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caps 390 > Endocrine > Flashcards

Endocrine Flashcards

1
Q

autocrine

A

hormone binds to receptors on same cell

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2
Q

paracrine

A

hormone target nearby cells

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3
Q

endocrine

A

hormone travels far, targeting many cells and organs

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4
Q

pituitary gland

A

Link between CNS and periphery
- anterior and psoterior lobes secrete diff peptides, and are anatomically and functionally distinct
- 8 hormones
- regulates every cell in the body

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5
Q

hormones

A

circulate in blood, easy to measure

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6
Q

lipophilic hormones

A

thyroid and steroid hormones
- free to enter brain
- regulate all CNS functioning

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7
Q

sex steroids

A

Estradiol, progesterone, testosterone
- many brain regions
- reproductive processes, behaviour, cognition, emotions, feelings
- explains ind and sex-based brain differences

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8
Q

peptide hormones

A

made of AAs, complex chain or string
- hydrophilic
- ex. oxytocin + vasopressin (9 AAs)

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9
Q

steroid hormones

A

4 fused carbon rings + single side chain
- specificity determined by side chain
- lipophilic
- circulate bound to binding globulin (thyroxine binding globulin and sex hormone binding globulin)

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10
Q

thyroid hormones

A

complex of 2 AA residues (tyrosine)
- lipophilic
- circulate bound to TBG

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11
Q

peptide hormone mode of action

A

peptide interacts w g protein-coupled, membrane-associated receptor
- transduction to secondary messengers in cell, mediating rapid effects

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12
Q

thyroid and steroid hormone mode of action

A

free hormone in blood diffuses freely across cell membrane
- binds to cognate intracellular receptor (soluble nuclear receptor)
- receptor complex functions as a TF, mediating delayed genomic effects

  • steroids sometimes also have cell surface receptors
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13
Q

anterior pituitary

A

Produces and releases ACTH, TSH, FSH-LH, PRL, GH

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14
Q

posterior pituitary

A

Releases AVP, ADH, OT

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15
Q

which pituitary cells produce hormones

A

each hormone in the pituitary is produced by a specific kind of cell
- corticotropes make ACTH
- lactotropes make prolactin
- Each of these cells is regulated by diff nuclei in hypothalamus

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16
Q

capillary endothelium of the CNS

A

Forms tight, continuous junction (blood-brain-barrier)
- specialized regions can circumvent this barrier

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17
Q

Median eminence

A

Below the hypothalamus, links to pituitary
- where nerve axons exit brain
- direct and indirect paths for

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18
Q

indirect path

A

Cell in hypothalamus produces CRH, transports to nerve terminal ending in ME, where CRH enters into portal circulation of the anterior pituitary. Through portal circulation, CRH makes its way to corticotropes, stimulating the synthesis of ACTH.

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19
Q

direct path

A

Cell in hypothalamus produces AVP, sent along axon through ME, and stored at nerve terminal in posterior pituitary. Released into circulation when neurons are activated.

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20
Q

hypothalamic nuclei

A

medial preoptic N., Suprachiasmatic N., Ventromedial N., Arcuate N., Supraoptic N., Paraventricular N.
- Nucleus: group of nerve cell bodies in CNS

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21
Q

paraventricular nucleus

A

bilateral to ventricle 3
- More medial part (parvicellular) goes through indirect pathway (anterior pituitary)
- More lateral part (magnocellular) goes through direct pathway (posterior pituitary)

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22
Q

RNA-RNA hybridization

A

Method of detecting presence of specific dna or rna sequence in cells or tissues
- Synthesize complementary RNA probe with radio-, fluorescent-, or antigen-labelled bases

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23
Q

anterior lobe developmental origin

A

oral ectoderm -> rathke’s pouch -> regressing rathke’s stalk -> anterior pituitary
- non-nervous tissue
- pars distalis (indirect)

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24
Q

posterior lobe developmental origin

A

neural ectoderm -> neurohypophyseal bud -> pituitary stalk develops into median eminence + posterior pituitary

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25
Q

secretory granules

A

readily-releasable hormone pools within
- line up towards perivascular space for release
- ex. CRH stim corticotrope cells of ant. pit. to exocytose ACTH granules and to synthesize and accumulate more ACTH
- cells with lots of secretory granules are chromophilic

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26
Q

gonadotrope

A

anterior pituitary, synth and release FSH + LH
- stim by GnRH from hypothalamus
- secretory granules = chromophilic

basophil (stain blue)

