Lect 1 - Neurotransmitter Flashcards
how cells communicate synapses etc
what are the two types of synapses
- electrical - the flow of ions between cell membranes
2. chemical - communication between excitable cells. via neurotransmitters vesicles etc
what is a typical electrical synapse, where are they typically found, do they typically transmit slow or fast
gap junctions - allows small ions and molecules to pass in both directions between cells
glial cells and neurons
typically better at transmitting slow
outline the steps of chemical synapse
- neurotransmitters are made and packaged in vesicles
- action potential arrives at the terminal
- voltage-gated Ca2+ opens, and Ca2+ flood in
- Ca2+ make vesicle fuse with presynaptic membrane
- transmitters diffuse across synaptic cleft and binds to specific membranes
- bound receptors cause channels to open on postsynaptic membrane
- neurotransmitter is removed
describe how synaptic vesicles are formed
- made in ER and pass through golgi for maturation, packaging
- travels via fast axonal transport system to nerve terminal
- peptide are already in the vesicle, but non-peptide neurotransmitters are made in nerve terminal and transported into vesicle
difference in peptide v non-peptide neurotransmitter entering vesicles
pep may already be in vesilces
6 steps to synaptic vesicle hypothesis
- bunch of filled vesicles in the vicinity
- docked in active zone,ready to do
- fuse and release
- clathrin endocytosis re-internalised
- clathrin removed, moves to endosomal compartment
- new ones are made from the recycled
what is the role of Ca2, when does it enter the cell
Ca2 signals the fusion of synaptic vesicles and release of neurotransmitters
Ca2 only enters as cell is depolarizing as electrostatic charges are not favourable (but chemical gradient is)
what happens to neurotransmitters in the synaptic cleft, why is it important to also remove neurotranmittes
it will bind to receptors on the postsynaptic membrane
then excess transmitter is removed - this ensures clear directions, i.e. quickly on or quickly off
what are the 3 ways NT activates receptors, note their differences
- inotropic - ion channels aka ligand channels. transmitter bind to receptor that is a channel - these are fairly quick
metabotropic - g-protein complex, binds to receptor, then subunit goes and does something - take extra step, but downflow can be amplified (little bit of signal bit effect)
- auto-receptors - work out how much shit is there, then either inhibit release or reduce synthesis - feedback roles, regulate postsynaptic cell
how to inactivate n.transmitters
- reuptake - taken out of cleft, pumped else where. this can be achieved by the presynaptic terminal or glial cells. e.g. astrocytes removes glutamate
- degradation - breaks shit down achieved by enzymes (AChE)
- diffusion - diffuse away from site, such as peptides
what are the 3 types of postsynaptic signals
- excitatory - results in influx of Na+/K+, lead to depolarisation. e.g. ACh, Glu
- inhibitory - influx of Cl-, leads to hyperpolarization. e.g. GABA, Gly
- neuromodulatory - modulates function of surrounding cells. e.g. dopamine, serotonin
how are APs generated in the post-synaptic cell
if NT opens channels, there will be a series of either mEPSP or mIPSP that will result in Na+ or Cl- going into the cell
the sum of these PSPs must bring resting memberane potention to threshold before AP is generated
differentiate spatial and temporal summateion
spatial is different one feeding in at the same time
temporal is one after another adding up
what are motor neurons
motor neurons link CNS to the skeletal muscle
what is a motor unit
motor neuron that innervates a motor fibre
