Lactation of suckling by the baby. The milk ejection reflex (also called let-down reflex) is not always consistent, especially at first. Once a woman is conditioned to nursing, let-down can be triggered by a variety of stimuli, including the sound of any baby. Even thinking about breastfeeding can stimulate this reflex, causing unwanted leakage, or both breasts may give out milk when an infant is feeding from one breast. However, this and other problems often settle after two weeks of feeding. Stress or anxiety can cause difficulties with breastfeeding. The release of the hormone oxytocin leads to the "milk ejection" or
Period (gene) nucleus as well as areas outside the SCN. Additionally, while Drosophila PER moves between the cytoplasm and the nucleus, mammalian PER is more compartmentalized: mPer1 primarily localizes to the nucleus and mPer2 to the cytoplasm. Familial advanced sleep-phase syndrome known to be associated with mutations in the mammalian Per2 gene. People suffering from the disorder have a shorter period and advanced phase where they go to sleep in the early evening (around 7pm) and wake up before sunrise (around 4am). In 2006, a lab in Germany identified particular phosphorylated residues of PER2 that are mutated in people suffering of FASPS.