Master Posterior Pituitary with Picmonic for Physician Assistant

The posterior pituitary is an endocrine gland primarily composed of the nerve terminals of axons extending from the hypothalamus. It is important in the neuroendcrine reflex, which occurs when sensory neurons are stimulated resulting in action potential in hypothalamic cells and exocytosis of hormones from the posterior pituitary. Vasopressin is one of the hormones released from the posterior pituitary. Vasopressin is synthesized in the hypothalamus but stored in the posterior pituitary and released in response to synaptic input from osmoreceptors that detect increased osmolality of blood plasma. This hormone affects the kidney into retaining more water and also can constrict blood vessels. The second hormone released from the posterior pituitary is Oxytocin. It is released via a neuroendocrine reflex in response to stimulation of the nipples during breastfeeding that causes the mammary glands to contract and release milk. Stimulation of the nipples causes action potential generation in the oxytocin cells of the hypothalamus, which travels down to the nerve endings in the posterior pituitary and results in the exocytosis of Oxytocin. It also causes uterine smooth muscle contraction during the second and third stages of labor.