Why are neurons called excitable cells? Mention special features of the membrane of the neuron.

Neurons are called excitable cells because these membranes are in a polarised state. Different types of ion channels are present in the neural membrane, i.e., are selectively permeable to different ions.
When a neuron is suitably stimulated an electric disturbance is generated, which swiftly travels along its plasma membrane. 
Arrival of the disturbance at the neuron's ending or output zone, triggers events that may cause stimulation of adjacent neuron. These are excitable cells due to differential concentration gradient of ions (specially natural ${\mathrm{K}}^{+}$) across the membrane.
The special features of membrane of neuron are
(i) Excitability Neurons are able to percieve stimulus and enter a state activity caused by change in electrial potential difference across its covering membrane.
(ii) Conductivity Change in potential difference, spreads through the membrane to the whole neuron.
(iii) Connectivity Neurons are connected to several others, receiving and transmitting impulses to various directions.
(iv) Response The processed message may elicit a response in the form of a sensation.