Final Study Flashcards
What does MOB stand for?
Main Olfactory Bulb
What does MOE stand for?
Main Olfactory Epithelium
What does AOB stand for?
Accessory Olfactory Bulb
What does VNO stand for?
Vomeronasal organ
What do OSN, OBP, OR stand for?
Olfactory Sensory Neurons
Odor Binding Proteins
Olfactory Receptors
What do PN and IN stand for?
Projection Neurons
Inhibition Neurons
What are some similarities between insect and mammal olfactory systems?
both have increased surface area in their olfactory organs from lining of tiny hairs (MOE in mammals and antennae in insects) (sensilla on antennae, hairs in nasal cavity)
most odorant receptors are G-protein coupled receptors
OSNs converge onto glomeruli in the brain (can receive input from different OSNs with the same OR type)
olfactory signals are sent from the glomeruli to higher brain centres for further processing
lateral inhibition from INs refine odor signals (increased sensitivity)
What are some differences between insect and mammal olfactory systems?
Mammals process olfactory information in olfactory lobes in their brains, insects have antennal lobes
mammals send olfactory signals from glomeruli to piriform cortex, amygdala, and hypothalamus; insects send to mushroom bodies and lateral horn for further processing
mammals send olfactory signals to brain centers via projection neurons called mitral and tufted cells; insects use other PNs
local interneurons increase specificity by lateral inhibition in insects; periglomerular and granule interneurons in mammals
What type of receptors are ORs?
typically G-protein coupled receptors that trigger intracellular signal cascades when activated
Describe the basic odorant pathway in mammals
odourant –> OBP –> MOE (4 zones) –> MOB (4 zones) –> Olfactory Tract –> amygdala, hypothalamus, piriform cortex
Describe the Olfactory Tract in mammals
the bundle of nerve fibers that serve as the main connection between the MOB and the higher order processing centers in the brain (no information processed, just relaying)
Describe the basic pheromone processing pathway in mammals
pheromone –> PBP –> VNO –> AOB –> medial amygdala –> hypothalamus
or
…. VNO –> epithelium –> basal to posterior AOB and apical to anterior AOB –> medial amygdala –> hypothalamus
Describe the signal cascade pathway of odourants in mammals
odourant –> OBP –> OR –> MOB but the pathway triggered is
OR –> GPCR –> Adenylyl cyclase –> cAMP increased –> cAMP-gated cation channel opens –> Ca++ and Na+ influx –> Ca++-gated Cl- channel opens –> Cl- out
Describe the signal cascade pathway of odourants in mammals in less than 1% of OSNs that occur in the MOE
Describe the signal cascade pathway of pheromones in mammals
pheromone –> PBP –> PRs –> AOB
pathway triggered is PR = GPCR –> Phospholipase C –> increase IP3 and DAG –> cation channel opens –> influx of Ca++ –> Ca++-gated Cl- channel opens –> Cl- out
What makes octopuses record breakers in their ability to learn, memorize, problem solve?
- large central brain and unsegmented, but highly specialized and distributed peripheral nervous system
- 2/3 of their neurons are in their arms = each arm is capable of processing sensory information, making decisions and executing motor actions independently from one another and from the brain = multi-tasking and problem-solving - high neural density = ~500 million neurons = advanced learning, memory and adaptability to environmental challenges
- multisensory processing in suckers on tentacles - high neural density in suckers for tactile, chemical and even light receptors - complex tasks like tool use for navigation
- learning and memory systems - have both short-term and long-term memory storage (vertical and superior frontal lobes) - recognize individuals, objects or retain info over time
- increased connectivity and faster communication of neurons - rapid transfer of information through en passant synapses
- division of labour is immense - 40 brain lobes that are highly specialized for vision, motor function, etc.
