Eureka Physiology

Question 1

Function of nephron?

Answer 1

Regulates plasma composition via processes if filtration, reabsorption and secretion

Question 2

What is glomerular filtration?

Answer 2

1st stage of urine production
-Hydrostatic pressure with glomerular capillaries forces plasma components through capillary wall into Bowmans space
(large components remain in capillary)

Question 3

What is the term for what happens in glomerular filtration?

Answer 3

Ultrafiltration

Question 4

What is albuminuria?

Answer 4

Albumin in urine

-Indicates pathological process affecting GF

Question 5

What is GFR?

Answer 5

Rate @ which fluid is filtered by glomerulus from blood into Bowman’s space

Question 6

How is GFR estimated?

Answer 6

By measuring clearance of substance which satisfies this criteria:

• Steady blood conc
• Freely filtered (passed unhindered across GF membrane)
• Neither absorbed nor secreted by cells of renal tubule

Question 7

What substances meet criteria for GFR?

Answer 7

Inulin (too tricky to measure and administer though)
THEREFORE
-Creatinine clearance is used

Question 8

Con with using creatinine clearance for GFR?

Answer 8

Some is secreted by renal tubules so the value is always overestimated by 10-20%

Question 9

Factors affecting GFR?

Answer 9

• Differences in hydrostatic pressure & oncotic pressure between tubule & capillaries (starling’s forces)
• Renal blood flow and perfusion pressure

Question 10

Where is fluid secreted along a capillary?

Answer 10

Arterial end

Question 11

Where is fluid reabsorbed along a capillary?

Answer 11

Venous end

Question 12

What happens to hydrostatic pressure as fluid travels along capillary towards venous end?

Answer 12

Decreases

Question 13

Regulation GF?

Answer 13

• Myogenic mechanism autoregulation occurs when SM in wall of blood vessels responds to pressure changes within vessel wall
• Tubuloglomerular feedback mechanism: tubular flow rate affects tone of renal blood vessels

Question 14

Flow diagram of myogenic mechanism when BP is increased?

Answer 14

Increased BP
|
Increased renal perfusion pressure & increased blood flow
|
Stimulates stretch receptors in smooth muscle fibres within wall of afferent arterioles: causing them to constrict
|
Results in resistance to flow in glomerulus increased
|
As a result, blood flow & GFR remain constant despite increase in perfusion pressure

Question 15

Function of glomerulus?

Answer 15

Filtration of blood to form filtrate

Question 16

Function of PCT?

Answer 16

Reabsorption of 65% of Na+ & water and most glucose, AAs, HCO3-, PO3-

Question 17

Loop of Henle function?

Answer 17

Concentration of urine via countercurrent exchnage mechanism

Question 18

Function of DCT?

Answer 18

• Reabsorption of Na+/Ca2+

- Reabsorption and secretion of K+/H+

Question 19

Function of CDs?

Answer 19

ADH: Mediated water reabsorption
Aldosterone: Mediated Na+ reabsorption
Secretion of K+/H+

Acid-base balance
K+ secretion

Question 20

What is the energy bank of tubular transport?

Answer 20

Na+ gradient

Question 21

What/ where do Na+K+ATPase pumps do their wee thing?

Answer 21

• On basolateral sides of cells of PCT

- Create Na+ gradient by pumping Na+ out of cells into Interstitial fluid, K+ into cells

Question 22

Where does tubular reabsorption mostly occur?

Answer 22

PCT

Question 23

What is tubular secretion?

Answer 23

Movement of substances from blood in peritubular capillaries into tubular lumen

Question 24

What is tubular reabsorption?

Answer 24

Movement of solutes out of luminal filtrate into tubular cells then into interstitium and into peritubular capillaries

Question 25

Function of PCT?

Answer 25

2/3rds of filtered Na+/H20 are reabsorbed into blood here as well as almost all glucose, AAs and some Phosphates and bicarbonates

Question 26

Function of Loop of Henle?

Answer 26

Concentrates urine achieved by counter current exchange mechanism

Question 27

What is descending loop permeable to?

Answer 27

Permeable to H20 Impermeable to Na+ Water moves freely out of this limb and into interstitium whereas Na+ remains within this tubule

Question 28

What is ascending loop permeable to?

Answer 28

Permeable to: Na+ | Impermeable to: Water

Question 29

Fluid in the PCT is...?

Answer 29

Isosmotic with interstitium

Question 30

Fluid entering descending loop of henle is...?

Answer 30

Isosmotic with interstitium

Question 31

What happens in thick section of ascending loop of henle?

