1. Hormones and the Endocrine System Ch 26

2. Introduction
Endocrine disruptors are toxic chemicals that interfere with the endocrine system.
Endocrine disruptors include
atrazine, an ingredient in weed killers and a contaminant found in farm water runoff that makes its way to ground and surface reservoirs, and
bisphenol A (BPA), used in many plastics that line bottles, canned goods, and other manufactured drinking water and food containers.

3. 26.1 Chemical and electrical signals coordinate body functions
The endocrine system is a group of interacting _____________and _______________ that produce and secrete chemical signals called ________________to initiate and maintain body functions.
In contrast, electrical signals of the nervous system coordinate immediate responses.
If hormones reach every cell in the body, why do only some cells respond to a specific hormone?
Checkpoint Question Response
Only target cells have the receptors that recognize the specific signal.
Student Misconceptions and Concerns
Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies on a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. (26.1–26.3)
Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. (26.1–26.3)

4. Communication Mechanisms
Stimulus
Communication Mechanisms
Nervous system
Endocrine System
Cell body
of neuron
Nerve
impulse
Axon
Signal travels
along axon to
a specific
location
Nerve
impulse
Axons
Figure 26.1b Signaling in the nervous system
Response: Limited to
cells that connect by
specialized junctions to
an axon that transmits
an impulse

5. 26.2 Hormones affect target cells using two main signaling mechanisms
Hormone signaling involves three stages:
Reception of the signal occurs when a ___________ binds to a specific __________ _______ on or in the target cell.
Signal transduction converts the signal from one form to another.
Response is a change in the cell’s behavior.
Student Misconceptions and Concerns
Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies on a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. (26.1–26.3)
Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. (26.1–26.3)
Teaching Tips
The two mechanisms by which hormones trigger changes in target cells can be compared using this analogy. If a house is like a cell, ringing the doorbell and having someone answer it is like using a signal transduction pathway. Pushing the doorbell, like a hormone binding to plasma membrane receptors, causes an internal change. Using steroid hormones, on the other hand, is like walking up to the house, opening the door, and walking inside to deliver a message. Here the signal passes through the surface and into the interior of the home/cell to directly communicate the message. (26.2)

6. 26.2 Hormones affect target cells using two main signaling mechanisms
Based on chemical properties, hormones can be classified into two groups.
The ___________-soluble hormones include polypeptides (proteins) and some modified versions of single amino acids. Most hormones produced by the endocrine glands are water-soluble.
The __________-soluble hormones include the steroid hormones, small molecules made from cholesterol.
Student Misconceptions and Concerns
Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies on a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. (26.1–26.3)
Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. (26.1–26.3)
Teaching Tips
The two mechanisms by which hormones trigger changes in target cells can be compared using this analogy. If a house is like a cell, ringing the doorbell and having someone answer it is like using a signal transduction pathway. Pushing the doorbell, like a hormone binding to plasma membrane receptors, causes an internal change. Using steroid hormones, on the other hand, is like walking up to the house, opening the door, and walking inside to deliver a message. Here the signal passes through the surface and into the interior of the home/cell to directly communicate the message. (26.2)

7. 26.2 Hormones affect target cells using two main signaling mechanisms
Water-soluble hormones cannot pass through the phospholipid bilayer of the plasma membrane, but they can bring about cellular changes without entering their target cells.
Student Misconceptions and Concerns
Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies on a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. (26.1–26.3)
Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. (26.1–26.3)
Teaching Tips
The two mechanisms by which hormones trigger changes in target cells can be compared using this analogy. If a house is like a cell, ringing the doorbell and having someone answer it is like using a signal transduction pathway. Pushing the doorbell, like a hormone binding to plasma membrane receptors, causes an internal change. Using steroid hormones, on the other hand, is like walking up to the house, opening the door, and walking inside to deliver a message. Here the signal passes through the surface and into the interior of the home/cell to directly communicate the message. (26.2)

8. Animation: Water-Soluble Hormone
© 2018 Pearson Education, Inc.

9. 26.2 Hormones affect target cells using two main signaling mechanisms
Lipid-soluble hormones, such as steroid hormones,
pass through the phospholipid bilayer and
bind to receptors inside the cell.
What is similar between the water soluble and the lipid soluble pathways?
Student Misconceptions and Concerns
Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies on a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. (26.1–26.3)
Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. (26.1–26.3)
Teaching Tips
The two mechanisms by which hormones trigger changes in target cells can be compared using this analogy. If a house is like a cell, ringing the doorbell and having someone answer it is like using a signal transduction pathway. Pushing the doorbell, like a hormone binding to plasma membrane receptors, causes an internal change. Using steroid hormones, on the other hand, is like walking up to the house, opening the door, and walking inside to deliver a message. Here the signal passes through the surface and into the interior of the home/cell to directly communicate the message. (26.2)

