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CTO quiz 5 > Endocrine > Flashcards

Endocrine Flashcards

0
Q

Neuroendocrine system

A

Dispersed cells in brain (neuroendocrine)

Release neurohormones via neurosecretion (long distance vs neurotransmitters)

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1
Q

General features of endocrine system

A

Ductless glands - release hormones into interstitial space - very vascular
Glands either dedicated, secondary fx, or dispersed cells (ex neuroendocrine cells in brain)
Receptors determine specificity
Can also include paracrine (interstitial) and autocrine (same cell), especially in dev’t (ex PDA) and inflammation
Vs nervous - long term modulation, act on all cells (vs muscles and glands)

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2
Q

Types of hormones

A

Proteins - insulin, growth hormone, PTH
Small peptides - ex vasopressin
Steroids - adrenal cortical, ovarian, testicular
Amino acid/arachidonic derivatives - catecholamines, thyroid, prostaglandin, prostacycline, leukotriene

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3
Q

Mechanism of action for hormones

A

Hormone = long distance vs paracrine and autocrine
Receptor -> specificity (different effects in different cells)
Water soluble -> transmembrane receptor/primary messenger -> secondary messenger
- also generally need transport proteins in plasma
Lipid soluble (ie steroid) -> diffuse across membrane -> nuclear receptor

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4
Q

Regulation of hormone response

A

In response to chronic hormone levels
Up-regulation: low levels -> more receptors -> more sensitive
Down-regulation: high levels -> fewer receptors -> less sensitive

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5
Q

Primary endocrine glands

A 
Thyroid
Parathyroid
Adrenal
Pituitary
Pineal
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6
Q

Organs with secondary hormone secretion

A 
Stomach, liver, small intestine, pancreas, kidneys
Hypothalamus
Thymus
Skin
Heart
Placenta
Ovaries, testes
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7
Q

General organization of hypothalamus/pituitary

A

Hypothalamus = superior
Pituitary = hypophysis = inferior
- pituitary is split into two lobes
- posterior = neurohypophysis (from diencephalon)
- anterior = adenohypophysis (from mouth/Rathke’s pouch)
Connected by hypothalamo-hypophyseal tract of axons within infundibulum

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8
Q

Function of posterior pituitary

A

aka neuropituitary
Only releases hormones produced in hypothalamus
Supraoptic + paraventricular nuclei -> ADH, oxytocin -> hypothalamo-hypophyseal tract -> stored in axons terminals as Herring bodies/neurosecretory granules -> released with AP
“Pituicytes” = glial cells around unmyelinated nerve fibers
ADH - high osmolality -> ADH -> water resorption -> low osmolality
oxytocin - positive feedback from suckling or contractions

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9
Q

Function of anterior pituitary

A

aka adenohypophysis
Makes hormones under control of hypothalamus
Higher brain centers -> hypothalamus -> 2 inhibiting/4 releasing hormones -> median eminence axon terminals -> hypothalamo-hypophyseal portal system -> anterior pituitary capillaries
Wide variety of cell types and hormones produced - chromophils (acidophils/basophils) and chromophobes (no hormones, progenitor or senescent)

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10
Q

Segments of anterior pituitary

A

Pars distalis - all of secretory cells, largest
Pars tuberalis - around infundibulum
Pars intermedia - vestigial, remains of Rathke’s pouch

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11
Q

Hormones of anterior pituitary

A

Trophic hormones - act on other endocrine glands - direct feedback
- all released by basophils!
- CRH -> corticotropes -> ACTH = adrenocorticotrophic hormone
- TRH -> thyrotropes -> TSH
- GnRH -> gonadotropes -> FSH, LH
Non-trophic hormones - act directly on tissue - metabolic feedback via effects
- released by acidophils
- GHRH -> somatotropes -> growth hormone -> adipose, IGF -> bone, muscle
- mammotropes -> prolactin (suckling reduces inhibition -> inc production)

Hypothalamic inhibition:
Somatostatin -> inhibits GH and TSH
PIH = dopamine -> inhibits PL

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12
Q

Feedback to anterior pituitary

A

Almost all systems are negative feedback (high levels -> decreased production)

Exception: oxytocin during childbirth -> positive feedback -> amplifying response

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13
Q

Regulation of thyroid

A

Hypothalamus -> TRH ->
Anterior pituitary -> TSH ->
Thyroid -> T3, T4
T3 -> negative feedback to hypothalamus and anterior pituitary

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14
Q

Histology of thyroid gland

A

Large follicles filled with colloid
Follicular cells - change shape with activity!
- squamous if inactive -> columnar if active
C cells - outside of follicle
Also capillaries within CT capsule - very vascular

