Endocrinology- Exam 1- Posterior Pituitary

What is another name for the pituitary gland?

Hypophysis

What is another name for the posterior lobe of the pituitary?

What is another name for the anterior lobe of the pituitary?

NBQ

-Neurohypophysis

-Adenohypophysis

T/F: the posterior pituitary produces ADH and oxytocin. TQ

FALSE: it stores and secretes these! It does NOT make any hormones!!

What is the role of the anterior lobe of the pituitary gland?

receive signals from the hypothalamus to make and secrete 7 important hormones (trophic hormones)

What is the name of the area between the hypothalamus and the pituitary gland?

Infundibulum

What is the inferior portion of the posterior pituitary called?

What is the superior end called?

-median eminence

-infundibulum/pituitary stalk

Are the axons that pass down from the hypothalamus to the infundibulum (superior) end of the posterior pituitary myelinated or non-myelinated?

non-myelinated

What is the pathway from the Hypothalamus to the Posterior Pituitary? Long card

hormones in hypothalamus-> travel down non-myelinated axons-> stored in nerve terminals of the post. pituitary-> once stimulated, neurosecretory vesicles are released from the post. pituitary and secreted into blood

What are the two hormones that are produced by the hypothalamus?

Which nuclei produces each?

TQ

-Oxytocin (paraventricular nuclei)

-ADH (supraoptic nuclei)

Oxytocin and ADH are both considered what type of hormones?

Peptide Hormones

Where does ADH/Vasopressin primarily act and what is its effect?

acts on collecting ducts of kidney to facilitate reabsorption of water into blood

What is unique about Oxytocin?

one of the few hormones involved in creating a positive feedback loop (labor/delivery)

When would we need to release of ADH/Vasopressin? (2) TQ

1. Decrease in Blood volume or low BP

2. Increase in blood osmolarity (dehydration)

What senses decrease in blood volume/low BP ?

baroreceptors

What senses blood osmolarity?

osmoreceptors

Where, SPECIFICALLY, does ADH act on the target tissue?

principal cells of the collecting ducts (of nephrons in the kidney)

What is the secondary effect of vasopressin (ADH) and when would we see this effect taking place? TQ

-vasoconstriction

-during rapid blood loss (ex: hemorrhaging) to help maintain increased blood pressure

Which ADH receptor utilizes the adenylyl Cyclase mechanism (cAMP)?

V2 receptor (kidneys)

which ADH receptor utilizes the phospholipase C mechanism (IP3, DAG, Ca2+)?

V1 receptor (vascular smooth muscle)

T/F: ADH concentrates sodium and waste products in the urine.

TRUE

ADH causes reabsorbing of water into the blood. This does what to blood volume and blood pressure?

What does it do to urine concentration?

TQ

-increase blood volume

-increase BP

-increase urine concentration (less diluted w water)

What are VRAs and what do they do?

Vasopressin receptor antagonists; block the action of ADH/Vasopressin

What population would likely be on a VRA (vasopressin receptor antagonist)?

Those with congestive heart failure, hyponatremia (low sodium in blood), liver cirrhosis and SIADH

What occurs during central diabetes insipidus?

What can this be caused by? TQ

-decreased output of ADH

- insufficient hypothalamus release, and/or trauma to pituitary

What are the physical characteristics of central diabetes insipidus? (think what hormone is depleted and the effects of this!) TQ (4)

1. Polyuria (can't hold urine)

2. Dilute urine

3. hypotension (decreased plasma volume)

4. Increased plasma concentration

In central diabetes insipidus (CDI), what is one way that the body tries to compensate for the lack of ADH?

Increasing aldosterone

In CDI compensation, aldosterone is produced from the _______________ ___________ and is released. This causes __________________ renal reabsorption of __________.

adrenal cortex; increase; sodium

Aldosterone increases reabsorption of water and electrolytes in the kidneys how?

increases renal reabsorption of sodium, excretes hydrogen and potassium ions

Overall, when the body compensates for CDI by secreting aldosterone, what happens to blood volume and blood pressure?

What happens to blood osmolarity?

