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