Neuronal Transmission Flashcards
What is the role of the neuronal membrane?
Separates the extracellular environment from the intracellular
What are the names of the membranes 2 sides?
Hydrophillic and hydrophobic
What is the NaK pump, and why does it happen?
Pumps 3 NA out and 2 K into the cell, and occurs to maintain the electrochemical gradient of the cell
What is the resting potential of a cell?
-70mV
What is the first movement during an action potential?
Na into the cell
What does the opening of K channels do?
Causes potassium to leave the cell and reversing the depolorisation
When will the cell be repolorised?
When the sodium channels close and potassium has left the cell
What is the rate law?
The size of the action potential stays the same, however the axons rate of firing can cause stronger or weaker contractions
Name the two types of synapse
Electrical and chemical
What are the three types of chemical synapse?
Axodendritic, axosomatic and axoaxonic
Name the stages in chemical transmission until CA influx
- Neurotransmitter synthesis
- Transport and storage
- Depolarisation/action potential
- Opening of voltage gated ion channels
- Ca influx into the cell
What is a neurotransmitter?
A type of chemical that is used to transmit information form the pre to the post synaptic neuron
Name the 2 types of receptor
Ionotropic and metabotropic
How do metabatropic receptors transmit a signal?
Through a second messenger system and activation of a G-protein
Following activation of the g-protein, GDP is exchanged for what?
GTP
After the exchange of GDP and GTP, what happens to the g-protein?
It splits and the subunits modulate other proteins such as enzymes
When does an EPSP happen?
Following depolarisation of the membrane
During inhibitory transmission, what charge of ions enters the cell?
Negative such as Cl-
Name the two processes that inactivate neurotransmitters
Reuptake receptors and deactivating enzymes
Autoreceptors use negative feedback to regulate synaptic transmission, what does this mean?
They inhibit further neurotransmitter release if there is too many in the synaptic cleft
Name the three categories of neurotransmitter
- Classical
- Neuropeptides
- Other small molecules
What is the differences in the synthesis of classical neurotransmitters and neuropeptides
Neurotransmitters are made in the terminal whereas neuropeptides are made in the soma
What is the effect of glutamate?
Excitatory, fluxing sodium into the cell
What does glutamate bind to?
AMPA, NMDA and kainate
The NMDA receptor also requires the binding of a o-agonist called what?
Glycine
Name one non-competitive agonist at the NMDA receptor
PCP
At resting state, why does the binding of glutamate not do anything at the NMDA receptor?
Due to the magnesium block, which is pushed out when the membrane is depolarised
What can NMDA receptors be blocked by?
MK801
What symptoms occur following blockage of the NMDA receptors?
Hallucinations like those of schiz
When might glutamate excitotoxicity occur, and what causes it?
After a stroke or chronic stress, excessive influx of calcium into the cell
What is the major inhibitory neurotransmitter called?
GABA
How is GABA synthesised?
From glutamate
Name a drug that increases GABA and how this leads to sedation/coma
GHB, increases the amount of available GABA at the synapse which leads to too much inhibitory transmission
Name the four other drugs that bind to the GABAa receptor but not the GABA site
- Ethanol
- Neurosteroids
- Barbituates
4.BZD
What are anxiolytics?
Drugs that increase GABA activity
What is the effect of the direct agonist, barbituates?
General depression of neuronal activity
What type of agonist are BZDs?
Indirect agonists
What is the difference between barbituates and BZDs?
The theraputic ration is different- easy to overdose on barbituates
What drug blocks the effect of GABA?
Flumanezil
Name the three neuromodulators
Dopamine, seretonin and acetylcholine
What does it mean to be a neuromodulator?
They modulate neuronal activity and don’t carry any primary activity themselves
Dopamine is involved in the nigrostriatal, mesolimbic and the mesocoritcal system, what role in behaviour do these systems play?
N = movement
ML = reinforcement and rewards
MC = planning and working memory
What is the essential amino acid used to make dopamine?
Tyrosine
Tyrosine is converted into what, that then becomes dopamine?
L-dopa
Name the drug that impairs the storage of monoamines into the synaptic vesicles
Reserpine
What does AMPT do?
It inactivates tyrosine, decreasing dopamine levels
Dopamine transporters can reuptake dopamine, however it can also be enzymatically degraded by COMTs or?
Monoamine oxidases
How do cocaine, amphetamines and methylphenidates affect dopamine?
They block the reuptake of dopamine into the terminals, leading to extended action of dopamine
Selegiline and entacapone prevent the breakdown of dopamine which means what?
The pool of releaseable dopamine is increased and therefore more dopamine is released
What amino acid is seretonin synthesised from?
Tryptophan
What is the name for the SSRI that increases seretonin in the synapase (prozac medical name)?
Fluoxetine
Until it was banned, what was fenfluramine used for?
Increasing the release of seretonin and inhibiting its uptake
What affect does MDMA have on seretonin?
Increases the rate of seretonin release into the terminals
Aceytlcholinesterase inhibitors, such as physostigmine, do what?
Block the breakdown of ACh, prolonging its actions in the synaptic cleft
What is myasthenia gravis caused by?
A lack of ACh receptors in certain parts of the body
Botunilinum toxins (botox) relaxes the muscles how?
By blocking the docking of vesicles that contain acetylcholine, to the muscles
To inhibit the cholinergic neurons from firing, glycine is required, what toxins affect the release of glycine and therefore result in permanent muscle contraction
?
Tetanus toxins
