Special senses Flashcards
what are papillae
raised structures on tongue
4 types of papillae
filiform, fungiform, circumvallates, foliate
filiform location and characteristic
Anterior 2/3rds of tongue. no taste buds, just gives tongue friction
fungiform location and characteristic
Anterior 2/3rds of tongue. have taste buds
Circumvallates location and characteristic
V-shape dividing anterior 2/3rds and posterior 1/3rd. there are 7 to 14 of these, have taste buds
foliate location and characteristic
side of tongue. have tastebuds
3 types of cells making up taste buds
supporting cells (specialised epithelium)
gustatory receptor cells
basal cells
gustatory receptor cell characteristics
NOT neurons. have a hair that sticks out of the taste pore
gustatory basal cells
Base of taste buds have basal epithelial cells essentially stem cells. Will become gustatory receptor cells when prompted by chemicals or damage
5 tastes and their sources
i. Sweet (sugars, alcohol, amino acids)
ii. Sour (acids, H+)
iii. Salty (inorganic salts, NaCl—any positive and negative ion together)
iv. Bitter (bases, nicotine, caffeine, toxins/poisons)
v. Umami (delicious, glutamate)
what must be present for taste to work
solution (saliva)
how do gustatory receptor cells activate
i. Two of the gustatory receptor cell types activate directly through Na+ channels (salty) and H+ channels (sour)
ii. Sweet, bitter, umami utilizes G protein gustducin to turn on ion channels
gustatory innervation and pathways
- Anterior 2/3rds of tongue: glossopharyngeal nerve to medulla -> thalamus -> cortex
- Posterior 1/3rd: facial nerve -> medulla -> thalamus -> cortex
- Taste buds on epiglottis: vagus nerve -> medulla -> thalamus -> cortex
where is the gustatory centre
insula
what two additional brain areas play a role in gustation
frontal cortex (quality discrimination) and hypothalamus (ANS control of rest/digest)
4 influences of taste
i. Smell makes up 70-80% of taste
ii. Thermoreceptors
iii. Mechanoreceptors (pressure, texture)
iv. Nociceptors—spicy
olfactory epithelium vs. resporatory epithelium
- Respiratory epithelium is made up of ciliated pseudostratified columnar epithelium and covers our respiratory tract. Present in the nasal conchae and meatuses
- Olfactory epithelium is found at the top of the nasal cavity. Present here are olfactory sensory cells (1st order neurons) with non motile cilia that bind to odorants. They are buried in mucus which acts like flypaper for odorants
olfactory basal cells
olfactory stem cells: become olfactory sensory neurons, replaced every 1-2 months. One of very few areas of nervous system with cell regeneration
olfactory glands
Bowman’s glands/olfactory glands manufactures mucus
how many smells do we smell and how
i. We can smell ≈10,000 different smells, way more than tastes
ii. We have 400-1,000 smell genes which make proteins (olfactory receptors). Each protein can bind to 2-3 types of odorants, and odorants can bind to 2-3 different proteins. The overlap combinations creates lots of different smells.
olfactory transduction
G proteins open up Na+ channels for stimulatory EPSP or open Ca+ channels which cause IPSP and causes adaptation
olfactory pathway
olfactory sensory cells (bipolar 1st order neurons) travel up through tiny holes in the cribriform plate of ethmoid bone, these holes are called olfactory foramina.
• Superior to foramina they synapse with second order neurons called mitral cells. The axons of mitral cells make up the olfactory cranial nerve.
• Processes from olfactory receptor cells and processes from mitral cells come together and form balls called glomeruli. Similar odorants are processed in the same glomerulus.
• Olfactory nerve bypasses the thalamus and goes to olfactory cortex, then to frontal cortex and hypothalamus and amygdala (limbic system)
another word for eyelid
palpebra
fissure
the opening between eyelids when open
commisures (canthus)
outer edges of eye lids
infected gland at bottom of eyelash
sty
chalazion
infected tarsal/meibomian gland
tarsal/meibomian gland
gland in eye lid
eye lid muscles
- Levator palpebrae superioris controls upper eye lid
* Orbicularis oculi: goes around eye, causes squinting
conjuntiva
• The conjunctiva is a mucus membrane, starts on inside of eyelid, doubles over on itself and covers the sclera that is visible up to the base of the cornea
divisions of conjunctiva
palpebral conjunctiva: lines the eye lids
bulbar conjunctiva: on the visible anterior sclera
conjunctival sac: the dip between the inside of the eyelid and the surface of the eye
lacrimal gland function & location
produces tears, located superiolaterally to eye
tear drainage path
• Tears drain across eye to lacrimal sac in medial corner through lacrimal punctum (tiny holes), then down lacrimal canaliculus to nasolacrimal duct & sac, to inferior meatus of nasal cavity.
