Synaptic Transmission Flashcards
Divergence
Neurone provides synaptic input to many other neurones
Convergence
Neurone has synaptic input from a variety of other neurones
What determines if a synapse is inhibitory or excitatory?
The contents of the synaptic vesicles which bridge the synaptic cleft
Define Spacial Summation
When many neurones exert the same effect on a post synaptic membrane, producing a much larger response
Define Temporal Summation
When several APs arrive in succession to have a greater effect than 1 AP alone
What does NT cause at the post synaptic potential in an ipsp?
Hyperpolarisation
What does NT cause at the post synaptic membrane in an epsp?
Depolarisation
Name the 3 classes of NTs
Amino acids
Amines & Purines
Peptides
Give examples of type 1 NTs (amino acids)
Glutamine
GABA
Glycine
Give examples of type 2 NTs (amines & purines)
ATP Adenosine ACh Dopamine NA Serotonin
Give examples if type 3 NTs (peptides)
Cholecystokinin
Metenkephalin
Substance P
Vasopressin
List in order the concentrations of type 1,2 & 3 NTs in the CNS
Type 1= relatively high conc
Type 2= slightly lower conc
Type 3= very low conc
Which is faster- ionotropic or metabotropic receptors?
I= fast, rec usually directly linked ion channels, open when NT binds.
M= slower, rec coupled effector ion channel (via G protein or 2nd messenger)
What are the major excitatory receptors if the CNS?
Glutamate receptors
What results from excessive activity if glutamate receptor?
Over active neurones
Seizures
Cell death
Why does excessive glutamate rec activity produce these effects?
Rec allow Ca entry= neurotoxicity at high levels
Name the 3 major types of glutamate receptor
NMDA
Non-NMDA-fast depolarising
Metabotropic
What type of receptor is the NMDA glutamate rec?
Ionotropic
What ions do the NMDA glutamate rec allow through?
What does this lead to?
Na+
Ca2+
Fast depolarisations
Name the ion non-NMDA-fast depolarising receptors are permeable to.
Name it’s agonist.
Na+
AMPA/ Kainite
What are the metabotropic glutamate receptors linked to?
G proteins & 2nd messenger couplings
More long term effects
Where are GABA receptors usually found & what is there usual action?
Short interneurons, many in the limbic system
Inhibitory
Short interneurons found in the limbic system play a role in….
Emotional responses:
Personal feelings
Emotional memories
What is the effect of alcohol on short interneurons?
Removes inhibitory responses
Person becomes upset/aggressive
What are the 2 main types of GABA receptor?
GABAa & GABAb
Describe the structure of GABAa
Similar to nicotinic cholinergic rec
2 x a subunits
2 x B subunits
1 x y subunit
When GABAa is activated, a channel permeable to …. is opened
Chloride
Mem hyperpolarises as GABA rec is inhib
Name drugs the GABA receptor’s Cl- permeable channel has binding sites for
Benzodiazepines
Barbiturates
Steroids
(Treat anxiety)
Describe GABAb rec structure
7 transmembrane domains
Coupled to a G protein
What channels do GABAb rec activate?
Outward K+ (cause hyperpol & ipsp)
Influence Ca channels
What are nAch rec permeable to?
Na+
Ca2+
Name the mAch subtypes
M1- M5
What are M1, M3, M5 receptors coupled to?
PLC
What are M2 & M4 receptors negatively coupled to?
Adenylyl Cyclase
Cause ⬇️ of cAMP upon activation
mACh rec degenerate in what disease?
Alzheimer’s
Dopamine is largely …… in the CNS
Inhibitory
What are the 2 dopamine receptor subtypes?
D1 & D2
All metabotropic
All lead to a G protein
Name 2 tracts where dopamine receptors are found
Mesostriatal (formation of organised thought/stabilise mood)
Nigrostriatal (voluntary movement)
What tract, especially in the basal ganglia, degenerates in Parkinson’s?
Nigrostriatal
Via which rec does 5HT exert and excitatory effect?
5HT2
Via which rec does 5HT exert an inhibitory action?
5HT1
What is the action of SSRIs
Block 5HT re uptake
5HT remains active in exerting its effect on post & pre synaptic membranes
