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BIOCHEMISTRY > ME04 - Posterior Pituitary > Flashcards

ME04 - Posterior Pituitary Flashcards

(49 cards)

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1
Q

Also called the Neurohypophysis

A

Posterior Pituitary Gland

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2
Q

Glial-like cells in Post Pituitary Gland; Do not secrete hormones

A

Pituicytes | Neurons secretes hormones

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3
Q

Function of Pituicytes

A

Act to support large numbers of terminal
nerve fibers and terminal nerve endings from nerve tracts that originate in the supraoptic and paraventricular nuclei of the hypothalamus

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4
Q

What are Neurohypophysial Hormones?

A

Anti-diuretic hormone (ADH) or vasopressin (Supraoptic Nuclei) and Oxytocin (Paraventricular Nuclei)

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5
Q

Carrier proteins that transports neurohypophysial hormones down to the nerve endings in the neurohypophysis
(requires several days)

A

Neurophysins

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6
Q

Formed primarily in the supraoptic nuclei

A

ADH

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7
Q

Formed primarily in the paraventricular nuclei

A

Oxytocin

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8
Q

Flow of Neurohypophysial Hormones

A

Nerve impulses transmitted in nuclei&raquo_space; Hormone + neurophysin immediately released from the secretory granules in the nerve endings by exocytosis&raquo_space; Hormone absorbed in nearby capillaries&raquo_space; Hormone separates from neurophysin (no function after leaving nerve terminal)

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9
Q

Differentiate ADH and Oxytocin in terms of molecular formula

A

Both are polypeptides, each containing nine amino acids
Vasopressin: Cys-Tyr-Phe-Gln-Asn-Cys-Pro-ArgGlyNH2
Oxytocin: Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-GlyNH2
DIFFERENCE: Phe, Arg for Vasopressin; Ile,Leu for Oxytocin

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10
Q

Causes decreased excretion of water by the kidneys

A

Injection of ADH (as small as 2 nanograms)

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11
Q

What happens to the collecting tubules and ducts without ADH?

A

Collecting tubules and ducts become almost impermeable to water and allows extreme loss of water into the urine

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12
Q

ADH causes insertion of aquaporins which causes absorption of water from the collecting tubules and ducts by osmosis. True or False?

A

True.

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13
Q

Effect of Low concentrations of ADH

A

Water Reabsorption

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14
Q

Effect of Higher concentrations of ADH

A

A potent effect of constricting the arterioles throughout the body

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15
Q

Stimulus on the Vasoconstrictor Effect of ADH

A

Decreasedbloodvolume
Decreased stretch signal from atrial stretch receptors,
baroreceptors of the carotid, aortic, and pulmonary regions

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16
Q

Primarily regulates secretion of ADH

A

Osmotic & volume stimuli

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17
Q

Most important physiologic stimulus/ MOST POTENT for ADH secretion

A

_ INC plasma osmolarity

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18
Q

Also potent stimulus for ADH secretion

A

Hypovolemia or volume contraction

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19
Q

Flow of Regulation of ADH

A

H2O is conserved in the body while Na & other solute continue to be excreted in the urine&raquo_space; causes dilution of the solutes in the ECF&raquo_space; correcting the initial excessively concentrated ECF

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20
Q

Factors for Inhibiting/Supressing ADH

Study These Flashcards
A

DEC serum osmolarity, ECF volume, Temp; ANP, GABA, CORTISOL, Thyroid Hormone, ETHANOL (30-90ML whiskey sufficient)

21
Q

Factors for Stimulating ADH

Study These Flashcards
A

INC serum osmolarity, ECF volume, CSF sodium, Temp, STRESS, EXERCISE, SENESCENCE, Drugs: Nicotine, Opiates, Barbiturates, Nausea Vomiting Pain Hypoglycemia

22
Q

Diseases involving ADH

Study These Flashcards
A

Diabetes insipidus (DI) ( Central & Nephrogenic)
Syndrome of Inappropriate Anti-diuretic Hormone
(SIADH)

23
Q

State of excess free water excretion

Study These Flashcards
A

Diabetes Insipidus (DI)

24
Q

Manifestations of Diabetes Insipidus (DI)

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A

Excretion of excessive amounts of dilute urine
Excessive thirst
Reduction of fluid intake will not affect the
concentration of the urine

