Olfactory bulb Flashcards
it is important to study the olfactory system because…
a. in many neurodegenerative diseases and especially Alzheimer’s disease, olfactory symptoms ofter occur prior to onset
b. to understand perception of food and consumption of food
c. brain circuitry underlying flavour perception is altered in obese people
d. all of the above
D
what is the difference between orthonasal and retronasal smell?
Orthonasal smell: direct nasal inhalation of air particles from the environment (we breath in air and sniff food and environment).
Retronasal smell: food consumed by the mouth is chewed–> releases volatile molecules which enter the nasopharynx and travels up to the olfactory epithelium and from there to the olfactory bulb and cortex.
retronasal smell is much more important for humans because of food perception
why does hot coffee taste better than cold coffee?
volatile layer of HOT coffee molecules travel to the nose much faster and in larger amounts because the high temperature increases broconian motion and diffusion of molecules
which of the following statements about olfactory receptor neurons (ORN) is/are correct?
a. ORNs can express various types of olfactory receptors
b. ORN are specific to smell types like ‘coffee’ or ‘chocolate’
c. ORN are not specific to single molecules but rather they react to chemical groups
d. odourants activate different ORNs in the same intensities
C.
which of the following statements is WRONG?
a. odour coding starts already at the level of nasal mucus
b. subtle structural changes result in fundamentally different smells
c. different odourants activate different receptors at changing intensities
d. odour coding starts in the olfactory cortex
D.
olfactory projection…(which of the following statements is/are correct?)
a. ORN are everywhere but they converge and project to 2 specific glomeruli in the olfactory bulb
b. this convergence is acquired during childhood (exposure)
c. odours are deconstructed to their components in the olfactory bulb, and then reconstructed and mixed in the cortex
d. single glomerulus project to a single neuron in the olfactory cortex
e. neurons in the olfactory cortex respond to groups of glomeruli.
A c e
what is the population code?
population code is a term that describes odour processing of olfactory signals in the cortex.
-> odours are deconstructed to their chemical components in the olfactory bulb, but when the info is projected to the cortex the signals are mixed.
-> large neuronal cell assemblies in the olfactory bulb respond to groups of glomeruli–> population code
-> distinction between odour components is lost
what are sister cells
group of mitral cells that send apical dendrites to the same glomerulus
which of the following statements is/are correct?
a. glomeruli have a Ih pacemaker current (H-channel) that activate upon hyperpolarisation
b. H-channel resets the neuron to a different potential - hyperpolarisatio and direct depolarisation after (Sag current)
c. H-channel is activated upon depolarisation
d. H-channel decreases response at the dendrite and increases input at the soma
e. cells from different glomeruli the H-current varies dramatically in comparison to sister cells
A b e
which of the following statements about information coding of smell is/are correct?
a. number of generated APs decreases with increasing odour concentration
b. changes in firing rate occurs in the bulb, and it is the strongest during adaptation to smell.
c. information coding depends on spatial population dynamics but not on temporal population patterns.
d. information coding contributes to generation of oscillations by the olfactory bulb.
e. all of the above
B d
the olfactory bulb transforms linear output from ORN into oscillations. Which frequencies correspond to which function of information processing (initiation, discrimination, memorisation)
Initiation- Theta (slow wave), associated with respiration
odour discrimination- low gamma (40-60 Hz) and high gamma (60-100 Hz)
memorising odours- ß (20 Hz)
which of the following statements about oscillations is/are correct?
a. oscillations can occur together (in parallel to each other)
b. Oscillations decrease with more exposure/inhalation of the same smell
c. studies have shown that oscillations differ in type and intensity according to behavioural state of the subject (hungry/satiated)
d. oscillations contribute to functional connectivity in the olfactory bulb
e. oscillations have spatial advantage
c
Mitral cells…
a. integrate primary and secondary dendritic shafts and connect glomerular and mitral cell input
b. generate unidirectional APs
c. the dendrites of mitral cells can be described as passive cables
d. when AP fire in mitral cells there is depolarisation of the cell
e. all of the above
A.
how could we prove the active conductance in dendrites of mitral cells
addition of TTX (blocks Na+ channel) decreases dendritic response.
describe the reciprocal feedback/recurrent inhibition in the olfactory bulb
mitral cell (MC) fires
AP travels via dendrite to granule cell (GC-inhibitory)
AP releases Glu from MC to GC
GC is depolarised –> EPSP in GC increases Ca2+ in dendritic spine of GC
Ca2+ triggers SV release of GABA from GC to MC
hyperpolarisation of MC
