Prefi:Lec:PosteriorPG Flashcards
It serves as an extension of the forebrain.
Posterior pituitary
What are the two hormones that posterior pt releases?
Oxytocin
Arginine Vasopressin/ADH
In neurohypophysis, where does AVP synthesized?
Supraoptic (bishop)
Magnicellular neurons of the supraoptic (rodriguez)
In neurohypophysis, where does oxytocin synthesized?
Paraventricular nuclei of the hypothalamus (bishop)
In neurohypophysis, what hormone is synthesized in the paraventricular nuclei of the hypothalamus
Oxytocin
In neurohypophysis, what hormone is synthesized in the magnicellular neurons of the supraoptic?
Arginine Vasopressin/ ADH
The avp and oxytocin hormones are synthesized and transported to the posterior pt via their axons, in what part of the hypothalamo?
Hypothalamo neurohypophyseal tract
what tract transits the median eminence of the hypothalamus and continues into the posterior pituitary thru the pituitary stalk?
Hypothalamo neurohypophyseal tract
The synthesis of each of posterior pt hormones is tightly linked to the production of a larger protein with a poorly understood function called __________.
Neurophysin
Statement 1: AVP is synthesized inside of the hypothalamus while Oxytocin is synthesized inside of the hypothalamus.
Statement 2: Both hormones are synthesized outside of the hypothalamus.
a. Only statement 1 is correct
b. Only statement 2 is correct
c. Both statement are correct
d. Both statement are incorrect
b. Only statement 2 is correct
T or F: Both hormones have an autocrine or a paracrine function.
True
The release of the hormones occurs in response to?
Serum osmolality or
by suckling
Hormones produced by the neurohypophysis are controlled by the _________.
Central Nervous System
What do you call the cyclic nonapeptide, with a disulfide bridge connecting AA residues 1 and 6?
Oxytocin
What do you call the hormone that is nonapeptide and very similar in composition to ADH?
Oxytocin
It is a hormone that is secreted in association with a carrier protein.
Oxytocin
What term used when oxytocin stimulates contraction of the gravid uterus?
“Ferguson reflex”
As a posttranslational modification in oxytocin, the ___________ is amidated.
C-terminus
Oxytocin has a CRITICAL ROLE in (1)___________ and plays a MAJOR ROLE in (2)____ and (3)____.
(1) lactation
(2) labor
(3) parturition (childbirth)
Oxytocin is also unique because its secretion responds to what? ___________. Explain.
Positive feedback loop
*circulating levels of oxy actually perpetuate further hormone secretion, instead of suppressing further hormone secretion as is the case with most anterior pit ho. In this way, uterine contractions propagate oxytocin release, which causes further uterine contractions, which cause further oxytocin release until parturition occurs.
What synthetic toxin used in obstetrics to induce labor?
Pitocin
Oxytocin has been shown to have effects on what functions?
Pituitary fxn
Renal fxn
Cardiac fxn
Metabolic fxn
Immune fxn
What hormone is released in response to neural stimulation of receptors in the birth canal and uterus, and of touch in the breast?
Oxytocin
What hormone plays a role in hemostasis at the placental site following delivery?
Oxytocin
What hormone stimulates muscle contraction during delivery and lactation?
Oxytocin
What is the former name of Arginine Vasopressin?
Anti-diuretic hormone (ADH)
What do you call the cyclic nonapeptide with an identical disulfide bridge that only have two amino acids?
AVP
Its major action is to regulate renal free water excretion, thus, ha a central role in water balance.
AVP
What is the major action of AVP?
to regulate renal free water excretion
Where does the vasopressin receptors in the kidney (V2) are concentrated?
•Renal collecting tubules
•Ascending limb of the loop of Henle
Vasopressin receptors in the kidney (V2) are coupled to _____________
Adenylate cyclase
V2 are coupled to adenylate cyclase, and once activated, they induce insertion of a water channel protein called _____________
Aquaporin-2
What do you call the hormone that is also a potent pressor agent?
