Download Chapter 45 Student Guided Notes

Chapter 45  Hormones and the Endocrine System
Student Guided Notes
Overview: The Body’s Long-Distance Regulators

An animal hormone is a chemical signal that is secreted into the ______________________________,
circulates in the ________________________ or _____________________________, and
communicates regulatory messages within the body.
○ A hormone may reach all parts of the body, but only specific __________________ cells have the
receptors that enable a response.

_____________________________________________________________ is the function of the
endocrine system, one of two basic systems for ___________________________________________
throughout the body. This system has slower communication as compared to the nervous system.

The other major communication and control system is the ________________________________, a
network of specialized cells called ________________________ that ___________________________
____________________________________________________. This system is for high speed signals.
Concept 45.1 Hormones and other signaling molecules bind to target receptors, triggering specific
response pathways.

Hormones are secreted into extracellular fluids and reach target cells via the _____________________.

Endocrine (hormone) signaling maintains ________________________________, mediates responses
to environmental stimuli, and regulates growth and development.

Local regulators are chemical signals that act over __________________________________, reaching
their target cells by _________________________. Examples include: growth factors, prostaglandins
and nitric oxide.

Local regulators can act on their target cells within ____________________ or ___________________,
eliciting responses more quickly than hormones can.

Local regulators are divided into _________________________ and _____________________ signals.
○ ____________________________ signals act on cells ____________________________________
_______________________________________.
○ Autocrine signals are secreted regulators that act on ______________________________________.

__________________________________ (PGs) are modified fatty acids, first discovered in prostategland secretions.
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
Released by many types of cells into interstitial fluids, PGs regulate nearby cells in various ways,
depending on the tissue.
○ In semen that reaches the female reproductive tract, PGs trigger the _________________________
______________________________________________________, helping sperm to reach the egg.
○ PGs secreted by the placenta cause the uterine muscles to become more excitable, helping to induce
uterine contractions during childbirth.
○ ____________________ and ________________________ can inhibit the effects of prostaglandins.

Growth Factors are among a group of polypeptide local regulators called cytokines, which play a role
in immune responses, which stimulate cell proliferation and differentiation in target cells.

Nitric oxide (a gas) is another important local regulator; highly reactive and potentially toxic; triggers
change in target cells for a few seconds and then rapidly breaks down; serves as a neurotransmitter and
local regulator.
○ Secreted by neurons = acts as a neurotransmitter
○ Secreted by WBC’s = kills bacteria and certain cancer cells
○ Secreted by endothelial cells in blood vessels = causes smooth muscles to relax thus dilating the
blood vessels

In synaptic signaling, neurons form _____________________________________________________
_______________________________________, such as ______________________________ and
___________________________________.
○ At synapses, neurons secrete molecules called __________________________________, which
diffuse a very short distance to _______________________________________________________.

In neuroendocrine signaling, specialized neurons called _____________________________ cells
secrete chemical signals that ____________________________________________________________
___________________________________.
○ These signals are a class of hormones called ________________________________.
○ One example is ADH (__________________________________________, or vasopressin), a
hormone critical to ______________________________ and ______________________________.
○ Endocrine glands secrete hormones directly into the surrounding fluid; they are ductless because
they secrete the hormones directly into the body fluids (blood).
○ In contrast, exocrine glands, such as salivary glands, have ducts that secrete substances (ex. Sweat,
mucous, digestive enzymes) onto body surfaces or into body cavities.
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Epinephrine is an example of a water-soluble hormone.
 A water-soluble hormone binds to a _______________________________, triggering events at the
__________________________________________ that result in a cellular response such as enzyme
activation, uptake or secretion of a molecule, or _____________________________________________.
 Signal Transduction Pathway 
○ Reception = signal molecule binds to a receptor protein
○ Signal Transduction = causes a change in the target/receptor cell
○ Response = change in the receptor cells behavior
 In response to a stressful situation, the ______________________ gland secretes ___________________
(_________________________.)
○
Affects the heart and metabolic rate; acts as a neurotransmitter, and is a good example of how the
endocrine and nervous systems are chemically linked
o
Nervous system = neurotransmitter
o
Endocrine system = “fight or flight” hormone
Many hormones have multiple effects.
 Many hormones elicit many different responses in the body, depending on the target cell. (SAME signal
= DIFFERENT responses…depending on action of target cell)
 Target cells may differ in the molecules that receive, transduce, or act upon the hormone signal.
 Only small amounts of regulators (ex. hormones) are necessary because the pathway triggers enzyme
cascades that can greatly amplify the signal.
Concept 45.2 Feedback regulation and coordination with the nervous system are common in endocrine
signaling.

