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Chapter 25
Hormones
PowerPoint® Lectures for
Campbell Essential Biology, Fourth Edition
– Eric Simon, Jane Reece, and Jean Dickey
Campbell Essential Biology with Physiology, Third Edition
– Eric Simon, Jane Reece, and Jean Dickey
Lectures by Chris C. Romero, updated by Edward J. Zalisko
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Biology And Society:
A Hormonal Fountain of Youth?
• Menopause:
– Typically occurs around age 50
– Is caused by decreasing levels of
– Estrogen
– Progesterone
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• Hormone replacement therapy (HRT):
– Has been used to relieve negative symptoms of menopause but
– May cause increased risks of stroke and cancer
• Bioidenticals are:
– Synthetic human hormones
– Produced by chemically modifying plant-derived hormones
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HORMONES: AN OVERVIEW
• Hormones are:
– Regulatory chemicals that affect specific sites in the body
– Produced by most plants and animals
– Made by endocrine glands
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• The endocrine system:
– Consists of all hormone-secreting cells
– Is the body’s main system for internal chemical regulation
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• 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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Endocrine
cell
Membraneenclosed
sacs
Blood
vessel
Hormone
molecules
Target cell
Adrenal glands
(type of endocrine
gland), which sit
atop the kidneys
Receptor
protein
Figure 25.1
• There are two general mechanisms by which hormones trigger
changes in target cells.
– Water-soluble hormones trigger responses without ever entering their
target cells.
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Watersoluble
hormone
Receptor
protein
Target
cell
Plasma
membrane
Relay
molecules
Signal
transduction
pathway
Cytoplasmic
response
or
Nucleus
Gene regulation
Figure 25.2-3
– Lipid-soluble hormones trigger responses after entering the target cell.
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Lipidsoluble
hormone
Target
cell
Plasma
membrane
Receptor
protein
Nucleus
Hormonereceptor
complex
Gene regulation
Figure 25.3-4
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
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• The major endocrine glands in humans are spread about the
human body.
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Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
(embedded
within thyroid)
Adrenal glands
(atop kidneys)
Pancreas
Ovaries
(female)
Testes
(male)
Figure 25.4
• Hormones have a wide range of target cells and effects.
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Table 25.1
Table 25.1a
Table 25.1b
The Hypothalamus and Pituitary Gland
• The hypothalamus:
– Is part of the brain
– Is the main control center of the endocrine system
– Receives information from nerves about the:
– Internal condition of the body
– External environment
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• The pituitary gland:
– Is a pea-sized structure that hangs below the hypothalamus
– Responds to signals from the hypothalamus
– Secretes hormones that influence many body functions
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Brain
Hypothalamus
Posterior pituitary
Bone
Anterior pituitary
Figure 25.5
• The pituitary gland consists of two parts:
– The posterior pituitary:
– Stores hormones
– Secretes hormones made in the hypothalamus
– The anterior pituitary:
– Synthesizes its own hormones, such as FSH and LH
– Secretes hormones directly into the blood
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• The hypothalamus:
– Operates through the posterior pituitary
– Directs the activities of the kidneys
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Hypothalamus
ADH
Posterior
pituitary
Anterior
pituitary
Blood
vessel
ADH
Kidneys
(ADH increases water reabsorption
and prevents dehydration)
Figure 25.6
• The anterior lobe of the pituitary also secretes growth hormone
(GH), which:
– Promotes development and enlargement of all parts of the body
– Can lead to:
– Dwarfism, if too little GH is produced
– Gigantism, if too much GH is produced
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(a) Overproduction of
GH during development
(b) Overproduction of
GH during adulthood
(c) Underproduction of
GH during development
Figure 25.7
• Endorphins:
– Are produced by the anterior pituitary
– Act as natural painkillers
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The Thyroid and Parathyroid Glands
• The thyroid gland, located in the neck just under the larynx,
produces:
– Calcitonin, which lowers calcium levels in the blood
– Several hormones involved in controlling:
– Oxygen consumption
– Metabolism
– Development
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• Hypothyroidism:
– Results from too little thyroid hormone in the blood
– Can result from:
– Dietary deficiencies of iodine
– A defective thyroid gland
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• Hyperthyroidism
– Results from too much thyroid hormone in the blood
– Can lead to:
– Overheating
– Profuse sweating
– High blood pressure
– Protruding eyeballs
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• The parathyroid glands:
– Are four disk-shaped glands embedded within the thyroid
– Produce parathyroid hormone, which raises calcium levels in
the blood
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• Calcitonin and parathyroid hormone (PTH) are antagonistic
hormones, because they have opposite effects on calcium levels
in the blood.
