Download Regulation (Endocrine)

The Endocrine System:
Another Communication Network
 The endocrine system is composed of clams that produce chemical messengers
called hormones.
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The function of this system is to help maintain homeostasis.
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Endocrine glands secrete hormones into the bloodstream or surrounding tissue.
These hormones will attach to specific receptor molecules (usually made of
protein sometimes steroid based) on the surface of cell membranes of other cells.

Target Cells -- the cells that receive the hormone. Usually located some distance
away from the gland.
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Hormones influence other cells after they have combined with a receptor protein.
Sometimes hormones attach to the proteins on the surface of the cell membrane
and sometimes they go through the cell membrane and attach with proteins in the
cytoplasm- these events will sometimes cause changes involving cellular
enzymes.
The hormone receptor complex sometimes goes into the cells nucleus and
interacts with the DNA -- affecting gene activity.

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Small amounts of hormone are usually needed to produce the required effect
because the target cells are usually sensitive.

To much of the hormone being released can be devastating to homeostasis and
can lead to permanent damage or death of the organism.
The amount of hormone released by gland is controlled by a feedback
mechanism.
Feedback mechanisms -- when the effect of the hormone causes that hormone to
stop being released. (Draw diagram)

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How are the nervous system and endocrine system different and similar?
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The nervous system and endocrine system are both communication networks.
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Messages sent by nervous system are usually rapid and cause brief changes.

Messages sent by the endocrine system are usually slower and cause longer
lasting changes.
(Examples)
The Human Endocrine System
 the nervous system and the endocrine systems are linked.

A portion of the brain called the hypothalamus receives information from blood
as it passes through.

It also receives information from nerve cells.
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The hypothalamus uses this information to control the pituitary gland.

Pituitary gland is called the Master gland because it releases hormones that
influence other endocrine glands.

When the hypothalamus detects a need for a hormone that the pituitary gland
releases it will secrete a tiny amount of the substance called releasing factor. The
pituitary gland is the target tissue for releasing factor- this will cause the pituitary
gland to release the appropriate hormone.

Adrenal gland -- located on top of each kidney. It releases a hormone called
cortisol. The adrenal gland will not release cortisol unless it receives a hormone
from the pituitary gland called ACTH.

Thyroid gland -- located in the neck. Produces a hormone that influences
metabolic rate.
Parathyroid glands -- located on the thyroid. Produces a hormone that influences
calcium metabolism.
pancreas -- located under the stomach. Produces the hormone called insulin.
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When Things Go Wrong:
Diabetes -- A Disease of the Endocrine System
Diabetes -- a disease that involves a decreased ability to use glucose.
Some types of diabetes involve the hormone called insulin.
Insulin is produced by the pancreas.
Its function is to allow glucose to enter cell membranes.
If there is no insulin the glucose cannot enter cells will accumulate in the blood.
If cells do not get glucose they will not have a source of energy and will eventually die.
Some cells can use lipids as a source of energy - the brain almost exclusively uses
glucose.
In a person without diabetes insulin allows glucose to enter the cells. When the level of
glucose in the blood becomes normal the pancreas will stop secreting insulin.
When the level of glucose increases, insulin will be released again. This is an example of
a feedback mechanism