Hypothalamus anatomically connected to anterior pituitary gland via hypophyseal portal system (blood system) Parvicellular cells are short neurons in hypothalamus that extend into hypophyseal portal system. Because they are short, use hormone secretory cells to release hormones into bvs that get carried into anterior pituitary gland. Clusters of hormone secreting cells inside anterior pituitary gland secrete hormones that go into bloodstream. Magnocellular cells are long neurons in hypothalamus that extend directly into posterior pituitary gland to release hormones. In response to those hormones, posterior pituitary gland releases their own hormones into bloodstream. 3 types of neurons in hypothalamus: magnocellular neuron: typical, wait in posterior pituitary to be released. Vasopressin aka arginine vasopressin (avp) or anti-diuretic hormone (adh) and oxytocin that act on many organs: parvicellular hypophyseotropic neuron: most neurons in hypothalamus. Cell body in hypothalamus with axon terminating in portal system in capillary bed: hypothalamic projection neurons: ordinary neurons that communicate with other neurons.