Transcript Intro Bio Chapter 25 Fall 2012

Chapter 25
Hormones
PowerPoint® Lectures for
Campbell Essential Biology, Fifth Edition, and
Campbell Essential Biology with Physiology,
Fourth Edition
– Eric J. Simon, Jean L. Dickey, and Jane B. Reece
Lectures by Edward J. Zalisko
© 2013 Pearson Education, Inc.
Biology and Society:
Sluggers and Steroids
• The 1998 major league home run records reflect
another chapter in baseball’s shameful “steroids
era.”
• The abuse of anabolic steroids by athletes
increases muscle mass and brings greater power
to a batter’s swing.
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Figure 25.0
HORMONES: AN OVERVIEW
• Hormones are produced by most plants and
animals.
• Animal hormones
– are made and secreted mainly by endocrine
glands,
– are usually carried by the circulatory system, and
– communicate regulatory messages to specific
sites in the body.
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HORMONES: AN OVERVIEW
• The endocrine system
– consists of all hormone-secreting cells and
– is the body’s main system for internal chemical
regulation.
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HORMONES: AN OVERVIEW
• Endocrine cells secrete into the bloodstream
hormones that
– can affect many cells in many different body
organs but
– only affect target cells, cells that have receptors
for that specific hormone.
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Figure 25.1
Endocrine
cell
Membraneenclosed
sacs
Blood
vessel
Hormone
molecules
Target cell
Receptor
protein
Adrenal glands
(type of endocrine
gland), which sit
atop the kidneys
HORMONES: AN OVERVIEW
• There are two general mechanisms by which
hormones trigger changes in target cells:
1. Water-soluble hormones trigger responses
without ever entering their target cells.
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Figure 25.2-3
Watersoluble
hormone
Receptor
protein
1
Target
cell
2
Plasma
membrane
Signal
transduction
pathway
Relay
molecules
Cytoplasmic
response
or
3
Nucleus
Gene regulation
HORMONES: AN OVERVIEW
2. Lipid-soluble hormones trigger responses after
entering the target cell.
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Figure 25.3-4
Lipidsoluble
hormone
1
Target
cell
Plasma
membrane
2
Receptor
protein
Nucleus
4
3
Hormonereceptor
complex
Gene regulation
THE HUMAN ENDOCRINE SYSTEM
• The human endocrine system consists of about a
dozen major glands that may have
– only endocrine functions or
– endocrine and non-endocrine functions.
• The major endocrine glands in humans are spread
about the human body.
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Figure 25.4
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
(embedded within
thyroid)
Adrenal glands
(atop kidneys)
Pancreas
Ovaries
(female)
Testes
(male)
THE HUMAN ENDOCRINE SYSTEM
• Hormones have a wide range of
– target cells and
– effects.
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Table 25.1
The Hypothalamus and Pituitary Gland
• The hypothalamus
– is part of the brain,
– is the main control center of the endocrine
system, and
– receives information from nerves about
– the internal condition of the body and
– the external environment.
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The Hypothalamus and Pituitary Gland
• The pituitary gland
– is a pea-sized structure that hangs below the
hypothalamus,
– responds to signals from the hypothalamus, and
– secretes hormones that influence numerous body
functions.
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Figure 25.5
Brain
Hypothalamus
Posterior pituitary
Anterior pituitary
Bone
The Hypothalamus and Pituitary Gland
• The pituitary gland consists of two parts:
1. The posterior pituitary
– is an extension of the hypothalamus,
– stores hormones, and
– secretes hormones made in the hypothalamus.
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The Hypothalamus and Pituitary Gland
2. The anterior pituitary
– synthesizes its own hormones, such as FSH and
LH, and
– secretes hormones directly into the blood.
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The Hypothalamus and Pituitary Gland
• The hypothalamus operates through the posterior
pituitary to direct the activities of the kidneys.
– The hypothalamus makes antidiuretic hormone
(ADH), which is stored and released by the
posterior pituitary.
