L5 - Synaptic Transmission Flashcards
What are the five steps that allow for synaptic transmission from one neuron to the next in the central nervous system?
1) an action potential depolarises the axon terminal
2) the depolarisation opens voltage-gated Ca2+ channels and Ca2+ enters the cell
3) calcium entry triggers exocytosis of synaptic vesicle contents
4) neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell
5) neurotransmitter binding initiates a response in the postsynaptic cell
How is neurotransmitter packaged into the synaptic vesicles?
the synaptic vesicles have transporters for the neurotransmitter they carry and utilise active transport for packaging
Why is calcium able to enter the cell during synaptic transmission when the membrane potential is at its peak?
this is because calcium has a very positive equilibrium potential meaning that it almost always enters the cell if permeability allows for that to happen
How is neurotransmitter removed once it has activated the necessary response?
re-uptake or breaking the neurotransmitter down using enzymes
What are five ways in which a drug could interact with/affect synaptic transmission?
1) activate/inhibit the receptors directly
2) imitate the neurotransmitter
3) blocking reuptake of the NT
4) causing spontaneous release of the NT
5) blocking the release of the NT
What are the two (broad) types of neurotransmitter and what is their effect? (E/I)
excitatory neurotransmitters: lead to a small depolarisation in the target cell
inhibitory neurotransmitters: lead to a small hyperpolarisation in the target cell
What are the two (broad) types of neurotransmitter receptor?
ionotropic (ligand-gated ion channels) and metabotropic (G protein-coupled receptors)
What is an ionotropic receptor?
an ion channel which opens and allows a specific ion to pass through when it comes in contact with the neurotransmitter
What is a metabotropic receptor? How does it work?
a G protein-coupled receptor which, when in contact with neurotransmitter, initiates a series of intracellular events (e.g upregulation of receptor expression, opening nearby ion channels, etc.)
What type of receptor is muscarinic?
G protein-coupled receptors
What type of receptor is nicotinic?
ionotropic receptors (Na+, K+)
What solution if added to the ECF would still enable a neuron to generate action potentials, but prevent it from releasing neurotransmitter?
low Ca2+, high Mg2+
Which type of neuron excites skeletal muscle fibers?
ɑ-motor neurons
What is the major difference in the action potential transmission between CNS neurons and a neuromuscular junction?
between CNS neurons there is no guarantee that an action potential in the presynaptic cell will result in an action potential in the postsynaptic cell, however in the neuromuscular junction an action potential will always be transmitted
Which type of receptors are found on the postsynaptic side of a neuromuscular junction? Are there lots of receptors or not many?
nicotinic (ligand-gated sodium channel) receptors are found in very high quantities (the postsynaptic side has a very large SA)
