Synaptic Transmission Flashcards
What is the function of gap junctions?
Permit ions to flow from one cell to another
Where are gap junctions present?
Myocardial cells, hepatocytes, intestinal smooth muscle ,
retinal cells and neurons
What is EPSP?
Transient depolarization in post synaptic membrane
Opening of ion channels permeable to both Na and K
What is a decrement of EPSP a function of?
Time and length constant of the membrane
Are potentials all or none in EPSP?
Potentials are graded
Summation may be temporal (t) or spatial (I)
What is the t-membrane time constant?
Time it takes Vm to move 63% of way towards final value
What makes up the temporal summation?
Rising and falling phase of the synaptic potential?
Define the membrane length constant.
Distance along a dendrite to the site where the change in Vm has decayed to 37% of its value
What properties increase the length constant?
Better insulation of membrane and conducting properties of inner core
What is electrotonic conduction?
Passive spread of voltage along neuron
What is EPSP summation comprised of?
Spatial and temporal summation
What can the temporal summation do?
Drive the membrane potential to the threshold for an action potential
Effect of changing the time constant
What are postsynaptic responses mediated by?
NMDA ionotropic glutamate receptor
What is the function of CaMKII?
Phosphorylates the AMPA receptor (1)
Trafficks AMPAR (2) and (3)
What is the effect of increasing AMPA receptors?
Results in a larger EPSP
What is the IPSP?
Hyperpolarizing response to transmitter release
Opening of Cl- channels in post synaptic membrane
What does the IPSP cause?
Membrane hyperpolarization
Stabilizes membrane potential near ECI
Increases membrane conductance - reduces size of EPSP
Define neurotransmitter.
Chemical substance secreted by a presynaptic neuron at the synapse, to act on a receptor on the postsynaptic neuron to excite it, inhibit or modify its sensitivity
What is the difference between chemical and electrical synapses?
Chemical synapses are one directional while electrical synapse transmission is bidirectional
What are ionotropic receptors?
Neurotransmitter receptors that directly open and gate ion channels
What are metabotropic receptors?
Neurotransmitter receptors that act through second messenger systems
