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Chapter Presentation
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Visual Concepts
Standardized Test Prep
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Chapter 50
Endocrine System
Table of Contents
Section 1 Hormones
Section 2 Endocrine Glands
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Chapter 50
Section 1 Hormones
Objectives
• State the major functions of hormones.
• Differentiate between endocrine and exocrine glands.
• Compare the structure of amino acid-based hormones with the
structure of steroid hormones.
• Compare how amino acid-based hormones act on their target
cells with how steroid or thyroid hormones act on their target
cells.
• Relate how neuropeptides and prostaglandins act like
hormones.
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Chapter 50
Section 1 Hormones
Function and Secretion
• Hormones are substances secreted
by cells that act to regulate the
activity of other cells in the body.
– Hormones affect all cells in the
body and are made and secreted
by endocrine glands.
• Endocrine glands are ductless
organs that secret hormones either
into the bloodstream or the fluid
around cells.
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Chapter 50
Section 1 Hormones
Function and Secretion, continued
• The endocrine glands can be found through out the
body and are collectively known as the endocrine
system.
• Endocrine glands, such as the pancreas, can also be
exocrine glands.
– Exocrine glands secrete substances through
ducts to specific locations inside and outside the
body.
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Chapter 50
Section 1 Hormones
The Endocrine System
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Chapter 50
Section 1 Hormones
Comparing Endocrine and Exocrine Glands
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Chapter 50
Section 1 Hormones
Types of Hormones
• Hormones can be grouped into two types based on their
structure. Hormones can either be amino acid-based hormones
or steroid hormones.
– Amino acid based-hormones are made of amino acids,
either a single modified amino acid or a protein made of 3200 amino acids, and are water soluble.
– Steroid hormones are lipid hormones that the body makes
from cholesterol and are fat soluble.
• Similar to steroid hormones are thyroid hormones.
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Chapter 50
Section 1 Hormones
Hormone Action
• Regardless of which type of hormone is being
activated, all hormones affect only their target cells.
– Target cells are specific cells to which a hormone
travels to produce a specific effect.
– On the target cells are receptors. Receptors are
proteins that bind to specific signal molecules,
such as hormones, that cause a cell to respond.
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Chapter 50
Section 1 Hormones
Hormone Action, continued
• Amino acid-based hormones
– Amino acid-based hormones bind to receptor proteins on the
cell membrane and are called first messengers.
– Second messengers are then activated. A second
messenger is a molecule that initiates changes inside a cell
in response to the binding of a specific substance to a
receptor on the outside of a cell.
• Changes to the cell through enzyme action then occur in
a cascade fashion.
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Chapter 50
Section 1 Hormones
How Amino Acid-Based Hormones Work
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Chapter 50
Section 1 Hormones
Action of Amino Acid-Based Hormones
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Chapter 50
Section 1 Hormones
Hormone Action, continued
• Steroid and Thyroid Hormones
– Steroid and thyroid hormones are similar because
they are both fat soluble.
– Because these hormones are fat soluble they can
pass through the cell membrane.
– Thus, these hormones can enter their target cells
and bind directly to receptor sites in the cytoplasm
or nucleus and directly activate enzymes.
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Chapter 50
Section 1 Hormones
How Steroid Hormones Work
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Chapter 50
Section 1 Hormones
Action of Steroid Hormones
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Chapter 50
Section 1 Hormones
Other Types of Hormones
• Two other types of chemical messengers that are
classified as hormones are neuropeptides and
prostaglandins.
– Neuropeptides are hormones secreted by the
nervous system and tend to affect many cells near
the nerve cells that release them.
– Prostaglandins are modified fatty acids that are
secreted by most cells and tend to accumulate in
areas where tissues are disturbed or injured.
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Chapter 50
Section 1 Hormones
Comparing Hormones and Prostaglandins
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Chapter 50
Section 2 Endocrine Glands
Objectives
• Identify the relationship between the hypothalamus and the
pituitary gland in the release of hormones.
• List the functions of the major endocrine glands and hormones.
• Explain the role of feedback mechanisms in maintaining
homeostasis.
• Compare how negative feedback and positive feedback
mechanisms are used to regulate hormone.
• Summarize how antagonistic hormones work as pairs to
maintain homeostasis.
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Chapter 50
Section 2 Endocrine Glands
Hypothalamus and Pituitary Gland
• Two organs, the hypothalamus and the pituitary
gland, control the initial release of many hormones
for the endocrine system.
