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PowerPoint Lectures for Biology, Seventh Edition
Lectures by Ching-wei Luo
Chapter 45Chapter 45
Hormones and theEndocrine System
Overview: The Bodys Long-Distance Regulators
Hormone definition:
Hormones may reach all parts of the body
But only certain types of cells (target cells) are equipped to
respond
Hormone (from the Greek Hormone (from the Greek hormanhorman, to
excite), to excite)
a chemical signal secreted into the circulatory system and
communicates regulatory messages within the body
Q
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Endocrine systemConstituted by hormonesecreting cells and
glands
Secretes hormones that coordinate slower but longer-acting
responses to stimuli
ductless
Two systems act individually and together in regulating an
animals physiology
Nervous systemConveys high-speed electrical signals along
specialized cells called neurons
rapid messages control the movement of body parts
Two systems act individually and together in regulating an
animals physiology
vesicle
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Endocrine cell NeuronSecrete signal molecules
neurosecretory cells: release neurohormones into the
bloodPathway Example
Stimulus Low bloodglucose
Receptorprotein
Pancreassecretesglucagon ( )
Endocrinecell
Bloodv essel
Liv erTarget
effectors
Response
Pathway Example
Stimulus Suckling
Sensoryneuron
Hypothalamus /posterior pituitar y
Neurosecretorycell
Bloodv essel
Posterior pituitarysecretes oxytocin( )
Targeteffectors
Smooth musclein breast
Response Milk release
Pathway Example
Stimulus Hy pothalamicneurohormonereleased inresponse toneural
andhormonalsignals
Sensoryneuron
Hy pothalamussecretes prolactin-releasinghormone ( )
Neurosecretorycell
Bloodv essel
Anteriorpituitarysecretesprolactin ( )
Endocrinecell
Bloodv essel
Targeteffectors
Response
Mammary glands
Milk production
(c) Simple neuroendocrine pathway
(b) Simple neurohormone pathway
(a) Simple endocrine pathway
Hypothalamus
Glycogenbreakdown,glucose releaseinto blood
negativepositive
FeedbackHomeostasis
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Three major classes of molecules function as hormones in
vertebrates
Hormone composition
Receptionsignal transductionresponse
Signaling by any of these molecules involves three key
events
Proteins and peptides (soluble)Amines derived from amino acids
(soluble)Steroids (insoluble)
Water-soluble hormones act on cell-surface
receptorsSECRETORYCELL
Hormonemolecule
VIABLOODSignal receptor
TARGETCELLSignal
transductionpathway
Cytoplasmicresponse
Nuclearresponse NUCLEUS
DNA
OR
(a) Receptor in plasma membrane
Receptor embedded in the plasma membrane
Signal transductionconverts an extracellular chemicalsignal to a
intracellular response
Cytoplasmic response
Nuclear response
eg: Glucagon (an 8-aa peptide)Camouflage mechanism
Response
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Steroids (estrogens, progesterone), thyroid hormones, and the
hormonal form of vitamin D
Intracellular Receptors for Lipid-Soluble Hormones
SECRETORYCELL
Hormonemolecule
VIABLOOD
TARGETCELL
Signalreceptor
Signaltransductionand response
DNA
mRNA
NUCLEUS
Synthesis ofspecific proteins
(b) Receptor in cell nucleus
Receptor: located in the nucleus or trapped in
the cytoplasm
Signal transductionusually perform the entire task of
transducing signals within a target cell.
Hormones: mostly nonpolar (lipidsoluble)
diffusible
The same hormone may have different effects on target cells that
have
eg. Epinephrine () : fightorflight hormone
A B
Response A Response B
Different receptors for the hormone
Different proteins for carrying out the response
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Different receptors different cell responses
Epinephrine
receptor
Epinephrine
receptor
Epinephrine
receptor
Vesselconstricts
Vesseldilates Glycogen
breaks downand glucose is releasedfrom cell
(a) skin, Intestinal blood vessel
(b) Skeletal muscleblood vessel
(c) Liver cell
Different intracellular proteins different cell responses
Glycogendeposits
Figure 45.4ac
EpinephrineResponds to short-term stress Resulting in decreased
blood flow to the digestive tract and increased delivery of glucose
to major skeletal muscles.
