PSY 2301 Lecture Notes - Lecture 12: Aplysia, Sensory Neuron, Second Messenger System
14 Nov 2018
School
Department
Course
Professor
Lecture 12 - Neural communication cont
& intro to drugs
Aplysia Studies
Aplysia and Basic Information
- “Preparation” of choice (animal, stimuli, responses)
- big slow neurons
- Simple behaviours
- Response to water jet, shock withdraw (WD) girls, siphon
Habituation
- Defined: lowered response to stimulus when stimulus is repeated
- Real life: implications for screening out background stimuli (eg feel of clothes)
- Aplysia habituates to waved in shallow water
- Behaviour: gill withdrawal weekend with repeated squirts of water
Sensitization
- Response to stimuli increases when other (big) stimuli are presented
- Aplysia - electrical shock to tail increases withdrawal response, for hrd
- Behavioural: tail shock → restoration (sensitization) of habituated gill withdrawal
response
Gill withdrawal (baseline, control state)
Gill no longer withdraws (habituation)
Why?
- Decreased influx of calcium ions
- Less NT release
- Less depolarization of postsynaptic membrane
- Single shock enhances the response (sensitization)
Why?
- An interneuron releases 5HT (serotonin) onto the sensory neuron
- Second messenger slows down k+ channels (less efflux)
- Therefore, prolonged action potential
- More influx of CA2+
- Increased NT release
- Greater depolarization of postsynaptic membrane
Document Summary
Response to water jet, shock withdraw (wd) girls, siphon. Defined: lowered response to stimulus when stimulus is repeated. Real life: implications for screening out background stimuli (eg feel of clothes) Aplysia habituates to waved in shallow water. Behaviour: gill withdrawal weekend with repeated squirts of water. Response to stimuli increases when other (big) stimuli are presented. Aplysia - electrical shock to tail increases withdrawal response, for hrd. Behavioural: tail shock restoration (sensitization) of habituated gill withdrawal response. An interneuron releases 5ht (serotonin) onto the sensory neuron. Second messenger slows down k+ channels (less efflux) There is a synaptic basis for learning, ie changes at the synapse (plasticity) underlie learning. This supports hebb"s assertion that neurons that fire together, wire together . The sensory neuron (whose axon is near the motor neuron) becp,is more efficient at communicating information to the motor neuron (so the synapse is called a hebbian synapse ) Habituated - reduces behavioural activity associated with fewer synapses.
