Synaptic plasticity is associated with structural and morphological changes in spines. In turn, these changes in synaptic weights are provided mainly by the insertion/removal of AMPA-type glutamate receptors in the post-synaptic membrane and a change in their conductance. At the same time, it is believed that changing the size of the spines on which the synapses are located does not directly affect the change in the input signal. A model has been proposed to demonstrate that structural changes in spines are an important factor in synaptic plasticity and vice versa. However, some experiments contradict this conclusion. Here, we explain how one plasticity type, with the inhibition of the other, can nevertheless be observed in the experiments. As a result, some new molecular mechanisms involved in plasticity in spines are proposed.