Endocrine Overview Flashcards

1
Q

glands

types of cells in them

types of glands and examples

A

synthesize, concentrate, or alter a product for the ultimate process of secretion

histology: cuboical or columnar epithelial cells on a basement membrane, surrounded by blood vessel plexus

  1. endocrine: secrete directly into bloodstream - usually affect distant tissues
  2. exocrine: secrete into ducts

ex. salivary, sweat, mammary glands. exocrine pancreas

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2
Q

autocrine vs. paracrine

A

autocrine action : when secretory products affect the secreting cells directly

paracrine action : when secretory products affect adjacent cells

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3
Q

four classes of endocrine product

A

cells can be generally classified by product

  1. glycoproteins (FSH, LH)
  2. proteins and peptides: (POMC proopiomelanoctin, calcitonin, PTH)
  3. steroids (gonads: testosterone/estrogen. adrenal cortex: corticosterone, aldosterone)
  4. amino acid derivatives (adrenalin - adrenal medulla, melatonin - pineal )
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4
Q

explain the role of post-translational modification in peptide hormone synthesis

A

most peptide hormones are synthesized from larger precursors containing multiple hormones (need ppost-trans proteolysis and/or mod to regulate fx)

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5
Q

explain the difference between the way protein/peptide hormones signal and lipid-soluble hormones signal

A

protein/peptide hormones

  • bind to cell surface receptors to activate second messenter systems

lipid soluble hormones

  • diffuse through pl membrane, maybe nuclear membrane and bind to receptors to regulate gene transcription
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6
Q

negative feedback

A

regulatory mechanism in which initiation of a response to an endocrine signal produces a signal that reduced or stop further signaling

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7
Q

pituitary gland

parts and embryonic origin

A

two distinct embryonic origins:

  • oral ectoderm - invagination of roof of mouth - Rathke’s pouch
    • anterior pit (pars distalis)
    • intermediate pit (pars intermedia)
    • tuberal pit regions
      • ALL THREE TOGETHER = adenohyposhysis
  • neural ectoderm - brain tissue - infundibulum
    • posterior pit (pars nervosa) (neurohypophysis)
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8
Q

pituitary gland

blood supply to the pituitary

A

blood supply is designed to allow hypothalamus (base of brain) to regulate secretion from adenohypophysis

key: endrocrine = need blood supply through which to be distributed through body

how this happens

  • primary plexus (at median eminence of hypothalamus) collects hypothal products and shunts into portal veins
  • portal veins connect to secondary plexus (in ant pituitary) which bathes cells of adenohypophysis

portal circ provides neurovascular link between hypothalamus and anterior pituitar

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9
Q

three types of cells in adenohypophysis

A
  1. acidophilic: GH or PRL (neither are glycosylated)
  2. basophilic: glycoprotein hormones containing sialic acid, ex. FSH, LH, POMC derivatives like ACTH
  3. chromophobic: dont stain bc of lack of secretory granules
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10
Q

FSH

  • secreted from
  • type of hormone
  • hypothalmic regulation via…
  • fx
A

follicle stimulating hormone

  • anterior lobe of adenohypophysis
  • glycoprotein
  • GnRH +, inhibin -
  • follicle devpt. spermatogenesis
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11
Q

LH

  • secreted from
  • type of hormone
  • hypothalmic regulation via…
  • fx
A

leutenizing hormone

  • anterior lobe of adenohypophysis
  • glycoprotein
  • GnRH +
  • follicle maturation. progesterone/androgen release
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12
Q

TSH

  • secreted from
  • type of hormone
  • hypothalmic regulation via…
  • fx
A

thyroid stimulating hormone

  • anterior lobe of adenohypophysis
  • glycoprotein
  • TRH +
  • stimulates TH synthesis/storage/release
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13
Q

MSH

  • secreted from
  • type of hormone
  • hypothalmic regulation via…
  • fx
A

melanophore stimulating hormone

  • intermediate lobe of adenohypophysis
  • 13 aa peptide
  • CRF +
  • pigmentation
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14
Q

ACTH

  • secreted from
  • type of hormone
  • hypothalmic regulation via…
  • fx
A

adrenocorticotropic hormone

  • anterior lobe of adenohypophysis
  • 39 aa peptide
  • CRF +
  • stimulates adrenal cortex secretion
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15
Q

GH

  • secreted from
  • type of hormone
  • hypothalmic regulation via…
  • fx
A

growth hormone/somatotropin

  • anterior lobe of adenohypophysis
  • protein
  • somatotropin releasing factor (GHRH, SRF) +. somatostatin -.
  • acts on long bones via somatomedin intermediates (IGFs)
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16
Q