A tropic hormone targets other endocrine glands.
A feedback loop connecting the response to the initial stimulus is characteristic of BOTH control pathways.

The response pathway for many hormones involves negative feedback, a loop in which the response
_____________________________________________. This feedback mechanism is used the majority
of the time and allows hormones to control homeostasis (ESPECIALLY important in homeostasis!)
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
Unlike negative feedback, which dampens a stimulus, positive feedback _______________________
_________________, leading to __________________________________________. Example:
____________________________ pathways 
○ In response to circulating oxytocin, the mammary glands secrete milk. Milk released in response to
oxytocin leads to more suckling and therefore more stimulation. Activation of the pathway is
sustained until the baby stops suckling.

While positive feedback amplifies _______________________________________________, negative
feedback _________________________________________________________________.
Homeostatic control systems may rely on pairs of negatively regulated hormone pathways, each
counterbalancing the other.
SEE FIGURE 45.9 p. 999 Human Endocrine Glands and Hormones
PANCREAS

The pancreas secretes bicarbonate ions to balance the pH from the acid chime in the stomach.

Insulin and glucagon are antagonistic hormones that regulate the concentration of glucose in the blood.

Alpha cells in the pancreas make GLUCAGON, and beta cells make INSULIN.

Both insulin and glucagon are protein hormones made of amino acids, NOT steroids.
○ When the blood glucose concentration exceeds the set point, insulin is released and triggers uptake
of glucose from the blood into body cells, ____________________________ blood glucose.
○ When the blood glucose concentration falls below the set point, glucagon is released and promotes
release of glucose into blood from liver glycogen, ____________________________ blood glucose.

Each hormone operates in a simple endocrine pathway regulated by negative feedback.

Diabetes mellitus is caused by a deficiency of insulin or a decreased response to insulin in target
tissues.
○ In people who have diabetes, blood glucose levels rise, but cells are unable to take up enough
glucose to meet their metabolic needs.

Type 1 diabetes (insulin-dependent diabetes)  an autoimmune disorder in which the immune system
destroys the beta cells of the pancreas (so you can’t make insulin!).
○ Type I diabetes usually appears in childhood and destroys the person’s ability to produce insulin.
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
Type 2 diabetes (non-insulin-dependent diabetes)  characterized by decreased responsiveness to
insulin in target cells because of some change in insulin receptors.
○ This form of diabetes occurs after age 40, and the risk increases with age.
○ Although heredity can play a role in type 2 diabetes, excess body weight and lack of exercise
significantly increase the risk.
○ Type 2 diabetes accounts for more than 90% of diabetes cases.
HYPOTHALMUS

In vertebrates, the hypothalamus (part of the lower brain) integrates vertebrate endocrine and nervous
functions.
○ A good example of how the two systems are structurally related is the neurosecretory cells located
in the hypothalamus (SEE BELOW).
○ One of several endocrine glands located in the brain, the hypothalamus receives information from
nerves throughout the body and brain.
○ In response, it initiates endocrine signals appropriate to environmental conditions.

The hypothalamus regulates the ____________________________________ located at its base.

Although the pituitary is called the “master gland”, it takes its orders from the hypothalamus!

Neurosecretory cells of the hypothalamus synthesize two hormones: _______________________ and
_____________________________________________________.
○ These hormones travel to the posterior pituitary, where they are stored and released in response to
nerve impulses transmitted by the hypothalamus.
POSTERIOR PITUITARY (SEE FIGURE 45.14 p. 1002)

The posterior pituitary is an extension of the hypothalamus.