Blast Animation: Signaling: Endocrine
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Calcitonin
Thyroid
gland
releases
calcitonin
Stimulates
Ca2+ deposition
in bones
Reduces
Ca2+ uptake
in kidneys
Ca2+ level in blood
falls to set point
Stimulus:
Rising blood
Ca2+ level
(imbalance)
Ca2+
level
Homeostasis: Normal blood calcium level
Ca2+
level
Stimulus:
Falling
blood Ca2+
level
(imbalance)
Ca2+ level in blood
rises to set point
Parathyroid
glands
release parathyroid
hormone (PTH)
Stimulates
Increases
+
2
Ca release Ca2+ uptake
from bones in kidneys
Increases
Ca2+ uptake
in intestines
PTH
Parathyroid
gland
Figure 25.8-6
The Pancreas
• The pancreas produces two antagonistic hormones that play
important roles in managing the body’s energy supplies:
– Insulin reduces blood sugar levels
– Glucagon increases blood sugar levels
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Body
cells
take up more
glucose
Insulin
Pancreas releases
insulin into the blood
Liver takes
up glucose
and stores it as
glycogen
Stimulus:
Rising blood glucose
level (for example, after
eating a carbohydrate-rich
meal)
Blood glucose level
falls to a set point;
stimulus for insulin
release diminishes
Glucose
level
Homeostasis: Normal blood glucose level
Glucose
level
Blood glucose level
rises to set point;
stimulus for glucagon
release diminishes
Stimulus:
Declining blood
glucose level
(for example, after
skipping a meal)
Pancreas releases
glucagon into the blood
Liver
breaks down glycogen
and releases glucose
to the blood
Glucagon
Figure 25.9-6
• Diabetes mellitus is a hormonal disease in which body cells are
unable to absorb glucose from the blood either because:
– 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 noninsulin-dependent diabetes)
• Diabetes can be treated.
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Figure 25.10
The Adrenal Glands
• The adrenal glands are paired structures resting atop the kidneys.
• Each adrenal gland consists of two glands:
– The adrenal medulla
– The adrenal cortex
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• The adrenal medulla secretes epinephrine and norepinephrine,
hormones that:
– Enable the body to respond to stress
– Produce the fight or flight response
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• Stressful stimuli activate nerve cells in the hypothalamus that
send signals to stimulate the adrenal medulla.
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• The adrenal cortex:
– Is also stimulated by the hypothalamus
– Secretes two hormones that provide a slower, longer-lasting response to
stress:
– Corticosteroids
– Glucocorticoids
Blast Animation: Signaling via Steroid Hormones
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STRESS
Adrenal
medulla
Adrenal
gland
Adrenal
cortex
Kidney
Nerve
signals
Hypothalamus
Releasing hormone
Nerve
cell
Spinal cord
(cross section)
Nerve cell
Anterior pituitary
Blood vessel
ACTH
Adrenal medulla
Epinephrine and
norepinephrine
Short-term stress response
1. Glycogen broken down to glucose;
increased blood glucose
2. Increased blood pressure, breathing
rate, heart rate, and metabolic rate
3. Change in blood flow patterns,
leading to increased alertness and
decreased digestive activity
Adrenal cortex
ACTH
Corticosteroids
Long-term stress response
1. Proteins and fats broken
down and converted to
glucose, leading to
increased blood glucose
2. Immune system may be
suppressed
Figure 25.11
The Gonads
• The gonads secrete sex hormones that:
– Affect growth and development
– Regulate:
– Reproductive cycles
– Sexual behavior
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• Males and females have the same three types of sex hormones:
– Estrogens
– Progestins
– Androgens
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• Estrogens:
– Maintain the female reproductive system
– Promote the development of specific female features
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• Progestins, including progesterone, are primarily involved in
preparing the uterus to support a developing embryo.
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• Androgens, including testosterone, stimulate the development
and maintenance of the male reproductive system.
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The Process of Science:
Can Pollution Cause Sex Changes?
• Observation: All of the female mosquitofish collected in a
Florida stream had anatomical features and behaviors normally
found only in males.
• Question: Was pollution from a nearby paper mill the cause of
these changes?
• Hypothesis: Runoff from the mill contained endocrine disruptors.
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• Experiment: Water and fish were analyzed from above and
below the paper mill.
• Results: Female fish with masculine features were found only
downstream of the paper mill.
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Paper mill
discharging
waste water
Contaminated
sample sites
Uncontaminated
sample sites
Normal female
Normal
male
Female with
male organ
Perdido Bay
Figure 25.12