Renal

Question 1

why do we need kidneys?

Answer 1

filter plasma and reabsorb what the body needs. leaves waste products, drugs,
toxins and excess (water), ions
and acid/bicarbonate in the urine.

Question 2

Kidney - gross structure.

Answer 2

renal cortex (coating), renal medulla (middle) ureter.

Question 3

kidney - nephron loop.

Answer 3

Renal corpuscle: Glomerulus + Glomerular capsule. Afferent arteriole (afferent: arrival). Peritubular capillaries (peri: around).

Question 4

basic nephron filtration.

Answer 4

substances (e.g. glucose and water) moves from the blood through the ‘sieve’ and into the nephron tubule. only small molecules can fit due to the small gaps. proteins and cells are too big.
in the glomerulus - like a sieve.

Question 5

basic nephron reabsorption.

Answer 5

proximal tubule. Reabsorption: movement of useful substances (e.g. glucose and water) out of the nephron tubule back into the blood (stay in the body).

Question 6

basic nephron secretion.

Answer 6

Secretion: removal of
waste products (e.g. drugs)
from the blood into the
nephron tubule and end up in the urine (leave the body).

Question 7

what epithelial cells line the renal tubules.

Answer 7

Apical membrane: faces the lumen (into the tube).
Basolateral membrane: faces the interstitial space (outside of the tube).

Question 8

para-cellular pathway. kideny

Answer 8

‘Between’ cells
* Transport proteins not required
* Only possible in cells with ‘leaky epithelia

Question 9

Trans-cellular pathway

Answer 9

Through’ cells
* Apical & basolateral membrane transport
* Requires: Permeability (membrane transport proteins etc.). Driving force (gradient or energy)
* Can be: Automatic. Controlled by hormones. Cells with ‘tight epithelia’ allows transcellular reabsorption only

Question 10

passive transport in kidney.

Answer 10

No energy required, driven by a gradient. Diffusion (solutes) or osmosis (water) down a gradient
Two types:
* Diffusion/osmosis – through the membrane or between cells without assistance.
* Facilitated diffusion – requires a channel or transporter.

Question 11

active transport in kidney.

Answer 11

Needs a driving force
Two types:
Primary – uses ATP for energy
.Secondary – uses the movement of one substance down its gradient (downhill), to drive the movement of another substance against its gradient (uphill).

Question 12

Kidney Epithelium – Water movement

Answer 12

osmosis.
Water can move via both the trans and the paracellular pathway – Water has to go via the transcellular pathway using channels = aquaporins (water channels).

Question 13

how does blood get into the glomerulus

Answer 13

Blood pressure in the glomerular capillaries’ forces fluid, ions & solutes into the nephron.

Question 14

Glomerular Filtration Rate

Answer 14

Together both kidneys’ filter:
* 125mL blood/min
Which equals
* 180L/day
This is the Glomerular Filtration Rate (GFR)
only 1.5L urine/day max 20L and min 500ml. therefore 99% reabsorped.
GFR gives an indication of how well the kidneys are functioning

Question 15

Renal Clearance

Answer 15

The amount of blood plasma that is completely cleared (cleaned up) of a substance per minute.
filtration - reabsorption + secretion = clearance.

Question 16

what is creatine clearance used to estimate and how do we find it?

Answer 16

assess the kidney function.
Creatinine is a chemical waste generated from muscle metabolism and filtered out in the kidneys (and not reabsorbed nor secreted). The amount of blood the kidneys can make creatinine-free is called the creatinine clearance. -125 mL/minute (similar to the GFR).

Question 17

proximal tubule.

Answer 17

reabsorb 90-99% of water and ions and all of the nutrients that are filtered back into the bloodstream.
90% of water. 90% of Na+. 100% of nutrients (e.g. glucose and amino acids)
has leaky epithelial therefore allowing for paracellular and trans-cellular movement.

Question 18

proximal tubule cell reabsorption to blood with apical.

Answer 18

high potassium inside and low sodium inside. therefore glucose and amino acids reabsorped using apical membrane. Sodium-coupled secondary active transport. driven by the Sodium electrochemical gradient. electrochemical gradient for sodium created by the Na+/K+ ATPase pumps. Sodium- a positive ion with a high conc outside the cells and low conc inside the cells.

Question 19

proximal tubule cell reabsorption to blood with basolateral.