- neural plasticity - rapid rewiring of neural circuits in response to new challenges or environmental changes - trial and error learning, problem-solving
Which parts of the nervous system are involved in learning and memory in octopuses?
vertical and superior frontal lobes for long-term memory storage
What are en passant synapses? What do they do?
connections formed along the axons of neurons rather than at the terminal ends
they distribute neuronal signals more broadly - a single neuron can communicate with multiple targets simultaneously
= increased connectivity
= faster communication
= plasticity
= localized learning and processing without central brain input
Compare the Nautilus lifestyle and behaviour to Octopus
nautilus: nocturnal, sessile/slow-moving, jet-propulsion, gas chamber for buoyancy
octopus: active swimmers and hunters
Compare the Nautilus anatomy to Octopus
NAUTILUS:
- external shell secreted by mantle
- many tentacles without suckers
- pinhole eyes without cornea or lens
- nerve cord, unsegmented but segregated and specialized
OCTOPUS:
- no shell
- 8 tentacles with strong suckers
- funnel (modified foot)
- eyes with cornea and lens
- highly specialized ganglia with very large brain
Compare the Nautilus sensory structures and functions to Octopus
NAUTILUS:
- tentacles for chemosensory reception - prey and predator detection, feeding, sticking to substrates
- pinhole eyes (no cornea or lens): limited vision
OCTOPUS:
- complex eyes with cornea and lenses: vision with resolution similar to vertebrates
- suckers and mouth have chemoreceptors - detect prey (taste and smell)
- suckers have mechanoreceptors for navigating environment
- cristae and macula for orientation in 3D space (proprioception)
- chromatophores, reflecting cells, and photoreceptors on skin for camouflage
Compare the Nautilus camouflage to Octopus
both camouflage
NAUTILUS: counter-shading of shell
OCTOPUS: active camouflage - behavioural, muscular (skin texture), and colour camouflage
What is the updated definition of the Eimer’s organ in star-nosed moles? how many appendages make up the star?
the domed epidermal sensory organ that is made up of a central cell column (CCC), Merkel cells, encapsulated corpuscles, and 2 circles of free-nerve endings (one in CCC for texture detection and one in peripheral circle for nociception)
11 appendages make the star
What 4 types of cells make up the Eimer’s organs?
CCC - central cell column
1. Merkel cells - CCC
2. encapsulated corpuscles - peripheral
3. 2x free nerve endings - one for texture (CCC) and one for nociception (peripheral circle)
Where are the Eimer’s organs located on the star?
epidermally
What types of stimuli is the star sensitive to? Which cells of the Eimer’s organ are responsible for this?
tactile / mechanosensory
Texture = free nerve endings + Merkel cells in the CCC
- detect pressure changes to the Eimer’s organs
pain / nociception = free-nerve endings + Pacinian corpuscles in the peripheral circle of Eimer’s organs
How does the region of the brain that is dedicated to somatosensory input in star-nose moles compare to that in other species of moles and shrews?
the isocortex in SNM has 3 regions committed to somatosensory input (triplicate representation) whereas other moles and shrews have only 2
most of the somatosensory areas in the isocortex of the SNM are dominated by the star and the forelimbs/palm = digging and determining texture
Why does the SNM have so much of its brain dedicated to somatosensory input?
they need to spend most of their time digging and searching for food so they need to be able to determine texture for what is food and what is rocks/dirt as well as whether there is too much abrasion to the skin (pain/friction)
Which 3 stimulus features are mediated by receptors?
Modality - 4 types of mechanoreceptors (Merkel, Ruffini, Meissner, and Pacinian corpuscles)
Intensity - of stimulation is signaled by the firing rates of individual receptors
Location - spatial distribution of the activated receptors
Duration - of stimulation is signaled by the time course of firing
(MILD)
Where are Merkel and Pacinian (encapsulated corpuscles) cells most dense in human hands?
finger tips and fingers
Which mechanosensory cells are rapidly adapting? which are slowly adapting?
