Veterinary Physiology-III

INTRODUCTION

• The neurohypophysis is composed of pituicytes and fine unmyelinated nerve fibres arising from the supraoptic and paraven­tricular nuclei of the hypothalamus and terminating in the neural lobe of the pituitary.
• Neurohypophyseal hormones are the secretions of neuro‑secretory cells of the hypothalamic nuclei which move along the axons of the hypothalamo‑hypophyseal tracts to the neuro-hypophysis, stored until the proper signal arises to cause their release into the circulation.
• Two octapeptide hormones are released from the neurohypop­hysis
• Antidiuertic hormone (ADH) or vasopressin produced from the supraoptic nucleus of hypothalamus
• Oxytocin produced from the hypothalamic paraventricular nucleus.
• These two hormones after their synthesis are complexed with a polypeptide known as neurophysin and transported as Hering bodies within the axons to the neurohypophysis. Neurophysin I and II aid in transport of oxytocin and ADH respectively.