What are the references and years they discovered the 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.

Answer 1

The importance of sodium (Na+) and potassium (K+) ions in excitable cells for the transmission of impulses was first discovered in the late 19th and early 20th centuries.

In the late 1800s, German physiologist Wilhelm Kühne discovered the presence of sodium ions in excitable cells through experiments with muscle tissue. He found that sodium plays a critical role in the generation and conduction of electrical impulses in muscle cells.

In the early 20th century, British physiologist Alan Hodgkin and Australian physiologist Andrew Huxley conducted groundbreaking research on the role of sodium and potassium ions in nerve cells. They discovered that sodium ions are responsible for generating action potentials in excitable cells, while potassium ions are crucial for repolarizing the cell membrane after an action potential.

In an unmyelinated post-synaptic neuron, the events at the neuronal junction begin with the release of neurotransmitters from the presynaptic neuron into the synaptic cleft. These neurotransmitters bind to receptors on the post-synaptic neuron, causing a change in membrane potential. This change in membrane potential triggers the opening of Na+ channels, allowing Na+ ions to enter the cell and depolarize the membrane.

This depolarization activates voltage-gated Na+ channels along the length of the neuron, leading to the generation of an action potential. The influx of Na+ ions into the cell further depolarizes the membrane, causing a rapid and self-propagating change in membrane potential.

Once the action potential reaches the end of the neuron, voltage-gated K+ channels open, allowing K+ ions to leave the cell and repolarize the membrane. This repolarization restores the resting membrane potential and allows the neuron to transmit the signal to the next neuron in the circuit.

In conclusion, sodium and potassium ions play a crucial role in the transmission of impulses in excitable cells, including unmyelinated post-synaptic neurons. The coordinated movement of these ions across the cell membrane is essential for generating and propagating action potentials, enabling the communication of signals throughout the nervous system.