7.2 Flashcards
(9 cards)
What happens once the action potential reaches axon terminals?
Conduction of signal: from presynaptic to postsynaptic neuron
Action potentials: cant jump across cells, reaches the axon terminals, stimulate release of chemical messengers (neurotransmitters)
describe the process of synapse propagation
- Action potential reaches terminal end of the pre-synaptic neuron
- Voltage gated Ca++ channels open
- Neurotransmitters exit the axon terminals via exocytosis
- Neurotransmitters diffuse across the synapse
- Neurotransmitters bind to the receptors on the post-synaptic neuron
- Post synaptic potential is stimulated
- Action potentials is initiated in the post-synaptic cell
What happens in the pre-synapses during propagation?
- Neurotransmitters are packaged into vesicles
- Vesicles mobilise and dock
- Vesicles detect a change in Ca++ concentration and bind to the membrane
- Vesicles fuse with the membrane and release the neurotransmitters into the extracellular space (the synaptic cleft)
- Empty vesicles get reabsorbed and reused
What are neurotransmitters?
Messenger molecules
Synthesised, stored and released by the neuron
Structurally classified as amino acids, amine/classical neurotransmitters, neuropeptides
Functionally classified: mode of action, resulting effect
What is the fate of neurotransmitters?
- Bind to receptors of post synaptic cells
- Destroyed by specific enzymes
- Re-absorbed by the presynaptic terminal
- Diffuse away
- Absorbed by glial cells
What can neurotransmitters exert?
Excitatory effect
Inhibitory effect
What is the excitatory effect?
NT binds to a specific postsynaptic receptor
Ligand gated Na+ channels open
Influx of positive ions into the cell
Membrane potential reaches threshold
Action potentials is initiated
Message is passed and carried on by the axon of the postsynaptic cell
What is the inhibitory effect?
NT binds to a specific postsynaptic receptor
Ligand gated Cl- channels open
Influx of negative ions into the cell
Membrane potential becomes more negative
Action potential are not initiated
Message is inhibited.
