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Body’s Long Distance Regulators
Chapter 45
Hormones & the Endocrine System
Types of Secreted Signaling Molecules
• Animals use chemical signals (hormones)
to communicate with each other and
between the different cells of the body
• Hormones (to excite) reach all parts of the
body
– target cells respond
Insect metamorphosis is regulated by hormones
• Secreted chemical signals include
– Hormones
– Local regulators
– Neurotransmitters
– Neurohormones
– Pheromones
Figure 45.1
Two systems regulate communication
• The endocrine system secretes
hormones that coordinate slower but
longer-acting responses including
reproduction,
p
, development,
p
, energy
gy
metabolism, growth, and behavior
• The nervous system conveys high-speed
electrical signals along specialized cells
called neurons; these signals regulate
other cells
Nervous System
•Sensory system
•Sends impulses
•Impulse passed through
neuron parts of body
neuron….parts
•Fast ..within seconds
Endocrine system
•Chemical system
•Produces hormones
•Hormone diffuse in blood
•Regulate growth
growth,
reproduction, metabolism
& behavior
•Slow…days or months
1
Fig. 45-13-3
Brain
Neurosecretory cells
Corpus cardiacum
PTTH
• Invertebrate regulatory systems also involve
endocrine and nervous system interactions
• Diverse hormones
– Regulate different aspects of homeostasis in
invertebrates
Corpus allatum
Low
JH
Prothoracic
gland
Ecdysone
Juvenile
hormone
(JH)
EARLY
LARVA
LATER
LARVA
PUPA
ADULT
Molting and development are controlled by
different hormones
• Brain hormone: release of ecdysone
• Ecdysone: molting, adult characteristics
• Juvenile hormone: retention of larval
characteristics
• Endocrine & Nervous system function together
• Ex. Epinephrine – hormone & neurotransmitter
• Neurosecretory cells – nerve cells that
secrete hormones
• Ecdysone promotes molting (in the presence of
juvenile hormone) and development (in the
absence of juvenile hormone) of adult
characteristics
• Endocrine system consists of hormone secreting
cells
Fig. 45-2a
Local Regulators
Blood
vessel
Response
(a) Endocrine signaling
Response
(b) Paracrine signaling
Response
• Local regulators are chemical signals that
travel over short distances by diffusion
• Local regulators help regulate blood
pressure, nervous system function, and
reproduction
• Local regulators are divided into two types
– Paracrine signals act on cells near the
secreting cell
– Autocrine signals act on the secreting cell
itself
(c) Autocrine signaling
2
Fig. 45-2b
Synapse
Neuron
• In paracrine signaling nonhormonal
chemicals called local regulators have
various functions and include
– Cytokines (Immune responses)
– Growth
G
th factors
f t
( ti l t cellll di
(stimulate
division)
i i )
– Nitric oxide (vasodilation)
– Prostaglandins: modified fatty acids, cause
aggregation of platelets before blood clotting,
promotes fever and inflammation
Response
(d) Synaptic signaling
Neurosecretory
cell
Blood
vessel
Response
(e) Neuroendocrine signaling
Signaling by Pheromones
Synaptic and Neuroendocrine Signaling
• Neurons (nerve cells) contact target cells at
synapses
• At synapses, neurons often secrete chemical
signals
g
called neurotransmitters that diffuse a
short distance to bind to receptors on the target
cell
• Neurotransmitters play a role in sensation,
memory, cognition, and movement
• Neurohormones are a class of hormones
that originate from neurons in the brain and
diffuse through the bloodstream
• Pheromones are chemical signals that are
released
l
d ffrom th
the b
body
d and
d used
d tto
communicate with other individuals in the
species
• Pheromones mark trails to food sources,
warn of predators, and attract potential mates
Fig. 45-3
Water-soluble
Lipid-soluble
• Three major classes of hormones in
vertebrates
– Proteins and peptides: GH, ADH, ACTH, Insulin &
Glucagon
– Amines derived from amino acids: Melatonin,,
Epinephrine, Norepinephrine, T3, &T4
– Steroids: Sex hormones, Glucocorticoids &
Mineralocorticoids
0.8 nm
Polypeptide:
Insulin
Steroid:
Cortisol
Amine:
Epinephrine
Amine:
Thyroxine
3
Fig. 45-5-2
Fat-soluble
hormone
Watersoluble
hormone
• Lipid-soluble hormones (steroid hormones)
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 or on the
surface of target cells
Transport
protein
Signal receptor
TARGET
CELL
OR
Cytoplasmic
response
Signal
receptor
Gene
regulation
Cytoplasmic
response
(a)
NUCLEUS
Gene
regulation
(b)
Cellular Response Pathways
• Water-soluble hormones are secreted by
exocytosis, travel freely in the bloodstream, and
bind to cell-surface receptors
• Lipid-soluble
p
hormones diffuse across cell
membranes, travel in the bloodstream bound to
transport proteins, and diffuse through the
membrane of target cells
• Signaling by any of these molecules involves
three key events
– Reception
– Signal transduction
– Response
Fig. 45-6-2
Epinephrine
Adenylyl
cyclase
G protein
• Binding of a hormone to its receptor
– Initiates a signal transduction pathway
– leading to specific responses in the cytoplasm
–g
gene expression,
p
synthesis
y
of enzymes
y
or
proteins…..
