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The Endocrine System
AP Chapter 45
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The endocrine system, along with the
nervous system, is responsible forcoordinating our responses.
The endocrine system is a slower system
and the nervous system is a fasterresponse.
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Chemical signals
Chemicals found in both systems and
also as part of other signaling
mechanisms bind to specific receptor
proteins on or in target cells.
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Secreted chemical signals include
Hormones produced by endocrine glands,
travel through the blood stream to target
organs
ex insulin, estrogen
Local regulators
(a) paracrine signals act on neighboring
cells, ex. cytokines, interferon,
prostaglandins(b) autocrine signals act on secreting cells
itself, ex cytokines
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Neurotransmitters - secreted by neurons at
synapses
ex- serotonin, nitric oxide (NO)
Neurohormones secreted by neurosecretory
cells, travel through the blood stream to target
organs or synapsesex- epinephrine
Pheromones released into the environment;
between individualsex insects marking trails,
mating, etc.
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Fig. 45-2
Bloodvessel Response
Response
Response
Response
(a) Endocrine signaling
(b) Paracrine signaling
(c) Autocrine signaling
(d) Synaptic signaling
Neuron
Neurosecretorycell
(e) Neuroendocrine signaling
Bloodvessel
Synapse
Response
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Chemical Classes of Hormones
Three major classes of moleculesfunction as hormones in vertebrates:
Polypeptides (proteins and peptides)
Amines derived from amino acids Steroid hormones
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Fig. 45-3
Water-soluble Lipid-soluble
Steroid:
Cortisol
Polypeptide:
Insulin
Amine:
Epinephrine
Amine:
Thyroxine
0.8 nm
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Lipid-soluble hormones (steroidhormones) pass easily through cell
membranes, while water-soluble
hormones (polypeptides and amines)do not
The solubility of a hormone correlates
with the location of receptors inside oron the surface of target cells
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Water-soluble hormones are secreted by
exocytosis, travel freely in the
bloodstream, and bind to cell-surface
receptors
Lipid-soluble hormones diffuse across
cell membranes, travel in thebloodstream bound to transport
proteins, and diffuse through the
membrane of target cells
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Fig. 45-5-1
NUCLEUS
Signalreceptor
(a) (b)
TARGETCELL
Signal receptor
Transport
protein
Water-soluble
hormone
Fat-solublehormone
Fi 45 5 2
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Fig. 45-5-2
Signalreceptor
TARGETCELL
Signal receptor
Transport
protein
Water-soluble
hormone
Fat-solublehormone
Generegulation
Cytoplasmicresponse
Generegulation
Cytoplasmicresponse
OR
(a)NUCLEUS
(b)
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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 responsedue to different transcription factors theyactivate
A hormone can also have different effectsin different species
Fi 45 8 1
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Fig. 45-8-1
Glycogen
deposits
receptor
Vesseldilates.
Epinephrine
(a) Liver cell
Epinephrine
receptor
Glycogenbreaks downand glucose
is released.
(b) Skeletal muscle
blood vessel
Same receptors but differentintracellular proteins (not shown)
Fig 45 8 2
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Fig. 45-8-2
Glycogen
deposits
receptor
Vesseldilates.
Epinephrine
(a) Liver cell
Epinephrine
receptor
Glycogenbreaks downand glucose
is released.
(b) Skeletal muscle
blood vessel
Same receptors but differentintracellular proteins (not shown)
Epinephrine
receptor
Different receptors
Epinephrine
receptor
Vesselconstricts.
(c) Intestinal blood
vessel
N ti f db k d t i ti
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Negative feedback and antagonistic
hormone pairs are common features of the
endocrine system
Hormones are assembled into regulatory
pathways
A negative feedback loop inhibits aresponse by reducing the initial stimulus
Negative feedback regulates many
hormonal pathways involved inhomeostasis
Fig 45 11
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Fig. 45-11Pathway Example
Stimulus Low pH in
duodenum
S cells of duodenumsecrete secretin ( )
Endocrinecell
Bloodvessel
PancreasTargetcells
Response Bicarbonate release
I li d Gl C t l f Bl d
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Insulin and Glucagon: Control of Blood
Glucose an example of antagonistic
hormone pairs
The pancreashas clusters of endocrine
cells called islets of Langerhanswith alpha
cells that produce glucagon and beta cellsthat produce insulin
Insulin reduces blood glucose levels by
Promoting the cellular uptake of glucose
Slowing glycogen breakdown in the liver
Promoting fat storage
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Glucagon increases blood glucose levelsby
Stimulating conversion of glycogen to glucose in
the liver
Stimulating breakdown of fat and protein into
glucose
Remember: GlucagonGlucose ON!
Fig 45-12-2
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Fig. 45-12-2
Homeostasis:Blood glucose level
(about 90 mg/100 mL)
Insulin
Beta cells of
pancreasrelease insulininto the blood.
STIMULUS:Blood glucose level
rises.
Liver takesup glucoseand stores it
as glycogen.
Blood glucoselevel declines.
Body cellstake up moreglucose.
Fig 45-12-4
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Fig. 45 12 4
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
Glucagon
STIMULUS:
Blood glucose level
falls.
Alpha cells of pancreas
release glucagon.
Liver breaks
down glycogen
and releases
glucose.
Blood glucoselevel rises.