Paracrine Signaling by Local RegulatorsVarious types of chemical
signals elicit responses in nearby target cells
More quickly than hormones can
Examples:Neurotransmitters
Cytokines/ growth factors : play a role in immune responses
nitric oxide (NO) : free radical, easy to breakdown (1998
Nobel)secreted by endothelial cellsactivates an enzyme that relaxes
the neighboring smooth muscle cells dilates the vessels and
improves blood flow
Viagra (sildenafil citrate)
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Prostaglandins (PGs) (1982, Nobel Prize)
First discovered in prostategland secretions-stimulate smooth
muscles of the females uterus to contract
Secreted by placenta cells during childbirth-induce labor
In the immune system
In the reproductive system
-induce fever and inflammation; intensify the sensation of pain
The antiinflammatory drugs: aspirin and ibuprofen
-regulate the aggregation of platelets In the circulation
system
Figure 45.5 platelets (pink and purple) develop a sticky outer
surface and adhere to each other
In the respiratory system
Prostaglandin E signals the muscle cells to relax
Prostaglandin F signals the muscle cells to contract
E F
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The major human endocrine glands
( )
Major human endocrine glands and their hormones
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Major human endocrine glands and their hormones
The pineal gland-Melatonin
The pineal gland, located within the brain
Secretes melatonin
melatoninhttp://en.wikipedia.org/wiki
Contains lightsensitive cells
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The primary functions of melatonin ()
Affects skin pigmentation in many vertebrates
Appear to be related to biological rhythms associated with
reproduction
Release of melatonin
Is controlled by light/dark cycles
main target cells are in the part of the brain called the
suprachiasmaticnucleus (SCN)
Relation Between the Hypothalamus and Pituitary Gland The
hypothalamus, a region of the lower brain
Contains different sets of neurosecretory cells
hypothalamus
pituitary
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Relationship Between the Hypothalamus and Pituitary Gland
Figure 45.7
Hypothalamus
Neurosecretorycells of thehypothalamus
Axon
Anteriorpituitary
Posteriorpituitary
HORMONE ADH Oxytocin
TARGET Kidney tubulesMammary glands,uterine muscles
The pituitary gland: a lima beansized organ located at the base
of the hypothalamus
The posterior pituitary( neurohypophysis): -an extension of the
hypothalamus-stores and secretes two hormonesfrom hypothalamus
Posterior Pituitary HormonesThe two hormones released from the
posterior pituitary
Act directly on nonendocrine tissues
Antidiuretic hormone (ADH)
Oxytocin
acts on the kidneys, increasing water retention and thus
decreasing urine volume.
acts on uterine muscles to contract during childbirth
causes the mammary glands to eject milk during nursing
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The anterior pituitary
A true-endocrine gland, controlled by the neurohormones from
hypothalamus
Synthesize and secrete at least eight different hormonesdirectly
into the blood.
Tropic Effects OnlyFSH, follicle-stimulating hormoneLH,
luteinizing hormoneTSH, thyroid-stimulating hormoneACTH,
adrenocorticotropic hormone
Nontropic Effects OnlyProlactinMSH, melanocyte-stimulating
hormoneEndorphin
Nontropic and Tropic EffectsGrowth hormone
Neurosecretory cellsof the hypothalamus
Portal vessels
Endocrine cells of theanterior pituitary
HORMONE FSH and LH TSH ACTH Prolactin MSH Endorphin Growth
hormone
TARGET Testes orovaries
Thyroid Adrenalcortex
Mammaryglands
Melanocytes Pain receptorsin the brain
Liver Bones
Pituitary hormones(blue dots)
Tropic hormones:
Hormones that regulate the function of endocrine organs
Tropic H Hx response
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Anterior Pituitary Hormones
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
The four strictly tropic hormones areThe four strictly tropic
hormones are
GlycoproteinHormone(~25kDa)
Gonadotropins: stimulate the activities of the male and female
gonads
Peptide; stimulates the production and secretion of steroid
hormones by the adrenal cortex.
