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Course: Stanford School of Medicine > Unit 1
Lesson 5: BreastfeedingBreastfeeding - Letdown Reflex
Learn how hormones help to coordinate a baby's need for milk (sucking or crying) with a woman's release of milk.
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- From1:11on, the complicated process begins and shoots up the spine and triggers several portions of the brain to react and communicate with the body. How long does this normally take? And if its the first time that a mother is feeding, does it take much longer because the body needs to exercise a pathway for the milk? I ask this as an expectant father. I also find the sympathetic production of milk (5:45) when another's child cries to be amazing.(22 votes)
- In my experience it is just a few seconds. It is about the same amount of time that it would take for you to notice pain if you nick yourself shaving. Answer to the second question: No, the breasts have gone thru a lot of changes during pregnancy to get ready to feed the baby. Sometimes pregnant women can even lactate and express milk from their breasts before the baby is born. Although this has not happened to me personally, I have seen it happen to others.(14 votes)
- How long does it take for a breast that is completely empty (say one that has just finished feeding a baby) to fill up with enough milk to nourish a baby for one "meal"?(12 votes)
- It depends on the size and the age of the baby, too. Newborns eat less, but more often, so it would be at least 45 minutes to an hour before enough milk (2 -4 ounces) can be produced. As the baby gets older and bigger, it takes longer. I have breastfed six children for their first 18 months. Drink plenty of water, get plenty of rest, and it does help to massage the breasts. It is also helpful to have a lactation consultant.(8 votes)
- Does any type of children's crying trigger the letdown reflex? For instance, if a one-year-old, a two-year-old, a ten-year-old cries, does the reflex happen?
How about sounds that are in the same general range of frequency as a baby's cry. Does that trigger the reflex?(13 votes)- Good question! I could not find anything about it in literature by a quick Internet search. I know that there are certain cries that signal pain much more strongly than hunger, and when I hear that kind of cry from a baby it does not cause the let-down effect. More like instant fight- of flight. But I don't claim to be able to know when the baby is hungry and when it's cold just from the crying.
My guess is that the relationship between age and triggering is partially cultural. When is a baby expected to be weaned, and for how long is it expected to rely almost wholly on mother's milk? I believe that the mewings of newborn babies have greater effect that those of older babies. Toddlers who are breast fed rarely cry when they are hungry if mum's around. They simply toddle over and start fumbling under her blouse.
I know that for me the needles and pins feeling of a milk let-down is evoked by hungry children of at least the age of 8-9 months, even if they don't cry, but simply start sucking their knuckles or pucker their lips and turn their head searching for the breast. But I don't get that feeling when I see a nearly two year old searching for a breast. Somewhere in between my brain evidently draws a line between "helpless baby who needs milk to survive" and "this one can manage on solid foods."
I don't know how I'd react if I saw a two year old that was clearly starving and crying, but I suspect the hormones would kick in. I don't think they would for a 4 year old in the same circumstances, but I don't know that. The let-down effect, by the way, is quite independent of the presence of milk and the ability to bear children. I first felt it shortly after reaching puberty, and still feel it even if I've stopped ovulating.(2 votes)
- If a woman has had (let me put this delicately) cosmetic enhancement done to the breast, can she still breastfeed (or, better yet, in what percentage of cases can she do so or not do so)? If not, what happens after pregnancy? How about if a woman has had a reduction?(9 votes)
- If the implants were placed behind the muscle, if the incisions made did not damage the 3rd and 4th, i believe, intercostle nerves, the chances are very good the mother can produce a full supply. However, if the reason the woman got the implants to begin with had to do with missing ductile tissue, the problem would haven nothing to do with the implants, but the anatomy of the breast to begin with. See your local IBCLC!(2 votes)
- Is the supposed rumor true, that after a woman breast feeds her baby her breasts are not as "perky" as they were before?(4 votes)
- Fat will be "eaten up" by milk production, but will return. But as VGruenewald said, the "sagging" has more to do with pregnancy and age than with breastfeeding.(2 votes)
- Do all woman have to breastfeed?(1 vote)
- Breastmilk is the most nutritious for the baby to drink.(5 votes)
- If we could initiate the hypothalamus of a male human to turn off the prolactin inhibitory cell. Could a human male breastfeed ?(3 votes)
- Lactation can be induced in men. http://en.wikipedia.org/wiki/Male_lactation(3 votes)
- Can someone explain to me what is meant by "higher" in neurobiology, as in "higher centres"? Does that mean physically higher than the hypothalamus in this case or higher as in "upstream" in this signalling pathway? I'm not familiar with this use of the word "high" but it makes me wonder why we call parts of the brain "high" or others "low".(3 votes)
- Higher is usually used as "more evolved". As in in humans are higher animals than dogs, and dogs are higher than worms etc.
