  Not all activities in living creatures can be explained by classical
dynamics. Application of quantum physics in biology helps to study the
unexplained phenomena in cells. More detailed research work is needed rather
than rejecting the concept of intervention of quantum physics in biology. Here
we have used some concepts introduced by Hameroff, Penrose \cite{hamer} and
some quantum models to show the quantum decoherence in neurons. Assuming a
quantum superposition of dimers in microtubules we have separately presented
two types of interaction with its environment. For interaction with bosonic
environment we have shown that the decoherence time scale depends on a constant
factor which depends on the interaction coefficients and amplitude of spectral
density. For interaction with spin environment we have pointed out one case
where the coherent superposition state of dimer is strong enough to survive
against the environmental induced decoherence.