PRL

  • secreted from
  • type of hormone
  • hypothalmic regulation via…
  • fx
A

prolactin

  • anterior lobe of adenohypophysis
  • protein
  • PRH +. dopamine -.
  • stimulates milk secretion
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17
Q

cell types in neurohypophysis

A
  1. axonal processes of unmyelinated nerve fibers originating in paraventricular nucleus (oxytocin cells) and supraoptic nucleus (AVP cells) of hypothalamus
  2. pituicytes, glial-like support cells for axons
  3. endothelial cells, make up fenestrated blood vessels of gland
18
Q

hypothalmic-neurohypophyseal signalling

A

paraventricular/supraoptic nuclei axons from hypothalamus converge at median eminence to form hypothatamy-hypophyseal tract which enters posterior lobe

  • axons end near cap plexus of neurohypophysis (NOT on other neurons/effector cells)
    • can affect fx of cells in adenohypophysis via portal circ
    • can also be transported to effectors
19
Q

hormones of posterior pituitary and how they reach the bloodstream/target organs

A
  • terminal parts of the axons contain stored hormone - Herring bodies
  • hormones are transported in granules through axon as:
    • prepro-oxyphysin: oxytocin + neurophysin I
    • prepro-vasopressophysin: vasopressin + neurophysin II
  • stimulation of hypothal leads to release of hormones from post pit into bloodstream to targets
    • oxytocin –> uterus and mammary glands
    • AVP –> kidney
20
Q

thyroid gland

  • embryology
  • histological features
A

embryology

derived from endoderm which evaginates from floor of mouth and contains tubules from fifth pharyngeal pouch that contain NC-derived “C cells”/parafollicular/clear cells

  • C cells secrete calcitonin (drops Ca levels, opposes PTH fx)

histology

single layer of cuboidal epithelium surrounding extracellular colloid (contains thyroglobulin) secreted by follicular cells)

  • thyroglobulin = TH precursor
21
Q

thyroid hormone

  • basics
  • synthesis
  • release
  • negative feedback role
A

basics:

synthesized from thyroglobulin + iodide

T3 (7% v active), T4 (35% not v active)

synthesis

  • TG is a 2-subunit glycoprotein synthesized by follicular cells and secreted into colloidal space
  • follicular cells pick up and concentrate iodide (20:1 or more over pl concentration), before…

three step I incorporation/TH synthesis process

  • oxidation: peroxidase take iodide to iodine
  • I + TG Tyr linkage
  • coupling of T1 or T2/liberation of Ala side chain = T3, T4

release

  • initiated by TSH, which stimulates follicular cell endocytosis of colloid
  • colloid delivered to lysosomes; proteolysis leads to release of TH and ultimate secretion of T3 and T4
    • T4>T3, but T4 can be converted to T3 in peripheral tissues

negative feedback

  • T3, T4 inhibit TRH secretion from hypothal
  • T3 T4 inhibit TSH secretion from ant pituitary
22
Q

physiological effects of thyroid fx

A

metabolic effects

growth effects: need both TH and GH for normal growth; TH- individuals are cretins (short stature, cog deficits from abnormal neural development)

23
Q

explain the role of I uptake/transport in terms of causes of thyroid disease, prevention of thyroid disease, and treatment of thyroid disease

A
  • low dietary intake of I
    • can lead to low TH and goiter (also due to high TSH signalling)
    • use of iodized salt can help treat I-deficiency goiters
  • thiocyanate, perchlorate, periodate all inhibit I uptake
    • can be used to treat hyperthyroidism
  • propylthiouracil and sulfonamide block iodination of Tyr in TG
    • can be used to treat hyperthyroidism
  • genetic disorders causing failure of I trap: conversion of I to I2 or I-Tyr coupling can lead to hypothyroidism
24
Q

Grave’s disease

A

hyperthyroid condition in which antibodies constitutively activate thyroid receptor