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15
Q

Production of thyroid hormones

A

Follicular cells make thyroglobulin (rich in tyrosine) ->
Iodinized (at tyrosine residues) and stored in follicle (weeks to months of supply) ->
Resorbed by follicular cell (via endocytosis) ->
Lysosome -> breaks down thyroglobulin -> free T3, T4 -> released

16
Q

Thyroid hormones

A

T3 - triiodothyronine
T4 - tetraiodothyronine

Both are joined tyrosine residues of thyroglobulin protein with iodinization of rings
Release 20:1 T4:T3, converted in kidneys/tissue
(T3 is 5x more active)

17
Q

Functions of thyroid hormones

A 
Essentially same function (at this point...)
Regulate BMR
Regulate heat production
Regulate growth (body and tissue)
Dev't of nervous system (peds only)
18
Q

Production of calcitonin

A

Produced in C (extrafollicular) cells of thyroid
Decreases serum calcium levels
- bone deposition
- decreased resorption in kidneys

19
Q

Location of parathyroid glands

A

Usually 4 glands in posterior capsule of thyroid
Lots of variation - migrate from 3/4 pharyngeal pouches during dev’t (vs thyroid migrates from tongue)
Need to preserve (and blood supply) in thyroidectomy

20
Q

Function of PTH

A

Increases serum calcium

  • > osteoblasts -> osteoclast-stimulating factor -> inc number and activity of osteoclasts -> bone resorption
  • > increased kidney resorption (and PO4 excretion)
  • > increased GI absorption
21
Q

Oxyphil cells

A

Large, acidophilic cells
Found in PTH glands of older people
Unclear fx/significance

Vs Chief cells - active

22
Q

Gross structure of adrenal glands

A

Different embryology, functions, etc

Cortex - superficial, split into three layers -
All layers steroid producing - smooth ER, lipid droplets, mitochondria
- zona glomerulosa -> aldosterone
- zona fasciculata -> cortisol - appears most foamy
- zona reticularis -> androgens
Medulla - deep - neural crest cells (ganglion without axons)

23
Q

Cortisol production and function

A

ACTH -> zona fasciculata -> cortisol
“Glucocorticoid”
Metabolic:
- catabolic in most tissues (lipids, protein, carbs -> ATP)
- anabolic in liver - gluconeogenesis, glycogenesis
- diurnal, energy throughout circadian rhythm
Anti-inflammatory/immunosupressive

24
Q

Aldosterone production and function

A

“Mineralocorticoid”
Part of RAAS system of fluid regulation
Angiotensin -> zona glomerulosa (cortex) -> aldosterone
-> Kidney -> resorb Na and Cl -> water, HCO3 follow
Can also be stimulated somewhat by ACTH, inhibited by ANP

25
Q

Adrenal medulla

A

Deep to cortex
Derived from neural crest cells ->
chromaffin cells/pheochromocytes

Acts as a sympathetic ganglion: preganglionic fibers -> epi and NE released into bloodstream

26
Q

Production of catecholamines (epi and NE)

A

In adrenal cortex
Two blood streams - direct and through cortex (“portal”) -> high glucocorticoid levels -> required for methyl transferase activity -> NE to epinephrine
(ie low cortisol levels -> more NE, high cortisol -> more epi)
Usually 80% epi

27
Q

Islet of Langerhands anatomy

A

Lots of capillaries (vs exocrine cells around duct)
Alpha cells (glucagon) around edges
Beta cells (insulin) in middle
Delta and F usually near surface but rare
More found in tail

28
Q

Pancreatic islet secretions

A

Alpha cells (20%) -> glucagon -> glycogenolysis, lipolysis
Beta cells (70%) -> insulin -> glucose to cells, inhibits lipolysis
Delta cells (5%) -> somatostatin -> inhibits
-> paracrine -> lower insulin and glucagon
-> anterior pituitary -> lower GH, TSH
-> stomach -> lower HCl
F cells -> pancreatic peptide
-> stomach chief cells -> inc enzymes
-> less bile and pancreatic enzyme release
-> lower motility of small intestine

29
Q

Pineal gland

A

Roof of diencephalon
Produces melatonin -> regulates light-dark cycles (induces sleepiness, inhibited by light -> NE -> less melatonin)
Corpora arenacea/”brain sand” is identifiable as midline on xray

30
Q

Control of hormone release

A

Humeral - direct response to blood stimuli - ex insulin, aldosteron, PTH
Neural - ex adrenal medulla
Hormonal/trophic - hypothalamus -> anterior pituitary

CTO quiz 5 (4 decks)

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