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Standardized Test Prep
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Chapter 42
Hormones and the Endocrine System
Table of Contents
Section 1 Hormones
Section 2 How Hormones Work
Section 3 The Major Endocrine Glands
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Chapter 42
Section 1 Hormones
Objectives
• Identify four major functions of hormones.
• Differentiate between endocrine and exocrine
glands.
• Compare the endocrine and nervous systems.
• Distinguish the functions of endorphins from the
functions of prostaglandins.
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Chapter 42
Section 1 Hormones
Coordination of Activities
• Reacting to fear, growing taller, and developing male
or female characteristics are all activities in the body
that are partially regulated by hormones.
• Hormones are substances secreted (released) by
cells that act to regulate the activity of other cells in
the body.
• Hormones act as chemical messengers, carrying
instructions that cause cells to change their activities.
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Chapter 42
Section 1 Hormones
Coordination of Activities, continued
• The functions of hormones include the following:
1. Regulating growth, development, behavior, and
reproduction
2. Coordinating the production, use, and storage of
energy
3. Maintaining homeostasis
4. Responding to stimuli from outside the body
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Chapter 42
Section 1 Hormones
Endocrine Glands and Tissues
• Endocrine glands are ductless organs that secrete
hormones directly into either the bloodstream or the
fluid around cells (extracellular fluid).
• All of the endocrine glands and hormone-secreting
tissues collectively make up the endocrine system.
• Some organs, such as the pancreas, are both
endocrine and exocrine glands. Exocrine glands
deliver substances through ducts (tubelike
structures).
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Chapter 42
Section 1 Hormones
Endocrine System
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Chapter 42
Section 1 Hormones
Anatomy of Human Endocrine Glands
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Chapter 42
Section 1 Hormones
Exocrine Glands
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Chapter 42
Section 1 Hormones
Comparing Endocrine and Exocrine Glands
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Chapter 42
Section 1 Hormones
Endocrine Glands and Tissues, continued
Hormones and Neurotransmitters Are Chemical
Messengers
• The chemical messengers of the nervous system are known as
neurotransmitters, while the chemical messengers of the
endocrine system are called hormones.
• Some nerve cells, however, are capable of secreting hormones,
and several chemicals serve as both hormones in the endocrine
system and neurotransmitters in the nervous system.
• Another difference between the endocrine and nervous systems
is that neurotransmitters are fast-acting and usually short-lived
messengers. Hormones are usually slower-acting and longerlived.
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Chapter 42
Section 1 Hormones
Endocrine Glands and Tissues, continued
Hormonelike Substances
• Their are many substances, such as neuropeptides
and prostaglandins, that regulate cellular activities
much as hormones do.
• Enkephalins and endorphins are neuropeptides.
Enkephalins inhibit pain messages traveling to the
brain. Endorphins regulate emotions.
• Prostaglandins are modified fatty acids that have a
variety of functions, including the constriction and
dilation of blood vessels.
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Chapter 42
Section 1 Hormones
Comparing Hormones and Prostaglandins
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Chapter 42
Section 2 How Hormones Work
Objectives
• Relate how hormones act only on specific cells.
• Summarize how amino-acid-based hormones
function.
• Summarize how steroid and thyroid hormones
function.
• Relate how negative feedback is used to regulate
hormone levels.
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Chapter 42
Section 2 How Hormones Work
Target Cells
• A target cell is a specific cell that a hormone binds to
and acts on (carries the message to).
• A hormone recognizes a target cell because the
target cell has specific receptors. The receptors are
located either on the surface of the target cell (on the
cell membrane) or inside the cell (in the cytoplasm or
nucleus).
• A hormone binds only to cells that have a particular
receptor protein, ignoring all other cells.
