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A Level Biology: Homeostasis 5 – ADH
Hi! Welcome to the second part of this video presentation on Osmoregulation. Today, we
are going to be looking at ADH.
First of all, some brief points to remember about ADH, as well as, in Osmoregulation.
The first point is that we gain water through our food and our drink and we also produce
water during respiration. Water is also lost through urine, feces, sweat and the water
vapor which we breathe out.
Now, there needs to be a balance between water gained and water lost. If there is an imbalance,
then it might cause ourselves to either gain or lose water through osmosis. Now, remember
that osmosis is the movement of water across a partially permeable membrane. It adds water
to an area where there’s less water.
The hormone ADH is produced in the pituitary gland which is located just below the hypothalamus
and this controls how much water is reabsorbed back into the blood within the kidney nephrons.
Why is osmoregulation so important?
If you take up blood cells for example, if we drink too much water then what can happen
is that our blood plasma becomes less concentrated. If that happens, then our cells might take
on water and cause them to burst. If we drink too little water, then our blood plasma might
become more concentrated, therefore our red blood cells lose water which causes them to
shrink and shrivel.
Here you got a diagram showing you the net flow of water moving from left to right. The
reason being that here, you got an area of high water concentration to an area of low
water concentration. The reason this area is lower is because there is a higher sugar
concentration here. (Pointing to the right part of the diagram.)
We are going to look at how ADH actually regulates blood water. Here you got the normal levels
and if there is a change from that stable level, if there is too little or too much,
that changes are detected by receptors. Information is then sent to the hypothalamus which is
the control center which tells it to stimulate either more ADH in the case of there being
too little or less ADH if there is too much water. If there is too much water, then less
ADH is released, which means that less water gets reabsorbed by the kidneys. Therefore,
you are going to get a less concentrated urine. If you got too little water in the blood,
more ADH is released and more water gets reabsorbed and you are going to have a more concentrated
urine. If you just go by color, this one would be more yellow and this one would be less
yellow.
Some key points to remember about ADH is that a.) It controls osmoregulation; b.) It’s
a hormone so it is a chemical messenger if it travels through the blood; and c.) It does
a very similar job to nerves but obviously it is a lot slower acting.
That concludes the short presentation. I hoped you enjoyed it. Don’t forget to keep a lookout
for some more videos coming out soon.
[end of audio – 03:53] A Level Biology: Homeostasis 5 - ADH
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