Lecture 5 - neuronal diversity and dendritic processing Flashcards
How were basket cells named?
Cells (dendrites) have elaborate branching patterns, others have holes where the soma of other cells sit (basket cells).
What happens when a current is injected into a dendrite?
A sum of the current leaks out while the rest goes along the dendrite.
The Em shifts away from the RPM.
But as it moves away from that point the current decays back to the RMP.
What is a short space constant?
where the charge drops off quickly
What is a long space constant?
where the charge is held
What does space constant reflect in an axon?
the ratio of internal resistance and membrane resistance.
In the synapse what type of deflection is there and why?
rapid and large deflection as the charge is all there at once (AP near)
In the soma what type of deflection is there and why?
deflection rises slowly as it takes time for the charge to reach there (AP not near)
What does the shape and size of somatic EPSPs indicate?
the location of the dendritic origin.
What happens if a synaptic event happens at the dendritic spine and why?
strong charge and large deflection because the spine of a dendrite is tiny
What happens if a synaptic event of similar charge to that of the spine happens at the dendritic tree and why?
weak charge and small deflection as the dendritic tree is a large structure - takes a while for the charge to spread
Describe the impedance mismatch and what does it allow?
If a current flows from a small structure to a large structure there is a large decrease in the voltage deflection.
BUT if the current flows from the large structure to the smaller structure there is only a small decrease in voltage deflection.
Allows for flow of electrical information better in one direction over another.
What are the 4 different types of spatial summation in passive dendrites?
- 2 excitatory inputs onto different dendrites that summate well and achieve a linear effects.
- 2 excitatory inputs onto the same dendrite when one synapse opens the membrane becomes leaky so the effect is smaller as it leaks out of the other synapse. Shunting.
- An inhibitory and an excitatory synapse on different dendrites has a normal inhibitory effect.
- An inhibitory and an excitatory synapse on the same dendrite means the charge starts to leave the cell so excitatory effect is dissipated. Additional shunting.
Where does the action potential go when it reaches the soma?
propagates backwards up the dendrite.
How many directions does an AP go in?
2 - from the dendrites to the soma to the hillock (generation takes place) and then backwards from the hillock to the soma to the dendrites.
What is the purpose of the AP travelling in 2 directions?
tells the dendrites an AP is happening.