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Chapter 42
Section 2 How Hormones Work
Hormones Acting on Target Cells
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Chapter 42
Section 2 How Hormones Work
Target Cells, continued
Types of Hormones
• Amino-acid-based hormones are hormones made
of amino acids (either a single modified amino acid or
a protein composed of 3 to 200 amino acids). Most
amino-acid-based hormones are water soluble.
• Steroid hormones are lipid hormones that the body
makes from cholesterol. Steroid hormones are fat
soluble.
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Chapter 42
Section 2 How Hormones Work
Receptors
Amino-Acid-Based Hormones
• Amino-acid-based hormones are not fat soluble, and
most bind to cell membrane receptors:
Step 1 Glucagon binds to a receptor protein on the
cell membrane.
Step 2 This change in shape eventually activates a
second messenger, a molecule that passes the
message from the first messenger (the hormone) to
the cell.
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Chapter 42
Section 2 How Hormones Work
Receptors, continued
Amino-Acid-Based Hormones
Step 3 The second messenger then activates or
deactivates certain enzymes in a cascade fashion.
Step 4 Eventually the activity of the target cell is
changed by the final enzyme in the cascade—even
though the hormone never enters the cell!
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Chapter 42
Section 2 How Hormones Work
How Amino-Acid-Based Hormones Work
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Chapter 42
Section 2 How Hormones Work
Action of Amino-Acid-Based Hormones
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Chapter 42
Section 2 How Hormones Work
Receptors, continued
Steroid and Thyroid Hormones
• How steroid hormones such as cortisol work is
summarized in the following steps:
Step 1 The hormone diffuses through the cell
membrane and binds to its receptor. The hormone
and receptor form a hormone-receptor complex in the
cytoplasm.
Step 2 The hormone-receptor complex enters the
nucleus of the cell and binds to DNA.
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Chapter 42
Section 2 How Hormones Work
Receptors, continued
Steroid and Thyroid Hormones
Step 3 Depending on the hormone and the target
cell, the binding either activates or inactivates a gene.
Step 4 The target cell’s activities are altered. For
example, cortisol stimulates the making of enzymes
that break down proteins and fats into glucose.
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Chapter 42
Section 2 How Hormones Work
How Steroid Hormones Work
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Chapter 42
Section 2 How Hormones Work
Action of Steroid Hormones
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Chapter 42
Section 2 How Hormones Work
Anabolic Steroid
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Chapter 42
Section 2 How Hormones Work
Feedback Mechanisms
• In many cases the level of a hormone in the blood
turns production of the hormone off and on through
feedback mechanisms.
• If high levels of a hormone stimulate the output of
even more hormone, the regulation is called positive
feedback.
• In negative feedback, a change in one direction
stimulates the control mechanism to counteract
further change in the same direction.
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Chapter 42
Section 2 How Hormones Work
Negative Feedback
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Chapter 42
Section 2 How Hormones Work
Comparing Positive and Negative Feedback
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Chapter 42
Section 3 The Major Endocrine
Glands
Objectives
• Evaluate the roles of the hypothalamus and the pituitary gland
in controlling other hormones.
• Summarize the roles of the thyroid and parathyroid hormones.
• Compare the roles of the hormones secreted in each area of
the adrenal gland.
• Relate how each of the two hormones secreted by the pancreas
regulates blood glucose levels.
• Describe the roles of reproductive hormones and of melatonin.
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Chapter 42
Section 3 The Major Endocrine
Glands
Major Endocrine
Glands
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Chapter 42
Section 3 The Major Endocrine
Glands
Endocrine Control
The Hypothalamus
• The hypothalamus is the area of the brain that
coordinates the activities of the nervous and
endocrine systems. It controls many body functions,
including body temperature, blood pressure, and
emotions.
• The hypothalamus receives information about
external and internal conditions from other brain
regions. The hypothalamus responds by issuing
instructions—in the form of hormones—to the
pituitary gland.
