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Building nervous systems > Memory in simple organisms- LTP and LTD > Flashcards

Memory in simple organisms- LTP and LTD Flashcards

1
Q

What are 2 ways of regulating synaptic sensitivity?

A
  1. Affecting activity of Ca2+ channel

2. Move channels away from the active zone

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2
Q

What does synaptotagmin do?

A

Detects when Ca2+ enter the presynaptic bulb-

leads to the release of neurotransmitter

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3
Q

What does plasticity mean?

A

Synapses become less responsive to stimulation-

due to there being fewer readily available vesicles

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4
Q

Difference between NMDA and AMPA receptors?

A

NMDA receptors- channel is blocked by Mg2+

Need to depolarise the membrane slightly to remove the Mg2+- then binding will open the channel

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5
Q

What is habituation?

A

A decrease in responsitivity of sensory neurons when a stimulus is repeated many times

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6
Q

What is sensitisation?

A

When the nervous system responds to an stimulus with increasing strength

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7
Q

What is the siphon- gill reflex?

A

When the siphon is touched- the gill withdraws

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8
Q

Where does habituation occur in the aplysia

A

Habituation occurs due to a decrease in sensitivity at the sensory-motor neuron synapse

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9
Q

What causes sensitisation in the aplysia?

A

L-29 neurons stimulate sensory neurons with serotonin- leads to longer depolarisations of the sensory neuron- causing more activation of the motor neuron

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10
Q

Why does habituation occur?

A

Due to the depletion of the synaptic vesicle pool

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11
Q

Why does sensitisation occur?

A

Due to serotinergic feedback from other sensory neuonrs

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12
Q

What is associative learning?

A

A learning process in which a new response becomes associated with a particular stimulus

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13
Q

What is non synaptic plasticity?

A

Changing in synapse strength not directly involving the synapse- modification of the intrinsic excitability of a neuron, unrelated to the amount of n.mitter

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14
Q

What are lymnaea cerebral giant cells involved with?

A

They permit feeding- not involved in feeding behaviour

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15
Q

What are the main neurons in a simplified hippocampal circuit

A

CA3
CA1
Dentate gyrus

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16
Q

What is the LTP phenomenon

A

A high frequency stimulus produces an increased amplitude of the post synaptic response, which is sustained (potentiation) in the CA3 to CA1 synapses

17
Q

What is co-operativity in LTP?

A

When two neurons converge and share a synapse- both neurons can be strengthened, even if one pathway is weak

18
Q

How does LTP occur

A

Often a postsynaptic event
Critical role for calcium
Calcium activated kinases, which changes the sensitivity of synapses

19
Q

Summary of early phase of LTP

A

Calcium activated calmodulin kinase 2
Autophosphorylation of CamK2=
1.Phosphorylates AMPA- increases activity
2.AMPAfication- BIGGER RESPONSES IN POST SYN NEURON

20
Q

Summary of late phase LTP

A

cAMP signalling may be critical
Protein synthesis and-
Change in GENE transcription

21
Q

What is the conclusion in regards to LTP and long term memory?

A

LTP is necessary for some memory formation

but is NOT sufficient

22
Q

What is the LTP phenomenon?

A

Long lasting reduction in synaptic efficacy

23
Q

What are the 2 types of LTD?

A
  1. Depotentiation

2. LTD de novo

24
Q

What are 4 general mechanisms for LTD induction?

A
  1. NMDA receptors
  2. Low frequency stimulation
  3. Ca2+ influx- activation of phosphatases
  4. Glu- can be 5-HT or endocannabinoids
25
Q

What are the receptors involved in LTD in the cerebellum?

A

Cav
metabotropic Glu-r
AMPA-r

26
Q

What occurs when a P.F is stimulated

A

Glu released
activation of AMPA-r= depol
activation of Glu-r= activation of second messengers

27
Q

What occurs when a C.F is stimulated?

A

Depol of P.cell
activation of Cav
intracellular Ca increases

28
Q

What occurs when both pathways are activated?

A

Second messengers increase [Ca]i even further
This activates PKC
PKC phosphorylates AMPA receptors- internalising them
=Depressed response from P.cell

29
Q

What is the Albus-Marr model?

A

CF input indicated a motor error and weakens the PF-P.cell synapse

30
Q

How does hippocampal LTD occur?

A

Low frequency stimulation of CA3-CA1 synapse-
SMALL degree of NMDAr activation
SMALL increase in [Ca]i
More phosphatases than kinases activated
=LTD

31
Q

Long term memory=?

A

Distributed, structural change

May be encoded outside the hippocampus

32
Q

What is the hippocampus important for?

A
  1. Formation of new memories (damage- anterograde amnesia)
  2. Important in spatial memory
  3. Good at associating different inputs- visual, auditory, smell
33
Q

What does stressful stimuli cause?

A

LTD

Building nervous systems (16 decks)

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