B5 More On Controlling Water Content

Question 1

What is the hormone that controls the concentration of urine?

Answer 1

anti-diuretic hormone (ADH)

Question 2

Which gland releases ADH into the bloodstream?

Answer 2

The pituitary gland

Question 3

What are the receptors in the hypothalamus sensitive to?

Answer 3

The water content of the blood

Question 4

How does the hypothalamus control the release of ADH?

Answer 4

It processes the information it receives from the receptors and instructs the pituitary gland to release ADH into the blood according to how much s needed.

Question 5

What affect does ADH have?

Answer 5

It makes the kidney tubules more permeable so that more water is reabsorbed back into the blood.

Question 6

How is the process of water content controlled?

Answer 6

By negative feedback.

This means when the water content gets too high or too low, a mechanism is triggered that brings it back to normal.

Question 7

See p81 for a diagram about negative feedback

Answer 7

.

Question 8

Explain the stages of returning the water content to normal if water gain is detected. 3

Answer 8

Hypothalamus detects water gain

Pituitary gland release less ADH

Less ADH means kidney reabsorbed less water

Question 9

Explain the stages of returning the water content to normal if water loss is detected. 3

Answer 9

Hypothalamus detects water loss

Pituitary gland releases more ADH

ADH makes kidney reabsorbed more water

Question 10

Complete the sentence

The more water your Kidneys reabsorbed, the less water you will pass out as …….

Answer 10

Urine

So you will produce a smaller volume of urine.

Question 11

What makes urine more concentrated?

Answer 11

If the kidneys reabsorbed more water, less water will pass into the urine but the kidneys will still excrete all the waste products, so the urine will be more concentrated.

(It contains less water)

Question 12

What osmotic challenges can vary the volume and concentration of the urine?

Answer 12

Sweating and dehydration.

Excess water intake.

Question 13

What can cause you to lose water via sweat?

Answer 13

When it’s hot or when you exercise you sweat more.

Question 14

What happens when you lose water through sweating?

Answer 14

Water loss detected by receptors in hypothalamus

Hypothalamus instructs pituitary gland to release mor ADH

The kidneys reabsorbed more water, so the water content of the blood increase

Only a small volume of concentrated urine is produced.

Question 15

What does the brain do when you are dehydrated?

Answer 15

It triggers feelings of thirst, making you wants to drink more, which helps to restore the water balance in the body.

Question 16

What happens when there is excess water intake?

Answer 16

Receptors in the hypothalamus detect an increase in the blood water content

Hypothalamus instructs the pituitary gland to release less ADH

The kidneys reabsorbed less water, so lots of urine will be produced, this lowers the blood water content.

Question 17

Describe the role of ADH in the body.(3 marks)

Answer 17

ADH helps to control the blood water content (1 mark) as it increase the permeability of the kidney tubules (1 mark) which increases the amount of water reabsorbed back into the blood (1 mark)

Question 18

Explain why a person may feel more thirsty than normal on a hot day. (3 marks)

Answer 18

When it’s hot, more sweat may be produced (1 mark).
Sweat causes water to be lost from the body (1 mark).
When the brain detects the fall in the water content of the blood, it triggers feelings of thirst (1 mark)