– ADH helps kidney cells reabsorb water,
preventing dehydration by decreasing urine
volume.
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Figure 25.6
Hypothalamus
ADH
Posterior
pituitary
Anterior
pituitary
Blood
vessel
ADH
Kidneys
(ADH increases
water reabsorption
and prevents
dehydration)
The Hypothalamus and Pituitary Gland
• The anterior lobe of the pituitary also secretes
human growth hormone (HGH), which
– promotes development and enlargement of all
parts of the body and
– can lead to
– dwarfism, if too little GH is produced, or
– gigantism, if too much GH is produced.
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Figure 25.7
(b) Overproduction
of HGH during
development
(a) Overproduction of HGH during
adulthood
(c) Underproduction
of HGH during
development
The Hypothalamus and Pituitary Gland
• Endorphins
– are produced by the anterior pituitary and
– act as natural painkillers.
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The Thyroid and Parathyroid Glands
• The thyroid gland
– is located in the neck just under the larynx and
– produces the hormones thyroxine and
triiodothyronine, which increase
– oxygen consumption and
– metabolic rate in all the cells of your body.
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The Thyroid and Parathyroid Glands
• Hypothyroidism
– results from too little thyroid hormone in the blood
and
– can result from
– dietary deficiencies of iodine or
– a defective thyroid gland.
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The Thyroid and Parathyroid Glands
• Hyperthyroidism (Graves disease)
– results from too much thyroid hormone in the
blood and
– can lead to
– overheating,
– profuse sweating,
– high blood pressure, and
– protruding eyeballs.
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The Thyroid and Parathyroid Glands
• The parathyroid glands
– are four disk-shaped glands embedded
within the thyroid and
– produce parathyroid hormone, which
raises calcium levels in the blood.
• Calcitonin
– is produced by the thyroid gland and
– lowers calcium levels in the blood.
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The Thyroid and Parathyroid Glands
• Calcitonin and parathyroid hormone are
antagonistic hormones, because they have
opposite effects on calcium levels in the blood.
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Figure 25.8
2
Calcitonin
Thyroid
gland
releases
calcitonin
Stimulates
Ca2+
deposition
Reduces
Ca2+
uptake
Ca2+ level in
blood falls
1
Stimulus:
Rising
blood Ca2+
Ca2+ level
Homeostasis:
Normal blood calcium level
Ca2+ level
6
3
Stimulus:
Falling
blood Ca2+
4
Ca2+ level in
blood rises
Release of
parathyroid
hormone (PTH)
Stimulates
Ca2+
release
Increases
Ca2+
uptake
Increases
Ca2+
uptake
Parathyroid
gland
5
PTH
The Pancreas
• The pancreas produces two antagonistic
hormones that play important roles in managing
the body’s energy supplies:
1. insulin, which reduces blood sugar levels and
2. glucagon, which increases blood sugar levels.
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Figure 25.9
Body
cells take
up glucose
Insulin
Pancreas
releases insulin
1
Stimulus:
Rising blood
glucose
2
Blood
glucose
level falls
Liver
stores
glucose as
glycogen
3
Glucose level
Homeostasis:
Normal blood glucose level
Glucose level
Stimulus:
Declining
blood glucose
4
6
Blood
glucose level
rises
Pancreas
releases glucagon
5
Liver
breaks down
glycogen
Glucagon
The Pancreas
• Diabetes mellitus is a serious hormonal disease
in which body cells are unable to absorb glucose
from the blood because either
– there is not enough insulin produced (type 1, or
insulin-dependent diabetes) or
– the target cells do not respond normally to insulin
(type 2, or non-insulin-dependent diabetes).
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The Pancreas
• Diabetes affects about 8% of all Americans.
• More than 90% of those affected have type 2
diabetes, which is associated with being
– overweight and
– underactive.
• People with diabetes use glucose meters to
measure the amount of glucose in the blood.
