And certain proteins cause the taste of unami. When there is salt, we feel that it's salty. When there is sugar, we feel that it's sweet. When the pH is high, we feel that it's bitter. When the pH is low, we feel that it's sour. So about taste sensation, the stimuli is actually the chemicals in our mouth. In the same way, the cell that senses the stimuli in any part of the body is the receptor, not the neuron. The neuron is the one that transfers the message (nerve impulse) to the brain. That said, it is not the neuron that senses the taste, but the taste receptor cell. When eating, the taste receptor cells in our taste buds detect concentrations of different chemicals and fire electric signals to sensory neurons, which in turn fire a nerve impulse to the brain. So basically each anatomical structure has different functions to offer. Therefore, for instance the Purkinje cell with its huge dendrical tree acts as an integrator of many different signals. Additionally, a huge dendritic tree means that it has a lot of potential for many many connections to other neurons. Therefore, weak signals will maybe not even arrive at the soma since they decay with time. If the dendrites are long, it takes longer until they reach the soma. So the axon is responsible for the temporal delay of the signal conductance, similarily to the dendrite. If the trunk is long, then it will take longer for your friend to catch the ball, if the trunk is short, you might even be able to give it personally to your friend.

Think of the signal as a ball that you want to give your friend you let it fall. A friend of yours is sitting on the grass next to the trees roots (which is the terminals in the neuron analogy). You are sitting in the area where all the branches come together and the trunk starts, this could be the same as the soma of a neuron since all dendrites come together. Different neuron structures change the way the signal is treated and conducted.

Cell axon vs dendrite