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Metabolic Endocrinology > Hypothalmic Axis > Flashcards

Hypothalmic Axis Flashcards

1
Q

the pituitary gland is also called the _____

A

hypophysis

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2
Q

what is the significance of the hypothalamo-pituitary axis?

A

connection from brain to body: allow brain to maintain homeostasis (control center for endocrine system)

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3
Q

What was believed to control/influence the body prior to discovery of hormones?

A

the 4 humours (choleric, phlegmatic, sanguine, melancholic)

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4
Q

Who first described the parts of the pituitary?

A

Rathke (19th century)

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5
Q

What did Aristotle identify the pituitary as?

A

connection between brain/body that 4 humours passes through

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6
Q

What are the 2 parts of the pituitary?

A

adenohypophysis (anterior pit.)

neurohypophysis (posterior pit.)

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7
Q

Who associated pituitary tumors with acromegaly? When?

A

Pierre Marie (1886)

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8
Q

Who pioneered a method to improve acromegaly patients? How?

A

Harvey Cushing (1909); removed part of pituitary

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9
Q

What experiment led to the discovery of growth hormone?

A

Evans & Long (1922) injected crude pituitary gland extract of animals -> increased growth

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10
Q

How were most hormone functions discovered?

A

animal experiments

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11
Q

What controls the pituitary?

A

Hypothalamus

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12
Q

The hypothalamo-pituitary axis is also known as: _____

A

adenohypophysial axis

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13
Q

What size is the pituitary? Where is it located?

A

0.5-1g (1cm diameter)

connected to hypothalamus stalk (under optic chiasm), within protective bone ‘saddle’ (sella turcica)

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14
Q

What physical changes happen in the pituitary during pregnancy and why?

A 
increased size (>30%)
need increased hormones for preg & lactation
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15
Q

What are the anatomical parts of the anterior pituitary?

A

pars tuberalis
pars intermedia
pars distalis

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16
Q

What are the anatomical parts of the posterior pituitary?

A

infundibular stalk

pars nervosa

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17
Q

How does the hypothalamo-hypophyseal tract develop? (2)

A

Rathke’s pouch (outgrowth of buccal cavity) -> detach and become anterior pituitary

Neuroectoderm outgrowh (from third ventricle) -> form infundibulum, pituitary stalk, median eminence, posterior pituitary

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18
Q

The anterior pituitary is formed from _____ cells, that develop from: ______.

A

ectodermal

Rathke’s pouch (outgrowth from buccal cavity/primitive mouth below)

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19
Q

What cells form the posterior pituitary? Where is their origin, and what else do they form?

A

neuralectoderm cells
from neurohypophyseal bud (downgrowth from forebrain floor)
forms infundibulum, median eminence, pituitary stalk

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20
Q

the pituitary is located below the ___ ____, encased in a cavity known as the ___ ___, within the ____ bone.

A

optic chiasma
turkish saddle
sphenoid

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21
Q

Describe the blood flow pathway through the pituitary and hypothalamus:

A

from body -> hypophysial artery -> median eminence capillary bed -> portal blood vessel -> anterior pituitary capillary bed -> vein -> back to body

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22
Q

Where are the major 2 capillary beds in the adenohypophysis located?

A

median eminence

anterior pituitary

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23
Q

What carries blood from the median eminence down to the anterior pituitary?

A

portal hypophysial vessel

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24
Q

There is some blood flow from the pituitary back to the hypothalamus, known as ___ flow. Why is this important?

A

retrograde flow

allow hormonal feedback from pit. to hypothalamus (short loop)

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25
Q

How does the hypothalamus control the anterior pit.?

A

through releasing or inhibiting hormones -> passed through hypothalamic-hypophyseal portal system

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26
Q

How does the hypothalamus control the posterior pituitary?

A

direct control (axons from hypothalamus extend down into posterior pit.)

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27
Q

True/False: the posterior pituitary does not make any hormones

A

True; hormones made by neuron cells from above, released through axons

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28
Q

True/False: posterior pituitary hormones cannot be stored

A

False; can be stored

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29
Q

The specialized neurons that make the posterior pit. hormones are known as ____ neurons

A

neurosecretory

30
Q

What are the posterior pit. hormones?

A

vasopressin (ADH)

oxytocin

31
Q

Describe the production and release of the posterior pituitary hormones:

A

produced in cell bodies of neurosecretory hormones (in hypothalamus) -> packaged in granules -> migrate to axons (in posterior pit.)

hypothalamus neurons stimulated -> trigger release from axon tips -> into capillaries/bloodstream

32
Q

_____ hormones are released from the hypothalamus into the _______, and flow through the ____ down to the anterior pituitary.

A

hypophysiotrophic
median eminence
HHPS (portal vein)

33
Q

True/False: a hypothalamic neurosecretory cell can produce a large variety of hormones

A

False: cells are highly specialized, can only produced 1 type of hormone

34
Q

How are the hypothalmic cells organized?

A

in bundles according to function (each section makes different hormone)

35
Q

what hypothalamic nuclei are responsible for the posterior pituitary? (2)

A

supraoptic nuclei

paraventricular nuclei

36
Q

Which hypothalamic nuclei are responsible for the anterior pituitary?

