Topic 7.3 - Control of Blood Water Potential

Question 1

What are the parts of the kidney?

Answer 1

Fibrous capsule
Cortex
Medulla
Renal pelvis
Ureter
Renal artery
Renal vein

Question 2

What is the fibrous capsule?

Answer 2

An outer membrane that protects the kidney

Question 3

What is the cortex?

Answer 3

A lighter coloured outer region made up of renal (Bowman’s) capsules,convoluted tubules and blood vessels

Question 4

What is the medulla?

Answer 4

A darker coloured inner region made up of loops of Henle, collecting ducts and blood vessels

Question 5

What is the renal pelvis?

Answer 5

A funnels shaped cavity that collects urine into the ureter

Question 6

What is the ureter?

Answer 6

A tube that carries urine to the bladder

Question 7

What is the renal artery?

Answer 7

Supplies the kidney with blood from the heart via the aorta

Question 8

What is the renal vein?

Answer 8

Returns blood to the heart via the vena cava

Question 9

What are nephrons?

Answer 9

Tiny tubular structures that are the basic structural and functional units of the kidney

Question 10

What are the parts of the nephron?

Answer 10

Renal (Bowman’s) capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tube
Collecting duct

Question 11

What is the Bowman’s capsule?

Answer 11

The closed end at the start of the nephron. Cup shaped and surrounds a mass of blood capillaries known as the glomerulus. The inner layer of the capsule is made up of specialised podocytes

Question 12

What is the proximal convoluted tubule?

Answer 12

A series of loops surrounded by blood capillaries. Its walls are made of epithelial cells which have microvilli

Question 13

What is the loop of Henle?

Answer 13

A long, hairpin loop that extends from the cortex into the medulla of the kidney and back again. It is surrounded by blood capillaries

Question 14

What is the distal convoluted tube?

Answer 14

A series of loops surrounded by blood capillaries. It’s walls are made of epithelial cells, but it is surrounded by fewer capillaries than the proximal tube

Question 15

What is the collecting duct?

Answer 15

A tube into which a number of distal convoluted tubules from a number of nephrons empty. It is lined by epithelial cells and becomes increasingly wide as it empties into the pelvis of the kidney

Question 16

What is the afferent arteriole?

Answer 16

A tiny vessel that ultimately arises from the renal artery and supples the nephron with blood. Enters the renal capsule of the nephron where it forms the glomerulus.

Question 17

What is the glomerulus?

Answer 17

A many branched knot of capillaries from which fluid is forced out of the blood. The glomerular capillaries recombine to form the efferent arteriole

Question 18

What is the efferent arteriole?

Answer 18

A tiny vessel that leaves the renal capsule. It has a smaller diameter than the afferent arteriole and so causes an increase in blood pressure within the glomerulus

Question 19

What are the stages of osmoregulation in the nephron?

Answer 19

The formation of a glomerular filtrate by ultrafiltration
Reabsorption of glucose and after b the proximal convoluted tubule
Maintenance of a gradient of sodium ions in the medulla by the loop of Henle
Reabsorption of water by the distal convoluted tubule and collecting ducts

Question 20

Where does blood enter the kidney from?

Answer 20

The renal artery

Question 21

What is the glomerular filtrate formed of?

Answer 21

Water, glucose and mineral ions squeezed out of the capillary

Question 22

What is movement of filtrate out of the glomerulus resisted by?

Answer 22

Capillary epithelial cells
Connective tissue and epithelial cells of the blood capillary
Epithelial cells of the renal capsule
The hydrostatic pressure of the fluid in the renal capsule space
The low water potential of the blood in the glomerulus

Question 23

What are the modifications made to reduce the barrier to flow of the filtrate?

Answer 23

The inner layer of the renal capsule is made up of highly specialised podocytes high allow the filtrate to pass beneath them
The endothelium of the glomerular capillaries has spaces up to 10nm wide between its cells

Question 24

How much of the filtrate is reabsorbed back into he blood, and where?

Answer 24

Nearly 85%, by the proximal convoluted tubule

Question 25

How are the epithelial cells in the proximal convoluted tubule adapted for reabsorption?

Answer 25

Microvilli provide a large surface area to reabsorb substance from the filtrate
Infolding at their bases to give a larger surface area to transfer reabsorbed substances into blood capillaries
A high density of mitochondria to provide ATP for active transport

Question 26

What is the process of reabsorption of glucose through the proximal convoluted tubule?

Answer 26

Sodium ions are actively transported out of the cells lining the tubule into blood capillaries which carry them away. Sodium ion concentration of these cells lowered
Na+ now diffuse down a concentration gradient from the lumen of the PCT into epithelial lining cell through carrier proteins
Carrier proteins are specific types, each of which carries another molecule along its the sodium, cotransport
The molecules cotranported into cells them diffuse into the blood

Question 27

What is the loop of Henle responsible for?

Answer 27

Water being reabsorbed front he collecting duct, concentrating the urine so that it has a lower water potential than the blood

Question 28

What are the features of the descending limb?

Answer 28

It is narrow, with thin walls that are highly permeable to water

Question 29

What are the features of the ascending limb?

Answer 29

It is wider, with thick walls that are impermeable to water

Question 30

What does the water potential of the blood depend on?

Answer 30

The concentration of solutes like glucose, proteins, sodium chloride and other mineral salts

Question 31

What may cause the water potential of the blood to lower?

Answer 31

To little water being consumed
Too much sweating
Large amounts of ions, eg sodium chloride, being taken in

Question 32

What detects a fall in water potential?

Answer 32

Osmoreceptors in hypothalamus of the brain

Question 33

When is ADH produced?

Answer 33

When water is lost and osmoreceptor cells shrink, causing the hypothalamus to produce ADH

Question 34

What effect does ADH have on the kidneys?

Answer 34

It increases the permeability to water of the cell surface membrane of the cells making up the distal convoluted tubule and the collecting duct

Question 35

What can cause the water potential of the blood to be increased?

Answer 35

Large volumes of water being consumed

Salts used in metabolism or excreted not being replaced in the diet

Question 36

How does the body respond to an increase in water potential of the blood?

Answer 36

The osmoreceptors in the hypothalamus detect the rise in water potential and increase the frequency of nerve impulses to the pituitary gland to edge crease ADH release
Less ADH via the blood leads to a decrease in the permeability of the collecting ducts to water and urea
Less water is reabsorbed into the blood from the collecting duct
More dilute urine is produced and the water potential of the blood falls
When the water potential of the blood has returned to normal, the osmoreceptors in the hypothalamus cause the pituitary to raise its ADH back to normal levels