Blood water potential (16)

Question 1

What is meant by osmoregulation?

Answer 1

control of blood water potential via homeostatic mechanisms

Question 2

What are the 7 structures of a kidney and where are they on a diagram?

Answer 2

1) fibrous capsule
2) cortex
3) pelvis
4) medulla
5) renal vein
6) renal artery
7) ureter

Question 3

What is the role of the fibrous capsule?

Answer 3

protects kidney

Question 4

What is the cortex and what does it consist of?

Answer 4

outer region
consists of Bowman’s capsules, convoluted tubules and blood vessels

Question 5

What is the role of the pelvis?

Answer 5

collects urine into ureter

Question 6

What is the medulla and what does it consist of?

Answer 6

inner region
consists of collecting ducts, loops of Henle and blood vessels

Question 7

What is the role of the renal vein?

Answer 7

returns deoxygenated blood from kidney to heart

Question 8

What is the role of the renal artery?

Answer 8

supplies kidney with oxygenated blood

Question 9

What is the ureter and its role?

Answer 9

tube that carries urine to bladder

Question 10

Were is a nephron found?

Answer 10

section of kindey

Question 11

What are the 5 structures of a kidney?

Answer 11

1) bowman’s capsule
2) proximal convoluted tubule
3) distal convoluted tubule
4) loop of Henle
5) collecting duct

Question 12

Describe the bowman’s capsule.

Answer 12

• at start of nephron
• cup-shaped
• surrounds glomerulus
• inner layer of podocytes

Question 13

Describe the proximal convoluted tubule?

Answer 13

• series of loops surrounded by capillaries
• walls made of epithelial cells with microvilli

Question 14

How does the distal convoluted tubule structure differ to that of the proximal convoluted tubule?

Answer 14

fewer capillaries

Question 15

Describe the loop of Henle.

Answer 15

hairpin loop that extends from the cortex into the medulla

Question 16

Describe the collecting duct.

Answer 16

Distal convoluted tubules from several nephrons empty into collecting duct, which leads into pelvis of kidney

Question 17

What are the 2 arterioles associated with a nephron?

Answer 17

wide afferent arteriole
narrow efferent arteriole

Question 18

Describe the wide afferent arteriole.

Answer 18

enters the renal capsule and forms the glomerulus

Question 19

Describe the narrow efferent arteriole.

Answer 19

branches to form capillary network that surrounds the tubules

Question 19

Describe the glomerulus.

Answer 19

branches knot of capillaries which combine to form the narrow efferent arteriole

Question 20

What are the 3 steps on how glomerular filtrate is formed?

Answer 20

1) ultrafiltration in Bowman’s capsule
2) high hydrostatic pressure in glomerulus forces small molecules (urea, water, glucose, mineral ions) out of capillary fenestrations against the osmotic gradient
3) basement membrane acts as filter so blood cells and large molecules (proteins) remain in capillary

Question 21

What are 2 ways cells in Bowman’s capsule are adapted for ultrafiltration?

Answer 21

• fenestrations between epithelial cells of capillaries
• fluid can pass between and under folded membrane of podocytes

Question 22

What is selective reabsorption?

Answer 22

when useful molecules from glomerular filtrate (e.g. glucose) are reabsorbed back into the blood

Question 23

Where does selective reabsorption occur?

Answer 23

proximal convoluted tubule

Question 24

What are 3 ways in which cells in the proximal convoluted tubules are adapated for selective reabsorption?

Answer 24

- microvilli for large surface area for co-transporter proteins - many mitochondria to produce ATP for active transport of glucose into intercellular spaces - folded basal membrane creating large surface area

Question 25

What is the transport process of selective reabsorption?

Answer 25

glucose from glomerular filtrate > (co-transported with sodium ions) > cells lining proximal convoluted tubule > (active transport) > intercellular spaces > (diffusion) > blood capillary lining tubule

Question 26

What is the role of the collecting duct?

Answer 26

reabsorption of water from filtrate into interstitial fluid via osmosis through aquaporins

Question 27

What are the 2 roles of the distal convoluted tubule?

Answer 27

- reabsorption of water via osmosis - reabsorption of ions via active transport (permeability of walls is determined by action of hormones)

Question 28

What is the role of the posterior pituitary gland in osmoregulation?

Answer 28

stores and secretes ADH produced by the hypothalamus

Question 29

What are the 4 steps that occur in the loop of Henle?

Answer 29

1) active transport of sodium ions and chloride ions out of the ascending limb 2) water potential of interstitial fluid decreases 3) osmosis of water out of descending limb 4) water potential of filtrate decreases as it goes down the descending limb

Question 30

Where is water potential, in the loop of Henle, at its highest?

Answer 30

top of ascending limb

Question 31

Where is water potential, in the loop of Henle, at its lowest?

Answer 31

medullary region

Question 32

What are 2 differences between the ascending and descending limbs in the loop of Henle?

Answer 32

Ascending is wider and impermeable to water. Descending is narrower and highly permeable to water.

Question 33

What 4 factors might cause blood water potential to change?

Answer 33

1) level of water intake 2) level of ion intake in diet 3) level of ions used in metabolic processes or excreted 4) sweating

Question 34

What are 2 reasons why it is important to maintain the sodium ion gradient?

Answer 34

- for counter current multiplier (filtrate in collecting ducts is always beside area of interstitial fluid that has a lower water potential) - maintains water potential gradient for max reabsorption of water

Question 35

What is the role of the hypothalamus in osmoregulation and how does this occur?

Answer 35

osmosis of water out of osmoreceptors in hypothalamus causes them to shrink, this triggers the hypothalamus to produce more ADH

Question 36

What does ADH stand for?

Answer 36

antidiuretic hormone

Question 37

What is the role of ADH in osmoregulation?

Answer 37

makes cells lining the collecting duct more permeable to water and urea

Question 38

How does ADH make cells lining the collecting duct more permeable to water?

Answer 38

1) binds to receptor 2) activates phosphorylase 3) vesicles with aquaporins on membrane fuse with cell-surface membrane

Question 39

How does urine become more concentrated?

Answer 39

when water potential in interstitial fluid decreases causing more water to be reabsorbed