Lecture 12: The HP unit

Question 1

what 2 structures meet to form the pituitary

Answer 1

Rathke’s pouch + Infundibulum process

Question 2

what is the source of melanocyte stimulating hormone (MSH)

Answer 2

pars intermedia of pituitary

Question 3

what is the target of vasopressin

Answer 3

collecting ducts of kidney

Question 4

what is the effect of vasopresson in the kidney

Answer 4

• increases number of aquaporins in CD
• increases water reabsorption by CD
• decreases urine production = antidiuretic

Question 5

what are the 2 sitmuli for vasopressin release

Answer 5

Osmoreceptors in hypothalamus (mainly)
decreased stimulation of carotid and aortic stretch receptors (important for large acute changes in blood volume)

Question 6

what two places are V2 receptors found within the kidney

Answer 6

distal tubule and collecting duct

Question 7

when vasopressin binds V2, it activates what pathways

Answer 7

Cyclic AMP (cAMP)

increases the permeability of the luminal membrane to water by inserting new aquaporin water channels

water enters cells from lumen , and then back into blood

Question 8

when there is a dramatic loss of blood, ____ receptors present in vascular smooth muscle tissue are stimulated to recover blood pressure

Answer 8

V1A

Question 9

what are the 2 stimuli that vasopressin responds to

Answer 9

• increased blood osmolality
• decreased blood volume

Question 10

Central (neurogenic) Diabetes Insipidus often occurs as a result of…

a

Answer 10

a head injury that results in disease or damage to ADH neurons

Question 11

Central (neurogenic) DI physiological symptoms

Answer 11

• deficiency of vasopressin release (low serum VP)
• collecting ducts impermeable to water
• large volumes dilute urine
• body fluids become concentrated

Question 12

what is the treatment for Central DI

Answer 12

Exogenous vasopressin or synthetic analogues (dDVAP)

Question 13

In Nephrogenic DI, the collecting ducts are ___________ to VP

Answer 13

non-responsive
there is a defect in V2 receptor, G-protein or intracellular signaling

Question 14

physiological effects of Nephrogenic DI

Answer 14

• water not reabsorbed, large volumes of dilute urine
• body fluids concentrated
• VP release is elevated, serum VP high

Question 15

possible txt for Nephrogenic DI

Answer 15

• Thiazide diuretics decrease renal filtration (GFR) and decrease Na reabsorption in distal tubule

Question 16

what is Syndrome of Inappropriate ADH (SIADH) a result of

Answer 16

• VP being released from an autonomous source (like a tumor)
• VP regulation not under inhibitory feedback control

Question 17

Symptoms of SIADH

Answer 17

• Hyponatremia (low serum Na, high urine Na)
• reduced serum osmolarity
• confusion, disorientation
• generalized muscle weakness, tremors, ataxia
• seizures and coma

Question 18

how can you test to differentiate b/w central or nephrogenic diabetes in a patient

Answer 18

VP response test
- specific gravity peaks in animals w/ primary VP deficiency
- but shows little change in animals w/ nephrogenic DI

Question 19

treatment for SIADH

Answer 19

• Hypertonic saline
• diuretics
• V2 antagonists (demeclocyline, conivaptan, tolvaptan)
• fluid restriction

Question 20

oxytocin promotes…

Answer 20

• parent offspring bonidng
• mate bonding in monogamous species
• social cohesion
• ensures delivery of term fetus
• milk release during lactation
• transport of sperm

Question 21

physiological effects of oxytocin in relation to reproduction

Answer 21

• strengthens uterine contractions at end of pregnancy
• milk release during nursing
• sperm transport in female reproductive tract

Question 22

f

Behavioral functions of oxytocin in relation to reproduction

Answer 22

• maternal offspring bond
• mate bonds

Question 23

what are the non-reproductive effects of OT

Answer 23

• slows heart
• reduced bp and its force of contraction by stimulating ANP

Question 24

what is the role of OT in birth

Answer 24

• labor is initiated when uterine oxytocin receptor concentration reaches a critical threshold
• *positive feedback cycle *increases until cervical dilation and devliery of baby complete

Question 25

OT and milk-let down demand

Answer 25

• suckling/milking causes paraventricular cells to release OT via posterior pit. into blood stream
• myoepithelial cells contract which moves milk into ducts and cistern
• milk let down

+ feedback mechanism