10/11 - Renal system I & II

Question 1

where is water absorption most active?

Answer 1

jejunum followed by ileum

Question 2

where does Na+ absorption occur?

Answer 2

all along intestine

Question 3

where does K+ net absorption occur?

Answer 3

jejunum and ileum

Question 4

colon absorption (2)

Answer 4

1. can absorb water against osmotic gradient
2. very active in Na+ absorption

Question 5

what can result in excessive los of K+?

Answer 5

severe diarrhoea

Question 6

what does blood plasma contain? (5)

Answer 6

1. water
2. ions
3. organic molecules
4. trace elements and vitamins
5. gases

Question 7

cellular elements of blood plasma (3)

Answer 7

1. RBC
2. WBC
3. platelets

Question 8

which type of molecules flow into bowman’s capsule? (5)

Answer 8

• molecules in plasma
  1. amino acids
  2. glucose
  3. nitrogenous waste
  4. CO2
  5. O2
• no proteins/lipids

Question 9

the nephron (2)

Answer 9

1. filtration unit
2. single cell layer

Question 10

4 major processes of nephron (4)

Answer 10

1. filtration
2. reabsorption
3. secretion
4. excretion

Question 11

where does 100% plasma filtration occur?

Answer 11

bowman’s capsule

Question 12

70% filtrate reabsorbed

Answer 12

proximal tubule (next to bowman’s capsule)

Question 13

20% filtrate reabsorbed

Answer 13

loop of Henle

Question 14

9% filtrate reabsorbed

Answer 14

distal tubule and collecting duct

Question 15

how much of total filtrate is excreted?

Answer 15

1%

Question 16

proximal tubule secretions

Answer 16

H+ secreted to acidify urine, drugs and ureic acid also secreted

Question 17

distal tubule and collecting duct secretions

Answer 17

urea and hormones

Question 18

filtration

Answer 18

transfer of soluble components (water and waste)

Question 19

reabsorption

Answer 19

absorption of ions and water

Question 20

secretion

Answer 20

transfer of H+, creatinine, drugs, K+ and urea

Question 21

excretion

Answer 21

urine containing water, wastes, ions, H+, creatinine, urea and drugs etc

Question 22

why does amount of urine change?

Answer 22

reabsorption changes depending on temperature, exercise, water and salt intake

Question 23

myogenic autoregulation when mean arterial pressure is low (4)

Answer 23

1. renal flow into afferent arteriole reduces
2. hydrostatic pressure reduces and blood pressure at efferent arteriole temporarily increases resulting in stretch on walls
3. triggers myogenic autoregulation in efferent arteriole
4. vasoconstriction at efferent arteriole increases blood pressure in glomerulus keeping pressure constant

Question 24

myogenic autoregulation when mean arterial pressure is high (4)

Answer 24

1. renal blood flow into afferent arterioles increased 2. afferent arteriole temporarily have stretch on walls 3. triggers myogenic autoregulation in afferent arteriole 4. vasoconstriction at afferent arteriole reduces blood pressure in glomerulus, keeping pressure constant

Question 25

mechanism keeping glomerulus filtration rate constant

Answer 25

myogenic autoregulation

Question 26

3 main functions of proximal tubule (3)

Answer 26

1. water reabsorption (70%) 2. sodium ion (Na+) absorption 3. glucose absorption (only tissue with glucose transporters)

Question 27

interstitial fluid (3)

Answer 27

1. type of body fluid between cells 2. component very similar to plasma 3. ion concentration in interstitial fluid helps transfer of ions from nephron cells back to peritubular capillary cells (tiny blood vessels)

Question 28

pathway of filtrate (5)

Answer 28

1. lumen of nephron 2. proximal tubule cells 3. interstitial fluid 4. peritubular capillary cells 5. lumen of capillary

Question 29

reabsorption of Na+ and H2O (5)

Answer 29

1. Na+ enters proximal tubule cells via epithelial Na+ channel down electrochemical gradient 2. Na+ moved out of lumen of nephron down electrochemical gradient 3. H2O enters proximal tubule via aquaporin (H2O channel), down osmotic gradient across nephron lumen side of proximal tubule 4. Na+ actively pumped out to interstitial fluid via Na+ K+ ATPase pump in proximal tubule cell membrane facing towards peritubular capillary 5. H2O leaves proximal tubule cell via aquaporin down osmotic gradient across cell membrane facing interstitial side

Question 30

active transport of Na+ (4)

Answer 30

1. Na+ actively pumped out from proximal tubule to interstitial fluid via Na+/K+ exchange ATPase pump 2. ATP used to pump out Na+ while K+ brought in 3. K+ let out via leak channel 4. ATPase pump/leak channel ensures low Na+ potential inside proximal tubule cell compared to lumen of nephron (electrochemical gradient across nephron lumen side of proximal tubule cell membrane)

Question 31

reabsorption of glucose (4)

Answer 31

1. Na+ moving down electrochemical gradient uses sodium-glucose transporter protein to pull glucose into cell against concentration gradient 2. glucose diffuses out of basolateral side of cell using glucose transporter proteins 3. Na+ pumped out by Na+ K+ ATPase pump 4. K+ let out by potassium leak channel

Question 32

what does a longer loop of Henle result in?