G protein-coupled
receptor
GTP
ATP
cAMP
Inhibition of
glycogen synthesis
Animation: WaterWater-Soluble Hormone
Second
messenger
Protein
kinase A
Promotion of
glycogen breakdown
4
Fig. 45-7-1
Fig. 45-7-2
Hormone
(estradiol)
Estradiol
(estrogen)
receptor
Hormone
(estradiol)
Estradiol
(estrogen)
receptor
Plasma
membrane
Plasma
membrane
Hormone-receptor
complex
Hormone-receptor
complex
DNA
Vitellogenin
mRNA
for vitellogenin
Figure 45.4
Pathway of Lipid Soluble Hormones
Major endocrine glands:
Hypothalamus
Pineal gland
Pituitary gland
• The response to a lipid-soluble hormone is
usually a change in gene expression
• Steroids, thyroid hormones, and the hormonal
form of vitamin D enter target
g cells and bind to
protein receptors in the cytoplasm or nucleus
• Protein-receptor complexes then act as
transcription factors in the nucleus, regulating
transcription of specific genes
Thyroid gland
Parathyroid glands
(behind thyroid)
Adrenal glands
(atop kidneys)
Organs containing
endocrine cells:
Thymus
Heart
Liver
Stomach
Pancreas
Kidneys
Ovaries (female)
Small
intestine
Testes (male)
Animation: LipidLipid-Soluble Hormone
Figure 45.14
Cerebrum
Pineal
gland
Thalamus
Hypothalamus
Cerebellum
Pituitary
gland
Spinal cord
• Hypothalamus : Master switchboard controls
endocrine system
– sends either hormonal or electrical messages to
the pituitary
Hypothalamus
• Pituitary gland: Master gland regulates
secretion of endocrine glands
Posterior
pituitary
Anterior
pituitary
5
Table 45-1b Table 45.1a
• The posterior pituitary stores and secretes
hormones that are made in the hypothalamus
• The anterior pituitary makes and releases
hormones under regulation of the
hypothalamus
Table 45-1c Table 45.1b
Fig. 45-11
Pathway
–
Example
Stimulus
Low pH in
duodenum
S cells of duodenum
secrete secretin ( )
Endocrine
cell
Blood
vessel
Target
cells
Response
Pancreas
Bicarbonate release
Simple Hormone Pathways
• Hormones released from an endocrine cell,
travel through the bloodstream, and interact
with the receptor or a target cell to cause a
physiological response
• For example, the release of acidic
contents of the stomach into the
duodenum stimulates endocrine cells
there to secrete secretin
• This causes target cells in the pancreas, a
gland behind the stomach, to raise the pH
in the duodenum
6
Figure 45.12
Example
Pathway

Stimulus
Feedback Regulation
Suckling
Sensory
neuron
• A negative feedback loop inhibits a
response by reducing the initial stimulus,
thus preventing excessive pathway activity
• Positive feedback reinforces a stimulus
to produce an even greater response
• For example, in mammals oxytocin causes
the release of milk, causing greater
suckling by offspring, which stimulates the
release of more oxytocin
Positive fe
eedback
Hypothalamus/
posterior pituitary
Neurosecretory cell
Neurohormone
Blood vessel
Target
cells
Posterior pituitary
secretes the
neurohormone
oxytocin ( ).
