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FHB Exam 4 > Endocrine 3: hypothalamus pituitary > Flashcards

Endocrine 3: hypothalamus pituitary Flashcards

1
Q

Define RAS.

A

Reticular Activating System

- regulates sleep/wake cycle

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2
Q

Define the hypothalamus-pituitary axis.

A
  • parvocellular neurons converge at the median eminence => hypothalamic releasing hormones travel to the anterior pituitary through the portal vein => affect anterior pituitary cell types => anterior pituitary hormone released into systemic circulation
  • magnocellular neurons extend from the hypothalamus to the posterior pituitary => post pit cells release pituitary hormone into systemic circulation
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3
Q

Define PVN.

A

ParaVentricular Nucleus

  • thyroid hormones
  • mood, thirst, blood pressure
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4
Q

Define POA.

A

PreOptic nucleus

  • most of the GnRH neurons located here
  • reproduction, body temp.
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5
Q

Define SCN.

A

SupraChiasmatic Nucleus
- circadian rhythms
- involved in melatonin
-

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6
Q

Define ARC.

A

ARCuate Nucleus

  • dopamine
  • feeding, mood
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7
Q

Define SON.

A

SupraOptic Nucleus

- blood pressure and plasma osmolarity

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8
Q

Define ME.

A

Median Eminence

  • floor of the hypothalamus
  • where axons of hypothalamic releasing hormone neurons converge and release hormone here into hypophysial portal system
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9
Q

GnRH

  • nuclei
  • pituitary target
  • function
A
  • scattered; mainly POA
  • gonadotropes, pituitary releases FSH/LH
  • reproduction
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10
Q

CRH

  • nuclei
  • pituitary target
  • function
A
  • PVN
  • corticotrope, pituitary releases ACTH
  • peripheral release of glucocorticoids
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11
Q

TRH

  • nuclei
  • pituitary target
  • function
A
  • PVN
  • thyrotrope, pituitary releases TSH
  • thyroid gland release thyroid hormones
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12
Q

GHRH

  • nuclei
  • pituitary target
  • function
A
  • ARC
  • somatotrope, pituitary releases GH
  • growth and hormone
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13
Q

Somatostatin

  • nuclei
  • pituitary target
  • function
A

(GHRH inhibitor)

  • PeriVN
  • somatotrope
  • inhibits GH
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14
Q

Dopamine

  • nuclei
  • pituitary target
  • function
A

the only hypothalamic releasing hormone that is not a peptide (amine)

  • ARC
  • lactotrope, pituitary releases prolactin
  • milk production
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15
Q

What does the size of hypothalamic releasing hormones indicate?

A

short half-life

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16
Q

Which HRHs use IP3/DAG/PKC? Which HRHs use cAMP?

A

IP3/DAG

  • TRH
  • GnRH

cAMP

  • CRH
  • GHRH
  • GHIH/somatostatin
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17
Q

Describe the location of GnRH neurons.

A
  • scattered throughout brain; mostly in POA
  • about 1500, but not all are needed
  • evolutionary reason = damage to one side of brain will still allow GnRH to function => reproduction
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18
Q

Describe the conservation of GnRH.

A
  • very ancient decapeptide (10 AA)

- only 4 AA vary between species

19
Q

Describe the structure of GnRH.

A 
PrePro = signal + GnRH + GAP
Pro = GnRH + GAP (GnRH Associated Peptide)
hormone = GnRH => anterior pituitary
20
Q

What is Kallman’s Syndrome?

A
  • prevalence: mostly in men b/c Kal1 is X-linked gene; if seen in women, due to Kal2 autosomal
  • during development, GnRH neurons fail to move from the nose, unable to cross through the cribiform plate => no GnRH neurons in the brain => no reproduction (sterile)
  • defect in olfactory neurons as well => anosmia (can’t smell)
  • symptoms = infertility and anosmia
21
Q

What is the hypophysial portal system?

