The Endocrine System

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The Endocrine System

• Short and Long Term Modulation

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Lecture Highlights

• The nature of hormones
• Hormones in insects
• The importance of negative biofeedback
• How hormones work at the cellular level
• Survey of major endocrine glands
• The interplay of hormones the human female
  reproductive system

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The Nature of Hormones

• Hormones are chemical messengers that are
  composed of large steroids or proteins
• Their molecules have high stability which
  prevents them from readily being broken down
• Hormones are produced by endocrine glands and
  travel via the blood stream rather than through a
  separate system of ducts

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The Nature of Hormones Contd.

• The hypothalamus of the brain plays the lead role
  in the deployment of hormones
• The hypothalamus directs the pituitary gland to
  produce chemical signals that reach various
  glands
• These glands then produce their own hormones that
  travel to target cells
• A negative biofeedback system operates to control
  hormone production

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Lets See How this Chain of Command Works by
Reviewing the Process of Water Retention in the
Kidney
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Lecture Highlights

• The nature of hormones
• Hormones in insects
• The importance of negative biofeedback
• How hormones work at the cellular level
• Survey of major endocrine glands
• The interplay of hormones the human female
  reproductive system

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Lets Look at a Very Well Documented Case of How
Hormones WorkHow Is Insect Metamorphosis
Controlled by Hormones?
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Lecture Highlights

• The nature of hormones
• Hormones in insects
• The importance of negative biofeedback
• How hormones work at the cellular level
• Survey of major endocrine glands
• The interplay of hormones the human female
  reproductive system

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Negative Biofeedback

• Lets review the importance of negative feedback
  in keeping the body in an optimal state through
  the process of homeostasis.

Optimum
Not so good
Not so good
Minimum level
Maximum level
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Lecture Highlights

• The nature of hormones
• Hormones in insects
• The importance of negative biofeedback
• How hormones work at the cellular level
• Survey of major endocrine glands
• The interplay of hormones the human female
  reproductive system

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How Do Hormones Work at the Cellular Level?
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Two Chemical Classes of Hormones

• Steroid-based hormones
• examples include the sex hormones estrogen,
  progesterone and testosterone
• soluble in the lipid bilayer of the cell
  membrane and easily pass thru
• escorted by protein receptors to the nucleus
  where they bind with the DNA
• gene transcription is thus altered
• a protein is produced

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Action of Steroid Hormones
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Two Chemical Classes of Hormones Contd.

• Peptide-based hormones
• examples include insulin and glucagon which
  together regulate sugar uptake and usage
• cannot enter cells but rather connect to surface
  receptor proteins that protrude thru the membrane
  into the interior
• the interior end of the protein then reacts with
  a 2nd. messenger that activates a variety of
  enzymes
• thus, we are seeing an indirect effect on cell
  activities with amplification of the chemical
  signal by the 2nd. messenger inside the cell
• examples include insulin and glucagon which
  together regulate sugar uptake and usage

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Action of Peptide Hormones
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Lecture Highlights

• The nature of hormones
• Hormones in insects
• The importance of negative biofeedback
• How hormones work at the cellular level
• Survey of major endocrine glands
• The interplay of hormones the human female
  reproductive system

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Survey of Some Human Endocrine Glands
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A Short Survey of The Major Endocrine Glands

• Pituitary gland
• Thyroid gland
• Pancreas
• Adrenal gland
• Ovary

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Central Roles of the Hypothalamus and Pituitary
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Pancreas

• Pancreatic cells produce digestive enzymes such
  as pancreatic lipase and pancreatic amylase
• The Islets of Langerhans produce the hormones
  insulin and glucagon
• When the latter cells malfunction, either early
  onset (Type I) diabetus or late onset (Type II )
  diabetus may occur

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Adrenal Gland

• Inner portion produces adrenalin which triggers
  the alarm response increased blood flow to
  heart and lungs, accelerated heartbeat, increased
  blood pressure, etc.
• Outer portion produces aldosterone which
  regulates the amount of salt in the urine

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Lecture Highlights

• The nature of hormones
• Hormones in insects
• The importance of negative biofeedback
• How hormones work at the cellular level
• Survey of major endocrine glands
• The interplay of hormones the human female
  reproductive system

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The Interplay of Hormones Human Female
Reproductive Hormones
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FINIS