Kidneys

Question 1

What are the two types of cells in the juxtaglomerular apparatus?

Answer 1

• Juxtaglomerular cells

• Macula densa cells

Question 2

Where are juxtaglomerular cells found and what do they do?

Answer 2

• Wrap around the afferent arteriole (that feeds into the glomerulus)

• They are mechanoreceptors sensitive to stretch

• Secrete the enzyme renin when blood pressure falls

Question 3

Where are macula densa cells found and what do they do?

Answer 3

• Found along the wall of the distal tubule

• Tall, closely packed cells sensitive to changes in Na+ and Cl-

• Receptors involved in negative feedback of glomerular filtration

Question 4

How is GFR regulated?

Answer 4

• Tubuloglomerular feedback - rapid delivery of Na+ and Cl- to the macula densa due to high BP, causing a decreased release of NO by juxtaglomerular apparatus causes constriction of afferent arterioles (as NO causes vasodilation)

• Neural regulation - increase in activity level of renal sympathetic nerves releases norepinephrine

• Hormone regulation - decreased BP or BV stimulates production of angiotensin 2, causing constriction of afferent and efferent arterioles

Question 5

Where is vasopressin released from and what does it cause?

Answer 5

• Posterior pituitary gland

• Binds to a Gs coupled receptor that initiates an intracellular signalling cascade leading to new synthesis of AQP2

• AQP2 is inserted into the apical membrane of collecting duct cells to increase water reabsorption

Question 6

What system is used in renal Na+ hormonal regulation?

Answer 6

Renin-angiotensin-aldosterone system (RAAS)

Question 7

How does the RAAS pathway increase blood pressure?

Answer 7

• Renin is released from juxtaglomerular cells in response to decrease in BP/BV (from stretch) which catalyses the conversion of angiotensinogen to angiotensin 1

• Angiotensin 1 is converted to angiotensin 2 in the lungs via ACE (angiotensin converting enzyme)

• Angiotensin 2 is a powerful vasoconstrictor and stimulates the release of aldosterone from the adrenal gland of the kidneys

• Aldosterone facilitates Na+ reabsorption in the kidneys, raising BP

Question 8

What are the differences between metabolic and respiratory alkalosis?

Answer 8

• Metabolic alkalosis is causes by an increase in bicarbonate or a loss of acid, leading to an elevated pH

• Respiratory alkalosis is caused by excessive loss of CO2 due to hyperventilation

Question 9

What are the differences between metabolic and respiratory acidosis?

Answer 9

• Metabolic acidosis is caused by an decrease in bicarbonate or excess acid (leading to an elevated pH

• Respiratory acidosis is caused by an accumulation of CO2 in the bloodstream

Question 10

How do you differentiate between metabolic and respiratory acidosis and alkalosis?

Answer 10

• Metabolic acidosis/alkalosis primarily involve changes in bicarbonate levels due to either acid production or bicarbonate loss/retention - in metabolic acidosis, bicarbonate is decreased whereas in metabolic alkalosis, bicarbonate is increased

• Respiratory acidosis primarily involve changes in CO2 levels due to either hypoventilation or hyperventilation - in respiratory acidosis, CO2 is increased whereas in respiratory alkalosis, CO2 is decreased