Here are some electrophysiology essays for 1st year medicine physiology. They are definitely not 1st class essays, but can perhaps serve as a starting point if you have to write about a similar topic.
CLICK TO EXPAND: The Membrane Potential and Its Ionic Basis
CLICK TO EXPAND: Propagation of Action Potentials Along the Axon
CLICK TO EXPAND: Events at the Neuromuscular Junction