endocrine systems12 endocrine systems
TRANSCRIPT
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Hormones &Endocrine System
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endocrine system secretes hormones
slower but longer-acting responses
roles include: reproduction, development,energy metabolism, growth & behavior
nervous system high-speed electrical signals along specialized
cells called neurons
these signals regulate other cells
Two systems communicatethroughout body:
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Signaling by Pheromones
Pheromones: chemicals that are released into the
environment & used to communicate with other individuals
Pheromones serve many functions, including marking
trails leading to food, defining territories, warning of
predators, and attracting potential mates
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MHC-dependent Mate Preferences in HumansCLAUS WEDEKIND, THOMAS SEEBECK, FLORENCE BETTENS AND ALEXANDER J. PAEPKE
(Proceedings of the Royal Society. B, Biological sciences 1995)
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Chemical Classes of
Hormones
Three major classes ofmolecules function as
hormones in
vertebrates
Polypeptides
(proteins and
peptides)
Amines derivedfrom amino acids
Steroid hormones
Water-soluble Lipid-soluble
Steroid:
Cortisol
Polypeptide:
Insulin
Amine:Epinephrine
Amine:Thyroxine
0.8 nm
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Signalreceptor
TARGETCELL
Signal receptor
Transportprotein
Water-soluble
hormone
Fat-solublehormone
Generegulation
Cytoplasmicresponse
Generegulation
Cytoplasmicresponse
OR
(a) NUCLEUS (b)
Water-soluble hormones
are secreted by
exocytosis, travel freely
in the bloodstream &bind to cell-surface
receptors
Lipid-soluble hormonesdiffuse across cell
membranes, travel in the
bloodstream bound to
transport proteins &diffuse through the
membrane of target cells
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Multiple Effects of Hormones
The same hormone may have differenteffects on target cells that have Different receptors for the hormone
Different signal transduction pathways
Different proteins for carrying out the response
A hormone can also have different effects in
different species
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Different receptorsSame receptors but differentintracellular proteins
Different cellular
responses
Different cellular
responses
Epinephrine Epinephrine Epinephrine
receptor receptorreceptorGlycogendeposits
Vesseldilates.
Vessel
constricts.
Glycogen
breaks downand glucoseis releasedfrom cell.
(a) Liver cell (b) Skeletal muscle
blood vessel
Intestinal blood
vessel
(c)
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Major endocrine glands:
Adrenalglands
Hypothalamus
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands
PancreasKidney
Ovaries
Testes
Organs containingendocrine cells:
Thymus
Heart
Liver
Stomach
KidneySmallintestine
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Feedback regulation and
antagonistic hormone pairs
are common in endocrine systems
Hormones are assembled into regulatory
pathways
negative feedback loop
inhibits response by reducing initial stimulus regulates many hormonal pathways involved
in homeostasis
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Pathway Example
Stimulus Low pH in
duodenum
S cells of duodenumsecrete secretin ( )
Endocrinecell
Bloodvessel
PancreasTargetcells
Response Bicarbonate release
SimpleHormonePathways
NegativeFeedback
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Pathway
Example
Stimulus Suckling
Sensory
neuron
Positivefeedback
Hypothalamus/posterior pituitary
Neurosecretory cell
Neurohormone
Blood vessel
Targetcells
Response
Posterior pituitary
secretes theneurohormoneoxytocin ( ).
Smooth muscle inbreasts
Milk release
SimpleHormonePathways
PositiveFeedback
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Insulin and Glucagon:
Control of Blood Glucose
Insulin (decreases blood glucose) and glucagon
(increases blood glucose)are antagonistic
hormones that help maintain glucose
homeostasis
The pancreas has clusters of endocrine cells
called pancreatic islets with alpha cells thatproduce glucagon and beta cells that produce
insulin
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Body cellstake up moreglucose.
Insulin
Beta cells ofpancreasrelease insulininto the blood.
Liver takesup glucoseand stores itas glycogen.
Blood glucoselevel declines.
Blood glucoselevel rises.
Homeostasis:Blood glucose level(70110 mg/m100mL)
STIMULUS:Blood glucose level rises(for instance, after eating acarbohydrate-rich meal).
Liver breaksdown glycogenand releasesglucose into
the blood.
Alpha cells of pancreasrelease glucagon intothe blood.
Glucagon
STIMULUS:Blood glucose levelfalls (for instance, after
skipping a meal).
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Insulin & Glucagontarget specific tissues
Insulin reduces blood glucose by promoting uptake by cells
slowing glycogen breakdown in liver
promoting fat storage
Glucagon increases blood glucose by stimulating conversion of glycogen to glucose
stimulating breakdown of fat & protein intoglucose
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Diabetes Mell i tus
Type 1 (insulin-dependent)
autoimmune disorder in
which the immune system
destroys pancreatic beta
cells
Type 2(non-insulin-
dependent)
insulin deficiency or
reduced response of target
cells due to change in
insulin receptors
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In response to a drop in blood glucose belownormal levels, what mechanisms aretriggered to get more sugar into the blood &
restore normal glucose levels?
