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GERR > Lecture 19: Hypothalamic-Pituitary Function > Flashcards

Lecture 19: Hypothalamic-Pituitary Function Flashcards

1
Q

what is the most common means of intercellular communication

A

chemical signalling

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2
Q

what cells do paracrine chemical messengers affect

A

neighbouring cells only

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3
Q

what cells do autocrine chemical messengers affect

A

secreting cells only

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4
Q

how are chemical messengers distributed

A

diffusion

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5
Q

what do neurotransmitters affect

A

nerves, muscles or glands

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6
Q

give examples of paracrine messengers

A
  • histamine
  • NO
  • some growth hormones
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7
Q

give examples of neurotransmitters

A
  • ACh
  • amines e.g. noradrenaline
  • amino acids e.g. glutamate
  • neuropeptides
  • NO
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8
Q

where are hormones secreted into and by what

A

into the blood by endocrine cells

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9
Q

where are neurohormones secreted and by what

A

into the blood by neurosecretory neurons

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10
Q

give examples of hormones

A
  • thyroid hormone

- adrenaline

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11
Q

give examples of neurohormones

A
  • ADH
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12
Q

name the 4 hormone classes and give examples of each

A
  • amine
  • -> norepinephrine
  • -> dopamine
  • -> thyroid hormone
  • peptide
  • -> oxytocin
  • -> ADH
  • -> neurohormones
  • -> glucagon
  • protein
  • -> human growth hormone
  • -> insulin
  • -> calcitonin
  • -> parathyroid hormone
  • steroid
  • -> testosterone
  • -> progesterone
  • -> oestrogen
  • -> mineralocorticoids
  • -> glucocorticoids
  • -> activated Vit D
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13
Q

name some stimuli for hormone release

A
  • direct neural innervation
  • releasing hormones
  • plasma levels
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14
Q

how can hormones be transported in blood

A

free or bound to plasma protein

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15
Q

which hormones are transported free

A

most amine, protein and peptide hormones

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16
Q

which hormones are transported bound

A

steroid (as they’re hydrophobic) and thyroid hormones

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17
Q

what types of plasma proteins bind to hormones for transport

A

majority globulins and albumin

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18
Q

describe the genomic/non-genomic effects a hormone can have

A

genomic –> alter protein synthesis so alter cell behaviour

non-genomic –> alter protein function

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19
Q

where can hormone receptors be found (cell)

A
  • on cell surface membrane
  • in cytoplasm
  • nucleus
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20
Q

function of hypothalamic-pituitary axis

A

stimulates secretion of a number of hormones e.g. thyroid

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21
Q

what connects the hypothalamus to the pituitary

A

infundibulum - has nerves and small bv

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22
Q

what cavity does the pituitary gland sit in

A

hypophyseal fossa

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23
Q

what can a bi-temporal hemianopia be a symptom of and what is it

A
  • symptom of pituitary tumour (can impinge on optic chiasma)

- loss of peripheral vision

24
Q

what is the optic chiasma

A

where optic nerves of both eyes cross over

25
Q

name the lobes of the pituitary gland and describe the tissue each lobe is made of

A
  • posterior (neurohypophysis) –> brain tissue
  • anterior (adenohypophysis)
  • -> glandular tissue
26
Q

describe how each lope of pituitary is connected to the hypothalamus

A
  • posterior –> neural pathway (axons)

- anterior –> vascular pathway

27
Q

what system do posterior pit. and hypothalamus form and what hormones does that system secrete

A
  • neuroendocrine system

- secretes ADH and oxytocin

28
Q

where do the cell bodies of the axons linking the hypothalamus to post. pit. lie

A
  • in two discrete nuclei
    1. paraventricular nucleus
    2. supraoptic nucleus
29
Q

where are ADH and oxytocin manufactured

A

in the cell bodies of the neurones connecting hypothalamus with post. pit. (then stored in axon terminals)

30
Q

which nuclei contains most the neurones that secrete oxytocin

A

paraventricular nucleus

31
Q

which nuclei contains most of the neurones that secrete ADH

A

supraoptic nucleus

32
Q

what is the function of oxytocin

A

stimulates uterine contraction (stimulates birth) and milk ejection

  • also known as love hormone
33
Q

what is the function of ADH (vasopressin)