extrinsic eye muscles & innervation
- 4 rectus muscles & 2 obliques
- Oculomotor: superior, medial & inferior rectus + inferior oblique
- Trochlear: superior oblique
- Abducens: lateral rectus
3 layers of eyeball
fibrous tunic
vascular tunic
sensory tunic
2 parts of fibrous tunic
sclera and cornea
cornea cell types and function
o Cornea is covered by stratified epithelium for protection
o Inside of cornea is simple squamous epithelium with Na+ pumps to keep water content low. this area is innervated but avascular
sclera
white layer surrounding everything: extension of dura mater
3 parts of vascular tunic
choroid (pigment)
ciliary body
iris
choroid (pigment) function
absorbs excess light to avoid unnecessary activation of photoreceptors
ciliary body structures
made up of ciliary muscles and processes. Processes have extensions referred to as suspensory ligaments/zonules, arranged sphincter-like around the lens
iris muscles controlling pupil size
o Sphincter pupillae: decrease pupil size (parasympatheric)
o Dilator pupillae: increase size (sympathetic)
2 layers of sensory tunic
pigmented layer, neural layer
which sensory tunic layer has photo receptors
neural layer
rods and cones sensory characteristics
cones do sharp color (blue, green, red) and focus. not very sensitive light.
Rods are responsible for seeing things in dim light, not a lot of color or sharp images/borders, peripheral vision
fundus
posterior wall of eye ball
optic disk
blind spot: this is the place where the optic nerve leaves so no photoreceptors are present
Macula lutea (fovea)
The fovea contains only cones, the macula contains mostly cones, and from the edge of the macula toward the retina periphery, cone density declines gradually
segments of the eyeball
Anterior: anything in front of the lens
Posterior: anything behind the lens
divisions of anterior segment
anterior and posterior chamber
Anything in front of lens but behind iris is posterior chamber
Anything in front of iris is anterior chamber
aqueous humor, location production and drainage
in the anterior segment. • Produced as blood diffuses through the ciliary processes
• Drains through scleral venous sinus
vitreous humor
gelatinous material in posterior segment which keep all the layers pushed up against the sclera
cataracts
• Lens fibers are composed of proteins called crystallins. When these proteins are not lined up properly due to vitamin deficiencies, smoking, diabetes etc. you get cataracts which make the lens cloudy
definition of wavelength
peak to peak distance
refraction
ability to bend light
diverging
light rays bending and moving away from each other
converging
light rays bending and coming together
where does refraction happen in the eye and how much
- 2/3rds happen at cornea
* 1/3rd happens at lens
focal points
the point where the light rays come together, should be on retina
near vision accommodation
the light rays are diverging so the lens has to change shape to correct the focal point
ciliary muscle function
Ciliary muscle relaxed = ligaments pull on and flatten lens. This sets the lens up for far vision, which means our eyes have to strain less for far than near vision
convergence of eyeballs
When we look at distant objects, both eyes are directed either straight ahead or to one side to the same degree, but when we fixate on a close object, our eyes converge
what happens to pupils at near vision
Constriction of pupils: lets in less light, so lens doesn’t have to work as hard when looking at things up close
myopia
nearsighted. Focal point in front of retina. Concave lens corrects
hyperopia
farsighted. Focal point behind retina. Convex lens corrects.
two segments of photoreceptors and their characteristics
- Outer segment: The outer segment is the receptive region of rods and cones, contains light sensors and dips into the pigmented layer of the retina. It has disks which are made up of visual pigments, aka photo pigments.
- Inner segment: connects to the cell body which is continuous with an inner fiber which synapses with the bipolar cells.
retinal
light absorbing molecule in outer segment of photoreceptors. changes shape when a photon is present
how many visual pigments are there
4
activation of photoreceptors (bleaching the pigment)
• When a photon hits the retinal of the visual pigment it changes shape and is no longer bound to opsin. This is called bleaching of the pigment. Cyclic GMP levels change depending on the presence of a photon
photoreceptor process without a photon
o WITHOUT a photon, cGMP is elevated causing a slight depolarization from the opening of Na+ and Ca+ channels. This causes an inhibitory neurotransmitter to be released onto the bipolar cell, which in turn hyperpolarizes the bipolar cell so it does not release neurotransmitter onto the ganglion cell. Bipolar cell wants to fire EPSP all the time, but is inhibited by the inhibitory neurotransmitter by the photoreceptor, unless there is presence of a photon.
photoreceptor process with a photon
o WITH a photon, cGMP decreases which stops Ca+ and Na+ entering the cell, preventing the release of inhibitory neurotransmitter onto bipolar cell. Lack of IPSP causes depolarization of the bipolar cell, which triggers neurotransmitter release onto ganglion cell, and AP to optic nerve.
light and dark adaptation
- Dark adaptation takes 15-30 minutes, allows you to see in very low light due to rods activating
- Light adaptation: Going from low light to high light quickly causes rods to turn off and cones to overactivate. Resetting cones takes 5-10 minutes.
visual pathway
- Light that hits the medial part of the retina crosses over at the optic chiasma.
