In order to estimate thermal fluctuations in erythrocyte and mechanoreceptor membranes the transverse fluctuations of plane and spherical bilayer membranes and the fluctuations of the surface of a part of such a membrane, possessing disc shape of the radius R are calculated. The obtained values of the transverse fluctuations are two orders smaller than in the paper . Total plane fluctuations of the disc with R=5.10(-7) cm are some orders higher than the threshold values epsilonpi of relative deformation in mechanoreceptor membranes, but their value in the frequency range of 0 dividied by 20 kHz is of the same order as epsilonpi. The estimates of fluctuations are also produced for Pacinian corpuscle membrane and for the globular protein molecule. The conditions necessary for high sensitivity of mechanoreceptor membranes are the large value of Young modulus E and low membrane viscosity eta.