Download Endocrine System

ENDOCRINE SYSTEM
The Endocrine System reg.
growth, dev., reprod., adjusts
metabolism.
ductless system; secretions in
interstitial fluid or blood
compare with exocrine (sweat
glands, gastric glands)
Hormones – chemical messengers
responsible for
regulations/adjustments
ENDO/NEUROENDO
Cell Signaling – cell
communication
neurotransmitters
hormones (through blood)
local regulators (diffuses
through interstitial fluids and
acts on nearby cells)
AUTO/PARA
local regulators cont’d…
autocrine regulation : acts on cells
that produce hormone
paracrine regulation: nearby cells
Includes: histamine, growth
factors, Nitric oxide (dilates blood
vessels) and prostaglandins (affects
cAMP levels; stimulate/inhibit smooth
muscle contractions; reduce/raise
blood pressure; induce labour)
pheromones (prod. By
exocrine glands;
communication between
animals of same species –
mating, territory, alarm)
neurohormones (secreted by
neuroendocrine cells that are
linked with nervous system
and endocrine system)
Hormones Classes
1. fatty acid derivatives
- prostaglandins, juvenile
hormones of insects
steroids
- molting hormone of
insects, cortisol,
testosterone,
progesterone, estrogen
amino acid derivatives
- simplest hormones; T3 and
T4 from tyrosine and iodide;
epinephrine and
norepinephrine from tyrosine;
Melatonin from trytophan
peptides or proteins
largest group; oxytocin
ADH, glucagons, secretin,
ACTH, calcitonin, insulin,
Growth hormone, TSH and
gonadotropic hormones
RESPONSE TO
HORMONES
A)Matching receptor?
If yes
B) Molecules/genes
affected after binding
Ie. Response to insulin
Ie Different response
to insulin between
muscle/adipose tissue
Regulation-hormone secretion
Negative feedback
typical regulation
restores homeostasis
ie. Low calcium levels stimulate
parathyroid gland to release
parathyroid hormone which raises
calcium levels and shuts off
parathyroid secretions.
Positive feedback
secretion of hormone
promotes further secretion
ie. Oxytocin secretion
stimulates more oxytocin
secretion
Mechanism of Hormone Action
Hormones only have effects when
they hit target cells
Receptor up and down
regulation
too much insulinreceptor down
regulation; low concentrations of
hormones can create more
receptors in “up” regulation
Peptide Hormones bind to cell
surface receptors in 2 ways:
a) G protein-linked receptors
(G = use of GTP) to intiate
signal transduction (convert
extracellular signal to
intracellular)
b) Enzyme-linked receptors –
not linked to G proteins (most
are receptor tyrosine kinases)
- bind signal molecules known
as growth factors (insulin, nerve
growth factor)
- activated receptor converts
amino acid tyrosine into cell
proteins
SIGNAL TRANSDUCTION
INVOLVES MANY RELAY
MOLECULES AND
AMPLIFICATION (prod.
dramatic response ie
adrenalin)
hormone does not enter cell;
relays info to secondary mess.
- secondary messenger signals
effector mol. that carry out action
(cAMP is a common secondary
messenger that is catalyzed by
adenylyl cyclase – it activates
protein kinases – and inactivated
by phosphodiesterases (conv.
kinase activity (phosphorylation)
on proteins alters its activity which
therefore leads to altered function
(ie change in metabolism)
Phospholipids and Ca2+ can
also function as secondary
messengers
(inositol triphosphate – IP3 –
opens calcium channels in ER
that releases calcium in
cytosol to regulate muscle
contractions, neural signaling
microtubule disassembly,
blood clotting, activation of
some enzymes)
3. Steroid, fatty acid hormones
(and thyroid hormones) enter cells
(hydrophobic) -pass plasma mem.
- bind receptors in cytoplasm or
nucleus forming receptor-hormone
complexbinds DNA turning genes
on or off (activating/inactivating
transcription.)
generally slow but long lasting
(steroid effects such as testosterone)
Antagonistic Hormones –
counteract each other
Insulin and Glucagon
Calcitonin and Parathyroid
hormone
Atrial natriuretic peptide
(ANP) and aldosterone
Islets of Langerhans
 Secrete insulin
Stim. cells to take up
glucose/lowers blood
glucose levels
 Secrete glucagon
Raises blood glucose conc.
 Diabetes mellitus
Results in decreased use of
glucose
Nervous and endocrine
regulation
 Integrated in the
hypothalamus, which
regulates the pituitary
gland
Oxytocin and ADH
 Produced by the
hypothalamus
 Released by the
posterior lobe of the
pituitary
Hypothalamus
 Secretes
Releasing hormones
Inhibiting hormones
 These regulate the
hormone output of the
anterior lobe of the
pituitary
Anterior lobe of the pituitary
 Secretes the growth
hormone, prolactin
 Several tropic hormones
that stimulate other
endocrine glands
Growth hormone (GH)
 Anabolic hormone that
stimulates body growth
 Stimulates the liver to
produce insulin-like
growth factors (IGFs),
which promote skeletal
and tissue growth
Credit: © Mediscan/Visuals Unlimited
Acromegaly, also called acromegalia, is a long-term problem in which bones of the face, jaw,
arms, and legs get larger. It occurs in middle-aged patients and is caused by too much growth
hormone. It is treated by x-rays to shrink the pituitary, or part of the pituitary gland is removed.
The most common cause is a somatotropin-secreting pituitary adenoma.
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Thyroid gland
 Secretes
Thyroxine
Triiodothyronine
 Stimulate the rate of
metabolism
Regulation of thyroid
secretion
 Depends mainly on a
negative feedback system
Anterior pituitary gland
Thyroid gland
Thyroid hyposecretion
 Childhood cretinism
 Adult myxedema
Thyroid hypersecretion
 Most common cause is
Grave’s disease
Goiter associated with both
hyposecretion and
hypersecretion
Parathyroid glands
 Secrete PTH
Regulates calcium level
in the blood
Stimulates calcium
release from bones
Calcitonin, secreted by the
thyroid, acts
antagonistically to PTH
Credit: © Mediscan/Visuals Unlimited
Rickets is a condition caused by a deficiency of vitamin D, especially in infancy and
childhood, with disturbance of normal ossification. The disease is marked by bending and
distortion of the bones under muscular action, by the formation of nodular enlargements on
the ends and sides of the bones, by delayed closure of the fontanels, pain in the muscles,
and sweating of the head. Vitamin D and sunlight together with an adequate diet are curative,
provided that the parathyroid glands are functional.
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Addison’s or Cushings?
Test?
Dexamethosone test – drug inhibitis
pituitary sec. of ACTH  for high cortisol
Synthetic ACTH injection  for low
cortisol
Addison’s  low cortisol
Cushing’s  high cortisol
STRESS RESPONSE
Adrenal glands
 Secrete hormones that
help the body cope with
stress
 Adrenal medulla secretes
Epinephrine
Norepinephrine

Adrenal cortex secretes
Mineralocorticoids (ie
aldosterone)
Glucocorticoids (ie
cortisol)
Adrenal gland
REPRODUCTIVE HORMONES
Estrogen inc. due to
stimulation from FSH and
LH
Estrogen has endo/auto
and paracrine functions
Stimulates cells to prod.
More estrogen (pos.
feedback)
Estrogen inhibits (at low
conc.) hypothalamus Neg.
Feedback
Estrogen stim.(at higher
conc) Hypo/ Ant.Pituitary
Pos. Feedback
Estrogen/Progesterone
inhibit hypo and ant.
Pituitary
Without fertilization
corpus luteum
degenerates and
estrogen/progesterone
levels fall