– The hypothalamus is the area of the brain that
coordinates many activities of the nervous and
endocrine systems.
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Chapter 50
Section 2 Endocrine Glands
Hypothalamus and Pituitary Gland, continued
• The hypothalamus responds to
information it receives from the
body by issuing instructions, as
hormones, to the pituitary gland.
• The pituitary gland has two
parts, anterior and posterior,
and stores and releases
hormones produced by the
hypothalamus.
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Chapter 50
Section 2 Endocrine Glands
Hypothalamus and Pituitary Gland, continued
• The nerve cells in the hypothalamus that secrete
hormones are called neurosecretory cells.
– These cells secrete two types of hormones to the
pituitary gland.
• Releasing hormones stimulate the anterior
pituitary to make and secrete hormones.
• Release-inhibiting hormones inhibit production
and secretion of anterior-pituitary hormones.
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Chapter 50
Section 2 Endocrine Glands
The Hypothalamus and
the Pituitary Gland
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Chapter 50
Section 2 Endocrine Glands
The Hormones Secreted by the Pituitary Gland
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Chapter 50
Section 2 Endocrine Glands
Anatomy of the Human Pituitary Gland
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Chapter 50
Section 2 Endocrine Glands
Thyroid Gland
• The thyroid gland is
located near the larynx and
helps maintain a normal
heart rate, blood pressure,
and body temperature by
increasing or decreasing
cellular metabolic rates.
• The thyroid gland is also
important for development.
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Chapter 50
Section 2 Endocrine Glands
Anatomy of the Human Thyroid Gland
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Chapter 50
Section 2 Endocrine Glands
Thyroid Gland, continued
• Abnormal thyroid activity can result in hypothyroidism
or hyperthyroidism.
• Overproduction of thyroid hormones is called
hyperthyroidism and can have symptoms that vary
from overactivity to high body temperature.
• A deficiency in a thyroid hormone is known as
hypothyroidism and can have symptoms that vary
from weight gain to retardation.
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Chapter 50
Section 2 Endocrine Glands
Hyperthyroidism
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Chapter 50
Section 2 Endocrine Glands
Hypothyroidism
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Chapter 50
Section 2 Endocrine Glands
Adrenal Glands
• Humans have an adrenal gland
located above each kidney. Each
adrenal gland has an inner core, the
medulla, and an outer core, also
called the cortex.
• The medulla and the cortex function
as separate endocrine glands.
– The medulla is controlled by the
nervous system, and the cortex
is controlled by the anterior
pituitary.
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Chapter 50
Section 2 Endocrine Glands
Adrenal Glands, continued
• Adrenal Medulla
– The adrenal medulla secretes the hormones that stimulate a
“flight-or-fight” response to a stress.
– In this response, the hormones epinephrine, also called
adrenaline, and norepinephrine are released.
• These hormones increases heart rate, blood pressure,
blood glucose levels, and blood flow into the heart and
lungs so the body can respond to the initial stress.
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Chapter 50
Section 2 Endocrine Glands
Adrenal Glands, continued
• Adrenal Cortex
– In the presence of some stresses the pituitary
gland will secrete the adrenocorticotropic hormone
(ACTH).
– This hormone stimulates the adrenal cortex to
produce the hormone cortisol.
• Cortisol promotes the production of glucose
from proteins to help cells make usable energy.
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Chapter 50
Section 2 Endocrine Glands
The Adrenal Gland
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Chapter 50
Section 2 Endocrine Glands
Adrenal Gland
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Chapter 50
Section 2 Endocrine Glands
Gonads
• Gonads are the gamete-producing organs that also
produce a group of steroid sex hormones.
– Gonads, ovaries in females and the testes in
males, are regulated by sex hormones, which
begin production at puberty.
• Puberty is the adolescent stage during which the sex
organs mature and secondary sex characteristics
appear.
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Chapter 50
Section 2 Endocrine Glands
Gonads, continued
• The production of sex hormones is stimulated by the
release of two hormones by the pituitary.
– The first hormone is luteinizing hormone (LH). This
hormone stimulates ovulation and the release of
progesterone in females and the release of
androgens, such as testosterone, in males.
– The second hormone is follicle-stimulating hormone
(FSH). This hormone stimulates the growth and
maturation of the ovarian follicles in females and
sperm production in males.
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Chapter 50
Section 2 Endocrine Glands
Gonads
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Chapter 50
Section 2 Endocrine Glands
Pancreas
• The pancreas contains both exocrine and endocrine
cells. The endocrine cells are called islets of
Langerhans.