Di b t M llit
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Diabetes Mellitus
Diabetes mellitus is perhaps the best-known endocrine disorder
It is caused by a deficiency of insulin or a
decreased response to insulin in targettissues
It is marked by elevated blood glucose
levels
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Type I diabetes mellitus (insulin-dependent) is an autoimmune disorder in
which the immune system destroys
pancreatic beta cells Type II diabetes mellitus (non-insulin-
dependent) involves insulin deficiency or
reduced response of target cells due tochange in insulin receptors
Fig. 45-10
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Fig. 45 10
Major endocrine glands:
Adrenalglands
Hypothalamus
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands
Pancreas
Kidney
Ovaries
Testes
Organs containingendocrine cells:
Thymus
Heart
Liver
Stomach
KidneySmallintestine
Coordination of Endocrine and
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Coordination of Endocrine and
Nervous Systems in Vertebrates
The hypothalamus receives information
from the nervous system and initiates
responses through the endocrine system Attached to the hypothalamus is the
pituitary gland composed of the
posterior pituitary and anterior pituitary
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The posterior pituitary stores andsecretes hormones that are made in the
hypothalamus
The anterior pituitary makes andreleases hormones under regulation of
the hypothalamus
Fig. 45-14
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g
Spinal cord
Posteriorpituitary
Cerebellum
Pinealgland
Anteriorpituitary
Hypothalamus
Pituitarygland
Hypothalamus
Thalamus
Cerebrum
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Hypothalamus
The hypothalamus secretes two
hormones which are stored in the posterior
pituitary.
1) oxytocin induces uterine contractions
during birth and milk production
2)ADH which decreases urine volume
Fig. 45-15
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Posteriorpituitary
Anteriorpituitary
Neurosecretorycells of thehypothalamus
Hypothalamus
Axon
HORMONE OxytocinADH
Kidney tubulesTARGET Mammary glands,uterine muscles
Th t i it it l d t
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The anterior pituitary gland secretes
releasing hormones and inhibiting
hormones.
TSH thyroid stimulating
FSH and LH stimulates gonads
ACTH - stimulates adrenal cortex Prolactin milk production
MSH stimulates production of
melanocytes (skin pigments)
GH growth hormone
Fig. 45-17
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Hypothalamicreleasing andinhibiting
hormones
Neurosecretory cellsof the hypothalamus
HORMONE
TARGET
Posterior pituitary
Portal vessels
Endocrine cells ofthe anterior pituitary
Pituitary hormones
Tropic effects only:FSHLHTSHACTH
Nontropic effects only:ProlactinMSH
Nontropic and tropic effects:GH
Testes orovaries
Thyroid
FSH and LH TSH
Adrenalcortex
Mammaryglands
ACTH Prolactin MSH GH
Melanocytes Liver, bones,other tissues
Tropic Hormones
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Tropic Hormones
A tropic hormone regulates the functionof endocrine cells or glands
The four strictly tropic hormones are
Thyroid-stimulating hormone (TSH) Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Adrenocorticotropic hormone (ACTH)
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Thyroid Gland
T3 and T4, regulates metabolism (needs
dietary iodine to function properly goiter)
Calcitonin lowers calcium in blood
deposition in bones and secretion into
kidney filtrate
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Parathyroid Gland
PTH parathormone raises calcium levels
in blood from bones and reuptake in
kidneys
Fig. 45-20-2
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PTH
Parathyroid gland(behind thyroid)
STIMULUS:Falling blood
Ca2+ level
Homeostasis:Blood Ca2+ level
(about 10 mg/100 mL)
Blood Ca2+
level rises.
Stimulates Ca2+uptake in kidneys
StimulatesCa2+ releasefrom bones
IncreasesCa2+ uptakein intestines
Activevitamin D
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Adrenal medulla
Epinephrine (adrenaline) raises
metabolic rate, fight or flight
Norepinephrine (noradrenaline) controls
blood pressure
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Adrenal cortex
Glucocorticoids glucose from noncarb
sources, such as muscles
Mineralocorticoids (aldosterone)
induces kidneys to reabsorb water and
salts
Both of these deal with long-term stress
Fig. 45-21c
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(b) Long-term stress response
Effects of
mineralocorticoids:
Effects of
glucocorticoids:
1. Retention of sodium
ions and water by
kidneys
2. Increased blood
volume and blood
pressure
2. Possible suppression of
immune system
1. Proteins and fats broken down
and converted to glucose, leading
to increased blood glucose
Adrenalgland
Kidney
Adrenal cortex
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Testes
Androgens (testosterone) gender, male
secondary sex characteristics
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Ovaries
Estrogen maintenance of female
reproductive system and development of
secondary female characteristics
Progesterone prepares uterus for child
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Pineal Gland
Melatonin biological clock
Hormonal pathways work with the
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Hormonal pathways work with the
hypothalamus and anterior pituitary to
coordinate responses
Ex in the gonads
GnRH (hypothalamus) affects FSH and LH
(anterior pituitary) which affects estrogens
and androgens (ovaries/testes)
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Which endocrine gland?
Too little of my hormone and you will
feel tired and sluggish and probably
gain weight.
THYROID
A malfunction in this gland can
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A malfunction in this gland can
result in a giant.
Anterior Pituitary
This gland prepares me for an
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This gland prepares me for an
emergency situation by increasing my
heartrate.
Adrenal
Glands
This gland is also used in the digestive
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This gland is also used in the digestive
system. It also comes into play when I
eat lots of M and Ms!
PANCREAS
This gland is called the master gland
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This gland is called the master gland
because it secretes nine hormones many of
which control other endocrine glands by
feedback control.
Pituitary
Gland
If this gland is not working
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If this gland is not working
properly, diabetes can result.
Pancreas
If this gland is not working properly, your
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If this gland is not working properly, your
nerves and muscles will not function
properly either due to calcium deficiency.
ParathyroidGland
Th l d d t f ti l i
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These glands do not function properly in
chromosomal mutations such as in Turners
and Klinefelters syndrome.
Gonads
This gland makes me wake up in the
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This gland makes me wake up in the
morning and ready to go!
Pineal Gland