Neuronal signalling 5 (2nd lecture) Flashcards
Outcome of Na,K antiporter?
Na is pumped out of the neuron
Why is the Na,K antiporter electrogenic?
causes a net movement of one positive charge from the neurone and causes repolarization
What maintains the unequal distribution of Na+ and K+/
Na/K pump
Which ion is the axonal membrane “leaky” to?
Potassium
Why is myelination important for energy conservation?
Resting potential only needs to be reestablished at the NoR instead of all the way along the memrane
Where is the NaK pump clustered?
Around the NoR
How is the resting potential on an axon resumed?
K+ channels close, repolarisation resets Na+ channels, ions diffuse away, NaK transporter maintains polarization
When does the axon resume a resting potential?
When an AP is not travelling down it
Does the measured AP change at any points along the axon?
No
How is the AP self propogating?
Na+ moves in where the AP is, diffuses away (in direction of AP)
This opens Na+ channels further down the axon due to membrane potential change, meaning the AP moves along
Why does diffusing Na+ within the axon not open ion channels behind it, flipping the AP?
The Na+ channels behind the AP are in a refractory period, meaning they cant open
Two main things AP propagation is dependant on?
Inhibition of activity in the area of the membrane where the AP has been, and activation of Na+ channels in the next area of the membrane
What can affect conduction velocity?
Diameter (larger is faster) myelination
Why are neurons myelinated?
Conduction velocity increased, size requirement diminished, reduced energy requirement and electrical insulation
In a myelinated neurons, what does the diffusing Na+ do?
Diffuse to the next NoR where it causes depolarisation
What does calcium enter via at the end of an AP, b4 a synapse?
Voltage gated/sensitive calcium channels
What does calcium do once inside the pre n?
binds to calmodulin and protein kinases
What does calmodulin do once calcium has bound?
Phosphorylates synapsin I
Effect of phoshoprylation on synapsin I?
Cant bind to vesicles, allowing vesicles to fuse with the cell membrane and release the NT
Types of calcium channel?
L-type, N-type, P-type
Where are L-type calcium channels found?
Skeletal muscle/cortex
Where are n-type calcium channels found?
CNS/PNS
Where are P-type calcium channels found?
cerebellum
Where is Ach found?
Neuromuscular junction
Amine NTs?
Noradrenaline, dopamine, serotonin
AA NTs?
GABA, glycine, glutamate
Peptide NTs?
endorphins, enkephalins, substance P
General role of neuropeptides?
Regulatory
Ionotropic receptors?
AMPA, NMDA, GABA and glycine receptors
Metabotropic glutamate receptor?
mGluR
Metabotropic GABA receptor?
GABAb
