मानव मस्तिष्क में 'आर्बर विटे' (Arbor Vitae - जीवन का वृक्ष) मुख्य रूप से किससे बना होता है?

Which type of neuron has a single process that divides into two branches, one acting as an axon and the other as a dendrite, commonly found in sensory pathways?

Which part of the nervous system is colloquially referred to as 'the brain in the gut'?