25
Total or partial loss of the ability to synthesize or release AVP
Central Diabetes Insipidus
26
Causes of Central Diabetes Insipidus
Causes: brain tumor head trauma brain surgery that damages the posterior pituitary or hypothalamus
27
Loss of free water leads to ? In Central Diabetes Insipidus
_INC in plasma osmolality
28
Hyperosmolality in Central Diabetes Insipidus cannot increase AVP sufficiently but usually results in a large increase in thirst. True or False?
True.
29
In many patients with central DI, the patient has:
a. high water intake and output b. normal plasma osmolality
30
In patients with Central DI, severe hyperosmolality becomes apparent only when?
Only when water intake is restricted
31
Levels of ADH is normal or elevated but the renal tubules cannot respond appropriately to ADH
Nephrogenic Diabetes Insipidus
32
Causes of Nephrogenic Diabetes Insipidus:
Failure of the countercurrent mechanism to form a hyperosmotic medullary interstitium ADH receptors in distal tubules & collecting ducts maybe non-functional or kidneys damaged Drugs : lithium (drug for bipolar disorder) & tetracyclines
33
In water deprivation test, differentiate Central DI, Nephrogenic DI and Psychogenic Polydipsia
In CENTRAL DI, DEC ADH in 6-8H (510,520,55) In Nephrogenic DI, DEC ADH in 6-8H (170,173,175) In Psychogenic Polydipsia (Increase water intake) DEC ADH in 6-8H (520,520,525) _
34
Treatment of Diabetes Insipidus - Central DI:
SyntheticanalogofADHlikedesmopressin (subcutaneous or nasal spray)
35
Treatment of Diabetes Insipidus - Nephrogenic DI:
Correct the underlying renal disorder for hypernatremia: low Na diet Diuretic that enhances sodium excretion: Thiazides
36
Overproduction of ADH not accounted for by hyperosmolality or non-osmotic stimuli to ADH
Syndrome of Inappropriate Anti-diuretic Hormone (SIADH)
37
Flow of SIADH
Excessive secretion of ADH _ reduces urine output _ retention of water and increase in volume of ECF _ secondary increase in urine output _ urine formed is concentrated _ Na+ and other ions excreted in urine _lowNa+inECF _ brain swelling _ seizures, coma , death
38
Treatment of SIADH (Aimed towards correcting hyponatremia and its symptoms)
Loop diuretic (furosemide): promotes free water excretion Isotonic and sometimes, hypertonic saline Fluid intake restriction to 0.5 to 1.0 L/day Aquaretics/vaptans: agents that competitively block ADH action and increase water excretion Demelocycline (an older tetracycline)
39
Powerfully stimulates contraction of the pregnant uterus Causes milk to be expressed from the alveoli into the ducts of the breast _ Facilitates bonding or attachment between mother & infant
OXYTOCIN
40
Functions of Oxytocin
At least partially responsible for causing birth of the baby: In a hypophysectomized animal, the duration of labor is prolonged Amount of oxytocin in the plasma increases during labor, especially during the last stage Stimulation of the cervix in a pregnant animal elicits nervous signals that pass to the hypothalamus and cause increased secretion of oxytocin
41
Inhibit OTC secretion and depress milk ejection
Psychogenic factors(STRESS) and sympathetic activation
42
OXYTOCIN IN LACTATION: Milk Letdown
Baby suckles mothers nipple >> Signals transmit through sensory nerves to the oxytocin neurons in the paraventricular (and supraoptic nucle) in the hypothalamus >> Released oxytocin from neurohypophysis carried by blood to the breasts >> Contraction of myoepithelial cells that lie outside of and form a latticework surrounding the alveoli of the mammary glands
43
OXYTOCIN as a Drug
Brand names: Syntocinon, Pitocin Used therapeutically to decrease immediate postpartum bleeding Used to induce labor OTC assists in ovulation & in the termination of the corpus luteum
44
More Reasons to Breastfeed
_ Oxytocin is not only extensively interconnected to the cortisol, noradrenaline and several neurotransmitter systems to produce long-term effects _ It is also highly correlated to resilience to stress, growth, healing and well-being.
45
How does Oxytocin influence Glucocorticoid receptor activity
Reduces excess cortisol in stress HPA-axis
46
How does Oxytocin influence Alpha2 receptor function
Blocks or modulates noradrenaline stress effects, eliciting calm behavior, decrease in arterial pressure and heart rate improved pattern of secretion of gastric hormones
47
How does Oxytocin influence Opiodergic activity
Reward and Pain-free
48
How does Oxytocin influence 5HT Synthesis
Happiness
49
How does Oxytocin influence Cholinergic Activity
Consumption, Coitus, Calm and Sleep

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