Endocrine & Cell Communication Part III:
Hormonal Communication

• Enduring Understanding 3.D Cells communicate by generating, transmitting and receiving chemical signals.
• EK 3D2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling c. Signals released by one cell type can travel long distances to target cells of another cell types.
1. Endocrine signals are produced by endocrine cells that release signaling molecules, which are specific and can travel long distances through the blood to reach all parts of the body.
2

The Process of Communication:
Signal-Transduction Pathway

Typical Signal Transduction Pathway

Ligand = Chemical Messenger
• Three major classes of molecules function as hormones in vertebrates (ligands)
– Polypeptides (proteins and peptides)
– Amines derived from amino acids
– Steroid hormones
5

a molecule that binds to a larger molecule

Typical Signal Transduction Pathway

Phase 1: Reception
The target cell detects the ligand
– G-protein linked receptors
– Ion channel receptors
– Tyrosine Kinase
– Steroid hormone receptors

Type of Receptor : G-protein linked

Type of Receptor:
Intracellular Receptor

Name three types of receptors in the signal transduction pathway
•
•
•

Action of G-Protein Linked Receptor

• Binding changes the receptor protein.
• Can set off a cascade reaction

• Set any of a variety of cell activities in motion.
– Activation of an enzyme
– Rearrangement of cytoskeleton features
– Activation of a specific gene

EXTRACELLULAR
FLUID
1 Reception
Receptor
Plasma membrane
CYTOPLASM
Signaling molecule

EXTRACELLULAR
FLUID
1 Reception
Receptor
Plasma membrane
2 Transduction
CYTOPLASM
Relay molecules in a signal transduction pathway
Signaling molecule

EXTRACELLULAR
FLUID
1 Reception
Receptor
Plasma membrane
2 Transduction
CYTOPLASM
3 Response
Activation of cellular response
Relay molecules in a signal transduction pathway
Signaling molecule

+
Types of Receptors
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Which is the receptor? G-Protein? Ligand?

Which Is A Receptor Through Which Ions Would Pass?

Which Of These Acts As A Second Messenger?

Water-soluble (hydrophilic)
Polypeptides
Lipid-soluble (hydrophobic)
Steroids
Insulin
0.8 nm
Amines
Cortisol
Epinephrine Thyroxine

• Water- and lipid-soluble hormones differ in their paths through a body
• Water-soluble hormones are secreted by exocytosis, travel freely in the bloodstream, and bind to cellsurface receptors
• Lipid-soluble hormones diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells

VIA
BLOOD
Signal receptor
TARGET
CELL
SECRETORY
CELL
Watersoluble hormone
Transport protein
Signal receptor
Lipidsoluble hormone
(a)
NUCLEUS
(b)

SECRETORY
CELL
Watersoluble hormone
Lipidsoluble hormone
VIA
BLOOD
Signal receptor
Transport protein
TARGET
CELL
OR
Signal receptor
Cytoplasmic response
Gene regulation
Cytoplasmic response
Gene regulation
NUCLEUS
(a) (b)

Pathway for Water-Soluble Hormones
• Binding of a hormone to its receptor initiates a signal
transduction pathway leading to responses in the cytoplasm, enzyme activation, or a change in gene expression

Pathway for Water-Soluble Hormones

Click here to view the animation
Specific Example
Notice the presence of the second messenger

Pathway for Lipid-Soluble Hormones
• The response to a lipid-soluble hormone is usually a change in gene expression
• Steroids, thyroid hormones, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus
• Protein-receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes

Pathway for Lipid-Soluble Hormones

Steroid Hormone Example: Testosterone

38

Compare protein and steroid hormones by completing this T chart
Characteristic Protein Hormone Steroid Hormone
Speed of response
Primary biomolecule composition
Method of leaving secretory cell
Location of receptor
Example
39

Compare protein and steroid hormones by completing this T chart
Characteristic Protein Hormone Steroid Hormone
Speed of response Rapid response, cascade Response is slower, gene expression cholesterol Primary biomolecule composition
Amino acid
Method of leaving secretory cell
Exocytosis
Location of receptor
Example
Membrane bound
Epinephrine diffusion
Intracellular
Testosterone
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• The same hormone may have different effects on target cells that have
– Different receptors for the hormone
– Different signal transduction pathways

• The hormone epinephrine has multiple effects in mediating the body’s response to short-term stress
• Epinephrine binds to receptors on the plasma membrane of liver cells
• This triggers the release of messenger molecules that activate enzymes and result in the release of glucose into the bloodstream

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Same receptors but different intracellular proteins (not shown)
Different receptors
Different cellular responses
Different cellular responses
Epinephrine
 receptor
Glycogen deposits
Epinephrine
 receptor
(a) Liver cell
Glycogen breaks down and glucose is released from cell.
Vessel dilates.
(b) Skeletal muscle blood vessel
(c)
Epinephrine
 receptor
Vessel constricts.
Intestinal blood vessel

• One reason that kittens sleep so much is because a growth hormone is released only during sleep.
• The levels of two stress hormones, cortisol and epinephrine which suppress the body's immune system, will actually drop after a dose of laughter.
• Chocolate is associated with the release of serotonin, the hormone that makes you feel relaxed, calm, and happy.
So are hugs.

Created by:
Debra Richards
Coordinator of Secondary Science Programs
Bryan ISD
Bryan, TX