10. Animation: Lipid-Soluble Hormone
© 2018 Pearson Education, Inc.

11. 26.4 The vertebrate endocrine system consists of more than a dozen major glands
Some endocrine glands primarily secrete hormones into the blood.
Examples- ____________________________________
Other glands have endocrine and nonendocrine functions.
Other organs (such as the stomach and heart) are primarily nonendocrine but have some cells that secrete hormones.
Example- some stomach cells secrete Gastrin (when food is in the stomach) to signal other cells to produce and release enzymes for digestion
Student Misconceptions and Concerns
Appreciating the precise actions of hormones requires a thorough understanding of the specificity of target cells. The fact that only certain target cells will respond to a given hormone signal allows hormones to be “broadcast” generally throughout the circulatory system without affecting every single cell. (26.4)
Teaching Tips
Students who have an especially difficult time waking up on a cloudy day may be feeling the prolonged effects of melatonin. Bright light suppresses melatonin levels. On cloudy days, and in northernmost parts of North America, when winters are very dark, it can be difficult to feel fully awake. (26.4)
Growth hormone levels typically decline as we age. Recent studies suggest that injections of engineered human growth hormone may promote muscle growth and decrease body fat. However, additional research is necessary to fully appreciate the benefits and potential risks of human growth hormone injections in the elderly. (26.4–26.5)

12. 26.4 The vertebrate endocrine system consists of more than a dozen major glands
The following figure shows
the locations of the major endocrine glands and
the main hormones they produce.
Student Misconceptions and Concerns
Appreciating the precise actions of hormones requires a thorough understanding of the specificity of target cells. The fact that only certain target cells will respond to a given hormone signal allows hormones to be “broadcast” generally throughout the circulatory system without affecting every single cell. (26.4)
Teaching Tips
Students who have an especially difficult time waking up on a cloudy day may be feeling the prolonged effects of melatonin. Bright light suppresses melatonin levels. On cloudy days, and in northernmost parts of North America, when winters are very dark, it can be difficult to feel fully awake. (26.4)
Growth hormone levels typically decline as we age. Recent studies suggest that injections of engineered human growth hormone may promote muscle growth and decrease body fat. However, additional research is necessary to fully appreciate the benefits and potential risks of human growth hormone injections in the elderly. (26.4–26.5)

13. 26.5 The hypothalamus, which is closely tied to the pituitary, connects the nervous and endocrine systems
The hypothalamus
is the main control center of the endocrine system,
receives information from nerves about the external environment & the internal condition of the body,
responds by sending out appropriate nervous or endocrine signals, &
directly controls the pituitary gland, which in turn secretes hormones that influence numerous body functions.
Student Misconceptions and Concerns
The abuse of growth hormones and steroids is of great concern in the world of professional and amateur sports. Although this is mentioned briefly in the text, consider emphasizing further the potential negative consequences of the abuse of these powerful hormones. The National Institutes of Health provides additional details on its website at (26.5)
Teaching Tips
Growth hormone levels typically decline as we age. Recent studies suggest that injections of engineered human growth hormone may promote muscle growth and decrease body fat. However, additional research is necessary to fully appreciate the benefits and potential risks of human growth hormone injections in the elderly. (26.4–26.5)

14. 26.5 The hypothalamus, which is closely tied to the pituitary, connects the nervous and endocrine systems
The pituitary gland consists of two parts:
The posterior pituitary stores and secretes two hormones synthesized in the hypothalamus.
The anterior pituitary is an endocrine gland that synthesizes and secretes hormones.
Student Misconceptions and Concerns
The abuse of growth hormones and steroids is of great concern in the world of professional and amateur sports. Although this is mentioned briefly in the text, consider emphasizing further the potential negative consequences of the abuse of these powerful hormones. The National Institutes of Health provides additional details on its website at (26.5)
Teaching Tips
Growth hormone levels typically decline as we age. Recent studies suggest that injections of engineered human growth hormone may promote muscle growth and decrease body fat. However, additional research is necessary to fully appreciate the benefits and potential risks of human growth hormone injections in the elderly. (26.4–26.5)

