During pregnancy, oxytocin causes labour contractions to begin. Oxytocin also is released when a woman's breasts are stimulated by suckling or pumping, causing milk to move from the ducts and out the tiny holes in the nipple let-down reflex. In the first few days after delivery, oxytocin also causes uterine contractions that help shrink the uterus back to its pre-pregnancy size. After breastfeeding is established, your body may release oxytocin when you hear a baby cry, think of your baby, or have sexual intercourse.
When this occurs, your breasts may leak milk whether or not you are actively breastfeeding or pumping. Your body may not release oxytocin when you are anxious, embarrassed, or distracted. You may need to breastfeed in a relaxing, quiet, familiar, private place for let-down to occur. The most important stimulus for release of hypothalamic oxytocin is initiated by physical stimulation of the nipples or teats. The act of nursing or suckling is relayed within a few milliseconds to the brain via a spinal reflex arc.
These signals impinge on oxytocin-secreting neurons, leading to release of oxytocin. Watch someone milk a cow, even with a machine, and what you'll see is that prior to milking, the teats and lower udder are washed gently - this tactile stimulation leads to oxytocin release and milk ejection.
A number of factors can inhibit oxytocin release, among them acute stress. For example, oxytocin neurons are repressed by catecholamines , which are released from the adrenal gland in response to many types of stress, including fright. As a practical endocrine tip - don't wear a gorilla costume into a milking parlor full of cows or set off firecrackers around a mother nursing her baby. Both the production of oxytocin and response to oxytocin are modulated by circulating levels of sex steroids.
The burst of oxytocin released at birth seems to be triggered in part by cervical and vaginal stimulation by the fetus, but also because of abruptly declining concentrations of progesterone.
Another well-studied effect of steroid hormones is the marked increase in synthesis of uterine myometrial oxytocin receptors late in gestation, resulting from increasing concentrations of circulating estrogen.
Antidiuretic Hormone. Hypothalamus and Pituitary: Introduction and Index. Updated Current research is focused on examining the role of oxytocin in various disorders including addiction, depression , post-traumatic stress, anxiety and anorexia.
Oxytocin production and secretion is controlled by a positive feedback mechanism where release of the hormone causes an action that stimulates more of its own release. For example, when contraction of the uterus starts during childbirth, oxytocin is released. This stimulates more contractions and more oxytocin to be released.
In this way, contractions increase in intensity and frequency. There is also a positive feedback involved in the milk-ejection reflex. Stimulation of the nipple during breastfeeding leads to increased oxytocin production and secretion into the blood, which then causes milk to be let down into the breast.
The positive feedback cycle is maintained until the baby stops suckling. The production of oxytocin during childbirth is also self-limiting; release of the hormone is stopped once the baby is delivered. At present, the implications of having too much oxytocin are not clear. This may cause difficulty in passing urine.
It may be possible to treat this condition by manipulating oxytocin levels; however, more research is needed before any possible treatments are available. Similarly, it is not fully understood at present if there are any implications of having too little oxytocin in the body. A lack of oxytocin in a nursing mother would prevent the milk-ejection reflex and prevent breastfeeding.
Low oxytocin levels have been linked to autism and autistic spectrum disorders e. Asperger syndrome — a key element of these disorders being poor social functioning.
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