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Lesson 10
Endocrine System
Warm - Up
1. What is a gland? Use a device to define the two
major types of glands.
2. Where do you suppose most endocrine glands
are located in your body?
Learning Goals
Define hormones and classify them as steroid
and water-soluble
Identify feedback inhibition role in hormone
production and release
identify the major endocrine organs in the
human body
The Endocrine System
The body systems that facilitate
cellular communication and control
are the nervous and endocrine
systems.
Endocrine glands secrete chemical
messengers called hormones
directly into the bloodstream.
Together, the glands and hormones
make up the endocrine system. It
has slower and longer acting effects
compared to the rapid actions of the
nervous system.
Endocrine Glands
Over 200 different hormones or
hormone-like chemicals in the human
body are secreted by endocrine glands.
Glands that function exclusively as
endocrine glands are the pituitary,
pineal, thyroid, parathyroid, and
adrenal glands.
Tissues and organs that secrete
hormones but also have other functions
are the hypothalamus, thymus,
pancreas, testes, and ovaries.
Hormones
Hormones are chemical
messengers that are carried from
the cells that secrete them to target
cells/organs. Animals accomplish
this transport through their
circulatory system.
They fall into two broad
categories:
water soluble
lipid soluble (steroids)
Secreting cells in glands of the endocrine system
release hormones into the bloodstream, through
which they are carried to target cells.
Water-Soluble Hormones (Protein)
Water-soluble hormones,
such as the amino acidbased epinephrine, bind to
receptor proteins on the
surface of the target cell.
This binding starts a
cascade of reactions inside
the target cells, amplifying
the effect of the hormones.
Lipid Based Hormones (Steroids)
Steroid hormones, such as testosterone,
estrogen, and cortisol are lipid-based
derivatives of cholesterol. They are
known as lipid-soluble hormones
because they can diffuse through the
lipid bilayer of cells.
Once steroid hormones are inside target
cells, they bind to receptor proteins,
which can activate specific genes,
causing changes in the cells such as cell
growth.
Tropic Hormones
Some hormones, called tropic
hormones, target endocrine
glands themselves and regulate
the production and release of
other hormones. These hormones
will then inhibit the release of the
tropic hormones.
The hypothalamus initiates many
of these feedback loops using
releasing hormones.
Tropic hormones act on other endocrine
glands. In these negative feedback loops, the
hormone secreted by the target gland will
affect other tissues in the body, such as the
bones and muscles
Examples of Tropic Hormones
Tropic hormones from the anterior pituitary include:
Thyroid-stimulating hormone (TSH or thyrotropin) – stimulates the thyroid gland to make and release thyroid hormone.
Adrenocorticotropic hormone (ACTH or corticotropin) – stimulates the adrenal cortex to release glucocorticoids.
Luteinizing hormone (LH) – stimulates the release of steroid hormones in gonads—the ovary and testes.
Follicle-stimulating hormone (FSH) – stimulates the maturation of eggs and production of sperm
The Pituitary Gland
Sometimes referred to as the “Master
Gland” the pituitary gland plays a large
role in regulation of other glands. It is
connected by a stalk to the
hypothalamus, and it shows a direct
link between the nervous and
endocrine systems.
Anterior and Posterior Lobes
The pituitary gland is composed of
two separate lobes. The posterior
lobe of the pituitary stores and
releases hormones such as
antidiuretic hormone (ADH) and
oxytocin, which have been produced
by the hypothalamus.
The anterior lobe produces its
own hormones, but their release is
regulated by the hypothalamus as
well.
Anterior Pituitary Hormones
Hormone
Target
Primary Function
Anterior Lobe
Thyroid Stimulating Hormone (TSH)
Thyroid Gland
Stimulates release of thyroxine from thyroid
Adrenocorticotropic Hormone (ACTH)
Adrenal Cortex
Stimulates release of corticosteroids from
Adrenal Cortex
Follicle Stimulating Hormone (FSH)
Ovaries, Testes
Stimulates follicle development in ovaries
Promotes development of sperm in testes
Luteinizing Hormone (LH)
Ovaries, Testes
Stimulates Ovulation and formation of corpus
luteum in females
Stimulates the production of testosterone in
males
Prolactin (PRL)
Mammary Glands
Stimulates and maintains milk production in
lactating females.
Growth Hormone (GH)
Most Cells
Promotes growth and cell replication
Posterior Pituitary Hormones
Hormone
Target
Primary Function
Posterior Lobe
Oxytocin
Uterus, mammary glands
Initiates strong contractions during childbirth
Triggers milk release in lactating females
Antidiuretic Hormone (ADH)
Kidneys
Increase water reabsorption by kidneys
Crash Course Hormones
Groups for Endocrine Organs
Your task will be to work with your group to summarize the
anatomy/physiology of your target organ, and any feedback loops that
regulate the release of its hormones (many involve the pituitary).
Once you have filled in the information for the chart, grab a piece of chart
paper and draw the outline of a person. Draw in your endocrine gland and
it’s target organs. Next, draw one feedback loop and add it to the chart
paper.
Table 1: Thyroid/Parathyroid
Table 2: Adrenal Medulla
Table 3: Adrenal Cortex
Table 4: Pancreas
Table 5: Sex Organs
Review
How does the endocrine system differ from the nervous system?
Name 5 different glands that are part of the endocrine system. Draw a diagram of
a person and place these glands in their correct anatomical position.
What are the differences between steroid-hormones and water soluble hormones?
How do these signalling molecules connect to the last unit of molecular genetics?
What are tropic hormones?
List one feedback loop you’ve learned about that involves hormones. What are the
hormones involved?