The electrical stimulation of a dorsal root fiber that synaptically connects with a motoneuron is observed to cause an electrotonic depolarization of the postsynaptic motoneuron. Which of the following changes in ion channels is the most likely cause for this depolarizing potential?
a. Opening of ligand-gated cation channel
b. Opening of voltage-gated anion channel
c. Closing of ligand-gated cation channel
d. Closing of volta

a. Opening of ligand-gated cation channel

Explanation:

Ligand-gated cation channel get opened as a result of binding or connection of a lidand which itself is a result of response stimulus. It can also be opened through a note response of stimulus called voltage gated channels.

The purpose of this phenomenon is to allow passage of ions through the membranes as a result of connection of chemical messenger such as neurotransmitter.

When the neurotransmitter is released into synaptic cleft, it connects or bind with motoneuron, thus causing the movement of ion through the cell membrane, and which then leads to hyperpolarization or depolarization

d, i believe because of it's activity level