4. Olfaction Flashcards
• ____ - how do electrical signals become sensation/consciousness
○ Continuous smooth experience - consciousness
• ____ bones - create turbulence > smelling occurs at the roof, in between your ____
• The rest of it below - ____ - lining of tissue coating the bones; most of airflow inhaled through nose > straight through nares and lung (99%), the turbinates make the etes that make the whispy swirls that reach the roof
• Turbinates also increase SA of nose > increase ____ density, filtering (airbound chemicals must phase into a water based level, must be solubilized [a big problem if they’re lipophilic]) and catching particles; breathe cold air into lungs (and die), must therefore ____ the air up by turbinates (inc. SA) in a process via ____ (blood through epithelium [body T], and as you flow air over bed of capillaries, cold air picks up heat from capillary bed and cool the blood
• The counter current exchange also preserves ____ in the body
○ The water gets pulled by the capillary bed out of the breath and the air coming in from the desert is dry. So you will moisten the air as it comes in b/c you don’t want the dry air
neurophysiology turbinate eyeballs respiratory epi olf receptor warm countercurrent exchange moisture
• T1 - through ____
• T2 - some olf epitheilum - ____ more prominent
• T3 - thorugh middle of olfactory epithelium - ____ go crazy
○ Black - forms a ____ and it curves around
○ Symmetrical
○ Increases epithelium for ____ bed (the density), increases ability to ____ and catch particles in air, regulate physiological processes
• T4 - eyeball, back of olfactory epithelium
○ Eyeball, brain, posterior portion of olfactory epithelium
respiratory epithelium bones bones T (turbinate bone) olf receptor filter
• Mouse nose
• ____ - air space; grey shows the epithelium layer on bone (black)
• Nature of bones - ____ > not only bone makes T, but the end of it makes another T
○ ____ programmed; animal-to-animal the same way
• ____ symmetrical
white
fractal
genetically
bilaterally
• Coronal through the nose of an animal
• Complicated nose known - sea otter
○ More than likely due to ____, not about moist (live in water), and not smell
○ Sea water (a lot of salt), processing salt via ____
cold
countercurrent exchange
• Scope onto olfactory epithelium
• There’s an array of filaments sticking out of the top of the neurons which is ____
○ They look like a ____ (a process that sticks up and a lot of cilia that stick up)
○ Like a cilia because there is a clear definition of ____ structure of the fiber units inside the cilia
• Each cell is densely packed with many ____
• The cell body is in the ____ - processes that go out towards the mucus, and one towards brain
○ To mucus - dendrite - end of it stops at outer edge of epithelium, and cilia penetrates through end of epithelium out into mucus layer; here it shows as ____ (particles has to go from air into aqueous phase)
○ Brain - axon
cilia hydra crystalline cilia epithelium aqueous phase
- Micrograph of epithelium
- ____ of neuron - in the epithelium; one dendrite sticks up, and edge of epithelium is where the ____ processes stick up
- Dark layer is the ____ layer where the cilia reside
- Stacking the cilia - bed of “seaweed” - a lot of surface area for ____
cell body
cilia
aqueous-mucous
receptor neurons
• Neurons closely packed; and there is overlap of cilia in the mucus layer > make a web/nest of cilia, and in between > support cells (____ cells)
○ Why are they here?
§ Provide structure, ____ support these cells
□ Olfactory neurons - ____ active cells: example: battery - elements within the battery, chemicals that are charged (anions/cations)
□ ____ flow - electricity
□ Reaches ____ - dead battery - reached point of low potential, ions have moved back completely to where they want to be
• Electrically active cells gets its potential from separating ions into different ____
○ Neuron compartments - outside and inside; can only control what’s inside it, but cannot control the extracellular part
• So an electrically active cell will always act like a battery
○ it gets its potential from separating ions into different compartments
○ You move some ions one way and others into another chamber
○ If you want the electricity out of the cell, the ____ is an electrical current allowing the ions to move across the membrane that was separating them into different chambers
○ The cell is no different from a battery
Trick Question:
If a neuron acts like a battery, where are its 2 compartments?
• ____ and ____ of the cell
• An electrically active cell can be a problem because it can control what’s inside it BUT it cannot control what’s ____ of it
• The ____ cells have some control on an electrically active cell by helping it control the
flow of ions
sustentacular physically electrically ion equilibrium compartments action potential outside inside outside support
- Pulled olfactory receptor neuron out of mouse - but membrane is liquid (lipid)
- Remove cell body and put into stream with water
- Take pipette with plume of odor > solubilize and puff out the odorant (can put dye in as well, so you see what it’s doing)
- Advance pipette from right to left, against flow of water, do so plume reaches just tip of ____ > some electrical activity (1st from top)
- Advance further upstream > cover more of ____; and once you get all of cilia and ____ > bigger response
- Cover entire dendritic knob and dendrite, and cover entire dendrite > no change
- Neurons have receptors where transduction occurs > happens within the ____ and nowhere else
cilia
cilia
dendritic knob
cilia
• Multiple proteins > olfactory receptor; it’s a ____ (7 TM, and ____) (second messenger receptor)
• Point of second messenger > ____ > due to action of enzyme, it can many second messages
• ____ system > change in membrane potential > opens ion channel
• Purpose of ionotropic and metabotropic receptor is the same > needs ____ to flow to get electrical current > need something to bind to ion channel and alter flow
○ ____ binds to ion channel and opens it
• Activate receptor > bumps into ____ > can be activated > can bump into enzyme and activate it; not bound together > they’re ____
○ Also ____ within the membrane
• G-protein > splits into A and Bgamma part upon activation > alpha: ____ (cyclizes nucleotride into cAMP)
GPCR metabotropic amplification ionotropic ions second messenger g-protein free-floating mobile adenylyl cyclase
• ____ channels (can have one for cGMP, etc.)
