In general, due to the cross-innervation of nerve fibres, a LMN lesion results in paralysis or weakness of both upper and lower parts of the face, whereas an upper motor neuron (UMN) lesion usually spares the upper part of the face (i.e patient can wrinkle forehead on that side). Note however that this is not always absolute.
Neurons have different shapes depending on their functions. Interneurons carry information between motor and sensory neurons. Sensory neurons carry information to the central nervous system. Motoneurons carry signals from the central nervous system to the muscles, skin, and glands and pyramidal neurons are involved with motor control and cognitive ability. health.howstuffwo...