In this paper, we investigate dynamics of voltage-gated ionic channels which are of great importance in integrating the  information received by neurons. Understanding  of dynamical behavior of voltage-gated ionic channels plays a major role for determining underlying mechanism of spike activity and predicting the neuronal behavior. Investigation is carried out based on Hodgkin-Huxley (H-H)  mathematical formalism. Ionic channel gate model is discussed briefly. Relaxation phenomenon is studied in the gate variables.  Then effects of temperature on dynamics of gate variables are examined. Finally voltage-clamped simulations are carried out to determine their dynamic behaviors based on squid giant axon.