• Inside to outside of cell - -60 to -70 mV; relative, sum all ions
• Ultimate goal of battery > lose its charge > go towards equilibrium; cell wants ions in equilibrium
○ Allow + charge to enter (____, double positive > can bind ____ channel > open and allow negative charge to go out)
○ Depolarizing hard (next slide)
cyclic nt gated
Ca++
Cl-
• ____ of primary signal CNG-channel being activated
amplification
How does the olfactory system turn itself off after stimulation or adapt to stimuli?
• Has to remove Ca++ via \_\_\_\_ > get rid of the Ca++, not worried about membrane potential * At same of calcium amplifying signal, the Ca++ is binding \_\_\_\_ > can inhibit CNG-channel * The enzyme is still making \_\_\_\_ * \_\_\_\_ will go to adenylyl cyclase and will stop it from making more cAMP * \_\_\_\_ > uncyclize the cAMP and makes it linear
Na+ calmodulin cAMP Ca++ phosphodiesterase
• How does the signal get into the brain?
• Olfactory epithelium > array of receptors across epithelium; mutant animal creates dye every time it expresses receptor > transgenic > every time you turn on gene, it can dye (protein) the cell that color
• Neurons convergence on single spot > ____
• Pit/opening inside oral cavity (nasal septum) > ____ > projects through area to the ____ olfactory bulb (not part of olfactory bulb) > important for social signaling, a ____ processing signal
• Tissue micrograph through animal’s head > each dot is a cell body of olfactory neuron > transverse entire ____ > located in a band > ____ of expression > they all send axons through bony plate of skull, into brain, and converge onto ____
○ Via ____ > the only place in the body where brain has access to outside world; inhale toxic chemicals or nasty viruses > free access from axon into brain
glomerulus vonroe nasal organ accessory pheromone epithelium zones glomerulus cribriform plate
• Glomerulus: area where there’s a lot of neural processing
◦ All kinds of neurons come together to make contact and talk to each
other. Not as depicted here (not an encapsulated structure. Just an area
that’s densely packed w/a lot of neural processes) “neuropill” from all
diff kinds of cells
• Blue and green: ____ inputs from olfactory receptor neuron
• Going to communicate with primary projection neuron from there
◦ Neuron that receives info and sends/projects deep into brain
◦ We will call these ____ (there are also “tufted cells”)
◦ Not only do they receive inputs from ascending primary receptor
neurons but they also have very large arms of ____ -
communicate w/lots and lots of neighbors. Project out sideways.
◦ Make use of arms through a couple kinds of inhibition - communication directly from ____ to glomerulus via ____ cells but also there are these guys called ____ (inhibitory neurons that
communicate with arms and also have arms)
◦ Might have a neighboring ____ act on this cell here (points at
granule cell) to cause the granule cell to act on neighboring mitral cell
to shut it down
• Can act on neighboring mitral cell and shut down –> ____ inhibition
◦ Activity occurring in one spot can shut down activity in neighboring cells
◦ Occurs through arms of mitral cells and inhibitory cells like granule cells
ascending mitral cells dendrites glomerulus periglomerular granule cells glomerulus lateral
Top: If you record from a single (in this case a projection neuron) mitral cell and stimulate
it by putting a ____ aldehyde in the nose, you get a lot of activity here. (Odor present during this dark bar)
• Middle: if you record from the same cell but with a ____ aldehyde, you get less activity
(what we do actually see here is normal breathing activity)
• Bottom: we see that a ____ aldehyde completely prevents from firing at all
• So we think there’s a receptor associated w/mitral cell that are activating glomerulus
and activating this ____ cell
◦ Receptors for 6C are on ____ cells (compared to the 5C)
◦ Activation of neighboring cell prevents from ____ (concept from previous slide)
◦ by the time we get to a 7C aldehyde its fully activating a ____ cell and
preventing the 5C one from responding
• This sharpens the tuning curve of what it’s responding to
◦ Cell doesn’t respond at all
◦ Rather than having a cell respond to one stimulus a lot and things that are just
slightly different from that a little bit and having a bell curve of activation, it ____ the tuning curve of what it’s responding to – would be silent instead of reacting a little bit
◦ Instead of having a bell curve of responding (which is based on if stimulus is spot on for receptor or not)
◦ Steep ____
◦ Principle in sensory systems everywhere: want to sharpen signal to be very ____ (also happens in vision)
5C 6C 7C mitral neighboring responding neighboring sharpens tuning curve
