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Renal, Endocrine, Reproductive Systems > Endocrine Overview > Flashcards

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
Q

Hashimoto’s disease

A

autoimmune disease against thyroglobulin or other thyroid components with resultant hypothyroidism

26
Q

importance of maintaining calcium homeostasis

sources of Ca for maintaining homeostasis

3 major calcitropic hormones

A

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
Q

parathyroid gland structure and cell types

A

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
Q

clear/C/parafollicular cells

A

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
Q

adrenal gland structure

A

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
Q

arterial supply to adrenal gland

A

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
Q

venous drainage of adrenal gland

A

whole adrenal gland drained by single central vein

L - into renal vein

R - into superior vena cava

32
Q

nerve supply to adrenal gland

A

myelinated (pregang) sympathetic fibers: end on medullary cells - regulate secretion of catecholamines

unmyelinated (postgang) sympathetic fibers: associated with cortical blood vessels

33
Q

adrenal medulla

  • cell types and functions
  • control of adrenal medullary cell secretion
A
  • 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
Q

effects of catecholamines

A
  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
Q

adrenal cortex layers and general features

A

cells of adrenal cortex have lots of SER (indicator of steroidogenesis)

  1. zona glomerulosa 15%
  2. zona fasciculata 78%
  3. zona reticularis 7%
36
Q

ZG general features

A
  • 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
Q

aldosterone function

A
  • secreted from ZG
  • regulated by RAS
    • triggered by low bp

effect: Na reabsorption in kidneys

38
Q

ZF general features

A
  • 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
Q

glucocorticoids

A
  • released in response to ACTH (adrenocorticotropic hormone) from hypothalamohypophyseal system
  • KEY HORMONE: cortisol
  • high glucocorticoid levels can decrease lymphocyte/plasma cell numbers –> immunosuppressive
40
Q

ZR general features

A
  • cells (smaller than those in ZF) in rows or colums
    • deep staining nuclei
    • some lipid droplets
  • secrete gonadocorticoids (androgens) in sm amounts
41
Q

control of cortical secretion

A
  • 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
Q

list some examples of post-translational modification that are used to process peptide hormones

A
  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

Renal, Endocrine, Reproductive Systems (5 decks)

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