<prompt> Posterior pituitary hormone secretion is mediated by:A portal capillary system from the hypothalamus to the posterior pituitaryThe fight-or-flight responseThe hypothalamo-hypophyseal tract originating from magnocellular neurons in the supraoptic and paraventricular nucleiThe reticular activating systems input to the hypothalamus  <response>: Ans. C. The hypothalamo-hypophyseal tract originating from magnocellular neurons in the supraoptic and paraventricular nucleiMagnocellular neurons of the paraventricular and supraoptic nuclei of the hypothalamus, whose axons reach the posterior pituitary via the hypothalamo-hypophyseal tract, secrete the posterior pituitary hormones. The portal capillary system from the hypothalamus to the pituitary gland is associated with the anterior pituitary. While pituitary function may be altered by the fight-or-flight response, the reticular activating system, or emotional state, none of these directly mediates posterior pituitary hormone secretion. 