My understanding of how neurons transmit signals is pretty basic - dendrites receive signals (both excitatory and inhibitory), transmitting them to the cell body where, if a sufficient depolarization builds up, the axon fires an action potential, sending the signal along. This entire process is carried out by various ion channels, especially voltage gated ones. My question is this - do we know how sensitive the speed and reliability of the process are to genetic variations that control how these ion channels are built? Is it robust enough to permit small variations, or is any change catastrophic? If it permits small variations, do we know how variable the human population is for features like signal fidelity (low rate for failing to fire when the neuron should, and low rate for firing in the absence of stimulus) and transmission speed?
Considering the difficulty of studying humans, is this sort of information known for mice, rats, primates, or etc?