Smooth muscle in
breasts
Response
Milk release
Figure 45.15
Hypothalamus
Posterior Pituitary Hormones
Neurosecretory
cells of the
hypothalamus
Neurohormone
• ADH and Oxytocin are released by posterior
pituitary
– Act directly on nonendocrine tissues
Axons
Posterior
pituitary
• Oxytocin
O t i
Anterior
pituitary
– Induces uterine & mammary gland contractions
and milk ejection
• Antidiuretic hormone (ADH)
HORMONE
ADH
Oxytocin
TARGET
Kidney
tubules
Mammary glands,
uterine muscles
– Enhances water reabsorption in the kidneys
Figure 45.16
Tropic effects only:
FSH
LH
TSH
ACTH
Neurosecretory
cells of the
hypothalamus
Nontropic effects only:
Prolactin
MSH
Anterior Pituitary Hormomes
• The anterior pituitary
Nontropic and tropic effects:
GH
Hypothalamic
releasing and
inhibiting
hormones
Portal vessels
– Is a true-endocrine gland
– Produces tropic and nontropic hormones
E d
Endocrine
i cells
ll
of the anterior
pituitary
Pituitary
hormones
Posterior
pituitary
HORMONE
FSH and LH
TSH
ACTH
Prolactin
TARGET
Testes or
ovaries
Thyroid
Adrenal
cortex
Mammary
glands
MSH
GH
Melanocytes Liver, bones,
other tissues
7
Figure 45.17a
Pathway
Example
Cold
Stimulus
Figure 45.17b
To
hypothalamus

Neurosecretory cell
Hypothalamus secretes
thyrotropin-releasing
hormone (TRH ).
Releasing hormone
Blood vessel
Neg
gative feedback
Sensory neuron
Hypothalamus
Pathway
Anterior pituitary
Tropic hormone
Endocrine cell
Example
Anterior pituitary secretes
thyroid-stimulating
hormone (TSH, also known
as thyrotropin ).
Thyroid gland secretes
thyroid hormone
(T3 and T4 ).
Hormone
Anterior pituitary
Tropic hormone
Anterior pituitary secretes
thyroid-stimulating
hormone (TSH, also known
as thyrotropin ).
Target
cells
Response
Hormone Cascade Pathway
• A hormone can stimulate the release of a series
of other hormones, which activates a
nonendocrine target cell; this is called a
hormone cascade pathway
• The release of thyroid hormone results from a
hormone cascade pathway involving the
hypothalamus, anterior pituitary, and thyroid
gland
A tropic hormone regulates the function of
endocrine cells or glands
Four Tropic Hormones by Anteroir Pituitary
1. Follicle-stimulating hormone (FSH): stimulates
development of eggs & sperm
2. Luteinizing hormone (LH): stimulates hormone
production in ovaries and testes
2. Thyroid stimulating hormone (TSH): stimulates
the release of T3 & T4 – controls metabolism.
3. Adrenocorticoptropic hormone (ACTH): long
term response to stress
Body tissues
Increased cellular
metabolism
• Hormone production in the anterior pituitary is
controlled by releasing and inhibiting
hormones from the hypothalamus
• For example, the production of thyrotropin
releasing hormone (TRH) in the
hypothalamus stimulates secretion of the
thyroid stimulating hormone (TSH) from the
anterior pituitary
• TSH then stimulates release of thyroid
hormone by the thyroid gland
Nontropic Hormones by Anterior Pituitary
• The nontropic hormones produced by the
anterior pituitary include
• Target nonendocrine cells
– Prolactin: stimulates lactation
– Melanocyte-stimulating hormone (MSH): skin
pigmentation, fat metabolism
– -endorphin: inhibits sensation of pain
8
Non Pituitary hormones: Thyroid hormone
Growth Hormone (GH)
• The thyroid gland
• Growth hormone (GH) is secreted by the anterior
pituitary gland and has tropic and nontropic
actions
• Promotes growth directly and has diverse
metabolic effects
• Stimulates the production of growth factors by
other tissues
• Low levels results in dwarfism, high levels results
in gigantism, overproduction of GH causes
acromegaly
– two lobes located on the ventral surface of the
trachea
– Produces two iodine-containing hormones,
triiodothyronine (T3) and thyroxine (T4)
Thyroid Hormone
• The thyroid hormones
– stimulates metabolism
– influences development and maturation
• Hyperthyroidism, excessive secretion of thyroid
hormones,, causes high
g body
y temperature,
p
, weight
g
loss, irritability, and high blood pressure
• Graves’ disease is a form of hyperthyroidism in
humans
• Hypothyroidism: Thyroid deficiency results in
Cretinism-retards skeletal muscle growth and
mental development.