Answer 19

facilitated diffusion. - Driven by the:
* Concentration gradients
* created by the secondary
active transport of glucose and
AA’s through the apical
membrane.

Question 20

how does chloride reabsorb in the proximal tubule?

Answer 20

Where sodium goes:
* Chloride follows via the paracellular pathway, down its electrical gradient.

Question 21

distal tubule.

Answer 21

Fine-tuning reabsorption
* 1-10% of water
* 1-10% Na+ and Clions
* Acid (H+) and bicarbonate (HCO3-) – pH control are reabsorbed, depending on what the body needs. hormones control. tight epithelial: transcellular movement only.

Question 22

what causes water and sodium reabsorption

Answer 22

ADH - water. aldosterone (+renin) - sodium. Hormones act by adding or taking away channels for
sodium and water

Question 23

what does water need to reabsorb into the body?

Answer 23

driving force - osmotic gradient
permeability - as the distal tubule has tight epithelial we cannot use a paracellular pathway.
transcellular pathway - needs water channels (aquaporins) for water to enter and exit the cells.

Question 24

how does osmolarity of water change in the nephron loop?

Answer 24

Osmolarity increases from renal cortex to medulla. Driving force for water reabsorption in the distal tubule.

Question 25

what happens to our cells when we are dehydrated?

Answer 25

they shrink. the water from the ECF decreases meanging the ICF water will move out to the ECF = cells shrink.

Question 26

how does ADH control water reabsorption.

Answer 26

osmoreceptors in the hypothalamus detect the increase in ECF osmolarity. increase the release of ADH from the posterior pituitary into the blood. increased aquaporins in the apical membrane.

Question 27

Effect of Exercise on urine production of urine

Answer 27

high-intensity exercise - increases of sympathetic - low blood flow to the kidney - filtration rate in glomerulus decreases.

hormone - increase secretion of ADH, increase aquaporins in apical membrane, increase water reabsorption.

DECREASED urine production.

Question 28

what does aldosterone need for the kidney to reabsorb sodium?

Answer 28

driving force - electrochemical gradient.
permeability - cannot use paracellular, must use trans-cellular. which need sodium channels to enter the cells. and will be pumped back out by the Na+/K ATPase pump.

Question 29

how does our body get effected by blood loss or vomiting and diarrhoea?

Answer 29

= isomotic fluid loss. no gradient for water to move in or out of cells. only a change in ECF and therefore blood volume and pressure.

Question 30

how does aldosterone adapt to the loss of ECF volume?

Answer 30

pressure receptors in the kidney detect the blood volume/pressure change causing renin to be released. this stimulates the release of aldosterone from the adrenal cortex, which increases sodium channels in the apical membrane of distal tubule cells. increased sodium reabsorption, decreased sodium excretion.

Question 31

how does aldosterone also impact ADH?

Answer 31

renin stimulates Increased release of ADH from the posterior pituitary.
Increased aquaporins in apical (top)
membrane of distal tubule cells.
Increased water reabsorption.

Question 32

why is ADH fast and aldosterone faster ?

Answer 32

Blood Osmolarity
* EMERGENCY!
* FAST response.
Blood Volume/pressure
* Less urgent
* S l o w e r response

Question 33

isomotic

Answer 33

ECF solutes = ICF solutes

Question 34

Hypo-osmotic

Answer 34

ECF has less solutes than ICF. Example: Overhydration.

Question 35

hyperosmotic

Answer 35

ECF has more solutes than ICF. Example: Dehydration.

Question 36

why is the change in blood osmolarity an emergency?

Answer 36

When the osmolarity of the blood (ECF) increases/decreases water will move out/in of the cells.

Question 37

what does exercise do to ECF osmolarity?

Answer 37

Dehydration during exercise:
* lose more H2O than Na+
* ECF osmolarity increases

Question 38

what is hyponatremia?

Answer 38

(hypo = under, natremia = sodium).
caused by overhydration during training or competition + feedforward ADH release at the start of exercise. Our body is anticipating losing water but combined with overhydration, we will be keeping too much water.

Question 39

2 simple recommendations for hyponatremia in sports?

Answer 39

1) Athletes - don’t overdrink during competition
2) Organisers - restrict fluid availability during cycling & running legs of race

Question 40

why is blood volume change less urgent for our body?

Answer 40

because there is another body system that can rapidly adapt to changes in volume and pressire: cardiovascular.