Lecture 5 - Synaptic Transmission I, General Features Flashcards
what is meant by the statement that ‘every single neuron is both pre and post synaptic’?
each presynaptic cell is postsynaptic to its afferent inputs
what are electrical synapses also called?
gap junctions
what is the function of electrical synapses?
to conduct ions from cell to cell very fast
what are electrical synapses opened by?
opened by voltage, pH, Ca2+ and receptors
what is the function of gap junctions?
to form pores between cells that open and close in response to a change in MP
what takes time to be synthesised in electrical synapses?
more gap junctions to modify the phosphorylation
what opens the pores of gap junctions?
a conformational change
what are chemical synapses?
the synapse where neurotransmitter is released via exocytosis
what is the relationship between chemical synapses and vesicles?
neurotransmitter exocytosed from a chemical synapse is not always packaged into vesicles
what is gaseous neurotransmission?
gaseous transmitters that diffuse out of a cell of origin and directly into other cells, that can act inside the cell of origin or in a distant cell from the point of release
what are the 2 types of synaptic integration?
temporal summation and spatial summation
what is temporal summation?
the summation between excitatory postsynaptic potentials (EPSP’s) from the same presynaptic input that occur close enough together in time
what is an excitatory postsynaptic potential (EPSP)?
the change in membrane voltage of a postsynaptic cell following the influx of positive ions (usually Na+) as a result of the activation of ligand-gated ion channels
what is spatial summation?
the summation between events that occur close enough together in space from different presynaptic inputs but still close enough in time, the summation is initiated in different dendrites
what are the 2 methods of neurotransmitter exocytosis and recycling?
classical full fusion and ‘kiss and run’ fusion
what is classical full fusion (neurotransmitter exocytosis and recycling)?
vesicles fuse to the membrane and get ready for release by moving to the surface to become part of the membrane, this causes the vesicle contents to spill out into the extracellular space and flatten out to look like part of the membrane
what is ‘kiss and run’ partial fusion (neurotransmitter exocytosis and recycling)?
fusion is only partial as the vesicles fuse to the membrane but do not flatten out to look like part of the membrane resulting in less diffusion of neurotransmitters
what is sublinear summation (also known as shunting)?
when excitatory postsynaptic potentials (EPSP’s) are initiated in different inputs close together on the same dendrite
what is another name for sublinear summation?
shunting
what is an example of sublinear summation/shunting?
the 3rd and 4th excitatory postsynaptic potentials (EPSP’s) start from different inputs on the dendrite but are close together therefore they add together. However, some channels are already open when the 4th EPSP starts so the summation cant just be added together by simple addition
what is synaptic modulation?
an observed change in synaptic function
how long does synaptic modulation last?
lasts seconds to minutes
what determines the length of synaptic modulation?
increased presynaptic calcium and/or neurotransmitter availability
what determines the length of synaptic modulation facilitation?
long term potentiation and depression
how long does synaptic modulation facilitation last?
with multiple presynaptic mechanisms lasts hours to days
