synaptic transmission Flashcards
Opening Na channels
depolarises the cell (excitatory)
Opening K+ channels
hyperpolarises the cell (inhibitory)
Opening Cl- channel
hyperpolarises the cell (inhibitory)
Opening Ca+ channels
depolarises the cell (excitatory)
EPSPs
excitatory post synaptic potentials
- Excitatory PSPs
○ Depolarise the membrane (more +ve)
○ Open some Na+ or Ca+ channels
○ Increases probability of AP
IPSPs
Inhibitory post synaptic potentials
Inhibitory post synaptic potentials
○ Hyperpolarise membrane (more negative)
○ Open some Cl- or K+ channels
○ Decreases probability of AP
post synaptic potentials
- PSPs are not all or nothing
- They are graded
- ESPSs and IPSPs are summed (spatially and temporally) to decided whether the neurone generates an AP
Threshold for AP generation
- If the axon trigger zone exceeds -55mV, all voltage gated Na+ channels open and AP is generated
all voltage gated Na+ channels open and AP is generated when
If the axon trigger zone exceeds -55mV
The sum of all IPSPs and EPSPs cause
either depolarisation of hyperpolarisation
IPSPs cause
hyperpolarisation
EPSPs cause
depolarisation
2 ways neurones generate PSPs
direct electrical transmission
by use of a chemical mediator
○ Direct electrical transmission
§ Rare
§ Cardiac muscle, some types of smooth muscle and some neurons
By use of a chemical mediator
§ Common
§ Neuron and muscle, neuron and neuron, sensory receptor cells and neurons
direct electrical synapses
- APs (ions) travel through gap junctions between presynaptic and postsynaptic neurons
- Synapse has gap junctions - hole in the plasma membrane of both cells where ions can flow through
○ Allows Na to flow into the post synaptic neurone
- Synapse has gap junctions - hole in the plasma membrane of both cells where ions can flow through
Chemical synapses
- Neurotransmitter molecules cross the synapse and signal the post synaptic neuron by binding receptors and inducing change
○ Glutamate decarboxylase
Takes off a carboxyl group and it changes from glutamate to GABA
choline acetyltransferase
puts Acetyl CoA and choline together to make acetyl choline
adrenaline made from
modified tyrosine
how are neurotransmitters stored
in vesicles