Lec 26

Question 1

Primary hormone for water regulation

Answer 1

vasopressin

Question 2

Osmolality change to cause vasopressin secretion

Answer 2

1% or 3mOsmol/kg

Question 3

Osmolality amount to equal 0 vasopressin

Answer 3

decreases by about 10mOsmol/kg @ 280mOsmol/kg

Question 4

Osmolality by which Maximum effective concentration of vasopressin is reached

Answer 4

increases by 10mOsmol/kg @ 300mOsmol/kg

Question 5

Plasma volume change to cause vasopressin secretion

Answer 5

15% decrease in Blood volume to evoke change (less sensitive than osmolality)

Question 6

Thirst

Answer 6

As blood volume depletes thirst increases and AVP is released after a 15% decrease

Question 7

Vasopressin:target

Answer 7

Nephrons of the kidneys

Question 8

Portions of a nephron affected by Vasopressin

Answer 8

Cortical collecting duct(CCT)[most], Outer medullary collecting duct(OMCD) , Inner medullary collecting Duct (IMCD)[least]

Question 9

Changes in permeability of specific compartments of the nephron

Answer 9

is due to Vasopressin

Question 10

Renal Medulla : osmolality

Answer 10

very high 1200 (increase in water permeability in collecting ducts=concentrated urine)

Question 11

What is the concentration/osmolarity of urine as it enters the distal convoluted tubules?

Answer 11

100 mOsm/liter

Question 12

In the face of excess water: is vasopressin present?

Answer 12

No, collecting tubules impermeable to H20 to get rid of it

Question 13

Dilute urine

Answer 13

Due to no vasopressin, low osmolality, large volume of dilute urine, no h20 reabsorbed

Question 14

Concentrated urine

Answer 14

due to vasopressin present, high osmalality, distal and collecting tubules permeable to h20, Peritubular capillaries reabsorb h20.

Question 15

Peritubular capillaries

Answer 15

absorb scarce H2O in urine when vasopressin is present making ducts permeable.

Question 16

Osmolarity of Urine in the face of water deficit

Answer 16

1200 mOsm/L

Question 17

Osmolarity of Urine in the face of excess water

Answer 17

100 mOsm/L

Question 18

Aquaporins

Answer 18

A tetramer* – (monomers made up of 269 AA) integral membrane proteins whose role is to allow h20 flow. 13 members are present and 6 of them are found in the kidney

Question 19

Exploding cell assay

Answer 19

demonstrate the existence of water channels using Xenopus oocytes. Channels = increased permeability

Question 20

AQP1

Answer 20

high water permeability (proximal tubules and thin descending limb)

Question 21

AQP2

Answer 21

variable water permeability of the collecting ducts is due to the regulation of AQP2 by Vasopressin

Question 22

Nephron structures that contain AQP1

Answer 22

Proximal convoluted tubule (PCT)
Proximal straight tubule (PST)
Thin descending limb (tDLH)

Question 23

Action of Vasopressin: AQP2

Answer 23

activated AC, increases cAMP that acts on AQP3 and AQP4 to release H20. cAMP also leads to a translocation of AQP2 to the membrane abutting the tubule membrane and an increase in AQP2 synthesis. (acts on CREB)

Question 24

CREB

Answer 24

cAMP response element binding protein - synthesizes more AQP2 to be translocated to the lumen membrane

Question 25

Diabetes Insipidus

Answer 25

rare condition marked by excessive thirst and the excretion of large quantities of dilute urine. Similar to Osmotic diuresis )diabetes melitus) and chronic renal failure, both have high rates of solute excretion.

Question 26

Diabetes Mellitus

Answer 26

osmotic diuresis , gets rid of large amounts of dilute urine

Question 27

Central/Neurogenic DI

Answer 27

Central/Neurogenic = failure of vasopressin secretion causing large decrease in urine production and large increase in urine osmolality in response to treatment with vasopressin or a synthetic analogue called desmopressin.

Question 28

Desmopressin

Answer 28

a treatment for Central/Neurogenic DI and bed wetting- increase in urine osmolality-
* a longer lasting analogue of vasopressin contains D-Arg @ position 8

Question 29

Nephrogenic DI

Answer 29

inability of the kidneys to respond normally to vasopressin. Treated with replacement therapy with a diuretic to reduce elevated Na concentrations. Nephrogenic DI can be caused by Mutations in the gene for AQP2.

Question 30

Mutations in gene for AQP2

Answer 30

leads to Nephrogenic DI

Question 31

Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Answer 31

(tumor, meningitis, trauma, or drugs)excessive secretion of vasopressin, decreased osmolality, low levels of plasma Na (hyponatremia) and cell swelling. Treatment = fluid restriction and infusion of hypertonic Na.

Question 32

Suckling

Answer 32

oxytocin release is stimulated by suckling due to mechanoreceptors in the nipple stimulating the Hypothalamus .
releases PRL, OT, and GnRH

Question 33

Parturition

Answer 33

childbirth; initiated by oxytocin by an increase in the number of oxytocin receptors in the myometrium that occurs in the response to increased levels of estrogen prior to birth.

Question 34

Milk ejection reflex(milk let down)

Answer 34

Suckling causes Hypothalamus to send nervous pathway to posterior pituitary to increase Oxytocin.

Question 35

Milk secretion

Answer 35

Suckling causes hypothalamus to inhibit Dopamine release from arcuate nucleus that removes the inhibition . the anterior pituitary increases the release of prolactin. causes milk secretion

Question 36

4 effects of Suckling

Answer 36

1. stimulates sensory nerves from the breast to the spinal cord to the brain
2. arcuate nucleus of the hypothalamus, inhibits Dopamine release. Increasing PRL release
3. supraoptic and paraventricular nuclei of the hypothalamus triggers production and release of OT in the posterior pituitary
4. in preoptic area and arcuate nucleus, GnRH is inhibited. thus inhibiting the release of FSH and LH and inhibits the ovarian cycle.