Question

Explain nerve irritability and conductivity. Include resting state of the neuron, depolarization, propagation of the action potential, repolarization, and communication at the synaptic cleft. Include also the ions involved and a specific neurotransmitter.

Answer 1

Sounds like someone hasn't been paying attention in class....

You should really read up on this yourself since you're basically asking for a summary of the first half of a university class on neurophysiology.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/ExcitableCells.html

But..... the ions involved are primarily Sodium (Na+) and Potassium (K+). The resting state of the neuron is due to the fact that you have a lot of negative charges inside the cell and the cell is only slightly permeable to sodium, so it is sequestered outside of the cell, thereby separating positive from negative charges. Resting potential is usually around -70mV.

Propagation of an action potential is due to sodium influx bringing the inside of the cell near threshold to depolarize voltage gated channels further downstream of the open one, so each time sodium comes in, it will bring the cell to threshold and then continue to excite the cell, potassium will then leave, but there will still be enough sodiums inside the cell that they're repelled by the sodium that entered further upstream so they move downstream depolarizing and opening more and more voltage gated sodium channels etc...

Communication at synaptic cleft? Presynaptic neuron releases neurotransmitter who binds to a receptor on the postsynaptic cell, and that can either be an ionotropic receptor meaning that a voltage gated channel will then open as well, or a metabotropic receptor meaning that then a second messenger system would then be needed to engage a cascade effect inside the cell to open the ion channels to generate an EPSP/IPSP (excitatory/inhibitory post-synaptic potential)...