2.9.5 Regulating Water Content in the Blood Flashcards
What is Osmoregulation
Osmoregulation is the process of maintaining water and salt concentrations (osmotic balance) across membranes within the body
Give an example of Homeostasis in the human body
Osmoregulation
What is the cytoplasm of all cells largely composed of?
water
- as is the blood plasma
Why is maintaining water levels in the body vital
to prevent harmful changes occurring to cells of the body as a result of osmosis
If body cells lose or gain too much water by osmosis they do not function efficiently, why?
1. Too much water in the blood results in cells swelling as water moves into them, this has a diluting effect and can lead to cell lysis (bursting)
There are two sources of water in the body, what are they?
Water produced as a result of aerobic respiration
Water in the diet
Water is lost from the body in the following ways;
Via the lungs during exhalation (breathing out)
Lost from the skin as sweat (along side mineral ions and urea)
Can water lost through the lungs or skin be controlled?
cannot be controlled
the volume of water lost in the production of urine can be controlled by, what?
the kidneys
Water reabsorption occurs along, what?
the nephron tubules in the kidneys
The control of water reabsorption by the tubules is an example of, what?
negative feedback
What is negative feedback
When the feedback causes the corrective measures to be turned “off”, so returns the system to its original or (normal) level
If the water content of the blood is too high then less water is reabsorbed, if it is too low then more water is reabsorbed, what hormone is this controlled by?
the hormone ADH
What releases the hormone called ADH
the pituitary gland in the brain constantly releases a hormone called ADH
How much ADH is released?
depends on how much water the kidneys need to reabsorb from the filtrate
What does ADH affect?
the permeability of the tubules to water
If the water content of the blood is too high, what happens?
- The pituitary gland releases less ADH which leads to less water being reabsorbed in the tubules of the kidney (the tubules become less permeable to water)
- As a result, the kidneys produce a large volume of dilute urine
If the water content of the blood is too low, what happens?
- The pituitary gland releases more ADH which leads to more water being reabsorbed in the tubules of the kidney (the tubules become more permeable to water)
- As a result, the kidneys produce a small volume of concentrated urine
Urine produced by the kidneys contains a mixture of, what?
- Urea
- Excess mineral ions
- Excess water
The colour and quantity of urine produced in the body can change quickly, how so?
- Large quantities of urine are usually pale yellow in colour because it contains a lot of water and so the urea is less concentrated
- Small quantities of urine are usually darker yellow/orange in colour because it contains little water and so the urea is more concentrated
There are various reasons why the concentration of urine will change, including, what?
- Water intake – the more fluids drunk, the more water will be removed from the body and so a large quantity of pale yellow, dilute urine will be produced
- Temperature – the higher the temperature the more water is lost in sweat and so less will appear in the urine, meaning a smaller quantity of dark yellow, concentrated urine will be produced
- Exercise – the greater the level of exercise, the more water is lost in sweat and so less will appear in the urine, meaning a smaller quantity of dark yellow, concentrated urine will be produced
