Synapse 2 Flashcards
What do dendrites do?
Help compute the response of the neuron
How do dendrites help compute the response of the neuron?
Timing and multiplicity of inputs
Dendritic morphology and end bulb position
Different types of electrical activity
What’s dendritic morphology?
Spines
Branching
Length
What does position of dendritic end bulbs do?
Governs input to cell body and AP output
Single EPSP:
Single input of action potential
No action potential triggered
Spatial summation:
Multiple inputs of action potential
Temporal summation:
Train of inputs of action potential
What triggers an action potential?
2 coincident EPSP - summed
What stops 2 EPSP triggering an action potential?
Adding a coincident IPSP
IPSP
Inhibitor postsynaptic membrane potential
EPSP
Excitatory postsynaptic membrane potential
What governs output of a neuron?
Summation of EPSPs/IPSPs
What prevents a neuron from firing?
IPSP
What determines level of excitation of a neuron?
Dendrite structure and synapse location
What does the strength of postsynaptic membrane potential depend on?
Placement of excitatory or inhibitory nature of the inputs
What length spines of dendrites produce a lower EPSP?
Longer spine
Electrical activity in dendrites:q
EPSP and IPSPs are passive electrical activity - set axonal response
What forms of electrical activity in dendrites are active self propagating?
The dendritic spike
What do dendritic spikes do?
Boost the depolarisation in dendrites
Can leak into cell body to stimulate an action potential
When do dendritic spikes especially occur?
When stimulation is intense in space or time (coincidence detection)
What can dendritic spikes do on post synaptic membrane?
They can act locally on post synaptic membranes
Generate long term potentiation - in learning and memory
What’s involved in post synaptic integration?
Computation
What is computation?
Spatial and temporal summation of multiple PSPs / dendritic spikes is required to achieve threshold
Includes effects of dendritic spine and tree morphology
What does post synaptic integration act as?
Decision making process
What is memory due to?
Strengthened synapses
New synapses
What does long term potentiation include?
EPSP is increased
What may result in stronger synapses?
Increased neurotransmitter release
Increased sensitivity
Increased number of receptors
Increased size of post synaptic machinery
What causes reception of signals?
Highly branched processes
Dendrite tree and dendritic spines
What is long term potentiation associated with?
Making new synapses in vivo on dendritic spines
What is long term potentiation?
Synaptic connections become stronger with frequent activation
What’s involved with the formation of a new dendritic spine?
Filopodia formation
Thin spine formation - formation of new synapse
Spine head widening
Multiple spine formation - increase in synaptic transmission
What does neuroplasticity result in?
Stronger/weaker synapses
More/less synapses
How does neuroplasticity to result in stronger synapses?
Upregulation of neurotransmitter secretion
Receptor expression
Phosphorylation control (signalling)
How ones neuroplasticity result in more synapses?
Sprouting
Branching
Dendritic spine formation
What is changes in synaptic transmission driven by?
Local signalling pathways
What is structural changes driven by?
Signalling to the nucleus - driving transcription
What is Hebb’s learning rule?
That there is a learning pathway to a sequence
Learning is a predicting sequence
How does Hebb’s learning rule suggest synapses strengthen/stabilise?
Correlated pre/postsynaptic activities
How does Hebb’s learning rule suggest synapses weaken?
Uncorrelated pre/postsynaptic activities
What may synaptic change be due to?
Increases and decreases in synaptic strength leading to behavioural plasticity
What is similar between behavioural learning and synaptic plasticity?
Temporal and molecular properties
What does behavioural learning appear to use?
Similar underlying cellular and molecular mechanisms
E.g. addiction
What do addictive drugs cause?
Large release of dopamine in reward centre
What does dopamine do in addictive drugs?
Reinforces repeat and return behaviours to the drug
What seems to be the start of behavioural changes in Addie drugs?
Synaptic plasticity in glutaminergic synapses
What can addictive drugs do to the frontal lobe?
Less active executive control
Why is normal dose of pleasure less effective in addictive drugs?
Down regulation of transmission (reduced vesicles)
Down regulation of reception (reduced receptors)
Examples of multi-neuron networks:
Feedforward excitation and inhibition
Lateral inhibition
Feedback/recurrent excitation and inhibition
Convergence/divergence
What do inhibitory microcircuits include?
Interneurons
Short axons
Fast acting
Inhibition mostly by GABA
Location of central pattern generators:
Spinal cord (+elsewhere)
What do central pattern generators do?
Communication in white matter in spinal cord
What’s involved in regional specialisation and communication?
Central pattern generators
Give an example of an inhibitory interneurons:
Stimulation of touch can help block transmission of pain impulses to brain
What results in a higher degree of convergence in a neuron?
More dendrites
What is neuronal divergence?
Information from a single neuron is passed to a number of other neurons simultaneously
No loss of signal strength
