Have the patient repeat this movement with the other foot. An inability to perform this motion in a relatively rapid cadence is abnormal. The heel to shin test is a measure of coordination and may be abnormal if there is loss of motor strength, proprioception or a cerebellar lesion. If motor and sensory systems are intact, an abnormal, asymmetric heel to shin test is highly suggestive of an ipsilateral cerebellar lesion.
Auxins promote stem elongation, inhibit growth of lateral buds (maintains apical dominance). They are produced in the stem, buds, and root tips. Example: Indole Acetic Acid (IA). Auxin is a plant hormone produced in the stem tip that promotes cell elongation.
And the mechanism that's thought to be behind it is brilliantly simple. Cells in the root and shoot tips contain little packets of starch, called statoliths. The starch is dense so the statoliths always settle at the bottom of the cell. The position of the statoliths determines which direction auxin is released in. Tilting the plant on its side makes the statoliths roll and settle on the side of the cells, causing auxin to be released in that direction, and the cells there to elongate.