A

hypothalamic-hypophysiotropic nuclei

37
Q

What controls the hypothalamus?

A

signals from all other parts of brain -> neurotransmitters

38
Q

What are the main neurotransmitters? (5)

A 
norepinephrine
epinephrine
dopamine
serotonin
acetylcholine
39
Q

What happens to hormone production if the hypothalamus is removed?

A

no posterior pit. hormones
most anterior pit. hormones stop
GH, FSH, LH fall to basal levels (very low)
PRL increases

40
Q

What anterior pituitary hormones show some degree of autonomy in secretion?

A

GH, FSH, LH (will still have some low levels without hypothalamus)

41
Q

How is PRL control different from the other pit. hormones?

A

hypothalamus does INHIBITORY control, not stimulatory

42
Q

What are the subgroups of cells in the anterior pituitary gland? What do they produce?

A
  1. somatotrophs (GH)
  2. mammotrophs (PRL)
  3. thyrotrophs (TSH)
  4. gonadotrophs (LH, FSH)
  5. corticotrophs (ACTH, beta lipotropin)
43
Q

What is the target(s) of ACTH?

A

adrenal gland
adipocytes
melanocytes

44
Q

What anterior pit. hormone causes responses in almost all cells?

A

GH

45
Q

What antierior pit. hormone targets the breasts and gonads?

A

PRL

46
Q

Classify the anterior pit. cells based on their cell type (2 types)

A
  1. basophils: thyrotrophs, gonadotrophs, corticotrophs

2. acidophils: somatotrophs, mammotrophs

47
Q

How are basophil hormones and acidophil hormones different?

A

basophil hormones more heavily glycosylated; protected from degradation (longer half life)

48
Q

What hormone would have a longer half life: GH or FSH?

A

FSH

49
Q

What is TRH and its role?

A

thyrotrophin releasing hormone (from hypothalamus)

stimulate release of TSH & PRL
minor stimulation of FSH release

50
Q

What is GnRH and its role?

A

gonadotrophin releasing hormone (from hypothalamus)

stimulate release of LH, FSH

51
Q

What hypthalmic hormone stimulates release of GH? What is its counterpart?

A

GHRH

somatostatin (SMS) will inhibit GH

52
Q

What hormone works counterpart to TRH?

A

somatostatin (will inhibit TSH and PRL)

53
Q

How is PRL controlled (primary control)

A

inhibited by dopamine from hypothalamus

54
Q

___ and ____ promote FSH release

A

GnRH

TRH (minor)

55
Q

Characteristics of hypothalmic hormones affecting anterior pituitary:

A

fast action
short half-life
bind to GPCR

56
Q

What type of G proteins are used by trophic vs. inhibitory hypothalmic hormones?

A

trophic (stimulatory): Gas, Gaq

inhibitory: Gai

57
Q

What are the different feedback loop types in the hypothalmic-pituitary axis?

A
  1. short feedback loop: AP hormones -> hypothalamus
  2. Fast feedback loop: from ultimate hormone -> hypothalamus & adenohypophysis
  3. Long feedback loop: ultimate hormone -> CNS, hypothalamus, adenohypophysis
58
Q

What is the general release pattern of hypothalmic hormones, and why is this important? (2)

A

pulsatile release

  • synchronized with target tissue
  • must keep renewing stimulus (short half life of signals)
59
Q

Role of the pineal gland:

A

take info from light signals -> help set biological rhythm

60
Q

Major hormone of pineal gland:

A

melatonin (made from Trp)

61
Q

How do melatonin levels change throughout the day, and throughout life stages?

A

production begin in evening -> peak at night -> fall low in day

highest in youth -> decline with age

62
Q

Why does melatonin secretion decrease with age?

A

sleep is less crucial (no more development)

calcification of pineal gland

63
Q

Describe the pathway controlling circadian rhythm from light stimulus

A

light -> retina -> SCN -> b-adrenergic receptor on pinealocyte -> activate cAMP pathway -> convert Trp to melatonin -> body (and also back to SCN for feedback)

64
Q

What acts as the circadian pacemaker ‘clock?’

A

SCN (suprachiasmatic nucleus)

65
Q

What is the effect of darkness on melatonin?

A

levels increase (up to 10-fold)

66
Q

functions of melatonin:

A

core body temp
induce sleep
depress reproductive activity in animals

67
Q

additional melatonin functions (possible)

A

antioxidant (anti-aging properties?)
enhance immunity (correlation, not necessarily causation)
help adjust jet-lag
sleeping aid in elderly

68
Q

possible side effects of melatonin supplements:

A

daytime sleepiness
hypothermia
desensitized receptors
adverse effects in those with seizure disorders
adverse interaction with coumadin/warfarin

69
Q

What is ‘chronotherapy?’

A

optimatl timing of medication, surgery, chemotherapy to align with hormone levels for maximum effectiveness

70
Q

examples of chronotherapy:

A

asthma meds in morning (when attacks are the worst)
arthritis meds at night (when pain is worst)

breast cancer surgery after ovulation (when estrogen is low; to prevent tissue regrowth from estrogen acting as mitogen)

Metabolic Endocrinology (6 decks)

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