Flashcards in Sensory Systems pt 2 Deck (62):
what are the different parts of chemoreception?
what is the only sensory modality that doesn't go through the thalamus?
what is the only special sense where the primary neuron itself carries the info to the CNS
what is the role of epithelial cells in olfaction?
olfactory neurons have a single dendrite that extends down from cell body to the olfactory epithelium, and a single axon that extends to the olfactory bulb
what types of neurons are involved in olfaction?
are olfactory neurons ever replaced?
what modification allows the receptors to detect odor?
dendrites end in non-motile cilia that express odorant receptors proteins
what are the different "sheath layers" for the 1o olfactory sensory neuron
epithelium, cribiform plate, and bone, then they synapse w 2o neurons in the olfactory bulb
what are the odorant receptor proteins?
how many different odorant receptor proteins are there?
1000s, which is why our sense of smell is so good
how many different types of receptor proteins are there per neuron
what is the relationship between odorant receptor proteins and odorants
each receptor can recognise more than one odorant
each odorant can stimulate more than one type of receptor
what is the relationship between acid and alcohol versions of a smell?
acid = shitty
alcohol = litty
what are the five basic tastes?
sweet, sour, salty, bitter, umami,
what are the taste receptors?
non-neural epithelial cells
how are taste epithelia modified
with microvili for more SA
how is taste transmitted?
sweet, umami, or bitter:
1. ligand bind to GPCR, releasing Ca2+ to enter cell
2. signal cascade
3. NT or ATP is released
4. 1o sensory neuron fires and AP are released to brain
salty and sour:
-mediated by ion channels, not GPCRs
what's a tongue map?
true or false - taste bud to taste receptor is a 1:1 ratio
false, all taste buds will have all the different receptors.
what is the taste pathway in the brain?
taste info travels through cranial nerves to medulla --> thalamus --> gustatory cortex
how does signal transduction in hair cells work?
at rest - 10% of ion channels are open, tonic signal is sent by sensory neuron
excitation - hair cell bends and depolarizes, increases AP frequency in associated sensory neuron
inhibition - if hair cells bends in opposite direction, it hyperpolarizes, and neuron signalling decreases
what are the three ear bones?
malleus, incus, stapes (in that order)
what are the different fluids in the cochlea? where are they each found? what is the composition of each
perilymph - high Na+, low K+ (like plasma); in vestibular and tympanic ducts
endolymph - low Na+, high K+ (like ICF); in cochlear duct only
what does the cochlear duct contain?
endolymph and the organ of corti
what is the place coding hypothesis?
sound waves trigger activity along different areas of the cochlea - sounds at a lower frequency are picked up farther down the cochlea
similar to 'labelled line coding'
what is the temporal code hypothesis?
frequency of sound waves determines frequency of APs travelling along auditory nerve, perceived as pitch
low pitch = low frequency = low firing of 1o neurons
what is the problem with temporal code hypothesis?
we can hear sounds up to 20k Hz but no neuron can fire at this speed
what is the current hypothesis for pitch determination?
neurons work as a team, carrying temporal code - pooled neural response to pitch
place coding DOES play a role
low pitches --> temporal code
high pitches --> place code
what are the different types of hearing loss?
what is conductive hearing loss?
problem in outer and middle ear (earwax or fluid)
central hearing loss
damage to neural pathway between ear and cerebral cortex (uncommon)
sensorineural hearing loss
damage to structures of inner ear (eg death of hair cells bc of loud noises, or bacterial infection)
can mammalian cells regenerate?
no, but they're working on it
what is the vestibular apparatus? two components?
maintains equilibrium (balance); movement through space + position of head
true/false - vestibular apparatus functions all on its own
No, it's integrated w information from muscles (proprioception) and visual info
how do vestibular apparatus operate?
detected by hair-cells in fluid filled chambers
-otolith organs (in the utricle, saccule) for LINEAR ACCELERATION
-semicircular canals for ROTATIONAL ACCELERATION
how do hair cells detect spin?
hair cells in the semicircular canals are pushed on by the cupula and activated
how do hair cells detect linear acceleration?
otoliths move in response to gravitational forces, perched on the otolith membrane above hair cells that are grouped in maculae, within utricles and saccules
what is the role of utricles?
what is the role of saccules?
what are the neural pathways for equilibrium?
cranial nerve -->
2. vestibular nuclei (medulla) -->
2a. somatic motor neurons controlling eye movements
2b. reticular formation --> thalamus --> cerebral cortex
canal of schlemm
circular canal that drains fluid from aqueous humor, similar to choroid plexus in that it maintains the composition and environment of your eye
special place that allows for fine vision (eg reading)
what is the neural pathway?
optical nerve --> optical chiasm --> optical tract --> thalamus --> visual cortex (in occipital lobe)
what is the autonomic 'reflex' pathway for pupillary light?
detector: photoreceptors in retina
afferent: optic nerve
intergrating centre: thalamus/brainstem = midbrain
efferent: motor neurons travelling along oculator nerve
effectors: smooth muscle regulating pupil diameter
what is the sympathetic response in regulating pupil diamater? parasympathetic?
how does phototransduction happen?
conversion of light into changes in the membrane potential by photoreceptor cells in the retina
what are the photoreceptors?
rods and cones
what is the role of modified ganglion cells?
mediate pupillary light reflex, circadian rhythms, other non-visual responses to light
what is the cellular organization of retina?
ganglion cells attached to bipolar cells attached to rod or cone attached to pigment epithelium
horizontal cells that integrate info
colour vision - only red, green, blue
path of light in retina
pigment epi --> rod/cone --> bipolar cell --> ganglion cell --> optic nerve
where is AP generated in retina
what is fovea composed of; what does it need to work;
only cones - this is where you focus for high res vision, and you NEED bright light for it
small receptive field
convergence in the retina
multiple rods to a single bipolar cell, multiple bipolar cells to a single ganglion
rods and cones structure
have disks with lots of membrane area with transmembrane proteins (opsin), and a vitamin that interacts w opsin called RETINAL
outer segment with a tip that touches the pigment epi of retina + inner segment that contains cell nucleus and organelles for ATP and protein synthesis + basal segment with synaptic terminal that releases glutamate to bipolar cells
opsin (protein) + retinal (vitamin)
-retinal looses affinity for opsin, and is released
-G protein = phosphodiesterase decreases  of cGMP, closing channels (cation Na+ and Ca2+ influx stops, K+ efflux continues so hyperpolarization)
-glutamate decreases release to bipolar cells (proportional to brightness of light)
-action potential generated in ganglion cells - they determine receptive fields on retina
-retinal slowly returns n is reunited w opsin
rod and cone function in darkness
-constant release of glutamate to bipolar cells (dark current)
-Na+ and Ca2+ influx is greater than K+ efflux, so rod is depolarized slightly (-40mV)
retinal formations and when
cis-retinal = light
trans-retinal = dark