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Chemical Signaling
Within the Animal Body
Chapter 27
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Outline
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Hormones
Pituitary Gland
 Posterior
 Anterior
Pancreas Gland
Thyroid Gland
Parathyroid Gland
Adrenal Gland
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Hormones
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Hormone is a chemical signal produced in one part
of the body that is stable enough to be transported
in active form across the body.
Three advantages to chemical signals:
 Can spread to all tissues via blood.
 Can persist much longer than electrical signals.
 Many chemicals can act as hormones.
- Different hormones can be used for different
tissues.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Hormones
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Hormones produced by endocrine glands.
 Completely enclosed in tissue.
 Secreted into exocrine glands.
Hormones controlled by Neuroendocrine
system.
 Hypothalamus is control center.
- Issues commands to pituitary which
sends signals to various hormoneproducing glands.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Major Glands of Endocrine System
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Hormones
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How Hormones Work
 Plasma membrane of target cell has
embedded receptor proteins that match
shape of potential signal hormone.
Communication Path
 Issuing Command
 Transporting Signal
 Hitting Target
 Having Effect
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
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Steroid Hormones Enter Cells
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Steroid hormones are manufactured from
cholesterol.
 Can pass across lipid bilayer of plasma
membrane and bind to receptors within cell.
- Alters gene activity and hormone’s effect.
Anabolic Steroids are synthetic compounds
that resemble testosterone.
 Cause muscle cells to produce more
protein.
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Peptide Hormones Act at Cell Surface
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Binding of peptide hormone to receptor
triggers change in cytoplasmic end of
receptor protein.
 Triggers events within cell cytoplasm
through second messengers.
- Single hormone molecule can result in
formation of many second messengers
in cytoplasm.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Copyright © McGraw-Hill Companies
Permission required for reproduction or display
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Pituitary Gland
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Pituitary gland is located in bony recess of
brain below hypothalamus and produces
nine major hormones.
 Two Glands
- Posterior - regulates water conservation.
- Anterior - regulates other glands.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Pituitary Gland
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Posterior Pituitary
 Releases peptide hormone vasopressin.
- Regulates kidney retention of water.
 Releases oxytocin which initiates uterine
contraction during childbirth and milk
release in mothers.
Both oxytocin and vasopressin are
synthesized inside neurons of hypothalamus,
transported down nerve axons, and stored in
posterior pituitary.
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Pituitary Gland
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Anterior Pituitary
 Produces seven major peptide hormones:
- Thyroid-stimulating hormone
- Luteinizing hormone
- Follicle-stimulating hormone
- Adrenocorticotropic hormone
- Growth hormone
- Prolactin
- Melanocyte-stimulating hormone
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Pituitary Gland
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Hypothalamus controls anterior pituitary
hormones by secreting releasing and
inhibiting hormones into blood capillaries at
base of hypothalamus.
 Capillaries drain into hypothalamohypophyseal portal system.
Each releasing hormone delivered to anterior
pituitary regulates secretion of specific
hormone.
 Negative Feedback Inhibition
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Hormonal Control of Anterior Pituitary Gland
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Pancreas
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Located behind the stomach and connected to
front end of small intestine by narrow tube.
 Secretes variety of digestive enzymes.
Islets of Langerhaus govern glucose levels.
 Insulin - Storage hormone that promotes
accumulation of glycogen.
 Glucagon - Secreted by alpha cells when
glucose levels fall. (releases stored glucose)
- Type I diabetes
- Type II diabetes
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Thyroid Gland
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Thyroid gland produces several hormones.
 Thyroxine - increases metabolic rate.
- Contains iodine
 Produces goiters
 Triggers amphibian metamorphosis
 Calcitonin - Stimulates bone uptake of
calcium.
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Parathyroid Glands
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Produce parathyroid hormone (PTH)
 Essential for survival.
 Regulates calcium levels in blood.
- Fail-safe to ensure calcium levels never
fall too low.
 Calcium ions are key components in
muscle contraction.
 Acts on kidneys to reabsorb calcium ions
from urine.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Adrenal Glands
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Mammals have two adrenal glands.
 Each composed to two parts:
- Medulla - inner core which produces
adrenaline and norepinephrine.
 Released in times of stress to trigger
rapid deployment of body fuel.
- Cortex - outer shell which produces
cortisol and aldosterone.
 Stimulates carbohydrate production
and promotes uptake of sodium from
urine.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Other Hormones
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Sexual Development
 Ovaries and testes produce estrogen,
progesterone, and testosterone.
Biological Clocks
 Pineal gland secretes melatonin.
- Entrained to light and dark cycles.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Other Hormones
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Nonendocrine Hormones
 Right atrium secretes atrial natriuretic
hormone which stimulates kidneys to
excrete salt and water in urine.
Molting and Metamorphosis
 Molting hormone
 Juvenile hormone
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Review
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Hormones
Pituitary Gland
 Posterior
 Anterior
Pancreas Gland
Thyroid Gland
Parathyroid Gland
Adrenal Gland
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Copyright © McGraw-Hill Companies
Permission required for reproduction or display
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies