Synaptic

Question 1

What features are required for a synapse to get stronger, include them all

Answer 1

Increase in probability of release, number of release sites and quantal size. Increase in unsilencing of synapses or synthesise of a new junction. Increase/change in AMPA receptors

Question 2

What is the process of LTP, describe in as much detail as possible

Answer 2

Glutamate binds to NMDA receptors and excites AMPA receptors. NMDA is the main source of calcium but calcium can also influx through back propagating dendritic action potentials which open voltage gated calcium channels as well as cytoplasmic calcium via release from intracellular stores and calcium can enter through voltage gated channels. Glutamate dislodges Magnesium ions allows calcium to enter. Calcium activates PKC and CamKII. CamKII is in the spine cytoplasm, associated in rings of 10 subunits. Calcium calmodulin STOPS kinase activity and CAMKII auto phosphorylates so the large calcium influx causes phosphorylation of one subunit by another. CamKII is constitutively activated until it is dephosphorylated. PKC and CamkII activity increases AMPA receptors at the postsynaptic membrane. Improves conductivity, increase of positive ions and able to fire more impulses. More proteins are created to mediate LTP, so CamKII and PKC activate ERKs which further increase protein

Question 3

Glutamate release at an excitatory junction, binds to what 3 receptors and does what?

Answer 3

a. AMPA receptors cause Na+ entry and depolarisation
b. NMDA receptors: nothing happens unless Mg is expelled, in which case Ca enters
c. mGluR receptors activate PLC via G-proteins

Question 4

Dendritic spines have what connections and insulations with each other?

Answer 4

they are electrically connected but biochemically insulated with their thin neck

Question 5

CaCamKII is most abundant where?
What is it bound to?
What may this protein phosphorylate

Answer 5

CaCamII is most abundant in the PSD and is bound to the tail of the NMDA receptor. It may phosphorylate AMPA receptors to increase their conductance and also PSD95 which is a receptor clustering protein which causes further clustering of AMPA.

Question 6

What are the enzymes activated by calcium in dendrites?

Answer 6

CaM Kinase II, Nitric oxide synthase, Phospholipase A2 (leading to AA), Calmodulin (Leads AC), Protein Kinase C and Calpain

Question 7

What are the retrograde messengers?

Answer 7

AA, Nitric oxide and carbon monoxide, O2, Cannabinoids (Adamantane)

Question 8

What are the 2 main stages of LTP

Answer 8

Early (electrical-chemical) and late (Structural)

Question 9

When NMDA is stimulated in terms of LTP so when magnesium is dispelled and calcium enters, what 5 things happen?

Answer 9

1. Change in probability of vesicle release (Earliest phase of LTP)
2. Change in size of current produced by each AMPA receptor
3. Change in number of AMPA receptors
4. Change in the electrical excitability of the dendritic membrane
5. Production of new dendritic spine

Question 10

NMDA receptors can be activatd by what two things?

Answer 10

Glutamate and glycine