What are the references and years of sodium (Na+) and Potassium (K+) are critically important ions in excitable cells for the transmission of impulses. Discuss this statement in an unmyelinated post-synaptic neuron, beginning with the events at the neuronal junction.
Sodium (Na+) and Potassium (K+) ions are critically important in excitable cells, including neurons, for the transmission of impulses. In unmyelinated post-synaptic neurons, the events at the neuronal junction start with the release of neurotransmitters from the pre-synaptic neuron into the synaptic cleft. These neurotransmitters then bind to receptors on the post-synaptic neuron, leading to the opening of ion channels.
One of the most common types of ion channels involved in the transmission of impulses in neurons is the ligand-gated ion channel. When neurotransmitters bind to the receptors on the post-synaptic neuron, these ion channels open, allowing the influx of Na+ ions into the cell. This influx of Na+ ions depolarizes the membrane potential of the post-synaptic neuron, triggering an action potential.
The depolarization of the membrane potential also leads to the opening of voltage-gated ion channels, allowing even more Na+ ions to enter the cell. This further depolarizes the membrane potential, propagating the action potential along the length of the neuron.
Once the action potential reaches the axon terminal of the post-synaptic neuron, voltage-gated Ca2+ channels open, leading to the influx of Ca2+ ions into the cell. This influx of Ca2+ ions triggers the release of neurotransmitters from synaptic vesicles, which then diffuse across the synaptic cleft to bind to receptors on the next neuron in the circuit, continuing the transmission of impulses.
At the same time, the action potential in the post-synaptic neuron also triggers the opening of voltage-gated K+ channels, allowing K+ ions to flow out of the cell. This efflux of K+ ions repolarizes the membrane potential, returning it to its resting state and allowing the neuron to receive and transmit further impulses.
Overall, the coordinated movements of Na+ and K+ ions play a crucial role in the transmission of impulses in unmyelinated post-synaptic neurons by depolarizing and repolarizing the membrane potential, facilitating the propagation of action potentials along the length of the neuron and the release of neurotransmitters at the synaptic junction.