Answer 32

more concentrated urine produced

Question 33

what uptake occurs in the ascending loop of Henle?

Answer 33

absorption of ions via primary active, secondary active and passive transport

Question 34

what uptake occurs in the descending loop of Henle?

Answer 34

absorption of water via aquaporin

Question 35

peritubular capillaries (3)

Answer 35

1. capillary blood vessel in the renal system 2. run right next to nephrons (surround proximal and distal tubules) 3. made of one layer of cells, have channels and transporters

Question 36

what are peritubular capillaries surrounding the loop of Henle called?

Answer 36

vasa recta

Question 37

loop of Henle counter-current multiplier (3)

Answer 37

1. filtrate entering descending limb becomes progressively more concentrated as it loses water 2. blood in vasa recta removes water leaving loop of Henle 3. ascending limb pumps out Na+, K+ and Cl-, filtrate becomes hypotonic

Question 38

explain counter-current role in vasa recta in reabsorption of H2O from loop of Henle (3)

Answer 38

1. create strong osmotic gradient across fluid in nephron and blood in peritubular capillary (flow in opposite directions) 2. ion conc highest in loop of Henle, ions transported from ascending loop to interstitial space via respective channels, co-transporters and ATPase pumps. ions then move to peritubular capillaries (flowing opposite direction to fluid in loop of Henle) 3. ion conc at loop of peritubular capillaries highest. aquaporins only present in descending loop of Henle, water molecules move from inside nephron to peritubular capillaries following osmotic gradient

Question 39

what does vasa recta mean?

Answer 39

vasa (vessel) recta (straight) (2 straight vessels that are loop of Henle and peritubular capillary run parallel to eachother)

Question 40

role of distal tubule

Answer 40

removes remaining 9% of water from nephron

Question 41

what is aldosterone? (3)

Answer 41

1. steroid hormone synthesised in adrenal cortex (outer portion of adrenal gland sits atop each hormone) 2. hydrophobic (remains in capillary) 3. acts on distal tubule and collecting duct cells

Question 42

how does aldosterone affect nephrons (4)

Answer 42

1. aldosterone molecules arrive at distal tubule - secreted into interstitial fluid and distal nephron cell (combines with cytoplasmic receptor) 2. hormone-receptor complex initiates transcription in nucleus 3. translation/protein synthesis makes new protein channels and pumps 4. aldosterone-induced proteins modulate and enhance activity of existing channels and pumps (blood absorbs more Na+)

Question 43

role of aldosterone

Answer 43

induces Na+ reabsorption to the blood

Question 44

kidney response to ingesting too much Na+ (4)

Answer 44

1. cardiac hormone (atrial natriuretic peptide) secreted from atria 2. causes decrease in number of aldosterone molecules in blood 3. decreasing number of Na+ channels in nephron cells 4. majority of Na+ remains inside nephron and excreted

Question 45

vasopressin (3)

Answer 45

1. 9 amino acid peptide protein hormone 2. protein that isn't filtrated at glomerulus 3. causes insertion of water channel (aquaporin) into apical membrane

Question 46

vasopressin effect on nephron (5)

Answer 46

1. vasopressin in blood arrives next to collecting duct, binds to vasopressin receptor on collecting duct cell 2. binding induces signalling leading to exocytosis of storage vesicles, leads to vesicles with aquaporins moved and fused to cell membrane facing collecting duct 3. more aquaporins moved to cell membrane - allows H2O molecules to enter collecting duct cells 4. storage vesicles with aquaporin also moved to medullary interstitial fluid side of membrane 5. H2O molecules let out to medullary interstitial space, loaded into peritubular capillary by osmosis

Question 47

role of vasopressin

Answer 47

increases H2O absorption in nephrons - diluting plasma - less urine produced

Question 48

erythropoietin (2)

Answer 48

1. peptide hormone 2. produced in kidneys

Question 49

role of erythropoietin (2)

Answer 49

1. produced when kidneys sense low oxygen level (concentration of O2 gas pressure (PO2) in the arterial blood should be just below 100 mmHg) 2. stimulates production of red blood cells