2.9.5 Regulating Water Content in the Blood

Question 1

What is Osmoregulation

Answer 1

Osmoregulation is the process of maintaining water and salt concentrations (osmotic balance) across membranes within the body

Question 2

Give an example of Homeostasis in the human body

Answer 2

Osmoregulation

Question 3

What is the cytoplasm of all cells largely composed of?

Answer 3

water

• as is the blood plasma

Question 4

Why is maintaining water levels in the body vital

Answer 4

to prevent harmful changes occurring to cells of the body as a result of osmosis

Question 5

If body cells lose or gain too much water by osmosis they do not function efficiently, why?

Answer 5

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)

Question 6

There are two sources of water in the body, what are they?

Answer 6

Water produced as a result of aerobic respiration

Water in the diet

Question 7

Water is lost from the body in the following ways;

Answer 7

Via the lungs during exhalation (breathing out)

Lost from the skin as sweat (along side mineral ions and urea)

Question 8

Can water lost through the lungs or skin be controlled?

Answer 8

cannot be controlled

Question 9

the volume of water lost in the production of urine can be controlled by, what?

Answer 9

the kidneys

Question 10

Water reabsorption occurs along, what?

Answer 10

the nephron tubules in the kidneys

Question 11

The control of water reabsorption by the tubules is an example of, what?

Answer 11

negative feedback

Question 12

What is negative feedback

Answer 12

When the feedback causes the corrective measures to be turned “off”, so returns the system to its original or (normal) level

Question 13

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?

Answer 13

the hormone ADH

Question 14

What releases the hormone called ADH

Answer 14

the pituitary gland in the brain constantly releases a hormone called ADH

Question 15

How much ADH is released?

Answer 15

depends on how much water the kidneys need to reabsorb from the filtrate

Question 16

What does ADH affect?

Answer 16

the permeability of the tubules to water

Question 17

If the water content of the blood is too high, what happens?

Answer 17

• 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

Question 18

If the water content of the blood is too low, what happens?

Answer 18

• 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

Question 19

Urine produced by the kidneys contains a mixture of, what?

Answer 19

• Urea
• Excess mineral ions
• Excess water

Question 20

The colour and quantity of urine produced in the body can change quickly, how so?

Answer 20

• 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

Question 21

There are various reasons why the concentration of urine will change, including, what?

Answer 21

• 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