Blood pH regulation (1.8)

Question 1

What is pH?

Answer 1

pH is a measure of the hydrogen ion concentration in a solution and as such is a measure of acidity or alkalinity. The more hydrogen ions in a solution, the greater the acidity of the solution.

Question 2

• pH 7 is __.
• pH 7 down to pH 0, indicates an increase in ____.
• pH 7 up to pH 14 indicates an increase in ____.

Answer 2

Neutral
Acidity
Alkalinity

Question 3

Why regulate the pH of body fluids?

Answer 3

Large numbers of hydrogen ions are produced by metabolism. These lower the pH so it is important that the body has mechanisms (buffer systems) to ensure that the pH remains in a range in which enzymes can function.

Question 4

Blood has a pH of ___.

Urine has a pH of ___.

Answer 4

7.35-7.45

6

Question 5

What is a buffer?

Answer 5

It is a chemical substance that prevents too great a change in pH by binding with hydrogen when the pH drops and by releasing hydrogen when the pH rises.

Question 6

There are various buffers (eg. _____, phosphate and ____) that combine with hydrogen ions to form compounds that are excreted in urine. In this way the hydrogen ions are got rid of and the pH of the blood is ___ and ____ maintained.

Answer 6

Bicarbonate
Ammonia
Regulated
Homeostasis

Question 7

Why can the filtrate that flows from the collecting duct finally be called urine?

Answer 7

This is because it contains all substances that the body does not and all the substances needed by the body have been reabsorbed.

Question 8

What will the composition, amount and colour of urine be affected by? (4)

Answer 8

• Diet
• Exercise
• Volume of liquids drunk
• Health

Question 9

How many litres of urine are produced daily?

Answer 9

1.0-1.5 litres

Question 10

• About __ of urine is water.
• ___ make up 1.5%.
• Small quantities of uric acid, creatinine and ____ ions also occur.
• There are also small quantities of drugs, colourants and ____.

Answer 10

96%
Salts
Ammonium
Preservatives

Question 11

How does urine move out of the kidneys? (3)

Answer 11

From the collecting ducts the urine:

• Passes into the renal calyx then into the renal pelvis
• It is then propelled along the two ureters to the bladder by peristaltic movements of the muscular walls
• It is stored in the bladder until it can be expelled through the urethra

Question 12

What is the expulsion of urine from the bladder called? (3)

Answer 12

• A fairly full bladder holds 200ml of urine but it can hold more than double this. Urination is a reflex action that is triggered by the filling of the bladder.
• Impulses from autonomic nervous system (ANS) stimulate the bladder muscles to contract and the internal sphincter to relax.
• At the same time the external sphincter opens voluntarily, so urine can flow out through the urethra