RAPID = Pacinian (encapsulated) corpuscle
SLOW = Merkel
How do rapidly adapting cells respond to stimulation vs. slowly adapting?
RAPID (Pacinian corpuscles) = fire at the application and removal of stimulation
SLOW (Merkel) = fire continuously throughout the application of the stimulus
What type of mechano-sensation do Merkel cells detect?
pressure receptors / intensity detectors
they assist the FNEs in CCC in the detection of texture
What type of mechano-sensation do Pacinian (encapsulated) corpuscles detect?
Vibration receptors / acceleration detectors
they assist the FNEs in the peripheral circle in the detection of pain/friction/abrasion
How is an AP generated in a Pacinian corpuscle? where is the first AP generated?
this Pacinian corpuscle (nerve ending) is surrounded/encapsulated by membrane layers with viscous fluid
pressure applied to the membrane deforms it and stretches mechano-gated Na+ channels and influx of Na+
first AP is generated at the first node of Ranvier in the Pacinian corpuscle
If an object has a SMOOTH surface, how will the Eimer’s organs respond? What response does this cause in the nerves?
the FNEs and Merkel cells in the CCC of neighbouring Eimer’s organs will be deflected in the same direction
causing the activation of similar free-nerve endings associated with the CCC
If an object has a ROUGH surface, how will the Eimer’s organs respond? What response does this cause in the nerves?
if Eimer’s organ neighbours are deflected in opposite direction = free nerve ending activation will be different between neighbours
How do the free-nerve endings in the Eimer’s organs help a SNM detect texture?
they compare the patterns of activation in the FNEs from neighbouring Eimer’s organs (deflection direction) - feel if there is vibration or texture
CRICKETS: what does AN stand for? what are they?
Ascending Neuron - 2 mirrored neurons that project toward the brain
what are tympana?
the ears of crickets located in their ‘knees’ of their front legs, if they had knees
What are ONs? Where are they? What type of information do they receive? what do they do with the information?
omega neurons are auditory interneurons in the prothoracic ganglion that receive excitatory input from auditory neurons
they COPY the song from ipsilateral (opposite side) and RECIPROCALLY INHIBIT the contralateral ON
If the sound source is from the left, explain what happens with the ON? what is the purpose of this?
sound source from the left = excites the left ON (ipsilateral) more than the right (contralateral)
= the left ON more strongly inhibits the right (contralateral/reciprocal inhibition) ON, reducing the inhibiting potential of the right
= stronger response from left ON
overall, the purpose SHARPENS DIRECTIONAL SENSITIVITY
What sharpens directional sensitivity in cricket hearing?
reciprocal inhibition of omega neurons (one side is inhibited so the signal is stronger at the side of the sound source)
How do male crickets make their sounds?
with the teeth on their exoskeleton as they close their wings
Explain how cricket ears are pressure-difference receivers
cricket ears have membranes that are pushed in or pulled out depending on the pressure applied to the tympana membrane received when auditory stimulus is applied
Explain how pressure-difference reception in the ears of crickets cause the females to zigzag toward the males
females receive maximal pressure differences (best signal) in the tympana when the sound source is perpendicular to her ears, so she has to move diagonally to the sound source, and each time she moves, the best signal will be received at the opposite ear
What happens to the AN-1 when the female cricket receives auditory input from the left? How does the female cricket respond?
the left AN-1 cell fires more than the right AN-1 = female cricket tracks to the left
What happens to the AN-1 when the female cricket receives auditory input from the right? How does the female cricket respond?
when the sound source is coming from the right, the right AN-1 cell fires more than the left = female cricket tracks ot the right
What happened in the study when the left AN-1 cell was hyperpolarized but the sound source came from the left? How did the female respond?
