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The Endocrine System. Communication throughout the body. What is the endocrine System? . It is one of the 2 regulatory systems in the human body It is made up of endocrine glands that secrete chemical messengers called hormones - PowerPoint PPT Presentation
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The Endocrine SystemCommunication throughout the body
What is the endocrine System? • It is one of the 2 regulatory systems
in the human body• It is made up of endocrine glands
that secrete chemical messengers called hormones
• Hormones travel through the blood allowing communication through all parts of the body
Jobs of the Endocrine System• Regulation of metabolism and tissue
maturation• Regulation of ion concentrations in
the blood• Maintaining water balance• Helps control production of immune
cells• Helps control heart rate and blood
pressure
. . . Still more!• Controls blood glucose and other
nutrients• Controls reproductive functions• Regulates uterine contractions and
milk production
What is an endocrine gland?• They are ductless organs that secrete their
hormones directly into the blood• Hormones cause a response in other cells, called
target cells, but only if the other cells have receptors.
Are there different types of hormones?• Yes!• There are two major categories:• Steroid hormones (lipid soluble)• Protein or peptide hormones (water soluble)
Steroid Hormones• Can pass through the cell membrane• Have receptor molecules inside the
cell• Usually take a longer period of time
to act• Can be reproductive hormones• Can be taken orally because they will
pass through the stomach walls
Protein Hormones• Cannot cross the cell membranes• Need receptor molecules on the
outside of target cells• Usually act very quickly• Cannot be taken orally because they
cannot pass through the stomach wall and will be digested
• A small amount can have a very big affect due to signal amplification
How do Steroid Hormones Work?• 1. They pass through the cell membrane• 2. They bind a receptor in the cytoplasm of a
target cell• 3. The receptor/Hormone complex enters the
nucleus• 4. Gene expression is started and new gene
products are formed
How do Protein hormones work?• 1. The water-soluble hormone binds a receptor
on the outside of the cell membrane• 2. A G protein activates an enzyme (adenylate
cyclase)• 3. This causes a series of intracellular changes
that can amplify the original signal• 4. Intracellular changes result in a change in
productivity, enzyme activation, gene expression, cell shape, or cell motion
How are Hormones controlled?• The Pituitary gland is the “master gland” that
controls the endocrine system• The pituitary gland is controlled by its close
neighbor, the hypothalamus (part of the nervous system)
Two types of feedback:Negative:• Used to maintain
values in a normal range
• Maintains homeostasis• Ex: Insulin and
glucagon keep blood glucose levels constant
Positive:• Used to break
homeostasis• Levels of hormones
cause more hormone to be produced.
• Ex: Oxytocin in child birth causes stronger and stronger contractions