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Chapter 42
Section 3 The Major Endocrine
Glands
The Hypothalamus and Pituitary Gland
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Chapter 42
Section 3 The Major Endocrine
Glands
Endocrine Control, continued
The Pituitary Gland
• The pituitary gland is an endocrine gland suspended
from the hypothalamus by a short stalk.
• The pituitary gland secretes many hormones, including
some that control endocrine glands elsewhere in the
body.
• The nerve cells in the hypothalamus make at least six
hormones that are released into a special network of
blood vessels between the hypothalamus and the
pituitary gland.
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Chapter 42
Section 3 The Major Endocrine
Glands
Hormones Secreted by the Pituitary Gland
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Chapter 42
Section 3 The Major Endocrine
Glands
Anatomy of the Pituitary Gland
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Chapter 42
Section 3 The Major Endocrine
Glands
Pituitary Gland
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Chapter 42
Section 3 The Major Endocrine
Glands
The Thyroid and Parathyroid Glands
• The thyroid gland,
located in the neck, is
wrapped around the
trachea.
• The parathyroid
glands are located on
the back of the thyroid
gland.
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Chapter 42
Section 3 The Major Endocrine
Glands
Anatomy of the Human Thyroid Gland
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Chapter 42
Section 3 The Major Endocrine
Glands
Thyroid Gland
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Chapter 42
Section 3 The Major Endocrine
Glands
Parathyroid Gland
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Chapter 42
Section 3 The Major Endocrine
Glands
The Thyroid and Parathyroid Glands,
continued
Regulating Metabolism and Development
• Thyroid hormones regulate the body’s metabolic rate
and promote normal growth of the brain, bones, and
muscles during childhood.
• Thyroid hormones also affect reproductive functions
and maintain mental alertness in adults.
• The underproduction of thyroid hormones is
hypothyroidism. The overproduction of thyroid
hormones is hyperthyroidism.
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Chapter 42
Section 3 The Major Endocrine
Glands
Hypothyroidism
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Chapter 42
Section 3 The Major Endocrine
Glands
Hyperthyroidism
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Chapter 42
Section 3 The Major Endocrine
Glands
The Thyroid and Parathyroid Glands,
continued
Regulating Calcium Levels
• A high level of calcium in the blood stimulates the
thyroid gland to produce a hormone called calcitonin.
Calcitonin causes calcium to be deposited in bone
tissue rapidly, lowering the blood-calcium level.
• Parathyroid hormone (PTH) is a hormone that is
produced by four parathyroid glands attached to the
back part of the thyroid gland.
• PTH is made and released in response to a falling
level of calcium in the blood.
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Chapter 42
Section 3 The Major Endocrine
Glands
The Adrenal Glands
• The body has two adrenal glands, which are
endocrine organs located above each kidney.
• Each almond-size adrenal gland is actually two
glands in one: an inner core, called the adrenal
medulla, and an outer shell, called the adrenal cortex.
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Chapter 42
Section 3 The Major Endocrine
Glands
The Adrenal Gland
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Chapter 42
Section 3 The Major Endocrine
Glands
Adrenal Gland
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Chapter 42
Section 3 The Major Endocrine
Glands
The Adrenal Glands, continued
Immediate Response to Stress
• The adrenal medulla acts as a warning system in
times of stress by releasing the “fight-or-flight”
hormones epinephrine and norepinephrine.
• The effects of these hormones are identical to the
effects of the sympathetic nervous system in
response to a stressful situation, but longer lasting.
• In stressful situations the fight-or-flight hormones
increase heart rate, blood pressure, blood glucose
level, and blood flow to the heart and lungs.
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Chapter 42
Section 3 The Major Endocrine
Glands
The Adrenal Glands, continued
Long-Term Response to Stress
• The adrenal cortex hormones provide a slower, more
long-term response to stress than epinephrine and
norepinephrine.
• Cortisol makes more energy available to the body.
• Aldosterone helps reabsorb sodium ions from the
fluids removed by the kidneys so that these ions are
not lost in the urine.