Answer 31

Impermeable to water Water is unable to follow Na+ to equilibrate osmolality of filtrate with that of iterstitium Therefore osmolality of interstitium is equal to osmolality of fluid in descending limb of loop & interstitium differing with the osmolality of interstitium being greater than that of filtrate (I don't know what I mean her either TBC)

Question 32

Because the descending limb is permebale to water...

Answer 32

Water leaves filtrate and moves into interstitium to equilibrate osmolality of interstitium with that of descending limb

Question 33

What does the counter current exchange mechanism allow?

Answer 33

Osmotic gradient to increase the deeper the tubule lies in medulla

Question 34

Fluid leaving loop of henle is?

Answer 34

Hypotonic

Question 35

Why is fluid leaving loop of henle hypotonic?

Answer 35

Action of Na+/K+-2cl- cotransporter in ascending limb & it's water impermeability

Question 36

What is water excretion altered by in ascending limb?

Answer 36

Action of ADH

Question 37

What is vasa recta permeable to?

Answer 37

Solutes and water

Question 38

What is osmolality of cap blood at bend of vessel?

Answer 38

= to interstitium osmolality

Question 39

What does distal convoluted tubule do?

Answer 39

Regulates balance of Na+/K+ as well as Ca2+ within body

Question 40

What type of reabsorption occurs within DCT?

Answer 40

Hormone mediated of Na+/Cl-

Question 41

What induces reabsorption of Na+/H20 IN CDs?

Answer 41

Aldosterone and ADH

Question 42

ADH deficiency/resistance =?

Answer 42

Diabetes insipidus Hence The frequent weeing and xsive thirst

Question 43

Where is urea formed?

Answer 43

Liver

Question 44

Where does urea concentrate urine?

Answer 44

Loop of Henle

Question 45

Why are all invasive procedures involving the kidney, such as biopsy, so risky?

Answer 45

-Kidneys are so highly vascularised | Damage to renal blood vessels can cause catastrophic bleeding

Question 46

How does a long loop of Henle help a desert animal survive?

Answer 46

They must produce v concentrated urine | - Long loop of Henle allows more water to be reabsorbed by kidney tubule = concentrated urine

Question 47

Why are females more prone to urinary tract infections?

Answer 47

Female urethra is shorter - Bacteria have shorter distance to travel to the bladder - Also closer to anus and therefore faecal bacteria

Question 48

What are the fluid compartments of the body?

Answer 48

2 major compartments - Intracellular space - Extracellular space ECF divided into - Intravascular space (plasma) - Interstitium (including lymph) - Transcellular space (pericardial and peritoneal fluid)

Question 49

How is Na+ involved in control of body fluid volume?

Answer 49

-Sodium is main determinant of plasma osmolality (Osmol/Kg) -As water follows sodium along an osmotic gradient, from low to high osmolality, when Na+ is reabsorbed by kidneys , water is too. -This is how control of plasma sodium is closely linked to control of Blood volume and pressure

Question 50

Why must XS acid be excreted?

Answer 50

Metabolism constantly creates acid as by-product | If left uncontrolled this alters structure and function of macromolecules and disturbs cellular metabolism | pH also alters degree of ionisation of weak acids and bases which can affect generation of ATP in electron transfer chain

Question 51

How are the K+ concentration and acid-base balance of blood related?

Answer 51

They are interconnected - Acidaemia is usually assoc with hypokalaemia -Alkalaemia assoc with hyperkalaemia - Overall effect is reduction in acid secretion and metabolic acidaemia, normalising K+ concentration can correct this

Question 52

Why might a patient with chronic respiratory condition develop a raised haemoglobin?

Answer 52

May have chronic hypoxia | May develop secondary polycythaemia This is because hypoxia stimulates release of erythropoietin, which in turn increases RBC production

Question 53

Functional units of kidneys?

Answer 53

Nephrons

Question 54

How is kidney part of endocrine system?

Answer 54

-Important endocrine roles in regulation of BP, RBC formation, and activity of vitamin D

Question 55

Does a foetus pass urine in the womb?

Answer 55

- Yes foetus begins to make urine from 8 weeks | - Excreted via the urinary tract into amniotic fluid

Question 56

Why would a kidney be found in the pelvis?

Answer 56

Kidneys normally ascend in embryonic development from pelvis to superior abdomen - The ascent can sometimes be interrupted

Question 57

Why might the kidney have more than one renal artery?

Answer 57

- Due to the way the vasculature develops - Relatively common for blood vessels to persist in development as the kidney ascends it receives transient blood vessels originating at aorta from progressively higher levels

Question 58

What cells produce erythropoeitin?

Answer 58

Renal peritubular fibroblasts