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27
Q

somatotrope

A

anterior pituitary, synth and release GH in response to GHRH from hypothalamus

acidophil (stain pink)

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28
Q

lactotrope

A

anterior pituitary, synth and release prolactin (PRL)

acidophil (stain pink)

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29
Q

thyrotrope

A

anterior pituitary, synth and release TSH in response to TRH from hypothalamus

basophil (stain blue)

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30
Q

corticotrope

A

anterior pituitary, synth and release ACTH in response to CRH from hypothalamus

basophil (stain blue)

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31
Q

folliculostellate

A

anterior pituitary support cells
- paracrine function
- no granules = chromophobic

32
Q

histology of anterior pituitary

A

weak staining
- little/no secretory granules
- could be immature secretory cell
- supportive function

intense staining
- lots of secretory granules
- eosinophils are bases, stain pink when interacting w acid dye
- basophils are acids, stain blue when interacting w basic dye

33
Q

anterior pituitary nerve supply?

A

no nerve supply
- hypothalamic neuron terminates in ME
- pituitary portal system brings hormones to xxtropes

34
Q

posterior pituitary nerve supply?

A

hypothalamic neurons terminate in post. pit.

35
Q

herring body

A

nerve terminal in posterior pituitary
- stores and releases hormones AVP and OT (secretory granules!!)
- look like swellings

36
Q

pituicyte

A

neuroglial support cells of the post. pit.
- physical and nutritive support

37
Q

anterior vs posterior histology

A

anterior stains more intensely because hormones are synthesized and stored in secretory granules. posterior is mostly nervous tissue, so it looks like the rest of the brain (low staining)

38
Q

thyroid gland

A

TRH from PVH, stimulates TSH synth + release from anterior pituitary, stimulates TH release from follicular cells of thyroid gland (Hypothalamic-pituitary-thyroid axis)

Increased Ca2+ blood conc stimulates calcitonin release from parafollicular cells

39
Q

thyroid follicle

A
  • follicular cells at edge
  • respond to TSH from ant. pit.
  • synth TH precursor, stored in thyroid colloid (interior of follicle)
40
Q

follicle cells

A

Produce TH in thyroid
- cuboidal
- capture iodide (I-)
- makes thyroglobulin (TGB) TH precursor
- microvilli on apical side, facing lumen
- colloid droplets

41
Q

parafollicular cell

A

functionally ind from from follicular cells
- respond to incr in blood Ca2+
- synth + secrete calcitonin
- secretory granules

42
Q

calcitonin

A

32 AA, linear
- synth + release stim by incr Ca2+ in blood
- inhibits release of Ca2+ from bone (decr circulating Ca2+)

43
Q

parathyroid gland

A

4 glands embedded in posterior thyroid
- responds to Ca2+ conc in blood
- ind of thyroid gland
- chief cells (PTH) and oxyphil cells

44
Q

chief cell

A

In parathyroid glands, secrete PTH
- dense cytoplasm
- chromophilic

45
Q

oxyphil cell

A

in parathyroid glands
- clear cytoplasm
- chromophobic
- could be inactive chief cells

46
Q

parathyroid hormone (PTH)

A

released from chief cells in parathyroid glands
- 84 AAs
- low Ca2+ levels stimulate its synthesis and release
- enhances:
- Ca2+ release from bone,
- Ca2+ absorption in intestine
- Ca2+ reabsorption in kidney
thereby incr Ca2+ levels

47
Q

calcium homeostasis

A

calcitonin (parafollicular, thyroid gland) decr Ca2+
PTH (chief cells, parathyroid gland) incr Ca2+

48
Q

thyroid and adrenal endocrine systems (commonalities)

A
  • catabolic in nature: thyroid hormone incr cellular activity, cortisol mobilizes glucose
  • feed-forward elements
  • negative-feedback regulation
  • PVN releases TRH (thyroid) and CRH (adrenal)
49
Q

thyroid system

A

PVN prod TRH -> ant. pit. thyrotropes prod TSH -> thyroid follicular cells prod T3 and T4

50
Q

adrenal system

A

PVN prod CRH -> ant. pit. corticotropes prod ACTH -> adrenal prod cortisol

51
Q

TH synthesis

A

thyroid follicular epithelial cells
1. Iodide capture
2. thyroglobulin production
3. thyroid peroxidase activity
4. thyroglobulin endocytosis