hyperpolarization of the left AN-1 cell caused reduced firing in the left cell and relatively more in the right cell = female tracked to the right (incorrectly)
Explain the underlying pathway for the AN-1 cell firing and consequent female cricket behaviour
ANs receive excitatory input from auditory neurons and are inhibited by contralateral ONs
ANs copy song ipsilaterally SO
if the sound comes from the left, while both of the AN-1 cells receive excitatory input, the song is only COPIED ipsilaterally and the contralateral AN-1 cell is INHIBITED (prevented/from firing) = only the left cell fires and so the female detects the sound is coming from the left
Explain why the female tracked in the wrong direction when the left AN-1 cell was hyperpolarized and sound came from the left?
the hyperpolarized cell has reduced firing response, while the right would still be contralaterally inhibited by the ONs, it still fired more frequently than the left did so the female detected the sound came more strongly from the right
What are the 3 anatomical components of cricket hearing?
2 tympana (eardrums) in each forelimb
tracheal tube - the air tube connecting the tympana
spiracles - the holes which external sound waves enter
How does external sound enter the tracheal system and what happens inside the tracheal tube?
sound enters the tracheal system through the spiracles
in the tracheal tube, sound waves interact causing phase differences due to the various travel distances and timings of their arrival = pressure variations in the tube = vibration of tympana
Each tympanum experiences sound pressure from where?
- direct external sound pressure from the sound wave reaching the tympana from outside
- internal sound pressure from the sound waves travelling through the tracheal tube
Explain what happens to the tympana when the sound source is on the left
EXTERNAL sound waves reach the left tympanum directly and apply pressure to the outer side = PUSH the membrane INWARD
INTERNAL sound waves (entered through the spiracle) travel through the tracheal tube and create pressure changes inside the tube that reach the INNER side of the left tympana = PULL membrane INWARD
same happens to the right but weaker pressure applied in both because the sound had to travel farther OR it might be cancelled out because of phase differences (arrival)
the interactions (reinforcement) between the internal and external pressure on the tympanum cause stronger vibrations on the left tympana than the right
How is the frequency of the male cricket’s song related to the size of the female cricket?
The wavelength of a male’s calling song determines how the sound waves interact inside the female cricket’s tracheal system
the pressure differences experienced by the tympana in the female cricket are influenced by the wavelength of sound relative to the dimensions of her L (inter-tympanal distance) and l (spiracle-tympanum distance)
What is L? what is l?
L = inter-tympanal distance/external distance between the 2 tympana
l = spiracle-tympanum distance - the internal distance between each spiracle and its corresponding tympanum
How does a longer L affect the cricket’s interpretation of the sound?
a longer L = more spatial separation = increase the pressure differences at the tympana depending on the wavelength of sound
How does a longer l affect the cricket’s interpretation of the sound?
a longer l changes the timing and phase of the internal sound wave = changes how it interacts with the external sound wave at the tympanum = how much pressure difference is created
What is the equation for wavelength and frequency? what is the speed of sound?
lambda = c/f
c = speed of sound = 343 m/s
What happens if the male’s frequency is comparable or shorter than the L + l distance of the female?
higher frequencies = shorter wavelengths
ex. frequency = 7 kHz
lambda = 343 / 7000 = 0.049 m = 4.9 cm
if the female’s L + l dimensions are comparable to or shorter than 1/2 wavelength (2.45 cm)
= sound waves interact strongly within tracheal tube = CLEAR phase differences at tympana = stronger ability to determine sound direction
What happens if the male’s frequency is lower than the L + l distance of the female?
lower freq = longer wavelengths
if wavelength is longer than L + l = phase differences are less strong and the sound waves interact weaker = reduce sensitivity to sound cues in female
ex. male freq = 5 kHz
lambda = 343/5000 = 0.0069 m = 6.9 cm
the female needs to have L + l ~ 3.45 cm
If a male of species A has higher frequency (ex. 7 kHz),
then the female that will best hear his call will likely be larger or smaller than
for the male of species B (ex. 5 kHz)?
