Neuroendocrine Reflex

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來自 University of Illinois at Urbana-Champaign 的課程

Lactation Biology

3 個評分

University of Illinois at Urbana-Champaign

Lactation Biology

3 個評分

Lactation and especially milk, which is the product of that unique mammalian process, are routinely encountered within our daily lives. Nevertheless, they often are poorly understood by many, even including many who are engaged in the business of producing milk. The overall course goal is to introduce fundamental concepts that form the basis for understanding the biology of lactation, the biology of the mammary gland, and the products of that important physiological process. As a learner in this course, you will be provided with a series of easily understood presentations that collectively will help you build a foundation for greater understanding of lactation. You will be able to engage with other learners so that you can extend your learning beyond the video presentations. Ultimately, you will be able to construct your own mental model for understanding the wide range of topics that relate to the biology of lactation. Upon completion of the course, you will be prepared to expand your knowledge and understanding of lactation from other sources and experiences as you pursue your individual interests. Before you start the course, I suggest that you identify a question or several questions about lactation that you already have on your mind. This could be from your own experiences, something you read about or saw, or something you have wondered about. Write down your question(s) and use that to help you decide how to engage with the content of this course. You might engage with the modules in the order they are presented, or start with a module that is of particular interest to you, or pick and choose modules in any order. I encourage you to engage in all of the types of learning activities that this course has to offer, including but not limited to, the discussion forums, quizzes, peer-review assignments, and concept maps and other learning aids.

從本節課中

Module 7: Milk Ejection

This module introduces the physiological process known as the milk ejection reflex. The neural and endocrine pathways of this process are discussed, as is a broad overview of the hormone responsible for milk ejection, oxytocin. In addition, the consequences of ineffective milk ejection and ways that have been tried to manipulate the milk ejection process are presented.

Introduction6:14

Neuroendocrine Reflex5:04

Timing of Milk Ejection4:43

Rise in Intramammary Pressure3:26

Mammary Structure Changes During Ejection4:09

Microstucture of Milk Ejection2:21

與講師見面

Dr. Walter Hurley, PhD
Professor Emeritus
Department of Animal Sciences

[SOUND] So let's take a look and

use our cow as an example of this milk

ejection process or milk let down.

What we're going to do is to start this process,

you need to somehow stimulate the mammary gland.

And you do that by washing the teats in the case of preparing the cow for

milking machine, suckling of the young, manipulating the mammary gland,

particularly the teats.

And what that's doing is it's deforming some of the pressure sensitive nerves that

are in the teats.

Then sends nerve impulses up to the spinal cord and across to the brain.

And that's represented here by this white line on our sample cow, here.

Again, what's happening is you're causing,

firing off nerve impulses through the inguinal nerves, up to the lumbar nerves.

It comes across to the brain and things are happening in the brain.

This process that we've represented here by the white line is called

the afferent pathway.

So the afferent pathway is the neural part.

The neural part of this neuro-secretory

pathway again sometimes is referred to as neuro-secretory, neuroendocrine pathway.

This is the neural part of it.

The afferent pathway.

Then what happens is in the brain, certain things happen.

And those things we're going to explore in much more detail in the next

video in the series.

The result though is an oxytocin release from the poster pituitary

goes back by the blood and oxytocin hormone.

In this case we think it was a hormone,

going back to the blood to the mammary gland.

That's called the efferent pathway.

Spelled with an E.

That's the endocrine part of the pathway.

Again, neural endocrine pathway.

So the whole thing as we think about it as a neuroendocrine pathway.

Once it gets to the mammary gland on the other hand it's not done yet.

That's not the full process.

Oxytocin getting to the mammary gland it then has to interact with

the myoepithelial cells.

These are the myoepithelial cells.

Some examples of those.

So in this case over here this is a mouse.

And what's happened here is they've digested the tissue away enough.

And this is a scanning electron micrograph.

So, you can actually see the outside of the structure.

So these bulbous sort of things are the backside or

the outside of the epithelial cells and the alveolus.

And where the C is,

these guys right here, those are the cell bodies of the myoepithelial cells.

You can see that there's a cell body.

And then they radiated out these appendages that go in different

kind of directions.

And those then are crossing over and overlapping.

You can see that to some degree, in this case, this is from a goat.

What they used here was silver stain.

And stains of nice and black and

you can see the overlapping appendages and here's a cell body right here.

This appendages going off and again those are overlapping.

Forms a really nice basket network around the back side of the alveolus.

So when they contract, they all contract together and

will squeeze the milk out of the lumen of the alveolus.

So here's some transmission of electron micrographs of these and

secretory cells here.

Nucleus, big nucleus here, secretory components.

The lumen's going to be actually appear out of the picture.

On the other side though, on the basal side, this will be where the arrow is.

A cross section through an appendage of one of those myoepithelial cells.

This picture is simply a blow up, a bigger image of those myoepithelial cell here.

Nucleus of the epithelial cell, secretory cell and

again secretory cell would be up here.

I put this back up here, simply to remind you again this idea that these

myoepithelial cells are contracting and squeezing milk out of the lumen

of the alveolus, the lumen of the small ducts.

And just to reiterate the fact that it is not squeezing milk out of the cells,

that secretory process of milk being produced in the cell,

being secreted in the lumen is separate and independent of milk ejection.

They are completely different things.

So this is contracting.

These are contracting squeezing milk out of the lumen and

down through the rest of the mammary gland.

So let's go back and review this process.

So we'll go ahead and use this for the moment.

So we have the afferent pathway and again at the side of the neural component.

Going, sending nerve impulses, stimulating the mammary gland, nerve impulses going

to the brain, that's our neural component, our afferent pathway.

That releases oxytocin, that becomes part of the efferent pathway,

the endocrine part of this.

Goes back to the mammary gland, causes milk ejection.

The milk.

[SOUND]

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