Final answer:
After a neurotransmitter binds to a receptor on a postsynaptic neuron, a sequence of events occurs including graded potential, action potential firing, exocytosis, local current flow, saltatory conduction, and opening of voltage-gated channels.
Step-by-step explanation:
The sequence of events after a neurotransmitter binds to a receptor on a postsynaptic neuron is as follows:
- The neurotransmitter binds to the receptor on the postsynaptic membrane, causing a ligand-gated ion channel to open.
- Graded potential occurs, which is a change in the electrical potential of the neuron due to the entry of ions through the opened ion channel.
- If the graded potential reaches the trigger zone and reaches a threshold, an action potential is fired.
- The depolarization of the postsynaptic membrane causes voltage-gated ion channels to open. In this case, voltage-gated Na+ channels open, allowing Na+ ions to enter the cell, further depolarizing the membrane.
- Exocytosis occurs, which is the release of neurotransmitter molecules from the presynaptic neuron into the synaptic cleft.
- Local current flow occurs, which is the movement of ions along the neuron.
- If the postsynaptic neuron reaches the axon hillock, voltage-gated Ca2+ channels open due to the depolarization of the membrane. This allows Ca2+ ions to enter the cell.
- Saltatory conduction occurs, which is the rapid propagation of action potentials along a myelinated axon.
- If the membrane potential of the postsynaptic neuron reaches the threshold, voltage-gated K+ channels open, allowing K+ ions to leave the cell.