Posterior pituitary hormones are made by the hypothalamus but secreted by the posterior pituitary; these
hormones act on specific structures rather than affecting other endocrine glands.

Oxytocin regulates __________________________________ by the mammary glands and
_____________________________________________________________ during birthing.
○ Oxytocin also influences behaviors related to ___________________________________________
_______________________________________________________________________________.

Antidiuretic hormone (ADH) also regulates both physiology and behavior.
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○ ADH acts on the _________________________ to increase their _____________________
____________________, thus decreasing urine volume and regulating ___________________
_____________________________.
ANTERIOR PITUITARY (SEE FIGURE 45.15 p. 1003)

The anterior pituitary is an endocrine gland that synthesizes and secretes hormones.
○ Secretion of each hormone by the anterior pituitary is regulated by one or more signals from the
hypothalamus.

Endocrine signals generated by the hypothalamus regulate hormone secretion by the anterior pituitary.

Prolactin (PRL) stimulates mammary gland growth and ______________________________ and
secretion in mammals.
○ PRL also regulates fat metabolism and reproduction in birds, delays metamorphosis in amphibians,
and regulates salt and water balance in freshwater fishes.
○ These varied roles suggest that prolactin is an ancient hormone whose functions have diversified
during the evolution of vertebrate groups.

Thyroid Stimulating Hormone (TSH)
○ TSH acts on the ____________________ gland to stimulate the release of __________________
_________________________.
○ Thyroid hormone increases the _________________________________, raising body temperature.

Follicle-stimulating hormone (FSH) and Lutenizing Hormone (LH) are also called gonadotropins
because they stimulate the activities of the gonads.

FSH stimulates production of ova and sperm

LH stimulates ovaries and testes
SEE LATER NOTES ON SEX HORMONES

__________________________________________________ hormone (ACTH) stimulates the
production and secretion of steroid hormones by the adrenal cortex.

Growth hormone (GH) acts on a wide variety of target tissues.
○ The major tropic action of GH is to signal the liver to release ______________________________
_________________, which circulate in the blood and directly stimulate bone and cartilage growth.

Abnormal production of GH can produce several disorders.
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○ Gigantism is caused by ______________________ (excessive GH production) during development.
○ __________________________________________ is caused by childhood GH hyposecretion and
can be treated successfully by genetically engineered GH.

_____________________________________________________ (MSH) regulates the activity of
pigment-containing cells in the skin of fishes, amphibians, and reptiles; has a role in fat metabolism
THYROID

Thyroid hormone increases the metabolic rate, raising body temperature.

An insufficient amount of thyroid hormones is known as ___________________________________,
producing symptoms such as ___________________________, _________________________, and
intolerance to _________________ in adults.

_______________________________________ is the excessive secretion of thyroid hormones, leading
to high _____________________________________, profuse ___________________, ____________
__________________________, irritability, and ___________________________________________.

The term thyroid hormone (TRH) refers to a pair of very similar hormones derived from the amino acid
tyrosine:
○ ________________________________________ (T3)  contains __________________________
○ __________________________________ (T4)  contains ________________________________;
this hormone stimulates and maintains metabolic processes

The thyroid gland secretes mainly T4, but target cells convert most of it to T3 by removing one iodine
atom.

All vertebrates require thyroid hormones for normal functioning of _____________________________
cells and branching of nerve cells during __________________________________________________.

Calcitonin which works antagonistically with parathyroid hormone (PTH) is also produced by the
thyroid. Its job is to _________________________ calcium levels in the blood.
Concept 45.3 Endocrine glands respond to diverse stimuli in regulating homeostasis, development, and
behavior.

Rigorous homeostatic control of blood calcium levels is critical because calcium ions (Ca2+) are
essential to the normal functioning of all cells (ex. skeletal muscle contraction.)
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PARATHYROID

The parathyroid glands, a set of ______________________________________________________
_______________________________________________, play a major role in blood Ca2+ regulation.

Parathyroid hormone (PTH) is released when the blood Ca2+ concentration falls ________________
the set point, and the level of blood calcium is ____________________.

