Lecture 5: Axonal Propagation and Synaptic Transmission

Question 1

Where is synaptic input received on a neuron, what properties determine how much current flows to the soma?

Answer 1

Input received at the dendrites, length and diameter play a role in determining the amount of current.

Question 2

Compare and contrast EPSPs and IPSPs

Answer 2

EPSPs: transient depolarization due to Na/K movement in response to NT binding. force pushing Na stronger than for K (Vm farther away from ENa so more Na moves than K)

IPSPs: transient hyperpolarization due to Cl- moving into the cell, K+ moving out

Question 3

Describe spatial and temporal summation

Answer 3

temporal: multiple PSPs arriving within a short time period
spatial: multiple PSPs arriving from multiple dendrites at the same time

Question 4

Describe signal transmission at a chemical synapse

Answer 4

depolarizing action potential opens CaV gated channels, influx of Ca causes exocytosis of synaptic vesicles containing NT, NT diffuses across synapse and binds to receptors

Question 5

Name the NT classes, give an example of an excitatory and inhibitory NT

Answer 5

Gaseous (NO)
Peptides (somatostatin)
small molecules
excitatory (glutamate=brain, Ach=PNS, NMJ)
inhibitory (GABA=CNS, glycine=spinal cord)

Question 6

Explain how axonal conduction is saltatory, describe 2 factors contributing to speed of conduction

Answer 6

jumps from node to node, at the nodes is where there is great density of Na channels, high conductance, and low resistance

speed of conduction depends on membrane resistance (myelination), axonal resistance (diameter), capacitance

Question 7

Describe difference between ionotropic and metabotropic receptors, give examples

Answer 7

Ionotropic are ion channels, fast response

metabotropic are GPCR - activate G protein, goes on to activate second messengers or affect ion channels

Question 8

How do you determine reversal potential?

Answer 8

apply EPSC, measure EPSP size for various starting RMP, the point where there is zero EPSP for that starting RMP is where the reversal potential is b/c there is no movement of charge even if ion channels open

Question 9

How are synaptic vesicles recycled?

Answer 9

either endocytosis using clatherin-coated pits
or kiss and run: benefits = not having to constantly make vesicles, have a store of them ready and get them back right away