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 SignalTransduction 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
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
Recap
EXTRACELLULAR
FLUID
1 Reception
Receptor
Signaling
molecule
CYTOPLASM
Plasma membrane
Recap
EXTRACELLULAR
FLUID
1 Reception
CYTOPLASM
Plasma membrane
2 Transduction
Receptor
Relay molecules in a signal transduction
pathway
Signaling
molecule
Recap
EXTRACELLULAR
FLUID
1 Reception
CYTOPLASM
Plasma membrane
2 Transduction
3 Response
Receptor
Activation
of cellular
response
Relay molecules in a signal transduction
pathway
Signaling
molecule
Types of Receptors
+
23
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)
Lipid-soluble (hydrophobic)
Polypeptides
Steroids
0.8 nm
Insulin
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 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
SECRETORY
CELL
Lipidsoluble
hormone
Watersoluble
hormone
VIA
BLOOD
Signal receptor
Transport
protein
TARGET
CELL
Signal
receptor
NUCLEUS
(a)
(b)
SECRETORY
CELL
Lipidsoluble
hormone
Watersoluble
hormone
VIA
BLOOD
Signal receptor
TARGET
CELL
Cytoplasmic
response
Transport
protein
OR
Gene
regulation
Signal
receptor
Cytoplasmic
response
NUCLEUS
(a)
(b)
Gene
regulation
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 Exocytosis
cell
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
Multiple Effects of Hormones
• 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
41
Same receptors but different
Different receptors
intracellular proteins (not shown)
Different cellular
responses
Different cellular
responses
Epinephrine
Epinephrine
Epinephrine
 receptor
 receptor
 receptor
Glycogen
deposits
Glycogen
breaks down
and glucose
is released
from cell.
(a) Liver cell
Vessel
dilates.
(b) Skeletal muscle
blood vessel
Vessel
constricts.
(c) Intestinal blood
vessel
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