1. Endocrine System
Chemical Control

2. Messenger Molecules
Cells must communicate with one another to coordinate cell processes within tissues and to maintain homeostasis.
Cell-to-cell communication is carried out via messenger molecules.

3. Three types of chemical signals are used for cell-to-cell communication.

4. Four methods of cell-to-cell communication are found in the human body, ranging from direct to remote communication.

5. Endocrine hormones
Produced by endocrine (“ductless”) glands and secreted into the bloodstream.
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6. Hormones and Receptors

7. Peptide and Amino Acid Derivatives Hormones
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When the hormone binds with the receptor protein, a secondary messenger molecule initiates the cell response.

8. Hormone–receptor binding activates an enzyme that catalyzes
peptide or amino
acid-derived
hormone
(first messenger)
Hormone–receptor binding
activates an enzyme that catalyzes
the synthesis of a second messenger,
such as cyclic AMP 2
The hormone binds to
a receptor on the plasma
membrane of a target cell 1
cyclic AMP-
synthesizing
enzyme
(cytoplasm)
(extracellular
fluid)
ATP
active
enzyme
receptor
product
cyclic AMP
(second messenger) 4
The activated enzymes
catalyze specific reactions
plasma membrane
inactive
enzyme
reactant
The second
messenger activates
other enzymes 3
nuclear
envelope
(nucleus)

9. Steroid Hormones
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These hormones may directly stimulate transcription of genes to make certain proteins.

10. receptor in the nucleus or to a receptor in the cytoplasm
steroid hormone
(extracellular
fluid)
The hormone binds to a
receptor in the nucleus or to
a receptor in the cytoplasm
that carries it into the nucleus 2
The hormone–receptor
complex binds to DNA and
causes RNA polymerase to
bind to a nearby promoter
site for a specific gene 3
A steroid hormone
diffuses through the
plasma membrane 1
DNA
plasma
membrane
hormone receptor
ribosome
RNA polymerase
The mRNA leaves the
nucleus, then attaches to a
ribosome and directs the
synthesis of a specific protein
product 5
RNA polymerase catalyzes
the transcription of DNA into
messenger RNA (mRNA) 4
mRNA
new protein
gene
nuclear
envelope
(cytoplasm)
(nucleus)

11. How do endocrine hormones “know” which cells are their target cells?

12. Role of the Hypothalamus
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Hypothalamus monitors the body for temperature, pH, other conditions.

13. Role of the Pituitary
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The anterior lobe of the pituitary receives signals from the hypothalamus, and responds by sending out the appropriate hormone to other endocrine glands.
The posterior pituitary receives oxytocin or antidiuretic hormone (ADH) from the hypothalamus, relays them to the body as necessary.