A. Insulin is released into circulation and, in response,
body cells take in & use up glucose.
B. Glucagon is released into circulation and, in response,
liver cells release glucose into the blood.
C. Secretin is released into circulation and, in response,
the pancreas secretes amylases into the intestine.
D. CCK is released into circulation and, in response,enzymes & bile are released into the intestine.
E. Amylase enzymes are released into circulation and, in
response, starches in the blood are digested to
glucose.
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Coordination of Endocrine and Nervous
Systems in Vertebrates
The hypothalamusreceives information
from the nervous
system and initiates
responses throughthe endocrine
system
The pituitary gland
iscomposed of the
posterior pituitary
and anterior pituitary
Pinealgland
Cerebellum
Spinal cord
Cerebrum
Thalamus
Hypothalamus
Pituitarygland
Posteriorpituitary
Anteriorpituitary
Hypothalamus
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Major Endocrine Glands and Some of Their Hormones
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Major Endocrine Glands and Some of Their Hormones
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Posteriorpituitary
Anteriorpituitary
Neurosecretorycells of thehypothalamus
Hypothalamus
Axon
HORMONE OxytocinADH
Kidney tubulesTARGET Mammary glands,uterine muscles
PosteriorPituitaryHormones
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Anterior Pituitary Hormones
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Tropic effects only:FSH
LHTSHACTH
Nontropic effects only:ProlactinMSH
Nontropic and tropic effects:GH Hypothalamic
releasing andinhibitinghormones
Posteriorpituitary
Neurosecretory
cells of thehypothalamus
Portal vessels
Endocrine cellsof the anteriorpituitary
Pituitaryhormones
HORMONE FSH and LH TSH ACTH Prolactin MSH GH
TARGET Thyroid MelanocytesTestes orovaries
Adrenalcortex
Mammaryglands
Liver, bones,other tissues
Anterior Pituitary Hormones
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Pathway Example
Stimulus Cold
Sensory neuron
Hypothalamus
Neurosecretory cell
Releasing hormone
Blood vessel
Anterior pituitary
Tropic hormone
Endocrine cellHormone
Target
cells
Response
Negative
feedback
Hypothalamus secretes
thyrotropin-releasinghormone (TRH ).
Anterior pituitary secretesthyroid-stimulating
hormone (TSH, also known
as thyrotropin ).
Thyroid gland secretes
thyroid hormone
(T3 and T4 ).
Body tissues
Increased cellularmetabolism
Thyroid Regulation:
A Hormone CascadePathway
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Disorders of Thyroid Function and Regulation
Hypothyroidism can produce symptoms such as
Weight gain, lethargy, cold intolerance Hyperthyroidism can lead to
High temperature, sweating, weight loss,
irritability, and high blood pressure
Graves disease, a form of hyperthyroidism caused
by autoimmunity, is typified by protruding eyes
Thyroid hormone refers to a pair of hormones
Triiodothyronin (T3), with three iodine atoms
Thyroxine (T4), with four iodine atoms Insufficient dietary iodine leads to an enlarged
thyroid gland, called a goiter
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Growth hormone (GH)is secreted by theanterior pituitary gland
and has tropic andnontropic actions
It promotes growthdirectly and has diverse
metabolic effects It stimulates production
of growth factors
An excess of GH can
cause gigantism, whilea lack of GH can causedwarfism
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Parathyroid Hormone and Vitamin D:
Control of Blood Calcium
Two antagonistic hormones regulate the homeostasis ofcalcium (Ca2+) in the blood of mammals
Parathyroid hormone (PTH) is released by the parathyroid
glands increases the level of blood Ca2+ by releasing Ca2+ from
bone
stimulates kidneys to activate vitamin D, which promotes
intestinal uptake of Ca2+
Calcitonin is released by the thyroid gland
decreases the level of blood Ca2+
stimulates Ca2+ deposition in bones and secretion by
kidneys
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Activevitamin D
Increases Ca2uptake inintestines
Stimulates Ca2uptake in kidneys
StimulatesCa2 releasefrom bones
Parathyroidgland (behindthyroid)
PTH
Blood Ca2level rises.
Homeostasis:Blood Ca2 level(about 10 mg/100 mL)
STIMULUS:
Falling bloodCa2 level
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Adrenal Hormones: Response to Stress
The adrenal glands are adjacent to the kidneys
Each adrenal gland actually consists of two
glands: the adrenal medulla (inner portion) andadrenal cortex(outer portion)
The adrenal medulla secretes epinephrine
(adrenaline) and norepinephrine(noradrenaline)
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Spinal cord(cross section)
(a) Short-term stress response and the adrenal medulla
Stress
Nervesignals
Nervecell
Nerve cellAdrenal medullasecretes epinephrineand norepinephrine.