A
  • vascular connection between hypothalamus and pituitary
  • superior hypophyseal artery supplies the pituitary gland
  • HRH neurons release hormone at the hypophysial portal vein => secondary capillary plexus
22
Q

How was the hypophysial portal system discovered?

A

George Harris - father of neuroendocrinology

  • transplanted pituitary gland to kidney…didn’t work => must remain near hypothalamus
  • cut off vascular connection between hypothalamus and pituitary…didn’t work => must be connected to hypothalamus
23
Q

What is the importance of hypothalamic and pituitary hormone pulsatility?

A
  • pulses in GnRH coordinate to pulses in FSH/LH from pituitary
  • protects from desensitization and downregulation of receptors
  • for GnRH, determines with pituitary hormone (FSH/LH) is released
24
Q

Describe the structure of FSH and LH.

A
  • constant alpha-glycoprotein subunit, different beta units
  • FSH-B unit + alpha = FSH
  • LH-B unit + alpha = LH
25
Q

Describe the mechanism of FSH/LH release from the pituitary.

A
  1. GnRH => ME => portal system => anterior pituitary gonadotrophs => GPCR
  2. DAG/PKC => synthesis of beta subunit (depending on pulse frequency)
  3. IP3/Ca2+ => release of FSH or LH
26
Q

What determines if FSH or LH is released from the pituitary?

A
  • fast GnRH pulsatility = LH

- slow GnRH pulsatility = FSH

27
Q

Define tuberoinfundibular system.

A

anterior pituitary connection

- hypothalamus => ME => portal system => ant. pit.

28
Q

Define neurohypophysial system.

A

posterior pituitary connection

  • hypothalamus => post. pit. => circulation
  • NO portal system
29
Q

Describe the structure and composition of the anterior pituitary.

A

AKA adenohypophysis

  • glandular, mostly epithelial cells
  • supplied by the superior hypophysial artery

Parts

  • pars distalis (90%)
  • pars tuberalis
  • pars intermedia
30
Q

Describe the structure and composition of the posterior pituitary.

A

AKA neurohypophysis

  • neural tissue, mostly magnocellular terminal axon and glial cells (pituicytes)
  • supplied by the inferior hypophysial artery

Parts

  • pars nervosa
  • infundibulum (stalk)
31
Q

What hormones does the posterior pituitary release?

A
  • oxytocin

- arginine vasopressin (AVP = ADH)

32
Q

Define pituicytes.

A
  • glial-like cells

- provide nutrients and support to posterior pituitary tissue

33
Q

Define Herring Bodies.

A
  • at the terminal end of magnocellular axons, they are unmyelinated
  • this area contains vesicles of AVP/OXY and their copeptide (neurophysin)
34
Q

What is the copeptide for posterior pituitary hormones?

A

neurophysin

- AVP/OXY

35
Q

What is unique about the ME?

A
  • connects the adenohypophysis tract

- lies outside the BBB, so it allows peripheral input to HRHs

36
Q

What are the main cell types in the adenohypophysis?

A

Acidophils (most) - somatotrophs, lactotrophs
Basophils - corticotrophs, gonadotrophs, thyrotrophs
Chromophobs - no hormones released; act as support for tissue

37
Q

How do adenohypophysis cells look on a histological slide?

A

dark = basophils
pink/orange = acidophils
light pink = chromophobes

38
Q

Define somatotrophs.

A

release GH and somatostatin

39
Q

Define lactotrophs.

A

release prolactin

40
Q

Define gonadotrophs.

A

release FSH/LH

41
Q

Define thyrotrophs.

A

release TSH

42
Q

Define corticotrophs.

A

release ACTH

43
Q

Describe the location of trophic cells in the anterior pituitary.

A 
center = corticotrophs = ACTH
sides = somatotrophs and lactotrophs (acidophils) = GH/PRL
top = thyrotrophs = TSH
scattered = gonadotrophs = FSH/LH
44
Q

Describe the circadian rhythms of GH and ACTH.

A 
GH = peak overnight; hence, sleep is crucial
ACTH = gradually increases overnight and peaks in morning (wake up signal)

FHB Exam 4 (16 decks)

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