  • thyrotoxicosis
  • exopthalmia (bulging eyes)
25
Hashimoto's disease
autoimmune disease against thyroglobulin or other thyroid components with resultant hypothyroidism
26
importance of maintaining calcium homeostasis sources of Ca for maintaining homeostasis 3 major calcitropic hormones
Ca is used in neuromuscular transmission, controlling enzyme activity, maintaining bone strength sources of Ca: * _BONE: hydroxyapatite_ (reason for PO4 levels altered by bone resorption/mineralization) * _INTESTINE: abs_ * _KIDNEY: reabs_ major calcitropic hormones 1. PTH 2. calcitriol (1,25 dihidroxy vit D) 3. calcitonin
27
parathyroid gland structure and cell types
parathyroid gland encapsulated and septated by connective tissue 1. **principal/chief cells:** abundant, pale/slightly acidophilic cytoplasm with lots of granules and lipid droplets. secrete PTH - increases pl Ca 2. **oxyphilic cells:** larger cells with smaller, heterochromatic nuclei with acidophilic cytoplasm and no secretory granules. unknown fx
28
clear/C/parafollicular cells
round cells with clear cytoplasm located outside of throid follicles **secrete calcitonin** * 32 aa peptide hormone * lowers pl Ca and PO4 by inhibiting bone resorption * directly inhibits osteoclast activity * increases Ca excretion in urine
29
adrenal gland structure
located in extraperiotoneal space superior to kidney 2 major parts: 1. **cortex:** outer zone with 3 layers 2. **medulla:** center of gland, composed of _chromaffin cells_ (derived from NC cells). 10% of gland. secretes epi/norepi.
30
arterial supply to adrenal gland
3 arteries that distribute blood in 2 ways * superior, middle, inferior suprarenal aa. form a plexus on the outside of the adrenal gland **distribution of blood from plexus** 1. blood distributed to ZG (fenestrated caps), through ZF (sinusoids), to ZR (capillaries) and on into medulla (same caps cont'd) 2. medullary arterioes proceed straight from plexus to medulla **why?** gives medulla dual arterial supply of _blood with cortex secretions_ and _blood with good oxygen/nutrient supply_
31
venous drainage of adrenal gland
whole adrenal gland drained by single central vein L - into renal vein R - into superior vena cava
32
nerve supply to adrenal gland
**myelinated (pregang) sympathetic fibers:** end on medullary cells - regulate secretion of _catecholamines_ **unmyelinated (postgang) sympathetic fibers:** associated with cortical blood vessels
33
adrenal medulla * cell types and functions * control of adrenal medullary cell secretion
* composed of chromaffin cells of two types * granules with dense cores : contain **norepi** * less densely staining, more homogenous : contains **epi** * **​epi production dependent on adrenal cortex stimulation** catecholamine (norepi/epi) release stimulated by **sympathetic nerve activation**
34
effects of catecholamines
1. stimulate glycogenolysis in liver and sk muscle (glycogen --\> glucose) 2. mobilize FFA from adipose tissue 3. increase basal metabolic rate via fright/fight/flight syndrome
35
adrenal cortex layers and general features
cells of adrenal cortex **have lots of SER (indicator of steroidogenesis)** 1. zona glomerulosa 15% 2. zona fasciculata 78% 3. zona reticularis 7%
36
ZG general features
* rounded clusters of cells with intesely staining nuclei, little cytoplasm, lots of SER * **mitochondria that are elongated and cristae that are broad/flat** * **​**secretes **mineralocorticoids:** maintain electrolyte balance (ex. aldosterone)
37
aldosterone function
* secreted from ZG * regulated by RAS * triggered by low bp _effect:_ Na reabsorption in kidneys
38
ZF general features
* large polyhedral cells in columns or cords 1-2 cells thick, separated by sinusoids * light staining spherical nuclei * acidophilic nucleus * lots of SER, developed Golgi complex, many mitochondria (rounded, tubular cristae) and lipid droplets with precursors of steroids * secrete **glucocorticoids**
39
glucocorticoids
* released in response to **ACTH (adrenocorticotropic hormone)** from hypothalamohypophyseal system * KEY HORMONE: **cortisol** * high glucocorticoid levels can decrease lymphocyte/plasma cell numbers --\> immunosuppressive
40
ZR general features
* cells (smaller than those in ZF) in rows or colums * deep staining nuclei * some lipid droplets * secrete **gonadocorticoids** (androgens) in sm amounts
41
control of cortical secretion
* ZG - mineralocorticoid secretion * indep of hypothalamohypophysial axis * mostly controlled by RAS * ZF/ZR - glucocorticoid/gonadocorticoid secretion * controlled by hypothalamohypophyseal axis for basal and stress-induced secretion * hypothalamus - corticotropin releasing factor (CRF) * ant pituitary - ACTH (response to CRF) * adrenal cortex - glucocorticoids/some androgens * negative feedback on ACTH!!! CRF-ACTH-glucocorts/androgens
42
list some examples of post-translational modification that are used to process peptide hormones
1. di-basic cleavage 2. C terminal trimming of basic residues 3. amidation of C terminal glycines ex. PTH needs to be amidated to bind to PTH-R