15. Neurosecretory
cell of
hypothalamus
The pituitary gland is often called the master gland because it controls several other hormone glands in your body
Blood
vessel
Releasing hormones
from hypothalamus
Endocrine cells of
the anterior pituitary
Pituitary hormones
Figure 26.5c Hormones of the anterior pituitary
TSH
ACTH
FSH
and LH
Prolactin
(PRL)
Growth
hormone
(GH)
Thyroid
Adrenal
cortex
Testes or
ovaries
Mammary
glands
(in mammals)
Entire
body

16. Negative Feedback Hypothalamus Inhibition TRH Anterior pituitary
TSH
Figure 26.5e Control of thyroid hormone secretion
Thyroid
Thyroid hormone

17. 26.6 The thyroid regulates development and metabolism
The thyroid gland is located in the neck, just under the larynx (voice box).
Thyroid hormones regulate many aspects of
metabolism, reproduction, and
development, including the profound reorganization of body tissues that occurs in a tadpole.
Student Misconceptions and Concerns
Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. (26.6–26.12)
As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. (26.6–26.12)
Teaching Tips
Hypothyroidism produces symptoms that are like turning down a furnace during a cold winter. When thyroid levels are low, cells produce ATP and heat at a slower rate, and the person feels colder and is more lethargic than others in the same room. This reminds students that aerobic respiration produces heat and ATP. Hyperthyroidism is just the opposite, with an overproduction of heat as the consequence. (26.6)

18. 26.6 The thyroid regulates development and metabolism
Thyroid imbalance can cause disease.
Hyperthyroidism leads to high blood pressure, loss of weight, overheating, and irritability.
Hypothyroidism leads to low blood pressure, being overweight, and often feeling cold and lethargic.
Iodine deficiency can produce a goiter, an enlargement of the thyroid.
20 million people (5-6%) in the US have some type of thyroid disease.
Student Misconceptions and Concerns
Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. (26.6–26.12)
As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. (26.6–26.12)
Teaching Tips
Hypothyroidism produces symptoms that are like turning down a furnace during a cold winter. When thyroid levels are low, cells produce ATP and heat at a slower rate, and the person feels colder and is more lethargic than others in the same room. This reminds students that aerobic respiration produces heat and ATP. Hyperthyroidism is just the opposite, with an overproduction of heat as the consequence. (26.6)

19. 26.7 The gonads secrete sex hormones
Sex hormones play a role in growth and development.
Reproductive cycles and sexual behavior are also regulated by sex hormones.
Estrogens, progesterone, and androgens (including testosterone) are steroid sex hormones produced by the gonads in response to signals from the hypothalamus and pituitary.
Student Misconceptions and Concerns
Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. (26.6–26.12)
As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. (26.6–26.12)
Teaching Tips
In humans, differences in the concentrations of sex hormones decrease between the sexes in late adulthood. Differences in secondary sexual characteristics such as muscle tone and hair growth may diminish as a natural part of aging. Students with interests in geriatrics may enjoy assignments or extra credit to investigate this topic. (26.7)
Active Lecture Tips
See the Activity “Applying Understanding of Female Hormones to Birth Control” on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. (26.7)

20. 26.8 Pancreatic hormones regulate blood glucose level
The pancreas is a gland with dual functions.
It secretes digestive enzymes into the small intestines.
It secretes two protein hormones, insulin and glucagon, into the blood.
Insulin and glucagon are said to be antagonistic hormones because the effects of one oppose the effects of the other.
The balance in secretion of insulin and glucagon maintains a homeostatic “set point” of glucose.
Student Misconceptions and Concerns
Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. (26.6–26.12)
As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. (26.6–26.12)
Teaching Tips
Unlike most refrigerators, many laboratory incubators maintain internal temperatures in a very narrow range by having separate heating and cooling systems that kick in quickly when temperatures get above or below the set point. These dual negative feedback systems are similar to the dual feedback systems that maintain a stable blood glucose level. (26.8)

21. © 2018 Pearson Education, Inc.

