Neurobiology 6

Question 1

Define declarative memory.

Answer 1

Memories that can be consciously accessed, e.g. facts and faces, and are stored in the hippocampus.

Question 2

Define non-declarative memory.

Answer 2

Memories that cannot be consciously accessed but that your body just knows how to do, these are mainly motor skills such as swimming and riding a bike, and are formed in the cerebellum.

Question 3

How was the hippocampal structure discovered?

Answer 3

Using rodent brains (also H.M).

Question 4

Describe the structure of the hippocampus.

Answer 4

Banana like structure.

Bilateral - spans both sides of the membrane.

Question 5

Where is the hippocampus found?

Answer 5

Under the neocortex.

Question 6

What is a place cell?

Answer 6

These are neurons in the hippocampus that fire when the animal occupies a location within its environment.

Question 7

Are these place cells a single neuron?

Answer 7

No - action potentials are fired by a population of simultaneously active cells.

Question 8

What is Hebb’s postulate?

Answer 8

When an axon of cell A is near enough to excite cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both of the cells such that cell A’s efficiency, as one of the cells firing B, is increased

Question 9

Define LTP.

Answer 9

A persistent strengthening of synapses based on recent patterns of activity.

Question 10

Why does LTP explain the conditioning process used in Pavlov’s dogs?

Answer 10

The food association pathway is being strengthened by the bell ringing.
If inputs arrive in the same critical time interval, then there will be long term potentiation and the association of the two separate neuronal pathways.

Question 11

What is the NMDA receptor permeable and blocked by?

Answer 11

Permeable to calcium ions and blocked by magnesium ions.

Question 12

What happens when glutamate binds to the NMDA receptor?

Answer 12

Allosteric mechanism - glutamate binds causes a conformation change - calcium allowed through. It takes longer to activate and remains open for longer.

Question 13

What do NMDA receptors require as a co-activator?

Answer 13

Glycine.

Question 14

What type of receptor is a NMDA receptor?

Answer 14

Pore-loop receptor (same family as AMPA).

Question 15

Summarise how AMPA and NMDA are involved in LTP.

Answer 15

NDMA is blocked by Mg at resting potential, if EPSP occurs AMPA receptors will mediate this. Prolonged depolarisation (summation of EPSP) results in the removal of the Mg and influx of Ca2+ - this triggers LTP.

Question 16

Describe the structure NMDA receptors.

Answer 16

2 NR1 subunits and 2 NR2A/B/C/D.

Question 17

What happens to AMPA receptors after LTP has been induced?

Answer 17

There is a permanent increase in AMPA receptors allowing for memory formation.

Question 18

Suggest 4 possible mechanisms for LTP.

Answer 18

A) Change in release properties – increase in the number of release sites, increase the concentration of glutamate released into the synaptic cleft.
B) Change in AMPA receptor properties – phosphorylation changes the probability of the channel opening in response to glutamate, or the amount of time the channel stays open.
C) Change in the number of AMPA receptors.
D) Synaptic growth

Question 19

What is the function of the C terminus of the NMDA receptor?

Answer 19

As a binding platform for signalling molecules - localises signalling enzymes.

Question 20

Define LTD.

Answer 20

A persistent weakening of synapses based on recent patterns on activity.