Wednesday, 3 June 2009

21. Maximal model taste circuit (human).

The general arrangement of our human neural groove/tube is the same as in all chordates. It is shown in cross-section in the upper half of the diagram and in frontal and side views in the lower half.

Although the basic taste circuit has become much more elaborate than in the worm, it still serves the same purpose, has the same major components (sensory neurons, interneurons, motor neurons), makes the same kinds of connections (chemical and electrical) and, according to the formal inversion theory, employs multiples of the same kinds of circuitry (left-right bicyclic inversion).

The examples of first and last neurons shown are those concerned with selection or rejection in feeding and breathing. Taste at the back of the tongue for example is sensed by the ninth cranial nerve (marked IX) and the muscles responsible for guarding the feeding and breathing portals by reacting to such stimuli are partly supplied by the same nerve as shown.

Other details of the diagram are not required for this introduction but are described in the main publication.

Taste is of course just one of the many ways in which chordates (and worms) convert energy from the outside world into neural energy inside their bodies, a process that we shall begin to generalise for human brains in the next post.

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