In the brain Lower would point to very basic/instinctive reflexes. More complicated = higher.
The highest brain function is consciousness/thinking, and this take part in the cortex of the brain. The auditory center is in the cortex.
This reflex is still subconscious, but the brain needs to distinguish between a baby's cry and other noises, which is hard/complicated.(1 vote)
- What is the let down reflex ?? and also can u please give me the summary of the video ?(2 votes)
- Does it matter how strong a baby suckles? Or does the suckling motion trigger the hormone?(1 vote)
- Nope. The strength of the suckle doesn't matter, as long as the seal of the baby's mouth is good, the tongue movement is sufficient, and the latch is deep enought - nipple goes almost to the throat!(2 votes)
Video transcript
Voiceover: Let's talk now about
how the mother's breast knows when it's time to secrete and
make milk to feed her infant. You might guess that
it has something to do with the fact that there will be a
hungry little guy there. You're right. I'll try and draw him without
making him look like an alien. They do open their mouths very, very wide. You'd be surprised, and it
does have something to do with the fact that the
baby begins to suckle. The baby does begin to suckle, and the actual suction
of that act does help to drain milk out of the breast. Remember we had the mammary glands here that contained the milk
and they were lined by those myoepithelial
cells, and they drained toward the nipple via
the lactiferous ducts. So, yes, it does have to
do with the baby suckling, but it's actually a little
bit more exciting than that. Let me tell you why it's so exciting. In the nipple itself, are these
things called mechanoreceptors. They detect when the
baby begins to suckle, and they send messages to the
mother's brain via her spinal cord. These are ascending sensory messages
that go toward the spinal cord and up the spinal cord
to the mother's brain. They go to a part of the
brain called the hypothalamus. The hypothalamus then does
two really important things. Firstly, the hypothalamus
sends an on message, sends a go message to
another kind of neuron called an oxytocin neuron. As you can probably guess,
an oxytocin neuron releases a hormone called oxytocin,
and I'll just get my pen to start working again. There we go. Then I'll just finish writing the
word neuron over here for you. The oxytocin neuron is secreting oxytocin, and it's secreting that
hormone from the posterior part of another segment in the mother's brain. That segment is called
the pituitary gland. The oxytocin is being released from the posterior pituitary in the mother. The function of that
oxytocin hormone is to cause these myoepithelial cells to contract. Secondly, the hypothalamus
has to do something else. It has to turn off a
different kind of neuron. It's sending an off
signal to a neuron called a prolactin inhibitory neuron.
I'll write this one down for you. This is a prolactin
inhibitory cell or neuron. The prolactin inhibitory cell's
job all year round basically, is to tell the cells that make prolactin another kind of hormone
to tell them to be off. This is the prolactin inhibitory neuron, and its message is to say, "You know what? "Don't make prolactin." I'll tell you what prolactin does in a minute. Obviously, this is our prolactin-making
cell, so our prolactin cell, and what the hypothalamus does in response to this incoming information that
hey there's a hungry baby out there, the hypothalamus is going
to turn off the off signal. That is going to result in
more prolactin being secreted, and what does prolactin do?
Well, maybe you can guess from it's name, pro, meaning that it's sorry, I'm writing pro.
We don't want to do that. Prolactin is basically
pro lactin, or pro milk. It is going to cause
something called lactogenesis, or the making of milk
inside the mammary gland. Together these two things,
these two hormones, prolactin, and I'll write it
in for you here, prolactin which is being released
from the anterior pituitary, the ant. pit., and also
oxytocin that's being released from the posterior pituitary. Those two hormones are going
to cause milk to be made via prolactin and milk to
be ejected, or shot out of the lactiferous ducts via the action of oxytocin on the myoepithelial cells. Now here is the best
part. You ready for this? This whole cascade of
events can also be triggered by the sound of a baby's cry. It doesn't even have to be your baby. The sound of a baby's
cry will be picked up by a mother, a lactating mother's ear, and that information
will be sent via other sort of higher centers in the brain. I'll just write higher centers. Those are auditory centers and
other higher parts of the brain. Those higher centers will send a message to the hypothalamus saying
initiate this cascade of events and cause milk to be ejected even if a baby isn't suckling. This is kind of a back-up mechanism because it means that
potentially any lactating mother in the vicinity could
nourish any hungry child. This whole pathway, this amazing ability to communicate between
the baby and the mother is called the let down
reflex, the let down reflex.