- The entire left visual field is processed on the right side of the brain and vice versa, no matter which eye picks it up.
- Impulses travel through the thalamus on their way to the primary visual cortex in the occipital lobe.
- Some optic fibers also extend to the superior colliculi of the midbrain
auricle
aka pinna. superior cartilaginous part of outer ear
helix
folded over, outermost part of outer ear (outside auricle)
Lobule
inferior part of outer ear (ear lobe)
external auditory meatus
external ear canal, lined with skin and small hairs. seruminous glands produce ear wax
barrier between external and middle ear
tympanic membrane (ear drum)
3 ossicles in order
hammer / malleus
incus / anvil
stapes / stirrup
tiny muscles of the middle ear
tensor tympani, attaches to hammer
stapedius, attaches to stapes
function of tensor tympani and stapedius
if a noise is too loud these muscles contract to pull the ossicles away from the tympanic membrane
antrum
connects the ear to the mastoid air cells via the epitympanic recess. ear infections can spread through this pathway
oval window
membrane between middle and inner ear. magnifies frequency and amplitude to be able to move through fluid in inner ear
round window
absorbs vibrations that have traveled through the cochlea so they don’t bounce back
pharyngotympanic tube
pathway from middle ear to nasopharynx
membranous labyrinth
inside the bony labyrinth, made up of the scala media. contains endolymph.
bony labyrinth
surrounds the cochlea and contains the membranous labyrinth
endolymph
resembles potassium rich plasma, present in membranous labyrinth/scala media
perilymph
resembles CSF, present in bony labyrinth/scala vestibuli and tympani
layers of the cochlea
scala vestibuli, media and tympani
location and 2 parts of vestibule
just inside oval window, utricle and saccule
stria vascularis
where endolymph comes from
helicotrema
at the top of cochlea where scala vestibuli and scala tympani meet
scala media aka
cochlear duct
what is sound
alternate zones of high and low pressure air creates wavelengths
frequency
wavelengths per second, measured in hertz
pitch
determined by high/low frequency. high frequency = high pitch
human hearing frequency range
20-20,000 hertz. we hear best 1500-4000 hertz
amplitude
loudness–more energy. measured in decibels
decibels-logarithmic scale
0= lowest audible sound
10dB= 10x more energy than 0
20dB=100x more than 0
transmission of sound
- sound waves vibrate tympanic membrane which vibrates ossicles
- sound is magnified as it moves through oval window
- pressure waves move through perilymph fluid in scala vestibuli
- if sound is w/in hearing range it travels through scala vestibule until it finds an area on scala media that it resonates with. high frequency sounds resonate with short, stiff fibres near base of basilar membrane. low freq sounds resonate w long, floppy fibres at the apex.
- Sound vibrates the basilar membrane which shakes the inner hair cells and vibrates the sectorial membrane
- movement of inner hair cells in one direction depolarises cell which transmits sound
spiral organ of corti
receptor organ for hearing, located in the scala media. strip of sensory epithelium made of hair cells which act as the sensory receptors of the inner ear
tip links
tops of cilia on inner hair cells. like bottle tops tied to a rope. when rope move toward kinocilium, bottle tops open and allow K+ and Ca++ in, causing depolarisation and AP
functions of outer hair cells
resets and stiffens tectorial membrane
auditory pathway
afferent cochlear nerve spiral ganglion medulla midbrain (startle reflex) auditory cortex
tallest cilia in hair cell
kinocilium
detects horizontal static movement
macula in utricle
detects vertical static movement
macula in saccule
otilithic membrane
membranes in maculae of the saccule and utricle that cilia of hair cells are stuck in (instead of tectorial in cochlea)
otoliths
little “rocks” on top of otolithic membrane. when head/body moves, the rocks help move the membrane which causes bending of the hair cells, creating action potentials.
picks up static movement
maculae of the utricle and saccule
picks up dynamic movement
ampullae of the semicircular canals
semicircular canals type of movement
respond to rotational movement
posterior semicircular canal
senses tilt of head toward either shoulder
superior semicircular canal
senses rotation from front to back nodding “yes”
horizontal semicircular canal
senses left to right rotation, shaking “no”
semicircular canal receptor names
cupula instead of tectorial/otolithic membrane
structure with hair cells is called crista ampullaris
2 types of equilibrium
static, dynamic
how does brain know what direction it’s moving
the endolymph moves in the same direction, but since there is an equilibrium system on both sides of the brain, it will depolarise on one side and hyper polarise on the other
3 sources of input for body position
vestibular system, visual receptors, somatic receptors
2 brain areas processing input for body position
cerebellum and vestibular nuclei in the brainstem
