Physiology

Question 1

in the R (relaxed) state, Haemoglobin has (less/more) affinity for O2
in the T (tense) state, Haemoglobin has (less/more) affinity for O2
This is useful in areas of low pH i.e. high respiration (CO2 –> H+ + HCO3-) as O2 is more readily released from Hb, and vice versa in the lungs

Answer 1

R state - high affinity for O2 - in the lungs
T state - low affinity for O2 - in lower pH, in respiring tissues

Question 2

describe the Bohr effect (related to Haemoglobin)

Answer 2

Stabilises the T state of Hb so that the more respiration a tissue is undergoing (thus the lower the pH), the more O2 is released from Hb there

Question 3

percentage of CO2 in blood carried as HCO3- ions

Answer 3

60% of all CO2 is transported through production of HCO3– ions in the red blood cell.

N.B. that by far the most important role of CO2 in the blood is to regulate the pH, not to be transported to the lungs for exhalation!

Question 4

percentage of CO2 in blood carried as carbamino compounds (including carbaminoHaemoglobin)

Answer 4

30%

CO2 diffuses into the red blood cells and is converted to H+ and HCO3– by carbonic anhydrase.
The H+ created binds to haemoglobin to produce deoxyhaemoglobin

HCO3– is transported back into the blood via an anion chloride-bicarbonate exchanger (aka anion exchanger/AE). The HCO3– can now act as a buffer against any hydrogen in the blood plasma.

Question 5

describe the Haldane effect (related to Hb)

Answer 5

high O2 reduces the CO2-affinity of Hb
so in the lungs, the Hb gets rid of CO2

High CO2 reduces the O2 affinity of Hb
so in areas of high respiration, Hb lets go of O2 and binds CO2

Question 6

percentage of CO2 in blood carried dissolved in plasma

Answer 6

10%

Question 7

What is the approximate ratio of CO2 molecules to HCO3 ions in the blood?

Answer 7

This ratio is roughly 1:20, therefore a rise of 1 CO2 requires a corresponding rise of 20 HCO3– to prevent alterations to blood pH by buffering the increase in acidity.

Question 8

name 3 anorexic (reduces appetite) hormones

Answer 8

GLP-1
PYY
Leptin

Question 9

which metabolic process produces the most energy required for uterine contraction during parturition?

Answer 9

oxidative phosphorylation by ATP synthase (according to given answers

Question 10

explain the origin of kernicterus

Answer 10

unconjugated bilirubin can cross the blood-brain barrier as it is lipid-soluble
It gets deposited in the basal ganglia

Question 11

most common cause of PMB

Answer 11

atrophy
Then HRT

Question 12

increase of cardiac output in the second stage of labour

Answer 12

50%

Question 13

in second stage of labour, there is auto-transfusion of how many ml of blood back into the circulation with each uterine contraction

Answer 13

300–500ml

Question 14

Spinal hypotension is caused by

Answer 14

block of preganglionic autonomic (according to given answers)

Question 15

what is the mechanism from the macula densa that causes the juxtaglomerular cells to release renin?

Answer 15

reduced renal blood flow, or reduced Na or Cl
causes macula densa of the DCT
to release PGI2 and PGE2 (prostaglandins) and nitric oxide
which cause the juxtaglomerular cells lining the afferent arterioles to release renin

Question 16

where do you find juxtaglomerular cells in the kidney

Answer 16

They are specialized smooth muscle cells in the tunica media of the walls of the afferent arterioles

Question 17

what proteins and channels does aldosterone work on in the DCT/collecting duct?

Answer 17

sodium-potassium ATPase
apical epithelial sodium channels, ENaC
potassium channels, ROMK
These actions increase sodium reabsorption while potassium and proton (H+) are secreted (hence metabolic alkalosis in Conns)

Question 18

what pH disturbance do you get in Conns?

Answer 18

metabolic alkalosis

Question 19

where is K+ reabsorbed in the kidney

Answer 19

PCT and ascending loop of Henle

Question 20

what molecule is actively secreted in the PCT of the nephron

Answer 20

creatinine

Very useful renal physiology website
https://open.oregonstate.education/aandp/chapter/25-5-physiology-of-urine-formation-tubular-reabsorption-and-secretion/#:~:text=This%20reabsorption%20occurs%20in%20the%20PCT%2C%20loop%20of,their%20capacity%20to%20reabsorb%20water%20and%20specific%20solutes.

Question 21

explain creatinine clearance, normal reference ranges and reference range in pregnancy, and when it is useful

Answer 21

Creatinine is often used to assess GFR. It is freely filtered, but a small amount is reabsorbed, and a larger quantity, up to 10% of urinary creatinine, results from tubular secretion.

A normal creatinine clearance is 100-150 ml/min. A clearance of less than 80 ml/min is significant except in people over 80 years.

It may reach 200 ml/min in pregnancy.

As GFR falls, creatinine clearance deviates further from the true GFR.