the hypothalamus, where they synapse with oxytocinergic third-order neurons. The somas of these neurons are located in the hypothalamus, but their axon and axon terminals are located in the infundibulum and pars nervosa of the posterior pituitary, respectively. The oxytocin is produced in the neuron's soma in the supraoptic and paraventricular nuclei, and is then transported down the infundibulum via the hypothalamo-neurohypophyseal tract with the help of the carrier protein, neurophysin I, to the pars nervosa of the posterior pituitary, and then stored in Herring bodies, where they are stored until the synapse between second- and third-order neurons. Following the electrical impulse, oxytocin is released into the bloodstream. Through the bloodstream, oxytocin makes its way to myoepithelial cells, which lie between the extracellular matrix and luminal epithelial cells that also make up the alveoli in breast tissue. When oxytocin binds to the myoepithelial cells, the cells contract. The increased intra-alveolar pressure forces milk into the lactiferous sinuses, into the lactiferous ducts (a study found that lactiferous sinuses may not exist. If this is true then milk simply enters the lactiferous ducts), and then out the nipple. Afterpains A surge of oxytocin also causes the uterus to contract. During breastfeeding, mothers may feel these contractions as afterpains. These may range from period-like cramps to strong labour-like contractions and can be more severe with second and subsequent babies. Without pregnancy, induced lactation, relactation In humans, induced lactation and relactation have been observed frequently in some cultures, and demonstrated with varying success in adoptive mothers and wet nurses. It appears plausible that the possibility of lactation in women (or females of other species) who are not biological mothers does confer an evolutionary advantage, especially in groups with high maternal mortality and tight social bonds. The phenomenon has been also observed in most primates, in some lemurs, and in dwarf mongooses. Lactation can be induced in humans by a combination of physical and psychological stimulation, by drugs, or by a combination of those methods. Several protocols for inducing lactation were developed by Dr. Jack Newman and Lenore Goldfarb and are commonly called the Newman-Goldfarb protocols. The "regular protocol" involves the use of birth control pills to mimic the hormone levels of pregnancy with domperidone to stimulate milk production, followed by discontinuing the birth control and the introducing use of a double electric breast pump to induce milk production. Additional protocols exist to support an