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 Three stages of the Signal- Transduction Pathway 1. reception 2. transduction 3. 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 5

Ligands LIGAND: a molecule that binds to a larger molecule

Typical Signal Transduction Pathway

Phase 1: Reception The 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

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 EXTRACELLULAR FLUID CYTOPLASM Reception Receptor Signaling molecule 1 Recap

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

Plasma membrane EXTRACELLULAR FLUID CYTOPLASM ReceptionTransduction Response Receptor Signaling molecule Activation of cellular response Relay molecules in a signal transduction pathway Recap

Types of Receptors 22 +

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) PolypeptidesSteroids 0.8 nm InsulinCortisol Amines EpinephrineThyroxine

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- soluble hormone SECRETORY CELL Water- soluble hormone VIA BLOOD Signal receptor TARGET CELL (a) (b) Signal receptor Transport protein NUCLEUS

Lipid- soluble hormone SECRETORY CELL Water- soluble hormone VIA BLOOD Signal receptor TARGET CELL OR Cytoplasmic response Gene regulation (a) (b) Cytoplasmic response Gene regulation Signal receptor Transport protein 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 and thyroid hormones 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

Compare protein and steroid hormones by completing this T chart CharacteristicProtein HormoneSteroid Hormone Speed of response Primary biomolecule composition Method of leaving secretory cell Location of receptor Example 35

Compare protein and steroid hormones by completing this T chart CharacteristicProtein HormoneSteroid Hormone Speed of responseRapid response, cascadeResponse is slower, gene expression Primary biomolecule composition Amino acidcholesterol Method of leaving secretory cell Exocytosisdiffusion Location of receptorMembrane boundIntracellular ExampleEpinephrineTestosterone 36

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 receptors Same receptors but different intracellular proteins (not shown) Different cellular responses Epinephrine  receptor  receptor  receptor Glycogen deposits Vessel dilates. Vessel constricts. Glycogen breaks down and glucose is released from cell. (a) Liver cell (b) Skeletal muscle blood vessel Intestinal blood vessel (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 Richards Coordinator of Secondary Science Programs Bryan ISD Bryan, TX