ACTH ()
The nontropic hormones include
Prolactin (PRL)
Anterior Pituitary HormonesAnterior Pituitary Hormones
Stimulates mammary gland growth and lactation in
mammalsRegulates fat metabolism and reproduction in birds
Melanocyte-stimulating hormone (MSH)
-endorphin
Regulates the activity of pigmentcontaining cells in the skin of
some fishes, amphibians, and reptiles. Act on neurons in the brain,
inhibiting hunger in mammals
Bind to brain receptors and inhibit the sensation of pain
Runners high effects
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The hormones play both tropic and nontropic effects Anterior
Pituitary Hormones
Growth hormone (GH)
Tropic action: signal the liver to release insulinlike growth
factors (IGFs), which circulate stimulate bone/cartilage
growth.
Non-tropic action: exerts diverse metabolic effects that tend to
raise blood glucose
Hyposecretion of GH in childhood
~about 4 feet (1.2 m) Dwarfism
Hypersecretion of GH during childhood
Gigantismas tall as 8 feet (2.4 m) http://www.mm52.com
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Acromegaly
Excessive production of GH in adulthood
(tyrosine)http://www.answers.com/topic/thyroid-hormone
The thyroid gland
Consists of two lobes located on the ventral surface of the
trachea
Produces two iodine-containing hormones, triiodothyronine (T3)
and thyroxine (T4)
T4 is converted to T3 by deiodinases
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Hypothalamus
Anteriorpituitary
TSH
Thyroid
T3 T4+ Figure 45.9
Secretion of thyroid hormones is regulated by hypothalamus and
anterior pituitary hormones
two negative feedback loops
TRHTSHreleasing hormone
thyroidstimulating hormone
Functions in mammals Thyroid hormones help maintain normal blood
pressure, heart rate, muscle tone, digestion, and reproductive
functions.
Important in bioenergetics, generally increasing the rate of
oxygen consumption and cellular metabolism
Hyperthyroidism
lead to high body temperature, profuse sweating, weight loss,
irritability, and high blood pressure.Graves disease
Fig 45.10
Tissue behind the eyes can become swollen and fibrous
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HypothyroidismCan produce symptoms such as weight gain,
lethargy, and intolerance to cold in adults.
GoiterA deficiency of iodine in the diet
TSH enlarging the thyroid
Hypothalamus
Anteriorpituitary
TSH
Thyroid
T3 T4+
TRH
Cretinism Inherited condition of thyroid deficiency or lacked of
thyroid hormones in childhoods
endemic cretinism in the Democratic Republic of Congo : Four
inhabitants aged 15-20 years : a normal male and three females with
severe longstanding hypothyroidism with dwarfism, retarded sexual
development, puffy features, dry skin and hair and severe mental
retardation. From Delange (229).
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Calcitonin (; from thyroid gland)a 32-aa peptide
parathyroid glands
four small structures embedded in the surface of the thyroid
Parathyroid Hormone; PTH (from parathyroid glands)
- Blood calcium homeostasis
CalcitoninThyroid glandreleasescalcitonin.
StimulatesCa2+ depositionin bones
ReducesCa2+ uptakein kidneys
STIMULUS:Rising bloodCa2+ level
Blood Ca2+level declinesto set point
Homeostasis:Blood Ca2+ level
(about 10 mg/100 mL)
Blood Ca2+level risesto set point
STIMULUS:Falling bloodCa2+ level
StimulatesCa2+ releasefrom bones
Parathyroidgland
IncreasesCa2+ uptakein intestines Active
vitamin DStimulates Ca2+ uptake in kidneys
PTH
Fig 45.11
Calcitonin and Parathyroid Hormone
Osteoclasts (direct)
Ca2+ reabsorption (direct)
Conversion of vitamin D
In kidney
In bone
(indirect)
Osteoblasts In bone
Ca2+ reabsorptionIn kidney
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Hormones in the pancreas
Insulin
Glucagon (peptide, 11 aa)Somatostatin (peptide, 14 aa)
islets of Langerhans
hormonesecreting cells make up only 12% of its weight
first discovered in hypothalamic extracts
identified as a hormone that inhibited secretion of growth
hormone.
a paracrine manner to inhibit the secretion of both glucagon and
insulin.
Somatostatin (endocrine and paracrine functions)
suppress pancreatic exocrine secretions
tropic
endocrine
paracrine
non-tropic
;
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antagonistic hormones that regulate the glucose concentrationin
the blood
Insulin and Glucagon
Beta cells ofpancreas are stimulatedto release insulininto the
blood.