-both increase

-osmolarity decreases

How is aldosterone synthesized? (long card, NEED TO KNOW)

1. Kidney senses low BP and secretes RENIN

2. Renin converts angiotensinogen to angiotensin I

3. The lungs secrete ACE (angiotensin converting enzyme) and converts angiotensin I to angiotensin II

4. Angiotensin II stimulates the zona glomerulosa (outer layer of adrenal cortex)

5. Zona glomerulosa makes and secretes aldosterone to act on principal cells of the collecting duct in the kidney.

which cells in the kidney responds to a state of low BP and produce renin? 100% TQ

What does renin then activate?

-granular cells / juxtaglomerular cells/ JG cells (NEED TO KNOW ALL AKAs)

-renin converts angiotensinogen from the liver to angiotensin I.

Central Diabetes Insipidus leads to ________________ plasma volume, ____________ plasma solute concentration, and __________________ blood pressure.

It also leads to ______________ polyuria and _________________ urine solute concentration.

TQs

decrease; increase; decrease

increase; decreased

Aldosterone secretions leads to ______________ reabsorption.

This then ______________ water reabsorption, ____________________ blood volume and _____________ blood pressure. TQs

-increased

-increased; increased; increased

When aldosterone is released, what three things change with the urine? TQ

1. Potassium secretion

2. Decreased urine output

3. Increased urine concentration (less diluted)

What happens when a patient has Nephrogenic Diabetes Insipidus (NDI)?

They have a decreased sensitivity to ADH in principle cells of the collecting duct; causing ADH levels to increase since the kidney is not responding!

T/F: In nephrogenic diabetes insipidus, the kidney overly concentrate urine.

FALSE- they cannot concentrate urine since they have a decreased sensitivity to ADH

How is Nephrogenic diabetes insipidus treated?

With thiazide duiretics - cause excretion of more NaCl so urine isn't as dilute

What is the main difference in characteristics between Nephrogenic Diabetes Insipidus and Central Diabetes Insipidus? TQ

In NDI, ADH is not low. it's high with a low response from the kidneys.

In CDI, ADH is low.

What are the physical characteristics seen with NDI? (5)

- Polyuria

-Dilute urine

-Hypotension (decreased plasma volume)

-Increased plasma concentration

-ADH levels are elevated in the blood

What occurs in Syndrome of inappropriate antidiuretic hormone secretion (SIADH)?

Excessive release of ADH leads to fluid overload in patients.

During Syndrome of inappropriate antidiuretic hormone secretion (SIADH), blood volume _________________, urine concentration is _________________ and plasma sodium/electrolytes are ________________.

increased; increased; diluted

How is SIADH treated?

with an ADH antagonist and water restriction

What can cause SIADH? TQ

-Strokes

-Head traumas

-Brain tumors

-Cancer

What is the major concern with someone suffering from SIADH?

Edema build up in deadly places (ex: cerebral edema)

Where is oxytocin synthesized? TQ

paraventricular nuclei (in hypothalamus)

Which mechanism/second messengers does oxytocin use? TQ

-Phospholipase C mechanism

-IP3, DAG, Ca2+

What is the primary action of oxytocin? TQ

What feedback mechanism does it use to do this?

-uterine contractions and dilation of the cervix, and also helps reduce bleeding post-partum

-positive feedback mechanism

T/F: Oxytocin is used for maintaining breast feeding through the first weeks of life.

FALSE- it does not maintain it, it only is necessary for the first initial "let-down" part

After birth, what does oxytocin do for its role in breastfeeding?

- milk ejaculation reflex ('let-down")

-oxytocin is secreted and mother's milk ducts contract, ejecting milk into the infants mouth.

T/F: suckling is required for oxytocin release during breastfeeding.

FALSE- though it usually is a trigger, it isn't required. Sight, sound, and smell of an infant can also stimulate milk "let-down"

What is the role of oxytocin in males?

moving sperm and affects production of testosterone

What are the 8 roles oxytocin has (male or female)?

- signal contractions (F)

-promote milk let-down (F)

-moving sperm (M)

-affect testosterone production (M)

-Bonding hormone

-Sexual response

-orgasm

-social interactions

what are the three pathologies discussed about ADH?

-Central diabetes Insipidus

-Nephrogenic diabetes insipidus

-SIADH

What is the secondary action of oxytocin?

(from fergie's chart summary)

love <3

What type of hormone is oxytocin?

peptide hormone