T/F: The dendrites of a neuron have a threshold potential which, if exceeded, could initiate an action potential within the shaft of the dendrite.
True, although this threshold is far higher than at the axon hillock so it is never exceeded.
Why does the axon hillock have the lowest threshold potential?
It is the region with the highest number of voltage-gated sodium channels
What two ways can an EPSP become strong enough to initiate an AP?
Spatial summation (recruit more excitatory neurons with a stronger stimulus)
Temporal summation (add multiple EPSPs close together)
Temporal summation (add multiple EPSPs close together)
T/F: Inhibitory neurons located on dendrite shafts decrease the strength of local EPSPs while inhibitory neurons located near the axon hillock decrease the strength of the collective EPSP of the cell.
True
A measure of the change in EPSP strength compared to the original EPSP.
Synaptic strength (efficacy)
What is the principle difference between axo-somatic inhibitory synapses and axo-axonic inhibitory synapses?
Axo-somatic inhibitory synapses act by lowering the strength of the graded potential, making it harder to reach threshold. Axo-axonic inhibitory synapses act downstream of the AP and act to limit the amount of neurotransmitter release.
What is a major function of axo-axonic inhibition in the various sensory pathways?
It serves to filter out "noise" allowing the subject to focus on the important stimulus more efficiently. For example, random noise in a room when you are having a conversation.
GABA inhibits via two receptors. What are they and how do they cause inhibition?
GABAb: close Ca++ channels and/or open K+ channels
GABAa: open Cl- channels
**think "a" is first letter, so it's the most simple. Only one ion.
GABAa: open Cl- channels
**think "a" is first letter, so it's the most simple. Only one ion.
A motorneuron sends ACh to _________ receptors at the NMJ while simultaneously sending ACh to _________ receptors on Renshaw cells.
Nicotinic (ionotropic); muscarinic (metabotropic)
Motor axons are _________ while motor neuron axon collaterals are _________.
Myelinated; unmyelinated
Norepinephrine, dopamine, seratonin are synthesized in the _________ of a neuron. They are neither __________ nor __________.
Terminal bouton; excitatory nor inhibitory
These are minor CNS neuromodulators that are synthesized in the soma and transported to the boutons.
Neuropeptides. Substance P (burning sensation) and enkephalin (opiate action)
Increasing/decreasing K+ conductance changes the __________ of action potentials.
Frequency (or duration)
T/F: A larger synaptic head tends to produce a stronger EPSP.
True. The larger head allows for more receptors.
T/F: Mentally retarded children will exhibit a larger number of dendritic spines in their neurons early on.
True. But these are largely immature and eventually disintegrate, leading to a lowered number of spines in adulthood (Slide 17, lecture 08)
Describe the steps of LTP.
1) Activation of NMDA receptors, Ca++ flows in
2) Ca++ binds to calmodulin, activates PKC
3) More AMPA receptors are recruited to the plasma membrane, increasing synaptic strength
**Additionally, the phosphorylation state of existing AMPA receptors can be changed to modulate their activity
2) Ca++ binds to calmodulin, activates PKC
3) More AMPA receptors are recruited to the plasma membrane, increasing synaptic strength
**Additionally, the phosphorylation state of existing AMPA receptors can be changed to modulate their activity
