Glomerular filtration rate (GFR)

Question 1

Glomerular filtration rate (GFR)

Answer 1

• GFR = The amount of filtrate the kidneys produce each minute
– Average: 125 ml/min
• GFRdependsonnetfiltrationpressure
• Anything that alters net filtration pressure will change GFR

Question 2

Some disease states affect GFR…

Answer 2

• Kidney stones
– Obstructs the urinary tract (eg. Ureters) - if block outflow from kidney
Which pressure will be affected? - gomellar hydrostaic pressure will increase
What effect will this have on GFR? - reduced

Question 3

Some disease states affect GFR…2

Answer 3

• Burns
– Damages the integumentary system
– Loss of protein-rich plasma Which pressure will be affected? - osmotic decreased
What effect will this have on GFR? - GRF increased

Question 4

GFR is regulated by the glomerular capillary blood pressure

Answer 4

• GFR remains constant when mean arterial blood pressure fluctuates within a normal range (80-180 mm Hg)

Question 5

The glomerulus

Answer 5

is “protected” from changes in arterial pressure by adjusting the diameter of the afferent arteriole

Question 6

arteriolar vasocontriction decreases GRF

Answer 6

vasoconstriction > decrease blood flow into glomerulus > dec. glom. capillary BP > dec. Net filtration pressure > dec. GFR

Question 7

arteriorlar vasodilation increases GRF

Answer 7

vasodilation > inc. blood flow into glomerulus > inc.. glom. capillary BP > inc.. Net filtration pressure > inc. GFR

Question 8

The juxtaglomerular apparatus regulates glomerular capillary blood pressure
- Macula densa

Answer 8

• Macula densa cells (distal tubule) detect changes in salt conc. in the filtrate

Question 9

The juxtaglomerular apparatus regulates glomerular capillary blood pressure
- granular cells

Answer 9

Paracrine signals act on granular cells (smooth muscle cells) to cause vasoconstriction or vasodilation of afferent arteriole

Question 10

The juxtaglomerular apparatus

Answer 10

The juxtaglomerular apparatus consists of modified tubular and vascular cells at the point where the distal tubule and arterioles meet

Question 11

What if there is a large drop in blood pressure (eg. Haemorrhage)?

Answer 11

The baroreceptor response causes the constriction of the afferent arteriole which dec. GFR

Question 12

short term adjustment in blood pressure

Answer 12

decr. blood pressure > detection by aorti arch and carotid sinus baroreceptors> inc. sympathetic activity (inc. CO) > arteriolar vasoconstriction (inc. TPR) > last 2 both increase. arterior blood pressure >

Question 13

long term adjustment in blood pressure

Answer 13

decr. blood pressure > detection by aortic arch and carotid sinus baroreceptors> inc. sympathetic activity > arteriolar vasoconstriction > afferent arteriolar vasoconstriction > dec. glom capillary BP > dec. GFR > dec. urine vol. > inc. salt and fluid conservation > incs. arteriolar BP