• Graves disease, a form of hyperthyroidism
caused by autoimmunity, is typified by protruding
eyes
• Thyroid
y
hormone refers to a p
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
Figure 45.19
Specialized role of Thyroxine in resorption of the
tadpole’s tail as the frog develops into an adult
(a)
((b))
• Two antagonistic hormones regulate the
homeostasis of calcium (Ca2+) in the blood of
mammals
– Parathyroid
y
hormone ((PTH)) is released by
y
the parathyroid glands
– Calcitonin is released by the thyroid gland
Tadpole
Adult frog
9
Fig. 45-20-1
Fig. 45-20-2
Active
vitamin D
Increases
Ca2+ uptake
in intestines
Stimulates Ca2+
uptake in kidneys
PTH
PTH
Parathyroid
P
th
id gland
l d
(behind thyroid)
STIMULUS:
Falling blood
Ca2+ level
Parathyroid
P
th
id gland
l d
(behind thyroid)
Stimulates
Ca2+ release
from bones
STIMULUS:
Falling blood
Ca2+ level
Blood Ca2+
level rises.
Homeostasis:
Blood Ca2+ level
(about 10 mg/100 mL)
Homeostasis:
Blood Ca2+ level
(about 10 mg/100 mL)
Parathyroid and Low blood calcium
Calcitonin and High blood calcium
• PTH, secreted by the parathyroid
glands…..increases Ca2+ levels
Ca2+from
– Release
bones,
– Stimulates the Kidneys to activate vitamin D
D,
which promotes uptake of Ca2+ …raises Ca2+
levels
• Calcitonin, secreted by the thyroid
gland…..lower Ca2+ levels
– Stimulates Ca2+ deposition
p
in the bones
– secretion of Ca2+ by the kidneys
Figure 45.13a-2
Figure 45.13a-1
Insulin
Beta cells of
pancreas
release insulin
into the blood.
STIMULUS
STIMULUS:
Blood glucose level rises
(for instance, after eating a
carbohydrate-rich meal).
Homeostasis:
Blood glucose level
(70–110 mg/100 mL)
Insulin
Body cells
take up more
glucose.
Blood glucose
level declines.
Beta cells of
pancreas
release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Blood glucose level rises
(for instance, after eating a
carbohydrate-rich meal).
Homeostasis:
Blood glucose level
(70–110 mg/100 mL)
10
Figure 45.13b-2
Figure 45.13b-1
Homeostasis:
Blood glucose level
(70–110 mg/100 mL)
Homeostasis:
Blood glucose level
(70–110 mg/100 mL)
STIMULUS:
Blood glucose level
falls (for instance, after
skipping a meal).
Alpha cells of pancreas
release glucagon into
the blood.
Glucagon
STIMULUS:
Blood glucose level
falls (for instance, after
skipping a meal).
Blood glucose
level rises.
Liver breaks
down glycogen
and releases
glucose into
the blood.
Alpha cells of pancreas
release glucagon into
the blood.
Glucagon
Insulin and Glucagon: Control of Blood Glucose
Target tissues for Insulin and Glucagon
• Insulin and glucagon are antagonistic
hormones that help maintain glucose
homeostasis
• The pancreas has clusters of endocrine
cells called islets of Langerhans with
alpha cells that produce glucagon and
beta cells that produce insulin
• Insulin reduces blood glucose levels by
– Promoting the cellular uptake of glucose
– Slowing glycogen breakdown in the liver
– Promoting fat storage
• Glucagon increases blood glucose levels by
– Stimulating conversion of glycogen to glucose
in the liver
– Stimulating breakdown of fat and protein into
glucose
Diabetes Mellitus
• Endocrine disorder
– deficiency of insulin or a decreased response to
insulin in target tissues
– elevated blood g
glucose levels
• Type I diabetes mellitus (insulin-dependent
diabetes)
– Is an autoimmune disorder
– the immune system destroys the beta cells of
the pancreas
• Type II diabetes mellitus (non-insulin-dependent
diabetes)
– either by a deficiency of insulin
– or by reduced responsiveness of target cells
due to some change in insulin receptors
11
Fig. 45-21a
Adrenal Hormones: Response to Stress
Stress
• The adrenal glands
– adjacent to the kidneys
– made up of two glands: the adrenal medulla
(inside) and the adrenal cortex (outside)
Spinal cord
Nerve
signals
Releasing
hormone
Nerve
cell
Hypothalamus
Anterior pituitary
Blood vessel
ACTH
Adrenal
medulla
Adrenal
cortex
Adrenal
gland
Kidney
Figure 45.21a
(a) Short-term stress response and the adrenal medulla
Stress
Adrenal Medulla
• Secretes epinephrine (adrenaline) and
norepinephrine (noradrenaline) in response to
stress
• fight-or-flight responses
• Increase glucose levels
levels, High blood pressure
pressure….
