Osmoregulation

Question 1

A [1] is the structural and functional unit of the kidney responsible for filtering blood and producing [2].

Answer 1

[1] nephron

[2] urine

Question 2

Each __________ contains millions of nephrons.

Answer 2

kidney

Question 3

Draw out and label a nephron

Answer 3

image

Question 4

TRUE or FALSE:

Nephrons span the cortex and medulla of the kidney

Answer 4

TRUE

Question 5

Filtering of blood, reabsorption of key molecules back into blood and formation of urine takes place via which steps and in which parts of the nephron?

Answer 5

1. Formation of glomerular filtrate
2. Selective reabsorption of glucose and water by the proximal convoluted tubule
3. Maintaining a gradient of sodium ions in the medulla by the loop of Henle
4. Reabsorption of water by the distal convoluted tubule and collecting ducts - osmoregulation via ADH

Question 6

Blood vessel found in glomerulus

Answer 6

capillaries

Question 7

Structure that surrounds the glomerulus

Answer 7

Bowman’s capsule

*aka renal capsule

Question 8

Describe how ultrafiltration occurs in a glomerulus (4 marks)

Answer 8

1. High blood/hydrostatic pressure;
2. Two named small substances pass out eg water, glucose, ions, urea, amino acids;
3. Through small gaps/pores/fenestrations in capillary endothelium;
4. (And) through basement membrane;

Question 9

Alport syndrome (AS) is an inherited disorder that affects kidney glomeruli of both men and women. Affected individuals have proteinuria (high quantities of protein in their urine).

Suggest how AS could cause proteinuria (2 marks).

Answer 9

1. Affects/damages basement membrane

OR More protein channels/carriers in basement membrane;

2. Proteins can pass into the (glomerular) filtrate/tubule;

Question 10

Part of nephron where majority of glucose and water is selectively reabsorbed

Answer 10

proximal convoluted tubule

Question 11

Water is reabsorbed via [1] and moves from the [2] cells lining the proximal convoluted tubule into the capillaries [3] a water potential gradient.

Answer 11

[1] osmosis

[2] epithelial

[3] down

Question 12

Describe selective reabsorption of glucose by epithelial cells lining the proximal convoluted tubule (3 marks).

Answer 12

1. Sodium ions are actively transported out of epithelial cells into the surrounding capillaries;
2. Creates a concentration gradient for sodium ions;
3. Sodium ions and glucose enter the epithelial cell by facilitated diffusion using co-transporter proteins;
4. Glucose moves into the capillaries by facilitated diffusion;

Question 13

q

Answer 13

Glucose by facilitated diffusion and active transport and water down a water potential gradient

Question 14

Describe and explain how three features of the cells in the proximal convoluted tubule allow the rapid reabsorption of glucose into the blood.

Answer 14

1. Microvilli provide a large surface area
2. Many channel/carrier proteins for facilitated diffusion;
3. Many carrier proteins / sodium-potassium pumps for active transport;
4. Many cotransport proteins for co-transport;
5. Many mitochondria produce ATP
   OR Many mitochondria for active transport;
6. Many ribosomes to produce carrier/channel proteins;

Question 15

q

Answer 15

Water is also reabsorbed

Question 16

The [1] limb of the loop of Henle [2] transports sodium and chloride out of the loop into the interstitial space immediately surrounding the loop of Henle.

This [3] the water potential and leads to water leaving the descending limb via osmosis. Only the descending limb is [4] to water. The ascending limb is impermeable to water.

Answer 16

[1] ascending

[2] actively

[3] lowers

[4] permeable

Question 17

The active transport of sodium and chloride ions out of the loop maintains a [1] gradient for longer along the entire length of the loop of Henle, which leads to more reabsorption of water via [2] from the descending limb into the capillaries that surround the loop of Henle.

Answer 17

[1] concentration

[2] osmosis

Question 18

TRUE or FALSE:

As the filtrate approaches the distal convoluted tubule, it is increasingly concentrated in urea and now starts to resemble urine.

Answer 18

TRUE

Question 19

q

Answer 19

1. Thicker medulla means a longer loop of Henle;
2. Longer loop of Henle means sodium ion gradient maintained for longer (in medulla)

OR (The longer the loop of Henle means) more sodium ions are moved out (into medulla);

3. TTherefore water potential gradient maintained for longer, so more water (re)absorbed

OR More water is (re)absorbed from the loop of Henle by osmosis;

Question 20

TRUE or FALSE:

Camels have a shorter loop of Henle

Answer 20

FALSE

Longer loop of Henle, more Na+ actively transported out, more osmosis

Question 21

Furosemide inhibits the absorption of sodium and chloride ions from the filtrate produced in the nephrons.

Explain how furosemide causes an increase in the volume of urine produced (3 marks).

Answer 21

1. Water potential of filtrate/tubule decreased;
2. Less water reabsorbed by osmosis (from filtrate/tubule);
3. From proximal convoluted tubule OR descending loop of Henle OR collecting duct;

Question 22

Define osmoregulation

Answer 22

control of blood water potential

Question 23

Osmoregulation is an example of ____________ feedback

Answer 23

negative

Question 24

where does ADH act on the nephron

Answer 24

distal convoluted tubule
AND
collecting duct

Question 25

Osmoreceptor location

Answer 25

hypothalamus

Question 26

Role of osmoreceptors

Answer 26

Detect changes in blood water potential

Question 27

Releases ADH

Answer 27

posterior pituitary gland

Question 27

Describe the effect of ADH on the collecting ducts in kidneys (3 marks)

Answer 27

1. Stimulates addition of channel proteins / aquaporins into cell-surface membrane; 2. Increases permeability to water OR More water reabsorbed; 3. By osmosis;

Question 27

Using your knowledge of the kidney, explain why glucose is found in the urine of a person with untreated diabetes (3 marks).

Answer 27

1. High concentration of glucose in blood/filtrate; 2. Not all the glucose is (re)absorbed at the proximal convoluted tubule; 3. Carrier/co-transport proteins are working at maximum rate OR Carrier/co-transport proteins/ are saturated;

Question 28

A decrease in blood pressure stimulates the release of ADH. Explain how the release of ADH will affect blood pressure (2 marks).

Answer 28

1. ADH increases reabsorption of water; 2. Increases volume of blood and pressure increases

Question 28

Alcohol decreases the release of ADH into the blood. Suggest two signs or symptoms which may result from a decrease in ADH (2 marks).

Answer 28

1. Dehydration/thirst; 2. Frequent urination OR Increase in volume of urine; 3. Less concentrated urine OR dilute urine

Question 29

Explain how urea is concentrated in the filtrate (3 marks).

Answer 29

1. Reabsorption of water / by osmosis; 2. At the proximal convoluted tubule / descending loop of Henle; 3. At the distal convoluted tubule / collecting ducts; 4. Active transport of Na+ and Cl- ions creates gradient;