AVP
Fill in the blank: AVP affects blood clotting by promoting factor ____ release from _________ and ________ release from the ___________.
•Factor VII; hepatocytes
•von Willebrand factor; endothelium
What factors doe AVP promotes that affects blood clotting?
•Factor VII
•von Willebrand factor
What are the vasopressin receptors that are coupled to phospholipase C?
V1a & V1b
Fill in the blank: Vasopressin receptors such as V1a and V1b are coupled to ______________.
Phospholipase C
What are the two receptors that regulate the release of vasopressin from the posterior pituitary?
• Hypothalamic osmoreceptors
• Vascular baroreceptors
T or F: As plasma osmolality increases, vasopressin secretion increases
T
*it result to a reduction in renal free water clearance, a lowering of plasma osmolality, and return to homeostasis
Fill in the blank: The __________ are extremely sensitive to even small changes in plasma osmolality.
Osmoreceptors
What is the average osmotic threshold for vasopressin release in humans?
Reference range?
• 284 mOsm/kg
• Ref range: 275-295mOsm/kg
Where does the vascular baroreceptors located?
left atrium, aortic arch, carotid arteries
It initiates vasopressin release in response to a fall in blood volume or blood pressure.
Vascular baroreceptors
How many percent does fall in arterial blood pressure in normal humans will trigger vasopressin release?
5% to 10%
It is a nonapeptide hormone that acts on the distal convoluted and collecting tubules of the kidneys.
AVP
What do you call the hormone that decreases the production of urine by promoting reabsorption of water by the renal tubules thereby maintains water homeostasis?
AVP
It regulates the total concentrationbof blood through water balance.
AVP
What hormone makes the renal collecting tubule permeable to water?
AVP
What is the major function of AVP?
Maintains osmotic homeostasis by regulating water balance
Principal regulator of ADH secretion:
Increased plasma osmolality (>295 mOsm/kg)
What are the physiologic stimuli to ADH secretion?
Nausea, cytokine, hypercarbia, pregnancy, hypoglycemia, nicotine
What are the physiologic stimuli to ADH release?
Dehydration (emesis), physical and emotional stress due to major surgery
Suppress AVP release
Low plasma osmolality (<284 mOsm/kg)
What are the inhibitors of ADH release?
Ethanol, cortisol, lithium, demeclocycline
What are the defects in AVP regulation?
Malignancies, pulmonary disease, CNS disorders, fungal infection
What are the stimuli of AVP? (notes)
•little amount of H2O (dehydration)
•increased osmotic pressure
•decreased blood pressure
•sympathetic simulation
AVP: 2 sites of action
kidneys & blood vessels
T or F: Secretion of AVP is indirectly related to the concentration of the plasma osmolality.
F : DIRECTLY RELATED
What are the types of ADH receptors?
• V1 receptors
• V2 receptors
• V3 receptors
What is the function of V1 receptors?
responsible for the increase in vasomotor tone with metabolic effects
What type of ADH receptors that are associated with diuretics?
V2 receptors
What type of ADH receptors that stimulates ACTH secretion?
V3 receptors
What disorder is characterized by the deficiency of AVP which results in severe polyuria (>=2.5 liters of urine/day)?
Diabetes Insipidus
What is the hallmark of diabetes insipidus?
Hypotonic urine
INC OR DEC: DI serum osmolality
Increased (>295mOsm/kg)
INC OR DEC: DI urine osmolality
Decreased (>300 mOsm/kg)
INC OR DEC: DI serum sodium
Increased (>145 mmol/L)
Give at least 2 clinical picture of DI.
• Normoglycemia
• Polyuria with low specific gravity
• Polydipsia (secondary polydipsia)
• Polyphagia (occassional)
What are two major types of diabetes insipidus?
• True DI/Hypothalamic/Neurogenic/Cranial/Central DI
• Nephrogenic DI
What is the deficiency of ADH caused by failure of hypothalamus to produce the hormone?
