Hormones & Psychology: Oxytocin (Part 1)

I find it crucial to discuss the endocrine system (hormonal system) and its role in behavior. I am quite disappointed that it is not a mandatory subject covered when doing a major in Psychology. It is well known that the nervous system works with the endocrine system to elicit different behaviors. Where some are found to be typical of either gender (influenced greatly by the hormone levels), other behaviors are triggered by experience and the processes of cognition in the brain. The endocrine system is also concerned with the never-ending nature-nurture debate as some hormone secretions depend on your genetic make-up (i.e. predisposition) and others depend on more direct environmental factors and past learning. [We know both genetic factors and environmental are responsible for behavior, therefore we should now focus on to what extent.] In that matter, as the nervous system elicits fast responses depending on the external stimuli, the endocrine system concerns itself with more bureaucratic (i.e. slow cascades of responses) with a few exceptions of course.

What is important to know about the connection between the nervous system and the endocrine system is that they communicate through the hypothalamus (a structure deeper in the brain that is not called a gland but that does secrete many hormones as well).When the hypothalamus secretes a hormone to release in the body or to trigger a cascade of other hormones in the body, this hormone has to pass by the gate called the pituitary gland in order to end up in the blood stream. Substances in the brain are highly controlled and separated from other substances in the rest of the body by the brain-blood barrier (a preventive measure in order to protect the brain from harmful substances). However, you might have guessed that drugs do end up fooling this barrier in order to elicit their effects on the brain. By now, I probably suffocated you with biology… In any case, I would like to discuss, now all that being said, about the hormone oxytocin and its role in behavior.

I haven’t yet done or found a good literature review on the subject of oxytocin. However, I would use a great book published recently on that matter (see its source below). Basically, oxytocin is made by the hypothalamus and secreted by the pituitary gland in the blood stream. Also, when I first learned about oxytocin, I was very intrigued that this hormone is one of the few exceptions that generate a positive feedback on its control center: the hypothalamus. In other words, upon secretion of oxytocin, high levels of this hormone will trigger even more release of that hormone. This being in contrast with most hormones that have a negative feedback on the brain, meaning that a high level of those hormones will trigger the brain to release less precursors (being hormones that will transform in another hormone) or other releasing hormones (hormones that trigger the release of another hormone). One of the major roles of oxytocin is of course during labor when you can understand the importance of a positive feedback as the contractions are getting stronger and more frequent. The second major role is the one of triggering the release of milk once the baby is born (mammary growth, milk production and release being controlled by the other hormones such as progesterone and prolactin). Here is a nice picture of the process of milk release by the mammary glands which is also called the oxytocin reflex or milk ejection reflex.

These bodily reactions are, as you noticed, automatic behaviors that any mother will go through and have no control over. However, some new research found that oxytocin has an important role in more complex behaviors. I would resume on this in a later post…
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BOOK SOURCE:

Neave, N. (2008). Hormones and Behaviour: A Psychological Approach. Cambridge, New York: Cambridge University Press.

I recommend you read Chapter 1 of this book since it is one of the best written summaries about the nervous system that I have read. It is concise, straightforward and covers the basic you need to know to get around in articles about the brain. Believe me I am quite annoyed with revisions and introductions on that matter and it is the first time I’ve read this part without being bored to death or pulling my hairs out.