A
  • vasoconstrictor –> increases vascular resistance and BP

- increases H2O permeability and absorption in renal collecting ducts

34
Q

what type of hormones are secreted by anterior pituitary, give the 7 examples

A

primarily tropic hormones

  • growth hormone
  • thyroid stimulating hormone
  • adrenocorticotrophic hormone (ACTH)
  • Prolactin (not tropic)
  • follicle stimulating hormone
  • luteinising hormone
  • melanocyte stimulating hormone (not tropic)
35
Q

what is a tropic hormone

A
  • hormones that influence/ regulate the secretion of hormones from another endocrine gland
  • stimulate and maintain endocrine target tissue
36
Q

what is the function of ACTH

A

stimulates adrenal gland to secrete corticosteroids

37
Q

which brain region regulates hormone secretion from pituitary gland

A

hypothalamus

38
Q

which hormones are secreted by neurohypophysis

A

ADH and oxytocin

39
Q

what are the two most important factors that regulate ant. pit. hormone secretion

A
  • hypothalamic hormones (hypophysiotropic)

- feedback by target gland hormones

40
Q

what connects the hypothalamus and ant. pit.

A

hypothalamic-hypophyseal portal system

41
Q

what is the importance of a portal system between hypothalamus and ant. pit.

A
  • venous blood so doesn’t enter systemic circulation
  • concentrated hormones can move from hypothalamus to ant. pit. w/o being diluted
  • rapid response to release of hypothalamic hormones –> direct travel
42
Q

decreased secretion of which hormone results FROM damage to hypothalamic-hypophyseal portal system…

  1. ADH
  2. Prolactin
  3. Oxytocin
  4. PTH
  5. TSH
A

answer = TSH

  • ant. pit. affected therefore rule out 1, 3 and 4
  • prolactin has two hypothalamic hormones governing its secretion –> releasing and inhibiting –> damage means there’s less inhibition so prolactin secretion can increase moderately
43
Q

what are the 3 hormones/ levels for hypothalamic pituitary target gland secretion regulation

A
  1. hypothalamus / neurohormone
  2. pituitary gland / tropic hormone
  3. peripheral gland / peripheral target-endocrine gland hormone
44
Q

describe long loop negative feedback

A

inhibits both pituitary gland secretion and hypothalamus secretion

45
Q

describe short loop negative feedback

A

hormone secreted by pituitary inhibits hypothalamus secretion

46
Q

what is important to consider when measuring hormone levels

A

diurnal and circadian rhythms

47
Q

describe primary hyposecretion

A

too little hormone is secreted due to abnormality within secreting gland itself

48
Q

name some cause of primary hyposecretion

A
  • genetic
  • dietary (e.g. lack of iodine)
  • chemical or toxic
  • autoimmune
  • cancer
  • iatrogenic
49
Q

describe secondary hyposecretion

A

gland is normal but too little hormone is secreted due to deficiency of tropic hormone –> assc w/ deficiency in ant. pit.

50
Q

describe tertiary hyposecretion

A

gland is normal but too little hormone is secreted due to deficiency of hypothalamic releasing hormone

51
Q

what is pan hypopituitarism

A

production and secretion of all pituitary hormones are reduced both ant. and post.

52
Q

name a cause of hypersecretion

A

tumours –> ignore normal regulatory input and continuously secrete excess hormone

53
Q

describe primary hypersecretion

A

abnormality within gland

54
Q

describe secondary/ tertiary hypersecretion

A

excessive stimulation from outside the gland (2nd = pituitary, 3rd = hypothalamus)

55
Q

outline some consequences of hypersecretion (in terms of ant. pit. hormones)

A
  • ^ ACTH –> corticosteroid excess –> Cushing’s
  • ^ prolactin –> impaired reproductive function
  • ^ ADH –> fluid retention and low plasma osmolality
  • ^ TSH –> Grave’s disease
  • ^ hGH (children) –> gigantism
  • ^ hGH (adults) –> acromegaly

GERR (46 decks)

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