vibration of the stapes on the oval window
vibration of ossicles causes…
pressure waves in the inner ear fluid (perilymph)
movement of inner ear fluid travels from the _____ _____ to the apex and then down the _____ _____
scala vestibuli, scala tympani
movement of inner ear fluid causes vibration of the _____ _____ and the ____ cells resting on top
basilar membrane, hair
since hair cell’s _____ are attached to the _____ membrane, movement of the hair causes them to bend
stereocilia, tectorial
bending of the hair cells’ stereocilia stimulates their _____-_____ channels to open, allowing _____ into the cell and _____ it
mechanically-gated, ions, depolarize
amplitude
variations in loudness
variations in loudness cause variations in the _____ of cochlear vibrations
intensity
pitch depends on what happening in the ear?
which part of the basilar membrane vibrates
at the basal end of the basilar membrane (near oval window), the membrane is _____ and moves with _____ frequency waves
stiff, high
what does the brain interpret as high-pitched
high frequency waves
at the apex of the basilar membrane, the membrane is more _____ and moves with _____ frequency waves
flexible, low
what does the brain interpret as low-pitched?
low frequency waves
auditory projection pathway: first order (sensory) neurons (2)
- receive input from hair cells through the cochlear nerve
- the cochlear nerve joins with the vestibular nerve to form the vestibulocochlear nerve (VIII)
each ear sends nerve fibers to _____ _____ of the _____ _____ to synapse with second order neurons in the _____ _____
both sides, medulla oblongata, cochlear nuclei
auditory projection pathway: second-order neurons
send axon fibers that ascend to the inferior colliculi of the midbrain to synapse with third-order neurons
auditory projection pathway: secondary neurons synapse with third order neurons in the inferior colliculi to do what?
sound location, fluctuation in pitch, and auditory reflexes (startle response, turning head in response to loud noises)
auditory projection pathway: third order neurons (2)
- cell bodies in inferior colliculi
- axons travel to the thalamus and synapse onto fourth-order neurons
auditory projection pathway: fourth order neurons (3)
- cell bodies in the thalamus
- axons travel to primary auditory cortex for the conscious perception of sound
- auditory system has extensive decussation, so damage to one side of the cortex does not cause unilateral hearing loss
who has the greatest hearing range?
young children
hearing loss in older individuals are caused by: (3)
- tympanic membrane becoming less flexible
- articulations between ossicles stiffen
- round window beings to ossify
tinnitus
buzzing, whistling, or ringing sound absent of external stimuli
causes of tinnitus includes: (4)
- inner ear hair cell damage
- otosclerosis of ossicles
- loud noises
- earwax blockage
otosclerosis
growth of bone tissue around the ossicles, usually the stapes that interfere with its movement
deafness
hearing loss
conductive deafness
conditions interfere with transmission of vibrations to inner ear
causes of conductive deafness (4)
- damage to the tympanic membrane
- otitis media
- blockage of auditory canal
- otosclerosis
sensorineural (nerve) deafness
death of hair cells or any nervous system elements concerned with hearing
equilibrium
sense of body orientation, movement, and balance
vestibular apparatus
contains receptors for equilibrium
what does the vestibular apparatus consist of?
three semicircular ducts and two chambers, the anterior saccule and posterior utricle
two chambers of the vestibular apparatus
- anterior saccule
- posterior utricle
static equilibrium
perception of orientation of head in space (erect or tilted): detected by saccule and utricle
dynamic equilibrium
perception of motion or acceleration
linear accelerations
change in velocity in a straight line, detected by the saccule and utricle
angular acceleration
a change in rate of rotation; detected by semicircular ducts
macula
consisting of har cells and supporting cells
macula sacculi
lives vertically on a wall of saccule
macula utriculi
lies horizontally on the floor of the utricle
kinocilium
one true cilium on a hair cell of a macula
otolithic membrane
a gelatinous membrane of hair cells
otoliths
calcium carbonate-protein granules that weight the otolithic membrane
saccule and utricle contribute to both _____ and _____ _____
static, dynamic equilibrium
static equilibrium
when head is tilted, heavy otolithic membrane sags, bending the stereocilia and stimulating the hair cells
dynamic equilibrium
linear acceleration detected as otoliths lag behind, bending the stereocilia and stimulating the hair cells
because the _____ _____ is nearly vertical, it responds to vertical acceleration/deceleration while the ____ ____ is horizontal, it responds to horizontal acceleration/deceleration
macula sacculi, macula utriculi
crista ampullaris
mound of hair cells and supporting cells
cupula
stereocilia and kinocilium embedded in this gelatinous cap
ampulla
a dilated sac filled with endolymph next to the utricle
crista ampullaris
mound of hair cells and supporting cells in each ampulla
all hair cells connected to sensory neurons that project axons as the….
vestibular nerve
fibers end in the ____ _____ on each side of the pons and medulla
vestibular nuclei
left and right nuclei receive input from ____ ears
both
vestibular nuclei relay information to five areas:
- cerebellum
- reticular formation of the brain stem
- spinal cord
- thalamus
- nuclei of oculomotor, trochlear, and abducens nerves
vestibular nuclei relay information to five areas: cerebellum
integrates vestibular information into its control of head and eye movements, muscle tone, and posture
vestibular nuclei relay information to five areas: reticular formation of the brain stem
thought to adjust blood circulation and breathing to postural changes
vestibular nuclei relay information to five areas: spinal cord
descend through two vestibulospinal tracts of spinal cord and innervate extensor (antigravity) muscle
vestibular nuclei relay information to five areas: thalamus
relay to cerebral cortex for awareness of position and motor control of head and body
vestibular nuclei relay information to five areas: nuclei of oculomotor, trochlear, and abducens nerves
to produce vestibulo-ocular reflex; keeps vision fixed on distant object while walking
