Chemical Signaling
Chemical
Communication
Briefly describe the two
major forms of
intercellular
communication in animal
bodies. Which organ
systems are responsible
for this communication?
Describe the type of
intercellular
communication called
“neuroendocrine”.
What defines a “target
tissue”?
Endocrine Function is often Controlled by Negative
Feedback
Describe the body
functions typically
coordinated by endocrine
communication.
If the thyroid gland is
removed from a mammal,
continued survival
depends
on replacement of
thyroid
hormones, T3 and T4.
It is not necessary to
replace Calcitonin.
Explain….
Basic Mechanisms of Chemical Signaling
•What characteristic of the
message is related to
where the target cell
presents the receptor?
Explain.
•What are the advantages
of activating a signaltransduction pathway?
•What kinds of proteins
might be made by the
action of a lipophilic
hormone?
Classes of Membrane Receptors (1):
Integrins
“Links” between the
extracellular matrix
and the cytoskeleton.
Integrins are important in morphogenesis during embryonic development.
Classes of Membrane
Receptors (2):
Ligand-gated ion channels
In order for this to occur, what must
be true about the distribution of ions?
How might the influx of ions induce
a biochemical response within a cell?
What other mechanisms of controlling
ion channels are there?
Classes of Membrane Receptors (3):
Receptor Enzymes
How is this mechanism of signal transduction different from one in
which proteins are made after reception of the signal molecule(s)?
Compare and contrast receptor enzymes and G-protein-linked reception and
transduction of extracellular chemical messages?
Classes of
Membrane
Receptors (4):
How is the intracellular
message controlled?
G-protein linked
receptor
What are the roles of energy nucleotides (nucleoside triphosphates) in
signal transduction?
For Practice:
Biological Signal Transduction
What are the chemical
characteristics of the
signal molecule?
… of the receptor?
What do protein
kinases do?
If this is the second
messenger, where is
the first messenger?
What are the two general ways that a cell may respond to an
extracellular chemical message (one that cannot enter the cell)?
…more practice
Identify the:
•Transducer
•Amplifier
•Second messenger
How would the cellular
response be different in this
model, if the G-protein were
inhibitory?
G-proteins linked
with specific receptors
are either excitatory (+)
or inhibitory (-).
Overview of the Transmembrane
Electrochemical Potential
How does the
Na-K pump
contribute to the
potential?
Why is the cell
membrane
described
as “polarized”?
Amplification
in Signal
Transduction
What is the first
messenger in this
pathway?
Under what
circumstances is this
signal released?
Can you explain the
advantage of this type
of signal transduction
in this example?
Target Cells:
More than one type of signal transduction
Terminating First Messenger Action
First Messengers may be
– excreted in urine (after being degraded in liver or kidney)
– destroyed by intracellular digestion (in a lysosome after
endocytosis)
– broken down by extracellular enzymes at the receptor (e.g
cholinesterase)
– transported into neighboring cells (e.g. Serotonin re-uptake)
Second Messengers may be
– removed from the cell (e.g. Ca2+ pumps)
– Broken down enzymatically (e.g. phosphodiesterase destroys
cAMP and cGMP)
Integration of Intercellular
Communication
All multicellular
animals utilize
neurosecretory
cells for internal
chemical
signaling
Many so-called
endocrine glands
contain neurosecretory cells, …
Which division of the mammalian nervous system is active during the
stress response? Describe the collaboration between the endocrine and
nervous systems in this example.
Integration of Intercellular
Communication
… and neurons may
secrete hormones.
Describe the structural
and functional
connections between the
anterior pituitary and the
hypothalamus.
Integration of Intercellular
Communication
Several hormones may
interact to produce a complex
result.
Discuss one other example of
the interaction between the
nervous and endocrine
systems; and
….between two or more
hormones.
As a hormone that stimulates
the release of another
hormone, Brain Hormone is
correctly classified as a
_______ hormone.
+
Growth w/o metamorphosis