Adrenalgland
Kidney
Effects of epinephrine and norepinephrine:
Glycogen broken down to glucose;
increased blood glucose Increased blood pressure
Increased breathing rate
Increased metabolic rate
Change in blood flow patterns, leading toincreased alertness and decreased digestive,excretory, and reproductive system activity
Hypo-thalamus
Stress and the adrenal gland.
Steroid Hormones from the Adrenal Cortex
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(b) Long-term stress response and the adrenal cortex
Stress
Releasinghormone
Hypothalamus
Anterior pituitary
Blood vesselACTH
Adrenal cortexsecretes mineralo-corticoids andglucocorticoids.
Effects ofmineralocorticoids:
Effects ofglucocorticoids:
Retention of sodiumions and water bykidneys
Increased bloodvolume and bloodpressure
Proteins and fats brokendown and converted toglucose, leading toincreased blood glucose
Partial suppression ofimmune system
Adrenalgland
Kidney
Steroid Hormones from the Adrenal Cortex
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Gonadal Sex Hormones
The gonads, testes and ovaries, produce most ofthe sex hormones: androgens, estrogens, and
progestins
All three sex hormones are found in both males
and females, but in significantly different
proportions
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The testes primarily synthesize androgens,mainly testosterone, which stimulate
development and maintenance of the male
reproductive system
Testosterone causes an increase in muscle and
bone mass and is often taken as a supplement to
cause muscle growth, which carries health risks
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Estrogens, most importantly estradiol, are
responsible for maintenance of the femalereproductive system and the development offemale secondary sex characteristics
In mammals, progestins, which includeprogesterone, are primarily involved in preparingand maintaining the uterus
Synthesis of the sex hormones is controlled byFSH and LH from the anterior pituitary
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Between 1938 and 1971 some pregnant women atrisk for complications were prescribed a syntheticestrogen called diethylstilbestrol (DES)
Daughters of women treated with DES are at higherrisk for reproductive abnormalities, includingmiscarriage, structural changes, and cervical andvaginal cancers
DES is an endocrine disruptor, a molecule thatinterrupts the normal function of a hormone pathway,in this case, that of estrogen
Endocrine Disruptors
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Caster Semenya And The IOCs Olympics
Gender Benderby Jesse Ellison The Daily Beast, Jul 26, 2012
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Melatonin and Biorhythms
The pineal gland, located in the brain, secretesmelatonin
Light/dark cycles control release of melatonin
Primary functions of melatonin appear to relate to
biological rhythms associated with reproduction
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All hormones
a) are lipid-soluble molecules.
b) are protein molecules.
c) elicit the same biological response from
all of their target cells.
d) are carried to target cells in the blood.e) are produced by endocrine glands.
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Thyroxine hormones exert negative feedback on
the production of thyroid stimulating hormone
(TSH), as best exemplified by
A. I.
B. II.
C. III.D. IV.
Thyroxines
Hormones are transported throughout the
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Hormones are transported throughout the
circulatory system, but they affect only
specific tissues or cells because
A. only the capillaries at the target will let thehormones out of the blood.
B. only the target cells have receptors for thehormone.
C. the nontarget tissues catabolize or destroy thehormones.
D. the hormones know where their targets arelocated.
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Epinephrine causes the constriction of someblood vessels and the dilation of others because
A. the target cells have different receptors for the same
hormone with different signal transduction pathways.
B. the vasoconstriction targets are incapable of
vasodilation.
C. the target cells have the same receptor and the same
signal transduction pathway.
D. the hormone is able to enter the cytosol of the
vasodilation targets but not the vasoconstriction targets.
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Thyroid hormones exert negative-feedback effects
at all levels of the hypothalamic-pituitary-thyroid
gland axis, so we should expect to find thyroid
hormone receptors at
A. the hypothalamus.
B. the anterior pituitary gland.
C. the targets of thyroid hormones throughout the
body.
D. all of the above.
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Oxytocin, the milk-release hormone secreted from
nerve endings (axon terminals) in the posterior
pituitary gland, is synthesized in
A. the anterior pituitary gland.
B. the hypothalamus.
C. the mammary glands.
D. the posterior pituitary gland.
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The role of the pancreas as an endocrine gland
that mediates glucose homeostasis is of great
importance to health, but a patient whose
pancreas has been surgically removed also loses
A. the bodys source of epinephrine.
B. the bodys source of growth hormones.
C. the bodys source of most of its digestive enzymes.
D. the ability to coordinate swallowing and breathing.
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The gas that causes vasodilation by
relaxing vascular smooth muscle, thus
enabling male sexual function, is
A. carbon dioxide.
B. nitric oxide.
C. carbon monoxide.
D. oxygen.
E. nitrogen.