Species A female will likely be smaller because a higher frequency has a shorter wavelength and her L + l distance has to be close to half the wavelength = small
Species B female will likely be larger because a lower frequency has longer wavelengths, so to get a clear phase difference her auditory path needs to be longer
Describe the auditory pathway in crickets
sound reaches tympanum
auditory nerve carries info from sensory neurons in tympana up the forelegs and terminates on the auditory neuropil of prothoracic ganglion
at the prothoracic ganglion, omega interneurons (ONs) receive the excitatory input > COPY song ipsilaterally and reciprocally (contralaterally) inhibit each other to sharpen directional sensitivity
ascending neurons (ANs) receive excitatory input from auditory nerve and project toward the brain; they COPY song ipsilaterally and are inhibited by contralateral ON
Brain neurons (BNCs) receive input from ANs and DO NOT COPY the song; they respond only to a specific syllable rate of the song
What are the 3 brain neuron classes identified by Schildberger?
BNC1 (low-pass) - receives info from AN1; responds to syllable rate at or BELOW recognition band (30 pulse/s)
BNC2 (high-pass) - responds to syllable rate at or ABOVE 30 syl/s
BNC2 (band-pass) - responds in a band-pass manner = only respond when syllable rate = recognition band (only occurs when both BNC1 and BNC2 (HP) are active simultaneously == AND gate
What are BNCs?
Brain Neuron Classes identified by Schildberger
BNC1 - low pass
BNC2 - High pass
BNC2 - band pass
Which auditory neurons in crickets copy the song?
Omega neurons and ascending neurons (both ipsilaterally)
Which auditory neurons in crickets inhibit activity of other neurons? what is the purpose of inhibition?
omega neurons reciprocally inhibit each other AND inhibit contralateral ascending neurons
the reciprocal inhibition of ONs = sharpens directional sensitivity
Which auditory neurons in crickets do NOT copy the song?
brain neurons
Which neurons in crickets are connected to the prothoracic ganglion?
omega neurons are INTERneurons and are stuck on the PG
ascending neurons originate in the PG but ascend toward the brain and connect to BNCs
Which neurons act as a bridge between the prothoracic ganglion and the brain in crickets?
ascending neurons
What is the prothoracic ganglion?
key structure in cricket nervous system involed in processing auditory information and controlling motor outputs of the forelimbs
What is a neuropil?
a cell with just fibers, the cell body is outside
What are the 2 components of ultrasound emitted by bats?
Describe the structure, purpose,
which types of environment they are best for,
example species
FM component: frequency-modulated
- STRUCTURE: rapidly changing sweep of frequencies (broadband/wide range)
- PURPOSE: fine spatial resolution = target distance and absolute size (shape)
- ENVIRO: forests
- SP: big brown bats
CF component: constant frequency
- STRUCTURE: single, long, steady frequencies
- PURPOSE: detecting and tracking prey - target velocity and flutter (presence)
- ENVIRO: open spaces
- SP: horseshoe bats and mustached bats
Why do echolocating bats use ultrasound?
ultrasound has both of CF and FM components which allow bats that use echolocation to send a sound with short wavelength and high frequency to receive an echo that will reflect off of small objects like insects
How do some bats determine their distance to a target? What component of ultrasound echolocation allows for this?
bats that use the FM component of echolocation
use the time between the pulse emitted and the returning echo to determine distance (intensity of echo decreases with distance)
How do some bats determine the absolute size (shape) of a target? What component of ultrasound echolocation allows for this?
FM component
they use the combination of time delay and angular size (amplitude) of the echo
small amplitude of echo + short delay = smaller object
small amplitude of echo + long delay = larger object
What characteristic of echoes does the amplitude or angular size effect?
loudness
larger amplitude = louder echo
How do some bats determine target velocity? What component of ultrasound echolocation allows for this?