• These cells secrete hormones that regulate the level
of sugar in the blood. The hormone insulin is one of
the hormones produced.
– Insulin lowers the blood sugar level by stimulating
body cells to store glucose or use it for energy.
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Chapter 50
Section 2 Endocrine Glands
Pancreas
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Chapter 50
Section 2 Endocrine Glands
Pancreas, continued
• A condition called diabetes mellitus occurs when
cells are unable to obtain glucose from the blood.
This results in a high glucose level in the blood
• There are two types of diabetes: Type I and Type II.
– Type I occurs when immune cells attack and
destroy the islet of Langerhans cells.
– Type II occurs when cells don’t have sufficient
insulin levels or when the organism’s cells have
become less responsive.
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Chapter 50
Section 2 Endocrine Glands
Diabetes Mellitus
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Chapter 50
Section 2 Endocrine Glands
Pancreas, continued
• A condition called hypoglycemia occurs when
excessive insulin is stored and not properly delivered
to body cells.
• This leads to a lowered blood glucose concentration,
which can cause such symptoms as overactivity and
dizziness.
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Chapter 50
Section 2 Endocrine Glands
Other Endocrine Glands
• There are several other glands in the endocrine
system, including thymus gland, the pineal gland and
the parathyroid glands.
• Thymus Gland
– The thymus gland is located beneath the sternum
and plays a role in the development of the immune
system by secreting thymosin.
• This amino acid-based hormone stimulates
formation of T cells.
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Chapter 50
Section 2 Endocrine Glands
Other Endocrine Glands, continued
• Pineal Gland
– The pineal gland is
located near the base
of the brain and helps
regulate sleep
patterns by secreting
melatonin.
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Chapter 50
Section 2 Endocrine Glands
Pineal Gland
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Chapter 50
Section 2 Endocrine Glands
Other Endocrine Glands, continued
• Parathyroid Gland
– The parathyroid glands is
made up of four glands
embedded in the two
thyroid glands.
• These glands secrete
the parathyroid
hormone, which
stimulates the transfer
of calcium ions from
the bones to the blood.
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Chapter 50
Section 2 Endocrine Glands
Parathyroid Gland
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Chapter 50
Section 2 Endocrine Glands
Other Endocrine Glands, continued
• Digestive Cells
– Some of the digestive organs also act as
endocrine cells by secreting a variety of hormones
that control digestive processes. Two hormones
that are secreted are gastrin and secretin.
• Gastrin is released by the stomach when food
is eaten.
• Secretin is released by the small intestine and
helps stimulates the release of various
digestive fluids from the pancreas.
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Chapter 50
Section 2 Endocrine Glands
Feedback Mechanisms
• The endocrine system plays an important role in the
maintenance of a stable internal environment, or
homeostasis.
• Maintenance of homeostasis is controlled by
feedback mechanisms. A feedback mechanism is one
in which the last step in a series of events controls
the first.
• Feedback mechanisms can be either negative or
positive.
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Chapter 50
Section 2 Endocrine Glands
Feedback Mechanisms, continued
• Negative Feedback
– When the final step in a
series of events inhibits
the initial signal in the
series it is called
negative feedback.
– An example of negative
feedback is the regulation
of thyroid hormones.
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Chapter 50
Section 2 Endocrine Glands
Negative Feedback
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Chapter 50
Section 2 Endocrine Glands
Feedback Mechanisms, continued
• Positive Feedback
– Positive feedback occurs
when the release of an initial
hormone stimulates release or
production of other hormones
or substances.
– An example of positive
feedback is the stimulation and
increase in luteinizing hormone
by estrogen.
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Chapter 50
Section 2 Endocrine Glands
Comparing Positive and Negative Feedback
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Chapter 50
Section 2 Endocrine Glands
Feedback Mechanisms, continued
• Antagonistic Hormones
– Antagonistic hormones work together in pairs
to regulate the levels of critical substances.
– Example: Both glucagon and insulin regulate
blood sugar levels.
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Chapter 50
Standardized Test Prep
Multiple Choice
1. What are the chemical messengers of the endocrine
system called?
A. neurons
B. hormones
C. blood cells
D. carbohydrates
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
1. What are the chemical messengers of the endocrine
system called?
