milk letdown reflex

in mothers who are nursing, an automatic release of milk from sacs within the mammary glands in response to infant suckling or associated stimuli (e.g., the infant’s cry). The milk letdown reflex is regulated by the hormone oxytocin: Suckling stimulates the production of oxytocin, which in turn stimulates contractions of the smooth muscle myoepithelial cells surrounding the mammary glands, leading to the expulsion of milk from the sacs into ducts that converge on the nipples. The actual production of milk by the mammary glands is regulated by the hormone prolactin. Also called milk ejection reflex.

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Psychology term of the day

November 18th 2024

recessive allele

the version of a gene (see allele) whose effects are manifest only if it is carried on both members of a homologous pair of chromosomes. Hence, the trait determined by a recessive allele (the recessive trait) is apparent only in the absence of another version of that same gene (the dominant allele). The term autosomal recessive is used to describe patterns of inheritance in which characteristics are conveyed by recessive alleles. For example, Tay–Sachs disease is an autosomal recessive disorder.