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 signalingc. 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.
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The Process of Communication:Signal-Transduction Pathway
Three stages of the Signal-Transduction Pathway1. reception2. transduction3. response
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
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Ligands
LIGAND: a molecule that binds to a larger molecule
Typical Signal Transduction Pathway
Phase 1: ReceptionThe target cell detects the ligand
• Membrane proteins–G-protein linked receptors–Ion channel receptors–Tyrosine Kinase
• Intracellular receptor–Steroid hormone receptors
Type of Receptor : G-protein linked
Type of Receptor: Ion Channel
Type of Receptor:
Intracellular Receptor
Name three types of receptors in the signal transduction pathway
• G-protein-linked receptors• Ion channel receptors• Intracellular receptors
Action of G-Protein Linked Receptor
Transduction
• Binding changes the receptor protein.
• Can set off a cascade reaction
Response
• Set any of a variety of cell activities in motion.–Activation of an enzyme–Rearrangement of
cytoskeleton features–Activation of a specific
gene
Plasma membrane
EXTRACELLULARFLUID
CYTOPLASM
Reception
Receptor
Signalingmolecule
1
Recap
Plasma membrane
EXTRACELLULARFLUID
CYTOPLASM
Reception Transduction
Receptor
Signalingmolecule
Relay molecules in a signal transductionpathway
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Recap
Plasma membrane
EXTRACELLULARFLUID
CYTOPLASM
Reception Transduction Response
Receptor
Signalingmolecule
Activationof cellularresponse
Relay molecules in a signal transductionpathway
321
Recap
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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?
Lipid-soluble (hydrophobic)Water-soluble (hydrophilic)
Polypeptides Steroids
0.8 nmInsulin Cortisol
Amines
Epinephrine Thyroxine
Cellular Response Pathways
• 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 cell-surface receptors
• Lipid-soluble hormones diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells
Lipid-solublehormone
SECRETORYCELL
Water-solublehormone
VIABLOOD
Signal receptor
TARGETCELL
(a) (b)
Signalreceptor
Transportprotein
NUCLEUS
Lipid-solublehormone
SECRETORYCELL
Water-solublehormone
VIABLOOD
Signal receptor
TARGETCELL
OR
Cytoplasmicresponse Gene
regulation
(a) (b)
Cytoplasmicresponse Gene
regulation
Signalreceptor
Transportprotein
NUCLEUS
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
Specific Example
Notice the presence of the
second messenger
Click here to view the animation
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
Steroid Hormone Example: Testosterone
Model Steroid Hormone Action using the Testosterone
Manipulative
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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
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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
Primary biomolecule composition
Amino acid cholesterol
Method of leaving secretory cell
Exocytosis diffusion
Location of receptor Membrane bound Intracellular
Example Epinephrine Testosterone
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Multiple Effects of Hormones
• 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
Multiple Effects of Hormones
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Different receptorsSame receptors but differentintracellular proteins (not shown)
Different cellularresponses
Different cellularresponses
Epinephrine Epinephrine Epinephrine
receptor receptor receptor
Glycogendeposits
Vesseldilates.
Vesselconstricts.
Glycogenbreaks downand glucoseis releasedfrom cell.
(a) Liver cell (b) Skeletal muscleblood vessel
Intestinal bloodvessel
(c)
Did you know…
• 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 RichardsCoordinator of Secondary Science ProgramsBryan ISDBryan, TX