A. neurons
B. hormones
C. blood cells
D. carbohydrates
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
2. X and Y are hormones. X stimulates the secretion of
Y, which exerts negative feedback on the cells that
secrete X. Suppose the level of Y decreases. What
should happen immediately afterwards?
F. Less X is secreted.
G. More X is secreted.
H. Secretion of Y stops.
J. Secretion of X stops.
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
2. X and Y are hormones. X stimulates the secretion of
Y, which exerts negative feedback on the cells that
secrete X. Suppose the level of Y decreases. What
should happen immediately afterwards?
F. Less X is secreted.
G. More X is secreted.
H. Secretion of Y stops.
J. Secretion of X stops.
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
3. Endocrine glands
A. function only after puberty.
B. function only before puberty.
C. release products through ducts.
D. release products into the bloodstream.
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
3. Endocrine glands
A. function only after puberty.
B. function only before puberty.
C. release products through ducts.
D. release products into the bloodstream.
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
Use the figure below to answer
questions 4 and 5. The
figure shows the level of
glucose in the blood.
4. What happens after food
is eaten?
F. Blood glucose levels
increase.
G. Blood glucose levels
decrease.
H. Blood glucose levels
remain the same.
J. Blood glucose levels
decrease then increase.
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
Use the figure below to answer
questions 4 and 5. The
figure shows the level of
glucose in the blood.
4. What happens after food
is eaten?
F. Blood glucose levels
increase.
G. Blood glucose levels
decrease.
H. Blood glucose levels
remain the same.
J. Blood glucose levels
decrease then increase.
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
Use the figure below to answer
questions 4 and 5. The
figure shows the level of
glucose in the blood.
5. Which hormones are primarily
responsible for the changes in
blood glucose levels about 2
hours after food is eaten?
A. insulin
B. estrogen and progesterone
C. epinephrine and
norepinephrine
D. aldosterone and
parathyroid hormones
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
Use the figure below to answer
questions 4 and 5. The
figure shows the level of
glucose in the blood.
5. Which hormones are primarily
responsible for the changes in
blood glucose levels about 2
hours after food is eaten?
A. insulin
B. estrogen and progesterone
C. epinephrine and
norepinephrine
D. aldosterone and
parathyroid hormones
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
Complete the following analogy:
6. Neurotransmitters : nervous system :: hormones :
F. feedback system
G. endocrine system
H. circulatory system
J. respiratory system
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
Complete the following analogy:
6. Neurotransmitters : nervous system :: hormones :
F. feedback system
G. endocrine system
H. circulatory system
J. respiratory system
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
Use the table below to answer question 7. The table
shows the relative levels of thyroid-stimulating
hormone (TSH) during a 12 hour period.
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
7. Thyroid stimulating hormone (TSH) is a hormone
that stimulates the release of the thyroid hormones
from the thyroid gland. At what time would you
expect thyroid hormone levels to be at their lowest?
A. 0 hours
B. 4 hours
C. 8 hours
D. 12 hours
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Chapter 50
Standardized Test Prep
Multiple Choice, continued
7. Thyroid stimulating hormone (TSH) is a hormone
that stimulates the release of the thyroid hormones
from the thyroid gland. At what time would you
expect thyroid hormone levels to be at their lowest?
A. 0 hours
B. 4 hours
C. 8 hours
D. 12 hours
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Chapter 50
Standardized Test Prep
Short Response
The pancreas is an organ that carries out many
functions related to digestion.
Explain why the pancreas is considered to be both
an exocrine gland and an endocrine gland.
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Chapter 50
Standardized Test Prep
Short Response, continued
The pancreas is an organ that carries out many
functions related to digestion.
Explain why the pancreas is considered to be both
an exocrine gland and an endocrine gland.
Answer: The pancreas releases chemicals into ducts
and hormones into the bloodstream.
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Chapter 50
Standardized Test Prep
Extended Response
Base your answers to parts A & B on the information below.
The endocrine system is involved in maintaining homeostasis.
Many of the activities regulated by the endocrine system
require maintaining a critical substance at levels that do not
vary much.
Part A Explain how pairs of hormones are involved in
regulating levels of critical substances.
Part B Describe a specific example of a pair of hormones that
work together to maintain the level of a critical substance.
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Chapter 50
Standardized Test Prep
Extended Response, continued
Answer:
Part A Antagonistic hormones work together to
regulate the levels of critical substance by
counteracting each other.
Part B Sample answer: Insulin causes blood
glucose levels to fall, and glucagon causes blood
glucose levels to rise.
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