52
Q
  1. iodide capture
A

(dietary) I- from bloodstream is actively transported into cell, then diffuses across apical membrane into colloid lumen

53
Q
  1. thyroglobulin production
A

cells produce thyroglobulin (main component: tyrosine residues)
active transport into colloid lumen

54
Q
  1. thyroid peroxidase
A

in colloid lumen:
1. oxidizes I- -> I2
2. organification/attachment of iodine molecules to TGB -> mono- or di-iodinated thyronines.
3. coupling of thyronines to create hormone precursors w/ 3 or 4 iodines

55
Q
  1. thyroglobulin endocytosis
A

TSH stimulates endocytosis of TGB.
Vesicle fuses with lysosome.
TGB degraded, leaving T3 and T4.
T3 and T4 secreted into circulation (basal membrane).

iodine atoms of uncoupled tyrosine residues kept and transported back to colloid lumen for future TGB.

56
Q

thyroid hormone mode of action

A

Lipophilic: circulate either freely or bound to TBG -> diffuse across cell membrane -> form complex with intracellular cognate receptor -> diffuse into nucleus, function on DNA.

57
Q

T3 vs T4

A

Thyroid release: T4&raquo_space;> T3
Activity/potency: T3&raquo_space;> T4 (800:1)
TBG affinity: T4&raquo_space;> T3
- T4 more protected from degradation

Target cells convert T4->T3 ; T4 is a precursor to T3

58
Q

thyroid hormone function

A
  • Na/K channel openings
  • mitochondrial biogenesis
  • heart + respiratory rate
  • lipid/carb metabolism
  • oxygen consumption
  • mitochondrial energy prod
  • development, growth, reproduction
59
Q

thyroid hormone dysfunction

A
  • iodine deficiency stops TH synthesis
  • excessive TSH stimulation -> goiter [increased cellular growth (hypertrophy) and proliferation (hyperplasia)]
60
Q

thyroid axis - negative feedback regulation

A

elevated T3 and T4 signal to PVN to stop secreting TRH, less TSH from thyrotropes in ant pit

Deficient iodine: less T3 and T4, PVN produces lots of TRH. lots of TSH released from ant pit thyrotropes -> goiter

61
Q

normal thyroid histology

A

inactive thyroid:
- follicular cells squamous
- wide colloid space (TGB storage)

active thyroid:
- follicular cells cuboidal
- smaller colloid space (TSH stimulated TGB endocytosis)

62
Q

graves’ disease + histology

A

immune system generates TSH-like Ig, increases TGB turnover even further
- incr density and packing of follicular cells: tall columnar
- small colloids
- goiter

63
Q

adrenal axis - negative feedback regulation

A

elevated cortisol signals to PVN to stop secreting CRH

less cortisol -> PVN prod more CRH -> ant pit (corticotropes) prod more ACTH -> adrenal prod more cortisol

64
Q

adrenal gland

A

above both kidneys, cortex and medulla regions

65
Q

adrenal cortex

A

Prod steroids
- pituitary-regulated
- neuroendocrine

66
Q

adrenal medulla

A

Prod catecholamine (adrenaline + noradrenaline)
- CNS-regulated
- sympathetic
- innervated by pre-ganglionic sympathetic 1st order neurons (come from spinal cord)

67
Q

cortical zones of adrenal

A

zona glomerulosa (outer)
zona fasciculata
zona reticularis (inner)

68
Q

z. glomerulosa

A

prod mineralocorticoids

69
Q

z. fasciculata

A

prod glucocorticoids

70
Q

z. reticularis

A

prod androgens

71
Q

mineralocorticoid

A

ex. aldosterone (steroid)
- promotes salt retention

72
Q

glocucorticoid

A

ex. cortisol (steroid)
- mobilizes glucose

73
Q

androgen

A

ex. dehydroepiandrosterone (steroid)
- anabolic - helps produce sex hormones

74
Q

adrenal steroid biosynthesis

A

cholesterol from plasma membrane converted to pregnenolone

pregnenolone converted to:
- aldo (z. gl., ACTH + angiotensin II regulated)
- cort (z. f., ACTH regulated)
- DHEA (z. r. ACTH-regulated

75
Q

adrenal cell histology - adrenocortical

A

steroid prod + storage
- lipid droplets
- lots of mitochondria (enzyme factory)

76
Q

adrenal cell histology - adrenomedullary

A

catecholamine producing
- secretory granules

caps 390 (13 decks)

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