Lecture 24- EPSPs, IPSPs, Synaptic Integration Flashcards
What is an EPSP?
Excitatory Post Synaptic Potential
A postsynaptic potential that makes the postsynaptic neuron more likely to fire an action potential
The first step in EPSP is _____. Neurotransmitter opens ______ gated _______ channels
The first step in EPSP is GENERATION. Neurotransmitter opens LIGAND gated IONOTROPIC channels
In the second step of EPSPs, EPSPs propagate along the ______ region membranes towards the ______ _____
In the second step of EPSPs, EPSPs propagate along the INPUT region membranes towards the TRIGGER ZONE
In the third step of EPSPs, many EPSPs must ______ to drive the membrane potential to _______
In the third step of EPSPs, many EPSPs must SUMMATE to drive the membrane potential to THRESHOLD
In the fourth step of EPSPs, EPSPs must be coordinated in ______ and _____ in order to summate
In the fourth step of EPSPs, EPSPs must be coordinated in SPACE and TIME in order to summate
What type of neurotransmitter is predominate in the CNS?
Glutemate
What are ligand gated ionotropic channels?
Transmembrane proteins in the postsynaptic membrane
What two roles do the ligand gated ionotropic channels carry out?
- Bind to the neurotransmitter
- Open ion channels in receptor protein
What happens after the vesicle releases neurotransmitter into the synaptic cleft?
Neurotransmitter binds to receptors which opens channels for Na+ to fall through (depolarization)
Where are voltage gated channels located in a neuron?
Conductive region
NOT the cell body/dendrites
Where are ligand gated channels located in a neuron?
Input region/dendrite
What is membrane resistance (Rm)
Resistance of the movement of ions across a membrane
How does fewer leak channels affect Rm?
Increases/higher Rm
How does many leak channels affect Rm?
Decreases/lowers Rm
Why does having more leak channels lower membrane resistance?
All the positive charge exiting through leak channels leaves the membrane flimsy
What is the amplitude of the potential arriving at the trigger zone largely dependent on?
The number of leak channels in the membrane
What does the number of leak channels in the membrane determine?
Membrane resistance
How does many leak channels/lower Rm affect EPSPs?
EPSPs are decayed by the time it reaches the Trigger Zone
How does few leak channels/higher Rm affect EPSPs?
Higher chance of EPSPs arriving at the Trigger Zone
What inhibitory process regulates leak channels? How does this work?
Cl- inhibitory synapses
Opening Cl- channels reduces Rm which allows control over opening the channels
What are the excitatory synapse steps?
- NT released
- NT binds to receptor
- Receptor channels open
- Ions enter
- Channels close
- NT comes off receptor
- Astrocytes lower concentration of NT
What is the EPSP amplitude proportional to?
Membrane resistance
High Rm=high chance of EPSP reaching Trigger Zone=higher amplitude of potential
What is the time constant equation?
T=RmCm
Tau=Membrane Resistance x Capacitance
What does it mean if Tau is shorter?
Narrower time frame for EPSPs to summate/add together
What does it mean if Tau is longer?
Longer time frame for EPSPs to summate/add together
What aspect does membrane resistance have an effect Tau?
Duration
What aspect does membrane resistance have an effect voltage?
Amplitude
How does increasing inhibitory synapses affect summation?
The IPSP lowers the membrane potential by increasing Cl- channels, reducing the likelihood of action potentials
Are cation and anion channels inhibitory or excitatory?
Cation=excitatory
Anion=inhibitory
Cl- is an anion channel that is inhibitory
