Anatomy & Physiology Introduction to Endocrinology Name ______KEY______________________
Chapter 9 – Endocrine System – Pages 265 – 269
Date _________________ Hour ___________
1. The first great controlling system of the body is the ___nervous__________ system that is built for
speed whereas the second great controlling system is the ____endocrine____________ system that is
much slower and uses chemical messengers called __hormones________.
2. What are some of the major processes within the human body that hormones and the endocrine system
regulate?
 Reproduction
 Growth and development
 Mobilizing body defenses against stressors
 Maintain electrolyte, water, and nutrient balance of the blood
 Regulating cellular metabolism and energy balance
3. What are the major organs of the endocrine system? ___small glands found scattered around the
body, such as the: pineal gland, hypothalamus, pituitary gland, thyroid gland, parathyroid
glands, thymus gland, adrenal glands, pancreas, ovaries, and testes________________
4. Define hormone: A chemical messenger secreted by an endocrine gland into the extracellular
fluids that is responsible for specific regulatory metabolic effects on certain body parts organs.
The Basic Overview of Hormones (Sequence of Events) – Be Sure to KNOW THIS FOR QUIZ!!
 Hormones are produced by specialized cells
 Cells secrete hormones into extracellular fluids
 Blood transfers hormones to target sites
 These hormones regulate the activity of other cells
5. Although there are different hormones, all hormones fit into two chemical categories – what are they?
 Amino acid-based hormones (proteins, peptides, amines)
 Steroid hormones (lipids made from cholesterol)
6. There is another group called prostaglandins which are made from highly active __lipids_________.
7. Steroid hormones are made from what molecule? ___cholesterol____________________
8. The specific tissue or organ that is affected by a particular hormone is called a ___target____________
tissue/organ.
9. The term hormone comes from the Greek language, and means “___to arouse__________” or bring
about their effects on the body’s cells by primarily ____altering_______________ cellular activity.
10. The book list four changes that often result from the binding of a hormone to its specific target
tissue/organ. What are they?
a. Changes in plasma membrane permeability or electrical state
b. Synthesis of proteins or certain regulatory molecules (such as enzymes) in the cell
c. Activation or inactivation of enzymes
d. Stimulation of mitosis/cell division
What is the difference between activation and inactivation?


Activation = to make active, or more active
Inactivation = to make inactive, or less active
11. Despite the many functions that hormones have in the human body, there are really only two
mechanisms by which hormones trigger changes in our cells. The two mechanisms depend on whether
the hormone is steroid based or non-steroidal. Please outline the steps for each mechanism below.
a. Steroid Hormones
1. The steroid hormone diffuses through the plasma membrane of their target cells
2. enters the nucleus
3. binds to a specific receptor protein within the nucleus
4. the resulting hormone-receptor complex binds to specific sites on the cell’s DNA
5. this activates certain genes to transcribe messenger RNA (mRNA)
6. The mRNA is then translated in the cytoplasm resulting in the synthesis of new
proteins
b. Non-Steroidal Hormones
1. The hormone binds to the membrane receptor (since it is unable to enter the target
cell)
2. This sets off a series of reactions that activates an enzyme
3. This activated enzyme catalyzes a reaction that produces a second messenger molecule
(such as cyclic AMP, G proteins, calcium ions, etc.)
4. The second messenger molecule oversees additional intracellular changes that promote
the typical response of the target cell to the hormone
12. The majority of hormones are regulated in the blood via negative feedback mechanisms. Explain
hormone negative feedback below.
 In general negative feedback mechanisms causes the stimulus to decline or end.
 Hormone secretion is triggered by some internal or external stimulus.
 The resulting rising hormone levels inhibit further hormone release and also promote
responses in the target cells.
 This results in blood levels of hormones varying only within a narrow range.
13. The many different stimuli that activate the endocrine organs fall into three major categories. What are
they? Briefly describe each and provide an example.
a. __Hormonal___________ - endocrine organs are stimulated into action by other hormones
(most common type)
Example: hormones released from hypothalamus stimulate the anterior pituitary gland
to secrete its hormones
b. __Humoral____________ - changing blood levels of certain ions and nutrients stimulate
hormone release (humor = ancient term for body fluids)
Example: low blood calcium levels trigger release of parathyroid hormone (PTH) from
parathyroid glands
c. __Neural______________ - nerve fibers stimulate the release of hormones
Example: sympathetic nervous system stimulation of the adrenals glands to release
epinephrine/adrenaline during periods of stress
The following questions will not be found specifically in chapter 9. Use the glossary, index, or Google
to help you find these.
14. Define homeostasis: A state of body equilibrium or stable internal environment of the body.
(textbook glossary)
Homeostasis, any self-regulating process by which biological systems tend to maintain stability
while adjusting to conditions that are optimal for survival. If homeostasis is
successful, life continues; if unsuccessful, disaster or death ensues.
15. Homeostasis is dynamic. What does this mean?
The stability attained is actually a dynamic equilibrium, in which continuous change occurs yet
relatively uniform conditions prevail.
(from: http://www.britannica.com/science/homeostasis)
16. What is a stimulus? An excitant or irritant; a change in the environment producing a response.
17. What is the basic explanation of the difference between a negative feedback system and a positive
feedback system?
Negative feedback mechanisms generally oppose or reverse the initial change that is occurring;
thus causing the change to decline or end.
Positive feedback mechanisms tend to cause a variable to change in the same direction as the
initial change; thus enhancing the stimulus
18. For each of the following, indicate whether it would be true of a negative feedback system (Neg) or a
positive feedback system (Pos):
a. __Neg___ returns the controlled condition to normal
b. __Pos___ can trigger “run-away” systems that can be life-threatening
c. __Pos___ reinforces the initial change in the controlled condition
d. __Neg___ regulate conditions in the body that are fairly stable over long periods of time
e. _Pos___ reinforce conditions that don’t happen very often
f. _Neg___ examples: blood pressure, body temperature,
blood sugar
g. _Pos___ examples: blood clotting, childbirth, ovulation
h. _Neg___ reverses the effect of a stimulus
i. _Neg___ restores homeostasis
j. _Pos___ often produced by diseases
Hypothalamus
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands
Thymus gland
Adrenal glands
19. Label the various endocrine glands on the diagram to the right.
Pancreas
Ovary (female)
Testis (male)