As the blood Ca2+ level rises, a _______________________ feedback loop inhibits _______________
___________________________________________________________________________________.

Calcitonin is released by the thyroid if the blood Ca2+ level rises ___________________ the set point,
and the level of blood calcium is ______________________________ (because it inhibits bone
resorption and enhances Ca2+ release by the kidney.)

Calcitonin and PTH are antagonistic hormones and work together to regulate the calcium levels in the
blood (example of homeostasis).
ADRENAL GLANDS
Adrenal hormones coordinate the response to stress.

The adrenal glands are located adjacent to the ______________________.
○ The ___________________________________ is the outer portion, and the _________________
____________________________ is the central portion.
ADRENAL MEDULLA

The adrenal medulla produces two hormones: ___________________________________________and
________________________________________________.
○ Both hormones are also neurotransmitters in the nervous system.

Either positive OR negative stress stimulates the secretion of epinephrine and norepinephrine from the
adrenal medulla.

These hormones act directly on several target tissues to give the body a rapid bioenergetic boost.
○ They increase the rate of _________________________________________ in the ______________
and ____________________________________, promote glucose release into the blood by
_______________________________, and stimulate the release of _________________________
from fat cells.
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
Epinephrine and norepinephrine also exert profound effects on the ______________________________
and ___________________________________ systems.

Epinephrine (which acts as a neurotransmitter) generally has a stronger effect on _____________
and ____________________________________, while the primary role of norepinephrine is in
__________________________________________________. (Think epi pen when a person is
in anaphylactic shock)

Epinephrine is a good example of how the endocrine and nervous system are chemically related
ADRENAL CORTEX

Hormones from the adrenal cortex also function in the body’s response to stress.
○ In contrast to the adrenal medulla, which reacts to nervous input, the adrenal cortex responds
to endocrine signals.

The hypothalamus release ACTH which reaches the adrenal cortex and stimulates the endocrine cells to
synthesize and secrete a family of steroids called ___________________________________.

The two main types of corticosteroids in humans are ___________________________________ and
____________________________________________.

Both hormones help maintain homeostasis when stress is experienced over a long period of time.

Glucocorticoids have a primary effect on bioenergetics, specifically on _________________________
________________________.
○ Increases glucose in the blood.
○ In response to stress, glucocorticoids make more glucose available as fuel AND helps make glucose
from non-carbohydrate sources such as fats and proteins  this helps in long term environmental
issues

Mineralocorticoids act principally on ____________________________________________________.

SEE FIGURE 45.20 p. 2007
***Both glucocorticoids and mineralocorticoids help deal with long term stress as opposed to
epinephrine and norepinephrine that work on short term stress.***
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GONADS
Sex hormones regulate growth, development, reproductive cycles, and sexual behavior.

The gonads are the primary source of the sex hormones, producing and secreting three major categories
of steroid hormones: _____________________, _________________________, and ______________.
○ All three types are found in both males and females but in _________________________________.
○ Their secretion is controlled by gonadotropins (FSH and LH) from the ________________________
__________________ gland.

Androgens (eg. testosterone) are synthesized by the _____________________.
○ Androgens promote the development and maintenance of male sex characteristics.
○ Androgens produced early in development determine whether a fetus develops as a male or a female.
○ At puberty, high levels of androgens are responsible for the development of ____________________
__________________________________________________________, including male patterns of
hair growth, a _______________ voice, and increased _______________________ mass and
_________________ mass typical of males.

Estrogens (eg. estradiol) are synthesized by the ovaries, and are responsible for the development and
maintenance of the ___________________________________________________________ and the
development of female secondary sex characteristics.

In mammals, progestins, which include progesterone, promote the growth of the uterine lining
(maintains the uterus!), which supports the growth and development of __________________________.
PINEAL GLAND

The pineal gland is a small mass of tissue _________________________________________________
________________ that is a primary source of the hormone melatonin, a ________________________
___________________________________.

The primary functions of melatonin are related to biological clock rhythms associated with reproduction
and activity.

Melatonin secretion is regulated by light/dark cycles.
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