Transmission between neurons Flashcards
What is a synapse?
The small gap between neurons.
Define: neurotransmitter
A chemical that carries information across the synapse between two neurons.
The presynaptic neuron’s terminal/bouton contains neurotransmitters in the…?
Vesicles.
The postsynaptic neuron has receptors that are…
Specific to a neurotransmitter.
When the AP arrives in the bouton of the presynaptic cell, …?
Ca2+ channels open and calcium floods into the bouton.
Calcium in the presynaptic bouton causes…?
The vesicles to fuse with the presynaptic membrane and release the neurotransmitter across the synaptic cleft.
What is exocytosis?
The fusion of the vesicles with the cell membrane.
The neurotransmitter diffuses across the cleft and…?
Binds onto post-synaptic neuron receptors.
The neurotransmitter binding with receptors triggers…?
A new AP (or something different depending on the neurotransmitter).
After release, neurotransmitters can be removed from the cleft by:
- Re-uptake (transporter molecules use energy to take it back into the presynaptic neuron)
- Diffusion
- Deactivation
How are neurotransmitters in the synaptic cleft deactivated?
An enzyme breaks it down into parts.
E.g. Acetylcholinesterase breaks up acetylcholine into acetate and choline.
Define: neuromuscular junction
Where a neuron joins a muscle to stimulate it.
What is curare?
A substance used in poison darts which blocks the action of acetylcholine and paralyses prey.
Name 5 neurotransmitters.
Acetylcholine (ACh) Serotonin GABA Glutamate Dopamine
What is ACh?
A neurotransmitter, found in both neuromuscular junctions and the brain, binds to nicotinic receptors which opens ion channels. Ions cross the cell membrane and initiate a second AP. At nicotinic receptors it’s fast (ionotropic) and excitatory.
What is serotonin?
A neurotransmitter found only in the brain which binds to receptors triggering G-protein. This activates a second messenger within the cell which opens the ion channels. It can also activate genes, change the synapse and cause learning. It’s slow (metabotropic) and excitatory.
Prozac increases its impact.
What is GABA?
Gamma-aminobutyric acid, a nt found throughout the brain. Binds to both fast and slow GABA receptors, which open the channels causing Cl- to cross the membrane, inhibiting the neurons.
Can neurons have multiple neurotransmitters, or multiple receptor types?
Receptor types - each neuron releases only one transmitter.
Is glutamate metabotropic or ionotrpic, and is it excitatory or inhibitory?
Ionotropic excitatory.
Is dopamine metabotropic or ionotrpic, and is it excitatory or inhibitory?
Metabotropic excitatory.
What do excitatory neurotransmitters actually do?
Sodium and calcium enter the cell, excitatory post-synaptic potential (EPSP), increases the membrane potential from -70mV making AP more likely.
What do inhibitory neurotransmitters actually do?
Potassium leaves the cell and chloride enters, inhibitory post-synaptic potential (IPSP), causes membrane potential to decrease making AP less likely.
How does a post-synaptic neuron ‘decide’ whether to send an AP?
It integrates its inputs (PSPs) and fires an AP if the membrane potential exceeds -55mV.