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Figure 25.10
The Adrenal Glands
• The adrenal glands are paired structures resting
atop each kidney.
• Each adrenal gland consists of two glands:
1. the central adrenal medulla and
2. the outer adrenal cortex.
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The Adrenal Glands
• The adrenal medulla secretes epinephrine and
norepinephrine, hormones that
– enable a rapid, short-term response to stress and
– produce the “fight-or-flight” response.
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The Adrenal Glands
• Stressful stimuli activate nerve cells in the
hypothalamus that send signals to stimulate the
adrenal medulla to secrete
– epinephrine and
– norepinephrine.
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The Adrenal Glands
• The adrenal cortex
– is also stimulated by the hypothalamus and
– secretes corticosteroid hormones (including
glucocorticoids) that provide a slower, longerlasting response to stress.
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Figure 25.11
STRESS
Adrenal
gland
Kidney
Adrenal
medulla
Adrenal
cortex
Nerve 1
signals
Hypothalamus
3
Nerve
cell
Releasing hormone
Anterior pituitary
Blood vessel
Spinal cord
(cross section)
Nerve cell
ACTH
4
Adrenal
medulla
Epinephrine and
norepinephrine
2
ACTH
Adrenal
cortex
5
Corticosteroids
Short-term stress response
Long-term stress response
• Glycogen broken down to glucose; increased blood
glucose
• Proteins and fats broken down and converted
to glucose, leading to increased blood glucose
• Increased blood pressure, breathing rate, heart rate,
and metabolic rate
• Immune system may be suppressed
• Change in blood flow patterns, leading to increased
alertness and decreased digestive activity
The Gonads
• The gonads secrete sex hormones that
– affect growth and development and
– regulate
– reproductive cycles and
– sexual behavior.
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The Gonads
• Males and females have the same three types of
sex hormones:
1. estrogens,
2. progestins, and
3. androgens.
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The Gonads
• Estrogens
– maintain the female reproductive system and
– promote the development of specific female
features, such as breasts and wider hips.
• Progestins, such as progesterone, are primarily
involved in preparing the uterus to support a
developing embryo.
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The Gonads
• Androgens, mainly testosterone, stimulate the
development and maintenance of the male
reproductive system.
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Evolution Connection:
Steroids and Male Aggression
• Testosterone and other androgens
– promote the development and maintenance of the
human male reproductive system and
– play a similar role in all vertebrates.
Evolution Connection:
Steroids and Male Aggression
• In addition to determining the male sexual
condition, in many vertebrates, androgens
– are responsible for male vocalizations and
– promote aggressive behavior.
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Figure 25.13
Evolution Connection:
Steroids and Male Aggression
• The different roles for androgens among
vertebrates illustrate two central aspects of life
resulting from Darwinian evolution:
1. the unity of life (a consistent effect on the
development of the male gonads) and
2. the diversity of life (the variety of secondary
effects).
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Figure 25.UN01
Figure 25.UN02
Figure 25.UN03
Figure 25.UN04
Figure 25.UN05
Figure 25.UN06
Figure 25.UN07
Watersoluble
hormone
Receptor
protein
Lipidsoluble
hormone
Receptor
protein
Signal
transduction
pathway
Cytoplasmic
response
Nucleus
Nucleus
or
Gene regulation
Hormonereceptor
complex
Gene regulation
Figure 25.UN08
Brain
Hypothalamus:
Master control center of
the endocrine system
Anterior pituitary:
Controlled by
hypothalamus;
produces and
secretes its own
hormones
Posterior pituitary:
Stores and secretes
hormones made by
hypothalamus
Blood vessels
Figure 25.UN09
releases
Thyroid
Ca2
in blood
causes
Ca2
in blood
Calcitonin
release
Parathyroids
causes
Parathyroid
hormone
Figure 25.UN10
causes
Glucose
in blood
causes
Glucose
in blood
Insulin
Pancreas
Glucagon