True DI/Hypothalamic/Neurogenic/Cranial/Central DI
What is the deficiency of ADH caused by failure of the kidney to respond ADH, problem in the receptors of the kidney do not recognize?
Nephrogenic DI
A deficiency of ADH that has NO ADH-Tertiary
True DI/Hypothalamic/Neurogenic/Cranial/Central DI
A deficiency of ADH that has normal ADH-primary dysfunction
Nephrogenic DI
What type of DI?
Water: not retained
Urine: diluted (plainly water)
True DI/Hypothalamic/Neurogenic/Cranial/Central DI
What type of DI?
Water: excreted
Renal failure, drugs, congenital defect
Nephrogenic DI
What type of DI that is characterized by either a complete absence of or low plasma AVP with effective AVP receptors
True DI/Hypothalamic/Neurogenic/Cranial/Central DI
What type of DI that results from damage to the hypothalamus or even the neurohypophysis which is responsible for the release of AVP?
True DI/Hypothalamic/Neurogenic/Cranial/Central DI
What type of DI that may also be caused by genetic abnormalities or mutations affecting the hypothalamus or pituitary gland, and medications?
True DI/Hypothalamic/Neurogenic/Cranial/Central DI
What are the other causes of True DI/Hypothalamic/Neurogenic/Cranial/Central DI?
Head trauma, infectious diseases, anemia, alcoholism, drugs
What type of DI that is seen as having normal plasma or elevated AVP but abnormally functioning AVP receptors (renal resistance to ADH secretion)?
Nephrogenic DI
What type of DI that is due to the kidney failure (due to renal disease) to respond to normal or elevated AVP plasma concentration?
Nephrogenic DI
T or F: Nephrogenic DI is either congentinal or acquired.
Forda true
What is the most common etiology for congenital nephrogenic DI?
X-linked receptor defect
What is the most common cause of acquired nephrogenic DI?
Medications
Nephrogenic DI may also be caused by using prohibited drugs such as ____________.
Propoxyphene (darvon)
What are the other causes of nephrogenic DI?
• Electrolyte imbalance
• Multiple myeloma
• Sarcoidosis
A type of DI that is also known as the compulsive water drinking disorder without a stimulus.
Primary polydipsia/psychogenic polydipsia/dipsogenic DI
It may be due to a faulty thirst hypothalamic mechanism.
Primary polydipsia/psychogenic polydipsia/dipsogenic DI
Primary polydipsia/psychogenic polydipsia/dipsogenic DI
Serim osmolality and sodium: (N/Inc/Dec)
Normal or low level
A type of DI that develops due to the excessive activity of the placental cysteine aminopeptidase (PCAP) or placental vasopressin.
Gestational DI
Fill in the blank: Gestastional DI develops due to the excessive activity of the (what enzyme) ____________.
Placental cysteine aminopeptidase (PCAP)/cystine aminopeptidase/Oxytocinase
What type of DI that results from the degradation of the AVP by PCAP during pregnancy?
Gestational DI
What is the diagnostic test in DI?
Water deprivation test/dehydration test
It is the gold standard test for diagnosing DI.
Water deprivation test/dehydration test
What type of test does measures the serum and urine osmolality?
Water deprivation test/dehydration test
How many hours/percent does that the patient needed to prepare for water deprivation test?
At least 8 hours no fluid intake/ 5℅ of the body mass has been lost
What are the patient preparatios before undergoing water deprivation test?
• At least 8 hours no fluid intake/ 5℅ of the body mass has been lost
• Avoid smoking and caffeine intake that might affect AVP release or urine output
What is the screening test for DI?
Urine osmolality
What is the urine osmolality of normal patients?
50 mOsm/kg
What is the urine osmolality of patient diagnosed with DI?
<300 mOsm/kg
T or F: Plasma Osmolality in DI is decreased.
F: Increased (little H2O in the body)
T or F: Urine osmolality in DI is increased.