• These hormones are members of a class of
compounds called catecholamines
• They are secreted in response to stress-activated
impulses from the nervous system
One hormone, different effects
Fig. 45-8-2
Same receptors but different
intracellular proteins (not shown)
Different receptors
Epinephrine
Epinephrine
Epinephrine
 receptor
 receptor
 receptor
Glycogen
deposits
Glycogen
breaks down
and glucose
is released.
(a) Liver cell
Vessel
dilates.
(b) Skeletal muscle
blood vessel
Vessel
constricts.
(c) Intestinal blood
vessel
Spinal cord
(cross section)
Nerve
signals
Hypothalamus
Nerve
cell
Adrenal medulla
secretes epinephrine
and norepinephrine.
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 to
increased alertness and decreased digestive,
excretory, and reproductive system activity
Nerve cell
Adrenal
gland
Kidney
Effects of Hormone Epinephrine and
norepinephrine
• Mediating the body’s response to short-term
stress
• Triggers the release of glucose and fatty acids
into blood
• Increased
I
d oxygen delivery
d li
tto b
body
d cells
ll
• Directs the blood toward heart, brain, and
skeletal muscles and way from skin, digestive
system and kidneys
• Epinephrine binds to liver cells and activate
enzymes that result in the release of glucose
into the bloodstream
12
Figure 45.21a
(a) Short-term stress response and the adrenal medulla
Stress
Spinal cord
(cross section)
Nerve
signals
Hypothalamus
Nerve
cell
Adrenal medulla
p p
secretes epinephrine
and norepinephrine.
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 to
increased alertness and decreased digestive,
excretory, and reproductive system activity
Nerve cell
Hormones of the Adrenal Cortex respond to
long term stress
• Glucocorticoids, such as cortisol
– Increase in glucose levels,
– suppresses immune system
• Mineralocorticoids,
Mineralocorticoids Ex.
Ex aldosterone
Adrenal
gland
Kidney
•
•
•
•
Gonadal Hormones
– Retention of salt & water....increases blood
pressure
• Adrenal cortex also produces small amounts
of Sex hormones
Testes
• The gonads, testes and ovaries, produce
most of the sex hormones: androgens,
estrogens, and progestins
• All three sex hormones are found in both
males and females, but in different amounts
• Synthesize androgens, Ex. testosterone
– stimulate the 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
Figure 45.22
Ovaries
• Estrogens, Ex. estradiol
RESULTS
Appearance of Genitalia
No surgery
Embryonic gonad
removed
XY (male)
Male
Female
XX (female)
Female
Female
Chromosome Set
– maintenance of the female reproductive system
– development of female secondary sex
characteristics
• Progesterone
– preparing and maintaining the uterus
• Synthesis of the sex hormones is controlled by
FSH and LH from the anterior pituitary
13
Endocrine Disruptors
• Between 1938 and 1971 some pregnant
women at risk for complications were
prescribed a synthetic estrogen called
diethylstilbestrol (DES)
g
of women treated with DES are at
• Daughters
higher risk for reproductive abnormalities,
including miscarriage, structural changes,
and cervical and vaginal cancers
• DES is an endocrine disruptor, interrupts the
function of estrogen
Melatonin and Biorhythms
• The pineal gland, located within the brain
– Secretes melatonin
You should now be able to:
1.
• Release of melatonin
2.
– Is controlled by light/dark cycles
• The primary functions of melatonin
– Appear to be related to biological rhythms
associated with reproduction
3.
4.
4
5.
6.
7.
Distinguish between the following pairs of terms: hormones
and local regulators, paracrine and autocrine signals
Describe the evidence that steroid hormones have
intracellular receptors, while water-soluble hormones have
cell-surface receptors
Explain how the antagonistic hormones insulin and glucagon
regulate carbohydrate metabolism
Distinguish between type 1 and type 2 diabetes
Explain how the hypothalamus and the pituitary glands
interact and how they coordinate the endocrine system
Explain the role of tropic hormones in coordinating
endocrine signaling throughout the body
List and describe the functions of hormones released by the
following: anterior and posterior pituitary lobes, thyroid
glands, parathyroid glands, adrenal medulla, adrenal cortex,
gonads, pineal gland
14