L26. Renal regulation and urine formation

Question 1

nephron

Answer 1

• where urine is made
• two types:
  > cortical and juxtamedullary
• consists of:
  > renal corpuscle
  > renal tubule
  > collecting duct
• blood is filtered in the corpuscle) to make urine
• which is collected in tubules and emptied into collecting ducts

Question 2

Renal corpuscle

Answer 2

• afferent arteriole
• glomerulus
• bowman’s capsule
• efferent arteriole

Question 3

Juxtaglomerular cells

Answer 3

• receptors
• in wall of afferent arteriole
• sense changes in BP
• secrete renin (hormone) when BP is low

Question 4

Parts of the renal tubule

Answer 4

• PROXIMAL CONVOLUTED TUBULE (PCT)
• LOOP OF HENLE
  > ascending and descrending limbs
• DISTAL CONVOLUTED TUBULE (DCT)
  > empties into collecting system

Question 5

Steps of urine formation

Answer 5

• glomerular FILTRATION (renal corpuscle)
• tubular REABSORPTION (tubule, loop, collecting duct)
• tubular SECRETION (distal convoluted tubule, collecting duct)

Question 6

Glomerular filtration

Answer 6

• from blood to nephron (Bowman’s capsule)
• selective only on size (anything large, like proteins can’t pass through)
• water and small solutes goes across

Question 7

Tubular reabsorption

Answer 7

• from nephron to blood

- selective- selects what needs to be returned

Question 8

What is reabsorbed?

Answer 8

• most water (99%)
• most ions
  > sodium, potassium
• all nutrients
• urea (50%)

Question 9

Control of water reabsorption

Answer 9

• 90% by osmosis
• obligatory (must follow solutes)
  >PCT and Loop of Henle
• 10% facultative- adapts to need
  > mainly due to ADH
  > collecting duct

Question 10

Tubular secretion

Answer 10

• from blood to nephron
• selective
• drugs, toxin, urea secreted

Question 11

Collecting system

Answer 11

• receive fluid from many nephrons
• begins in cortex
• descends into medulla
• carries fluid towards minor calyx

Question 12

Forces of filtration

Answer 12

• GLOMERULAR HYDROSTATIC
  > forces water out of capillary into capsule
  CAPSULAR HYDROSTATIC
  > water pushes back into capillary from capsule
  COLLOID OSMOTIC
  >proteins inside capillary draw water back into capillary

Question 13

Net filtration pressure (NFP)

Answer 13

• the driving pressure driving substances into capsule

Question 14

Glomerular filtration rate (GFR)

Answer 14

• volume of fluid filtered per minute
• afferent arterioles dilate
  > more blood flows in, increase GFR
• afferent arterioles constrict
  > less blood flows in, decrease GFR

Question 15

Regulation of GFR

Answer 15

• GFR needs to be constant
• Low GFR = cant excrete waste
• High GFR = less time for reabsorption

Regulated by:

• autonomic nervous system
• renal autoregulation
• hormones

Question 16

autonomic nervous system

Answer 16

• sympathetic stimulation causes:
• vasoconstriction of afferent arterioles
• decrease in GFR

Question 17

Renal autoregulation

Answer 17

- when BP is low 
  > GFR low 
- stop secretion of vasoconstrictors 
  > afferent arterioles dilate 
  > increase flow and thus filtration

Question 18

Hormonal

Answer 18

• hleps restore normal systemic and renal BP thus GFR
• when low BP, low GFR
  > kidney secretes renin into blood

Question 19

Atrial natriuretic peptide (ANP)

Answer 19

• cardiac muscle cells stretch
• inhibits secretion of ADH, aldosterone
• make more urine
• decrease blood volume and blood pressure