CF component via Doppler shift
the echo is Doppler shifted (frequency changes) from the frequency emitted by the bat
based on whether it is higher or lower than the frequency of the pulse, the bat can determine if its gaining or losing the target
how does the target’s velocity change if the bat’s echo returned at a higher frequency than the pulse?
echo higher frequency = bat is gaining on target
how does the target’s velocity change if the bat’s echo returned at a lower frequency than the pulse?
target is outdistancing bat
How does the bat compensate for an echo that is Doppler shifted above the frequency it can hear?
the bat lowers its CF frequency when it approaches the target so the echo comes back at its preferred frequency
How do some bats determine target flutter/presence? What component of ultrasound echolocation allows for this?
it combines amplitude of echo and frequency modulation (Doppler shift)
the length of the sound path of a bat’s pulse changes depending on whether the insect’s wings are up/down or out toward the bat
If the echo returns at a greater frequency than the pulse (Doppler) is the target’s wing out toward or away from the bat?
out towards the bat
shorter sound path = amplitude increased = echo is louder = higher frequency
If the echo returns at a lower frequency than the pulse (Doppler) is the target’s wing out toward the bat or up/down?
wings move away from bat
longer sound path = lower amplitude = echo quieter = lower frequency
What info does the azimuthal angle give bats?
bats have 2 ears for binaural input
What info does the elevation of their ears give bats?
bats can move their ears up and down to determine the height of their target
and compare echo amplitudes
What ultrasound component is most useful in forests? why? what about open spaces?
FOREST = FM component because the modulation of the frequency allows bats to distinguish between objects close together in space
and because FM is a broadband (wide range of) frequency = some will get lost but it ensures that some will return in the echo
- useful in a cluttered environment where some returning frequencies will get lost and many objects to distinguish between
OPEN = CF component because the single, steady frequency pulse will not get lost
What are 2 major features/anatomy of the bat auditory system that are specialized?
acoustic fovea = a specialized area of the inner ear that has increased sensitivity to a narrow range of frequencies
the outer ear = large pinnae with a skin flap (tragus) that directs sound toward the inner ear
What is the basilar membrane? how is it different in bats v. humans?
a component of the acoustic fovea (inner ear) that vibrates in response to sound waves and sends auditory information to the brain
in bats it has:
- structural discontinuity = abrupt thickening and lengthening where CF echo hits
- an expanded region dedicated to preferred frequencies with increased number of primary auditory neurons
vs. humans have evenly distributed frequencies across the basilar membrane = no specialization
What is the best excitatory frequency (BEF) in bats?
a parameter used to describe how bats perceive and process sound - particularly for echolocation
BEF = the frequency at which an auditory neuron is most sensitive - ie., it requires the least sound intensity for a response
usually corresponds to frequency range of echolocation
What is the Q10 dB in bats? How would you interpret a high Q10 dB vs. a low one?
a measure of the sharpness of tuning of a primary auditory neuron
Q10 dB = BEF / bandwidth at 10 dB above threshold
high Q10 dB = sharp frequency tuning (narrow bandwidth) = the neuron responds to a very specific range of frequencies
low Q10 dB = broad frequency tuning (wide bandwidth) = neuron responds to a wider range of frequencies
Would a bat relying on CF component (ex. horseshoe) have higher or lower Q10 dB? Explain
higher Q10 dB - they need sharply tuned auditory neurons to detect the Doppler-shifted echos - very small range of frequencies and very small shift in frequencies
Would a bat relying on FM component (ex. big brown bat) have higher or lower Q10 dB? Explain
lower because FM bats use broadband (wide range) sweeps for echolocation, so they need less sharply tuned auditory neurons in order to receive the wide range of frequencies
A horseshoe bat is an example of a bat that echolocates using which ultrasound component(s)?
both FM and CF
A big brown bat is an example of a bat that echolocates using which ultrasound component(s)?
FM only
A fruit bat is an example of a bat that echolocates using which ultrasound component(s)?
trick question! fruit bats do not use echolocation