22. 26.9 Diabetes is a common and serious endocrine disorder
Diabetes mellitus is caused by the body’s inability to _________ or ______insulin, thereby decreasing the absorption of glucose from the blood, thereby elevating blood glucose level. (Hyperglycemia)
Over-active beta cells secrete too much insulin into the blood when sugar is eaten & blood glucose level can below normal. (Hypoglycemia)
Student Misconceptions and Concerns
Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. (26.6–26.12)
As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. (26.6–26.12)
Teaching Tips
Scientists are exploring the use of pancreatic cell transplants as a new source of insulin for patients with type 1 diabetes. Pancreatic cells may be derived from donors and/or modified from other cells using stem cell technology. One website devoted to this subject is (26.9)
Active Lecture Tips
See the Activity “Using Diabetes as the Story to Discuss the Secretory Pathway of Proteins” on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. (26.9–26.10)

23. 26.10 The adrenal glands mobilize responses to stress
Nerve signals from the hypothalamus stimulate the adrenal medulla to secrete epinephrine and norepinephrine, which quickly trigger the “fight-or-flight” response.
ACTH from the pituitary causes the adrenal cortex to secrete glucocorticoids and mineralocorticoids, which boost blood pressure and energy in response to long-term stress.
Student Misconceptions and Concerns
Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. (26.6–26.12)
As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. (26.6–26.12)
Teaching Tips
The effects of the “fight-or-flight” response will likely last many minutes after the initial events that triggered the response. Telling a person with this response to calm down is unlikely to help. Instead, removing the person from the stimulus (if possible), having the person engage in mild exercise such as walking, and allowing many minutes of time will more likely reverse the condition. (26.10)
The authors mention that glucocorticoids may be used to relieve pain from athletic injuries. Students may not have carefully considered the benefits of pain. Consider emphasizing the adaptive nature of pain to your class. (26.10)
Active Lecture Tips
See the Activity “Using Diabetes as the Story to Discuss the Secretory Pathway of Proteins” on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. (26.9–26.10)

24. 1 3 4 5 2 Effects of mineralocorticoids Effects of glucocorticoids
Stress from physical
threat, cold exposure,
or exercise
Stress from low blood sugar
or decreased blood volume
or blood pressure
Adrenal
medulla
Adrenal
gland
Nerve
Adrenal
cortex 1
signals
Hypothalamus 3
Kidney
Releasing hormone
Cross section of
spinal cord
Anterior pituitary
Nerve cell
Blood vessel 4
Nerve cell
ACTH
Adrenal cortex 5
Adrenal medulla
ACTH 2
Mineralocorticoids
Glucocorticoids
Epinephrine and
norepinephrine
Effects of epinephrine and norepinephrine
Effects of
mineralocorticoids
Effects of
glucocorticoids
Figure How the adrenal glands control our responses to different stressful stimuli
Glycogen broken down to glucose; increased blood glucose
Retention of sodium ions and water by kidneys
Proteins and fats broken down and converted to glucose, leading to increased blood glucose
Increased blood pressure
Increased breathing rate
Increased metabolic rate
Increased blood volume and blood pressure
Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity
Immune system may be suppressed

25. You should now be able to
Define endocrine disruptors and give two common examples.
Compare the mechanisms and functions of the endocrine and nervous systems.
Distinguish between the two major classes of vertebrate hormones.
Name and describe the functions of the major vertebrate endocrine organs (hypothamus, pituitary, thyroid, gonads, pancreas, adrenals)
Know the origin and function of these hormones: epinephrine, norepinephrine, insulin, glucagon, oxytocin,& antidiuretic hormone.
Describe the interrelationships between the hypothalamus and pituitary glands , and other glands.
Describe the types, causes, and symptoms of diabetes.

26. Master control center of the endocrine system
Figure 26.UN03
Brain
Hypothalamus:
Master control center of the endocrine system
Anterior pituitary:
Composed of endocrine tissue
Controlled by hypothalamus
Posterior pituitary:
Composed of nervous tissue
Produces and secretes its own hormones
Stores and secretes hormones made by hypothalamus
Figure 26.UN03 Reviewing the concepts, 26.5

27. Internal communication and regulation
Figure 26.UN05
Internal communication and regulation
vertebrate systems
responsible are
endocrine system
(a)
signals used are
signals used are primarily
(b)
electrical
are secreted
into the
are produced by
bloodstream
(e)
Figure 26.UN05 Connecting the concepts, question 1
and bind with
such as
(c)
(f)
(g)
under the
control of the
producing hormones
involved in
located either
on target cell
surfaces
“fight-or-flight”
response
(d)
hypothalamus