F: Decreased (excreted large amount of H2O)
What is the confirmatory test for DI? (notes)
Overnight water deprivation test
How many hours needed for fasting in overnight water deprivation test?
8-12 hours – NO water and food intake
Statement 1: In neurogenic DI, ADH levels are high
Statement 2: In nephrogenic DI, ADH levels are low or normal
A. Only statement 1 is correct
B. Only statement 2 is correct
C. Both statement are correct
D. Both statement are incorrect
B.
*Statement 1: In neurogenic DI, ADH levels are LOW
Fill in the blank:
Time/Hours in Water deprivation test
• patient weight, pulse rate, BP should be taken _________
• serum osmolality is measured every __________
• urine volume and osmolality every ___________
• test is conducted usually for ____________
• hourly
• 4 hours
• 2 hours
• 8 hours
What is the reference range of osmolality in DI?
• 275-295 mOsm/kg (bishop)
• 280-295 mOsm/kg (McPherson and Pincus)
*Urine osmolality: 300-900 mOsm/kg (Bishop)
It is an additional test for the diagnosis of DI which differentiates neurogenic DI from nephrogenic DI.
Desmopressin
It is an additional test for the diagnosis of DI which differentiates neurogenic DI and primary polydipsia from nephrogenic DI.
AVP and Copeptin
It is an additional test for the diagnosis of DI which differentiates neurogenic DI from primary polydipsia.
3% hypertonic saline infusion (HSI) with copeptin
It is a 39-amino-acid C-terminal segment of pre-pro-arginine vaspressin.
Copeptin
It is secreted in response to the same stimuli as AVP and in equimolar amounts to AVP.
Copeptin
It is characterized by continuous secretion of ADH in the absence of stimulus.
Syndrome of inappropriate ADH secretion (SIADH)
It is described as having euvolemic hypoosmolar hyponatremia associated with hyperosmolar urine.
Syndrome of inappropriate ADH secretion (SIADH)
What is the deficiency that contains excessive free water retention coupled with hypoosmotic volume expansion.
Syndrome of inappropriate ADH secretion (SIADH)
In this condition, there is excess free water reabsorption in the distal renal tubule leading tona decreased osmolality of the ECF.
Syndrome of inappropriate ADH secretion (SIADH)
T or F: In SIADH, increased AVP secretion equals decreased water retention.
F: increased AVP secretion equals INCreased water retention.
Increased ADH or copeptin concentrations are often associated with what deficiency?
Syndrome of inappropriate ADH secretion (SIADH)
What are the causes of Syndrome of inappropriate ADH secretion (SIADH)?
• CNS disease
• Cancer
• Tuberculosis
• Pneumonia
• Medications
• Nicotine
What is the diagnostic feature for Syndrome of inappropriate ADH secretion (SIADH)?
Euvolemic hypoosmolar hyponatremia associated with hyperosmolar urine
(N, Inc, Dec)
SIADH urine volume
Decreased
(N, Inc, Dec)
SIADH serum sodium
Decreased (<135 mmol/L)
(N, Inc, Dec)
SIADH urine sodium
Normal or increased (>20 mmol/L)
(N, Inc, Dec)
SIADH serum osmolality
Decreased (< 275 mOsm/kg)
(N, Inc, Dec)
SIADH urine osmolality
Normal or increased (> 800 Osm/kg)
What is the diagnostic test for syndrome of inappropriate ADH secretion (SIADH)?
Water loading test (WLT)
What is the physical stimuli for oxytocin? (notes)
Sucking the nipple of the mother
It stimulate milk production of the mother. (notes)
Hearing a baby cry
Positive feedback of oxytocin (notes)
Increase in oxytocin = (N, Inc, Dec) ______ the contraction of uterus
Increase
T or F: Both major types of DI (neurogenic & nephrogenic) & primary polydipsia are collectively referred to as polyuria-polydipsia syndrome.
T