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Chapter 42
Section 3 The Major Endocrine
Glands
The Pancreas and Other Organs
Regulating Blood Glucose Levels
• The pancreas contains clusters of specialized cells,
called the islets of Langerhans. Two hormones
made by the islets interact to control the level of
glucose in the blood.
• Insulin is a hormone that lowers blood glucose
levels by promoting the accumulation of glycogen in
the liver.
• Glucagon has the opposite effect of insulin—it
raises blood glucose levels.
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Chapter 42
Section 3 The Major Endocrine
Glands
Pancreas
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Chapter 42
Section 3 The Major Endocrine
Glands
Maintaining Normal Blood Glucose Level
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Chapter 42
Section 3 The Major Endocrine
Glands
The Pancreas and Other Organs, continued
Regulating Blood Glucose Levels
• Diabetes mellitus is a serious disorder in which cells
are unable to obtain glucose from the blood, resulting
in high blood glucose levels.
• The kidneys excrete the excess glucose, and water
follows, resulting in excessive volumes of urine and
persistent thirst.
• Because cells cannot take up glucose, they use the
body’s supply of fats and proteins for energy.
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Chapter 42
Section 3 The Major Endocrine
Glands
Diabetes Mellitus
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Chapter 42
Section 3 The Major Endocrine
Glands
The Pancreas and Other Organs, continued
Regulating Reproduction
• The ovaries and the testes, which also produce
gametes, secrete hormones that regulate
reproduction.
• The ovaries secrete estrogens and progesterone,
and the testes produce testosterone.
• These hormones affect the formation of gametes
and control sexual behavior and cycles.
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Chapter 42
Section 3 The Major Endocrine
Glands
Gonads
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Chapter 42
Section 3 The Major Endocrine
Glands
The Pancreas and Other Organs, continued
Regulating Daily Rhythms
• The pineal gland is a pea-sized gland located in
the brain, which secretes the hormone melatonin.
• Melatonin seems to be released by the human
pineal gland as a response to darkness.
Therefore, the pineal gland is thought to be
involved in establishing daily biorhythms.
• The pineal gland may also play a role in mood
disorders such as seasonal affective disorder
(SAD) syndrome.
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Chapter 42
Section 3 The Major Endocrine
Glands
The Pancreas and Other Organs, continued
Regulating Daily Rhythms
The daily variation in body temperature is an example of
a biorhythm thought to be influenced by melatonin.
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Chapter 42
Section 3 The Major Endocrine
Glands
Pineal Gland
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Chapter 42
Standardized Test Prep
Multiple Choice
The chart below shows the effects of hormone injections on blood
glucose levels in rats. Rats in groups 1 and 2 were injected with
saline containing a hormone. Rats in the control group were
injected with only saline. Use the chart to answer questions 1–3.
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
1. Which hormone was likely contained in the injection
given to rats in group 1?
A.
B.
C.
D.
insulin
calcitonin
glucagon
oxytocin
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
1. Which hormone was likely contained in the injection
given to rats in group 1?
A.
B.
C.
D.
insulin
calcitonin
glucagon
oxytocin
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
2. Which hormone was likely contained in the injection
given to rats in group 2?
F.
G.
H.
J.
insulin
calcitonin
glucagon
oxytocin
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
2. Which hormone was likely contained in the injection
given to rats in group 2?
F.
G.
H.
J.
insulin
calcitonin
glucagon
oxytocin
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
3. What was the purpose of the control group?
A. to prove that saline also acts as a hormone
B. to determine whether the injection procedure
itself affected blood glucose levels
C. to make sure the hormones had not become
stale during storage
D. to make sure the needles and syringes worked
properly
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
3. What was the purpose of the control group?
A. to prove that saline also acts as a hormone
B. to determine whether the injection procedure
itself affected blood glucose levels
C. to make sure the hormones had not become
stale during storage
D. to make sure the needles and syringes worked
properly
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