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Endocrinology > Hypothalamus and pituitary > Flashcards

Hypothalamus and pituitary Flashcards

1
Q

Where is the pituitary gland located?

A

At the base of the brain in a bony pocket called sella turcica.

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2
Q

How is the pituitary gland connected to the brain?

A

Stalk of tissue called the infundibulum containing nerves and special veins (long portal veins)

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3
Q

What are the parts of the pituitary gland?

A

Anterior lobe- pars distalis+ pars tuberalis

Posterior lobe- pars nervosa + pars intermedia

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4
Q

What are the 2 parts of the hypothalamus? What do they do?

A
  1. Nuclei: clusters of nerve cells bodies that synthesize hypothalamic RH that regulats secretion of hormone from the anterior pit. gland and 2 posterior pit gland hormones (ADH/ OT)
  2. Bottom portion: median eminence. Axon terminals containing hypothalamic RH. These RHs are secreted FIRST into capillaries of a portal system.
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5
Q

What hormones are produced by the posterior pituitary gland?

A

OT and ADH

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6
Q

Nerve axons at the posterior pituitary mainly come from? Where do they terminate?

A

2 nuclei in the hypothalamus- supraoptic nucleus and paraventricular nucleus
Near capillaries in the posterior pituitary. Stores and release hormones here.

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7
Q

Describe the structure of the pars nervosa of the posterior lobe

A

Neurosecretory nerve fibers from PV and SON

- Hypothalamohypopsheal T

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8
Q

What cell is associated with the pars nervosa of the posterior lobe of the pituitary

A

pituicytes

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9
Q

Function of pars nervosa of posterior lobe of pituitary

A

release of oxytoxin and ADH

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10
Q

What does oxytoxin do?

A

stimulates contraction of smooth muscle in pregnant uterus and myoepitherlial cells in mammary gland.

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11
Q

What does ADH do?

A

regulates body retention of water. Increases contracility of arterial smooth muscle to increase BP. Increase water reabsorption

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12
Q

Describe the structure of ADH and OT

A

nonapeptides with S-S, similar structures and overlapping activities

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13
Q

Describe the synthesis of ADH and OT

A

synthesized as much larger molecules (pro-), stored in granules with neurophysins I and II

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14
Q

Describe the secretion of ADH and OT

A

Secreted-when action potentials reach nerve terminals; analgous to neurotransmitter release secreted together with their respective neurophysins

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15
Q

What 2 things cause secretion of oxytocin?

A

dilation of cervix, suckling

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16
Q

What is the main stimuli of ADH?

A

decrease ECF volume (also increase osmolarity)

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17
Q

Where are osmoreceptors located?

A

hypothalamus: OVLT (SON and PVN?)

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18
Q

What does the intermediate lobe of the pituitary gland do?

A

It MAY secrete MSH.

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19
Q

What major hormones are secreted by the anterior pituitary?

A

GH, PRL, ACTH, FSH, LH, TSH

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20
Q

Chemical nature of ACTH

A

peptide that is split from POMC (pro-opiomelancortin). 39 aa straight chain. C terminus has most antigenic activity.
Only 20 aa @ N-terminus needed for biological activity

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21
Q

What is ACTH1-24?

A

ACTH structure that has full activity

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22
Q

What is MSH do?

A

stimulates synthesis of melanin in melanocytes- darkens skin

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23
Q

Where is the structure of MSH? What does this cause?

A

lies within ACTH- excess ACTH causes hyperpigmentation

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24
Q

What hormones secreted by anterior pituitary are glycoproteins?

A

TSH, FSH, LH

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25
Q

What cells make up 15-20% of pituitary volume?

A

basophils

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26
Q

What is the structure of the anterior pituitary glycoproteins?

A

dimers of a and b subunits. A is very similar among all 3 hormones. B is fairly similar.

27
Q

What cells are stained to measure GH and PRL?

A

acidophils

28
Q

___ causes release of granules from posterior pituitary?

A

Action potentials

29
Q

How do hormones get from hypothalamus to posterior pituitary?

30
Q

How do hormones get from hypothalamus to anterior pituitary?

A

the hypothalamo-pituitary portal system- 2 capillary beds!

31
Q

What kind of tissue makes up the pituitary?

A

Anterior: glandular
Posterior: neural secretory

32
Q

Neural extensions to the posterior pituitary from the hypothalamus come from _____.

A

2 nuclei–> SON and PVN

33
Q

Oxytocin increases the contracility of _____

A

uterine smooth muscle and mypoepithelial cells of mammary glands–> milk let down

34
Q

2 main oxytocin stimuli

A

suckling and dilation of cervix

35
Q

What are the 2 main stimuli for ADH?

A

decrease in plasma volume by 5-10%

Increase osmolarity by 1-2%

36
Q

In what 2 ways is ADH an example of negative feedback?

A
  1. Water rebsorption negatively acts on osmolality so it doesnt act on SON and PVN
  2. Increase plasma volume negatively acts on volume receptors so they dont signal to CNS
37
Q

What are the effects of stalk section on nerve tracts to posterior pituitary?

A

(transient diabetes insipidus)

  1. Polyuria
  2. Polydipsia
  3. Nerve terminals develop and capillaries regrow (reversible)
38
Q

In order to have an affect hormones have to diffuse in the _____.

A

hypopophyseal veins

39
Q

What are the 6 cells in anterior pituitary? Which are basophils and which are acidophils?

A

Baso: FSH, LH, TSH, ACTH
Acid: GH, PRL

40
Q

What subunit of glycoprotein do you measure?

41
Q

Acidophils make up ____ of the ant. pituitary. What makes up this?

A

75%; 50% somatotrophs; 15-25 Lactotrophs

42
Q

Target tissue of ACTH

A

adrenal cortex

43
Q

Major actions of ACTH

A

increase adrenal growth, cortisol synthesis, cortisol secretion, plasma concentration of cortisol (–> vascular reactivity and gluconeogenesis)

44
Q

Variables that increase release of ACTH

A

increase CRH, Stress, morning time, decrease of cortisol, removal of adrenal/s

45
Q

Variable that decrease release of ACTH

A

decrease CRH, decrease stress, later in the day, increase cortisol, Rx ith glucocorticoids

46
Q

Target tissue of TSH

A

thyroid gland cells lining follicles

47
Q

Some major actions of TSH

A

increase thyroid growth, TH syn and secretion, TH concentration, iodide trapping, thy blood flow, and everything that T3 and 4 do–> increase metabolic rate

48
Q

Variables that increase TSH

A

increase TRH, decrease T4 and 3, low iodide diets, removal of thyroid gland

49
Q

Things that decrease release of TSH

A

decrease TRH, increase T4/3, increase SS, Rx with THs

50
Q

Increase GnRH increases the secretion of what?

A

FSH, LH in males and females

51
Q

What are all the RH and what do they increase?

A 
CRH--> ACTH
TRH--> TSH
GnRH--> LH and FSH
GHRH--> GH
SS--> decrease GH
Dopamine--> decrease PRL
52
Q

What is the long loop of feedback?

A

Target organ hormone negatively acts on Anterior pituitary and can -/+ affect hypothalamus

53
Q

What is the short loop of feedback?

A

ALWAYS -

hormone released from anterior pituitary - on hypothalamus

54
Q

Target tissue of PRL

A

Females: mammary glands
Males: testes, 2nd sex tissues

55
Q

Some major actions of PRL

A

Female: glandular tissue growth, milk synthesis
Male: potentiate LH and testost. actions

56
Q

Variables that increase PRL

A

Decrease PIH, Increase TRH, suckling

57
Q

Variables that decrease PRL

A

increase PIH, stop nursing

58
Q

Target tissue of GH

A

msot cells of body esp muscle liver, cartilage in growth plates

59
Q

Variables that increase GH

A

increase GHRH AND decrease SS

Deep sleep, hypoglycemia, acute stress

60
Q

Variables that decrease GH

A

decrease GHRH and/or increase SS

61
Q

To increase ADH secretion, there must be a _____% decrease in plasma volume and a ______% increase in osmolarity.

A

5-10%, 1-2%

62
Q

Which is more sensitive to changes in circulating volume, RAS or ADH?#

A

RAS. ADH responds only to large decreases.

63
Q

Low levels of ____ support increased secretion of ADH. #

Endocrinology (31 decks)

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