Glomerulus

Question 1

What is osmolality?

What is osmolarity?

Answer 1

Osmolality - solute per kilogram of solvent

Osmolarity - number of osmoles of solute per litre

Question 2

What is the normal glomerular filtration rate?

Answer 2

90-120 Females
100-130 Males
~125 ml/min

Question 3

What charge does the endothelial lining of the glomerulus have? How is this helpful?

Answer 3

Slight negative charge. Helps to repel negative ions such as albumin and facilitate movement of positive ions

Question 4

What are podocytes?

Answer 4

Cells that wrap around the capillaries of the glomerulus leaving slits between their pedicels to form a filtration barrier

Question 5

What factors contribute to the flow of filtrate?

Answer 5

Hydrostatic pressure of capillary -—>

hydrostatic pressure of bowmans capsule

Question 6

What is the myogenic mechanism of regulation?

Answer 6

Stretch receptors within the wall of afferent (and efferent) arteriole sense increases or decreases in pressure and relax or constrict smooth muscle wall in response

Question 7

What myogenic responses would cause a decrease in GFR?

Answer 7

Constriction of the afferent arteriole

Dilation of the efferent arteriole

Question 8

What myogenic response would cause an increase in GFR?

Answer 8

Dilation of the afferent arteriole

Constriction of the efferent arteriole

Question 9

What is tubuloglomerular feedback?

Answer 9

Mechanism linking sodium and chloride concentrations at the distal convoluted tubule with a response at the afferent and efferent arteriole to regulate GFR

Question 10

How does juxtaglomerular feedback regulate a high concentration of sodium ions?

Answer 10

Macula dense cells detect sodium and chloride concentration by symporters in their membranes
Water enters cells and causes swelling
Compresses juxtaglomerular granular cells which release ATP
ATP converted to adenosine
Adenosine binds to afferent arteriole at A1 receptors
Causes vasoconstriction

Question 11

How does tubuloglomerular feedback regulate a low BP (low sodium and chloride ion concentration) ?

Answer 11

Prostaglandin release attenuates constriction of the afferent arteriole
Rennin secreted by juxtaglomerular cells due to decreased NaCl delivery to macula densa cells or sympathetic nerve stimulation
Renin converts angiotensinogen to angiotensin1
Angiotensin 1 - angiotensin 2 - constriction of efferent arterioles
Aldosterone production also results in sodium retention and a global increase in BP