2 L6 Synaptic Plasticity 1 Flashcards
Define synaptic plasticity
The ability of synapses to change their strength or efficacy in response to activity, environmental factors etc. Can be short or long lasting
What is drosophila
Invertebrate (fruit fly)
Why is drosophila a useful model for studying genes
Small genome and rapid life cycle - Small nervous system - Easy to identify circuits
What is aplysia californica
Giant sea slug (invertebrate)
Why is Aplysia a useful model for studying genes
Small NS - Large neurons (easy to impale and record from) - Easy to identify individual neurons and circuits
Describe the siphon gill withdrawal reflex in aplysia
Tactile stimulus to siphon causes gill withdrawal
Describe when the siphon gill withdrawal reflex in aplasia undergoes learning
It undergoes learning when a noxious stimulus is applied
2 forms of simple learning
Habituation and Sensitisation
Define habituation
Learning to ignore a stimulus that lacks meaning- Decreased response to a repeated harmless stimulus
Define sensitisation
Enhanced response to stimuli after a noxious event
Compare habituation and sensitisation NT release
Habit.- Decreased NT release
Sens.- Enhanced NT release
Compare habituation and sensitisation neural circuit
Habit.- Involves sensory neuron to motor neuron synapse
Sens.- Involves facilitatory interneurons
What is the process of sensitisation depending on increased synaptic activity called
Facilitation
Describe presynaptic facilitation for a single tail shock (short lasting change)
Noxious stimuli activate interneuron L29 - L29 releases 5HT which activates 5HT receptors on presynaptic nerve terminal - Stimulates cAMP formation - Activates PKA - NT released
3 effects of PKA
Increases phosphorylation of K channels - Increases phosphorylation of Ca channels - Increases synaptic vesicle mobilisation
Describe presynaptic facilitation for multiple tail shocks
Higher levels of cAMP activates PKA which now moves to the nucleus. This alters gene expression - New proteins stimulate synapse growth - Creates a strengthened network
Hippocampus location and function
In temporal lobe of cerebral cortex - Plays important role in memory and learning
Trisynaptic circuit of hippocampus in rodent pathway
- Entorhinal cortex -> Dentate gyrus synapses (perforant path)
- Dentate gyrus -> CA3 synapses (mossy fibres)
- CA3 -> CA1 synapses (Schaffer colateral)
LTP features
Persistent - Associative - Specific to active synapses - Synaptically located - Elicited in brain regions associated with memory
What is LTP underpinned by
Increased glutamate receptor responsiveness and changes in gene expression
