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BIOCHEMISTRY > ME04 - Posterior Pituitary > Flashcards

ME04 - Posterior Pituitary Flashcards

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

A

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

21
Q

Factors for Stimulating ADH

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

A

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

23
Q

State of excess free water excretion

A

Diabetes Insipidus (DI)

24
Q

Manifestations of Diabetes Insipidus (DI)

A

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

25
Q

Total or partial loss of the ability to synthesize or release AVP

A

Central Diabetes Insipidus

26
Q

Causes of Central Diabetes Insipidus

A

Causes:
brain tumor
head trauma
brain surgery that damages the posterior
pituitary or hypothalamus

27
Q

Loss of free water leads to ? In Central Diabetes Insipidus

A

_INC in plasma osmolality

28
Q

Hyperosmolality in Central Diabetes Insipidus cannot increase AVP sufficiently but usually results in a large increase in thirst. True or False?

A

True.

29
Q

In many patients with central DI, the patient has:

A

a. high water intake and output
b. normal plasma osmolality

30
Q

In patients with Central DI, severe
hyperosmolality becomes apparent only when?

A

Only when water intake is restricted

31
Q

Levels of ADH is normal or elevated but the renal tubules cannot respond appropriately to ADH

A

Nephrogenic Diabetes Insipidus

32
Q

Causes of Nephrogenic Diabetes Insipidus:

A

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
Q

In water deprivation test, differentiate Central DI, Nephrogenic DI and Psychogenic Polydipsia

A

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
Q

Treatment of Diabetes Insipidus - Central DI:

A

SyntheticanalogofADHlikedesmopressin (subcutaneous or nasal spray)

35
Q

Treatment of Diabetes Insipidus - Nephrogenic DI:

A

Correct the underlying renal disorder for
hypernatremia: low Na diet
Diuretic that enhances sodium excretion: Thiazides

36
Q

Overproduction of ADH not accounted for by hyperosmolality or non-osmotic stimuli to ADH

A

Syndrome of Inappropriate Anti-diuretic Hormone (SIADH)

37
Q

Flow of SIADH

A

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
Q

Treatment of SIADH (Aimed towards correcting hyponatremia and its symptoms)

A

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
Q

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

A

OXYTOCIN

40
Q

Functions of Oxytocin

A

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
Q

Inhibit OTC secretion and depress milk ejection

A

Psychogenic factors(STRESS) and sympathetic activation

42
Q

OXYTOCIN IN LACTATION: Milk Letdown

A

Baby suckles mothers nipple&raquo_space; Signals transmit through sensory nerves to the oxytocin neurons in the paraventricular (and supraoptic nucle) in the hypothalamus&raquo_space; Released oxytocin from neurohypophysis carried by blood to the breasts&raquo_space; Contraction of myoepithelial cells that lie outside of and form a latticework surrounding the alveoli of the mammary glands

43
Q

OXYTOCIN as a Drug

A

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
Q

More Reasons to Breastfeed

A

_ 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
Q

How does Oxytocin influence Glucocorticoid receptor activity

A

Reduces excess cortisol in stress HPA-axis

46
Q

How does Oxytocin influence Alpha2 receptor function

A

Blocks or modulates noradrenaline stress effects, eliciting calm behavior, decrease in arterial pressure and heart rate improved pattern of secretion of gastric hormones

47
Q

How does Oxytocin influence Opiodergic activity

A

Reward and Pain-free

48
Q

How does Oxytocin influence 5HT Synthesis

A

Happiness

49
Q

How does Oxytocin influence Cholinergic Activity

A

Consumption, Coitus, Calm and Sleep

BIOCHEMISTRY (25 decks)

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