Insulin Body cellstake up moreglucose.
Blood glucose lev eldeclines to set point;stimulus for
insulinrelease diminishes.
STIMULUS:Rising blood glucoselev el (f or instance, aftereating
a carbohy drate-
rich meal)
Homeostasis:Blood glucose level
(about 90 mg/100 mL)
Blood glucose lev elrises to set point;
stimulus for glucagonrelease diminishes.
STIMULUS:Dropping blood glucose
lev el (f or instance, afterskipping a meal)
Alpha cells of pancreasare stimulated to releaseglucagon into
the blood.
GlucagonFigure 45.12
Promoting the cellular uptake of glucose (except brain
cells)Slowing glycogen breakdown in the liverPromoting fat
storageInhibit the conversion to glucose
Stimulating the conversion of glycogen to glucose in the
liver
Stimulating the breakdown of fat and protein into glucose
Diabetes Mellitus (~6.5% of US population) - the best-known
endocrine disorder
- marked by high blood glucose.
Diabetes ( diabainein): to pass through, refers to this copious
urinationMellitus (meli): honey, refers to the presence of sugar in
urine
Fat becomes the main substrate for cellular
respirationthreatening life by lowering blood pH.
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Type I diabetes mellitus (insulin-dependent diabetes)Is an
autoimmune disorder in which the immune system destroys the beta
cells of the pancreas
Type II diabetes mellitus (non-insulin-dependent diabetes)
reduced responsiveness of target cells due to some change in
insulin receptors
usually appears during childhood
heredity; excess body weight and lack of exercise
90% of people with diabetes have type II
Diabetes Mellitus
Adrenal Hormones: Response to Stress
Are adjacent to the kidneys
Are actually made up of two glands: the adrenal medulla and the
adrenal cortex
The adrenal glands
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Stress and the adrenal gland
Spinal cord(cross section)
Nervesignals
Nervecell
Releasinghormone
Stress
Hypothalamus
Anterior pituitary
Blood vessel
ACTHAdrenalgland
Kidney
Adrenal medullaAdrenal cortex
Effects of epinephrine and norepinephrine:1. Glycogen broken dow
n to glucose;
increased blood glucose2. Increased blood pressure3. Increased
breathing rate4. Increased metabolic rate5. Change in blood f low
patterns, leading to
increased alertness and decreased digestiveand kidney
activity
Effects ofmineralocorticoids:
1. Retention of sodiumions and w ater bykidneys
2. Increased bloodvolume and bloodpressure
Effects ofglucocorticoids:
1. Proteins and fatsbroken dow n andconverted to glucose,leading
to increasedblood glucose
2. Immune system maybe suppressed
(b) Long-term stress response(a) Short-term stress response
Nerve cell
Figure 45.13a,b
(negative/positive)
neuronblood
Hormones from the Adrenal Medulla Hormones from the Adrenal
Medulla ((Short-term response)
Epinephrine
(Tyrosine)
Norepinephrine
members of catecholamines, derived from tyrosine
(adrenaline)
(noradrenaline)
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epinephrine and norepinephrine mediate Short-term response
Main: give the body a rapid bioenergetic boost
increase the rate of glycogen breakdown in the liver and
skeletal muscles, promote glucose release
stimulate the release of fatty acids from fat cells
shunting blood away from the skin, digestive organs, and
kidneys
cause blood vessels in smooth muscles to contract and vessels in
skeletal muscles to relax
Profound effects on cardiovascular/respiratory systems increase
the heartbeat and dilate the bronchioles in the lungs
(prescriptions for heart stimulant or asthma)
Corticosteroids ( ) from the Adrenal Cortex
Glucocorticoids (), such as cortisol
Augmenting glucagon from the pancreas
Causing the breakdown of fat and muscle proteinshelping
withstand longterm environmental challenge.
Suppress certain components of the bodys immune system
Mineralocorticoids () , such as aldosteronePrincipally on salt
and water balance
Act on kidneys to reabsorb sodium ions and water from filtrate,
raising blood pressure and volume
Sex hormones, mainly male hormones (androgens)
Long-term response
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Steroidogenesis
Glucocorticoids
Mineralocorticoids
CYP19
CYP19
cholesterol