L19 - Learning and Memory II Flashcards
What is habituation? (3)
Non-associative learning
Repeatedly stimulating it the gill would withdraw less over time- adaptive as it doesn’t waste energy
synaptic depression - due to a reduction in Ca2+ influx per action potential and hence reduced neurotransmitter release
Synaptic depression
Shows if the presynaptic neuron was stimulated every time, the response in the post synaptic neuron would get smaller over time
What is Sensitisation?
Non-associative learning
The response decreases over time
Adaptive
Multiple shocks over several days leads to the synapse not habituating like it normally would- links to long term memory
Sensitisation of gill withdrawal involves presynaptic facilitation – a form of synaptic plasticity
The tail to the facilitating interneuron which uses serotonin
The interneuron synapses onto a pre-synaptic ending of the sensory neuron
Synaptic plasticity (Short term)
The serotonin acts on serotonin receptors on the sensory neuron -> releases cAMP -> activates protein kinase A -> acts to close K+ channels
When K+ channels are inhibited
a normal AP into a broadened AP - lasts longer because it takes longer for the membrane to depolarise.
Amount of neurotransmitter released is proportional to the amount of K+ inhibited
Synaptic plasticity (Long term)
One enzyme is produced (due to cAMP inducible gene) which causes persistent activation of the protein kinase which affects action potential and neuronal transmitter release.
Ubiquitin Hydrolase
Sensitisation of the gill withdrawal response involves: (3)
Increased neurotransmitter release at sensory neuron → motoneuron synapse (functional plasticity)
Activation of cAMP signalling cascade, leading over the long term to changes in gene expression
Increased number and area of active synaptic zones (structural plasticity)
What is clasical (associative) conditioning of the withdrawal response
- Involves similar cellular/molecular processes to sensitisation
- Tail shock (US) → gill/siphon withdrawal (R)
- CS is weak tactile stimulation of siphon
- Graph shows response to CS alone
Classical conditioning of gill withdrawal response
- When CS and US are paired, there is greater activation of adenylyl cyclase in the presynaptic terminal than with either stimulus by itself.
- This is because the CS action potential admits Ca2+ into the presynaptic terminal. The Ca2+ (by interacting with a protein called calmodulin) increases the response of adenylyl cyclase to G-proteins.
What is adenylyl cyclase enzyme?
molecular site at which an association between CS and US is made
activated by the G protein - activated by serotonin binding to the receptor - also activated by calcium ions
Two roots of activation if the 2 routes both occur then its activated more
