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Physiology > 5.2 HPT Axis > Flashcards

5.2 HPT Axis Flashcards

0
Q

Physiologically pituitary gland is divided into

A

Ant. Pituitary
Pars intermedia
Post. pituitary

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1
Q

Hypophysis is connected to the hypothalamus via

A

Hypophysial stalk

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2
Q

Differentiate anterior and posterior pituitary glands regarding their secretion

A

Anterior - release of RELEASING HORMONES from hypothalamus brings about secretion
Posterior - reception of NERVE SIGNALS from hypothalamus brings about secretion of stored ADH and Oxytocin

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3
Q

Anterior pituitary is the site where the anterior pituitary hormones are SYNTHESIZED, STORED, and RELEASED. However, in the posterior pituitary, hormones are NOT synthesized, ONLY STORED and RELEASED. What synthesized ADH and Oxytocin?

A

ADH - supraoptic nuclei

Oxytocin - paraventricular nuclei

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4
Q

The negative feedback is only applicable to the ANTERIOR pituitary because

A

The ANTERIOR Pituitary is responsive to hypothalamic RELEASING HORMONES (not nerve signals –> POSTERIOR)

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5
Q

Type of negative feedback where X-stimulating hormone inhibits the hypothalamus

A

Short loop

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6
Q

Type of negative feedback where X-releasing hormone inhibits the hypothalamus

A

Ultra short loop

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7
Q

Type of negative feedback where X-hormone inhibits hypothalamus or ant. Pituitary gland

A

Long loop

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8
Q

For most anterior pituitary hormones, the hypothalamic releasing hormones are MOST important as well EXCEPT _______, an inhibitory hormone exerts more control

A

Prolactin

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9
Q

Hormone that stimulates ACTH secretion

A

CRH - corticotropin releasing hormone

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10
Q

TRH or thyrotropin releasing hormone stimulates which hormone secretion

A

stimulated TSH secretion and PRL - Prolactin secretion

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11
Q

Precursor of ADH

A

Prepropressophysin

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12
Q

It is a carrier protein during axonal transport

A

Neurophysin

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13
Q

ADH and Oxytocin are both SECRETORY PEPTIDES, synthesized as larger precursor and cleaved into: 1. _________, 2. _________, and 3. __________.

A
  1. Active hormone
  2. Neurophysin
  3. Glycopeptide
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14
Q

It is the PRIMARY trigger of ADH secretion

A

Plasma osmolarity changes.
High plasma osm: increase ADH secretion
Low plasma osm: decrease ADH secretion

“Only a change of 1-2% plasma Osmolarity is needed to trigger ADH release.”

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15
Q

It is secreted in response to plasma osm changes and DECREASE in blood volume

A

ADH

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16
Q

TRUE or FALSE

Increased level of plasma osmolarity (>280 mosm/kg) increases the release of ADH

A

TRUE.
Why?
^ plasma osm -> ^osmoreceptors (w/c draws out water and causes shrinkage) -> signals sent to posterior pituitary -> ADH secretion occurs -> ^cAMP -> recruitment of aquaporins -> ^ permeability of H2O -> ^H2O absorption -> v plasma osm back to normal

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17
Q

True or False. In the presence of ADH, collecting tubules are impermeable to water, meaning no reabsorption occurs.

A

False.

In the ABSENCE of ADH, collecting tubules are IMpermeable to water, meaning NO reabsorption occurs.

In the PRESENCE of ADH, aquaporins are able to reabsorb water, increased PERMEABILITY.

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18
Q

Three factors that influence decrease in ADH secretion

A

Low plasma osm
High ECF volume
Alcohol

19
Q

Characterized by excess ADH

Effects are increase water retention, low plasma osm, hyponatremia, inappropriately concentrated urine

A

SIADH Syndrome of inappropriate ADH secretion

20
Q

Secretion of growth hormone is described as

A

Pulsatile - secretion is in pulses with MAXIMAL burst during SLEEP
Lifetime pattern - increasing with progression from birth, HIGHEST during PUBERTY, after which GH decreases

21
Q

Growth effects of GH. Is also mediated by

A

IGF-1

22
Q

True or false. GH inhibiting the hypothalamus is a long loop regulation.

A

FALSE.
GH inhibiting the hypothalamus is a SHORT loop regulation.
IGF-1 inhibiting the hypothalamus is a LONG loop regulation.

23
Q

Test used to determine excess of hormones

A

Suppression test

24
Q

Test used to determine deficit of hormones

A

Stimulation test

25
Q

excess GH

Gigantism: open epiphyseal plate; __________: closure of epiphyseal plate

A

Gigantism: open epiphyseal plate; ACROMEGALY: closure of epiphyseal plate

26
Q

GH: cytokine receptor; ACTH: ___________

A

GH: cytokine receptor; ACTH: G-protein coupled receptor

27
Q

GH: lifetime pattern; ACTH : _______ pattern

A

GH: lifetime pattern; ACTH : DIURNAL pattern

ACTH can be altered by changing wake-sleep cycle
NOTE: both GH and ACTH. Are pulsatile

28
Q

________ secretion follows ACTH secretion

A

Cortisol

29
Q

Request for cortisol administration is during

explain why

A

6-8AM because this is the peak of the diurnal pattern of ACTH secretion

30
Q

How can diurnal pattern of ACTH secretion be altered

A

Changing sleep wake cycle

31
Q

What does hypothalamus secrete to stimulate synthesis of ACTH

A

Corticotrophin Releasing Hormone (CRH)

32
Q

CRH increases the transcription of

A

POMC gene

33
Q

Effects of a lack in CRH

A
  1. Impair the ACTH diurnal rhythm

2. Affects the response to stress

34
Q

Function of BNP

A

Inhibits ACTH secretion and causes the expulsion of sodium and water in the urine

35
Q

Stimulates ACTH secretion

A 
Stress
Transition from sleep to wake
Norepinephrine
Ach
Serotonin
36
Q

Inhibit secretion of ACTH

A

GABA

Endorphins

37
Q

LH: estrogen and progesterone; FSH:

A

LH: estrogen and progesterone; FSH: estradiol and inhibin

38
Q

When there is an excess of one hormone, it can “sit” on the other hormones. Explain what “sit” on means

A

An excess in one hormone may sit on the receptor of another hormone causing the effects of that other hormone to be manifested
Ex. Excess HCG can sit on the TSH receptor and cause some of the effects of TSH such as stimulation of the thyroid gland

39
Q

The way by which releasing hormones of the hypothalamus reach the anterior pituitary

A

Hypophyseal portal system via the median eminence

40
Q

ADH is synthesized by

A

Supraoptic nuclei of hypothalamus

41
Q

Oxytocin is synthesized by

A

Paraventricular nuclei of hypothalamus

42
Q

Oxytocin and ADH have the same amino acid residues except for two aa residues:

A

ADH: arginine and phenylalanine
Oxytocin: leucine and isoleucine

43
Q

Direct metabolic effects of growth hormone

A 
Protein synthesis
Fat lipolysis
Inhibited uptake of blood glucose
Gluconeogenesis
Insulin resistance
44
Q

Indirect effects of growth hormone

A

Postnatal linear growth and somatic development
Proliferation of chondrocytes
Bone forming and soft tissue growth

Physiology (27 decks)

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