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Physiology > Lecture 12- The HP Unit > Flashcards

Lecture 12- The HP Unit Flashcards

1
Q

What are the two embryological structures that meet to form pituitary

A

Rathke’s pouch and infundibulum process

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2
Q

What is Rathke’s pouch

A

Forms in roof of oral ectoderm, forms anterior pituitary

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3
Q

What is the infundibulum process

A

Descends from the diencephalon, forms posterior pituitary

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4
Q

What part of the pituitary is the pars nervosa, and neurohyophysis

A

Posterior pituitary

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5
Q

What part of the pituitary is pars distalis and adenohypophysis

A

Anterior pituitary

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6
Q

What part of the pituitary is the intermediate lobe that is the source of melanocyte stimulating hormone

A

Pars intermedia

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7
Q

What part of the pituitary is made of a fatty sheath of tissue that supports the pituitary stalk

A

Pars tube rails

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8
Q

What are the two pathways from hypothalamus to pituitary

A
  1. Neural pathway
  2. Portal pathway
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9
Q

What’s is the neural pathway

A

Magnocellular neuron that project to the posterior pituitary to release hormones

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10
Q

What is the portal pathway

A

Small blood portal system to transport releasing hormones from the median eminence of the hypothalamus

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11
Q

What hypothalamic nuclei are responsible for releasing oxytocin and vasopressin

A

Paraventricular nuclei and supraoptic nuclei

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12
Q

What are the two hormones released in neural pathway

A

Oxytocin and vasopressin

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13
Q

Oxytocin and vasopressin differ by two amino acids. What amino acids?

A

Oxytocin has leucine and isoleucine whereas vasopressin has arginine and phenylalanine

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14
Q

What is the target of vasopressin

A

Collecting ducts of the kidney

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15
Q

What are the effects of vasopressin

A

Increase number of aquaporins in collecting duct, increase water reabsorption in collecting duct, decrease urine production

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16
Q

Is vasopressin a diuretic or antidiuretic

A

Antidiuretic

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17
Q

What is the intracellular mechanism (G-proteins…) of vasopressin

A

GPCR (Gs)—> increase cAMP—> translocation of vesicles—> exocytosis of aquaporins—> insertion in epithelial cell plasma membrane

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18
Q

What is the major stimuli for vasopressin release

A

Increased blood osmolarity sensed by osmorceptors in hypothalamus

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19
Q

What is the other mechanism that stimulates vasopressin release, more so in emergency, large volume loss

A

Decreased stimulation of carotid and aortic stretch receptors

20
Q

How do hypothalamic osmoreceptors restore normal osmolarity and ECF volume

A

Osmorecptors act on hypothalamus to increase thirst, increase water intake, and decrease ECF osmolarity and increase ECF water volume

21
Q

How do atrial baroreceptors act to increase ECG volume and decrease ECF osmolarity

A

Atrial baroreceptors act on hypothalamus to release vasopressin, causing ateriolar vasoconstriction, increase H20 permeability of CD, increase H20 reabsorption in CD, decrease urine output, increase ECF volume and decrease ECF osmolarity

22
Q

What does vasopressin bind to in distal tubule and collecting duct of kidney to stimulate exocytosis of aquaporins

A

V2 receptors, activating cAMP—> AQP-2 channels inserted into luminal membrane

23
Q

During an emergency response, decrease BP due to blood loss which receptor does vasopressin act on

A

V1A receptor present in vascular smooth muscle tissue

24
Q

What stimulates release of vasopressin

A

Decreased blood volume and increase blood osmolarity

25
Describe how central diabetes insipidus affects the levels of vasopressin, water intake, and urine
Posterior pituitary is unable to release VP so serum VP is low Collecting ducts are impermeable to water due to VP not exocytosing aquaporins Urine: diluted and large volumes
26
What is a potential treatment for central DI
Exogenous VP or synthetic analogues (because problem isn’t receiving VP at kidneys, problem is producing it)
27
Describe the role of nephrogenic diabetes insipidus in relation to VP, water permeability, body fluids
Collecting duct is not responsive to VP (defect in V2 receptor, GPCR, or intracellular signaling) Water not reabsorbed, large dilute urine Body fluids concentrated High serum VP
28
What is a possible treatment for nephrogenic DI
Thiazide diuretics: decreases GFR and decrease Na+ reabsorption in distal tubule
29
Why would exogenous VP be ineffective in treating nephrogenic DI
Problem is not with vasopressin release, VP is released normally but can’t act on V2 receptor
30
What test can you run for Diabetes insipidus
Water deprivation test
31
How does water deprivation test work
After 3-8hrs test USG if > 1.025 animal is normal to partial DI If urine remains dilute (1.003-1.024) lack of ADH activity * does not distinguish whether central or nephrogenic
32
What test can you run to differentiate between nephrogenic and central DI
VP response test
33
How does a VP response test work
Administer exogenous VP and then test USG, if >1.026 animals have primary/central VP deficiency, with little change (0.003-0.025) they have nephrogenic diabetes
34
What is desmopressin acetate
Synthetic analogue of ADH that can be used to treat primary/central DI
35
What is syndrome of inappropriate ADH (SIADH)
VP released from autonomous source (ex: tumor)
36
What are some symptoms of SIADH
Hyponatremia: low serum, high urine Reduced serum osmolarity Confusion, disorientation Generalized muscle weakness, tremors, ataxia Seizures, coma
37
What are some treatment options for SIADH
Hypertonic saline Diuretics V2 antagonists (demeclocycline, conivaptan or tolvaptan) Fluid restriction
38
Oxytocin promotes ___ and ___
Social bonding and reproduction
39
Does oxytocin promote monogamy or polygamy
Monogamy
40
In voles oxytocin increases partner preference in ___ females and OT antagonist blocks that response in ___ females
Unmated, mated females
41
In voles VP increases partner preference in ___ males and VP antagonists increases partner preference in ___ males
Unmated and mated
42
What hormone strengthens uterine contractions, causes milk release during nursing and facilitates sperm transport
Oxytocin
43
What hormone promotes the maternal offspring and mate bonds
Oxytocin
44
How does oxytocin affect heart rate and BP
Slows heart and reduces blood pressure
45
Labor is initiated when….
Uterine oxytocin receptor concentration reaches a critical threshold, positive feedback cycle progressively increases until cervical dilation and delivery of baby are complete
46
What is the role of oxytocin in milk let down demand
1. Suckling/milking- mechano and temperature receptors 2. PVN releases oxytocin via posterior pituitary 3. Myoepithelial cells contract, oxytocin causes contraction of myoepthelial cells which moves the milk into ducts and cistern 4. Milk let down result 5. Not milk production! Positive feedback mechanism

Physiology (10 decks)

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