A theoretical and numerical analysis of the Hodgkin-Huxley equations with the inclusion of stochastic channel dynamics is presented. It is shown that the system can be approximated by a one-dimensional bistable Langevin equation. Spontaneous action potentials can arise from the channel fluctuations and are analogous to escape by a particle over a potential barrier. The mean firing rate can be calculated using Kramers' classic result for barrier escape. The probability density function of the interspike intervals can also be estimated. The analytical results compare favorably with numerical simulations of the complete stochastic system.