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.

2

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

5

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

21

Recap

Plasma membrane

EXTRACELLULARFLUID

CYTOPLASM

Reception Transduction Response

Receptor

Signalingmolecule

Activationof cellularresponse

Relay molecules in a signal transductionpathway

321

Recap

23

Types of Receptors

+

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

36

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

37

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

38

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

41

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