1. Chemical Signals in Animals

2. Learning Objectives (3/2/09)
Differentiate between types of cellular chemical messages: autocrine, paracrine, and neuroendocrine
Compare the response time & duration for the two major systems of internal communication in animals: nervous and endocrine
Compare and contrast the mechanisms of lipophilic and lipophobic hormone action
Describe the bases for the creation and maintenance of the transmembrane electrochemical potential
Discuss the sequence of events in a variety of second messenger systems in signal transduction
Describe examples of hormone interaction in the integration of complex animal processes (e.g. water balance, and insect development)
Explain the role of neurosecretory cells in the hypothalamus in the regulation of endocrine function

3. Chemical Communication
p. 1055
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”?

4. Endocrine Function is often Controlled by Negative Feedback
See also p. 1065
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….

5. 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 signal-transduction pathway?
What kinds of proteins might be made by the action of a lipophilic hormone?

6. Classes of Membrane Receptors (1):
Integrins
“Links” between the
extracellular matrix
and the cytoskeleton.
Integrins are important in morphogenesis during embryonic development.

7. 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?

8. Classes of Membrane Receptors (3): Receptor Enzymes
See p. 173
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?

9. Classes of Membrane Receptors (4): G-protein linked receptor
How is the intracellular
message controlled?
What are the roles of energy nucleotides (nucleoside triphosphates) in
signal transduction?

10. 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)?

11. …more practice Identify the: G-proteins linked Transducer
Amplifier
Second messenger
G-proteins linked
with specific receptors
are either excitatory (+)
or inhibitory (-).
How would the cellular response be different in this model, if the G-protein were inhibitory?

12. Overview of the Transmembrane Electrochemical Potential
How does the
Na-K pump
contribute to the
potential?
Why is the cell
membrane described
as “polarized”?

14. 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?
p. 1075

15. Target Cells: more than one type of signal transduction

16. 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. Ca+2 pumps)
Broken down enzymatically (e.g. phosphodiesterase destroys cAMP and cGMP)

17. Integration of Intercellular Communication
See p. 1061
All multicellular animals utilize neurosecretory cells for internal chemical signaling
Many so-called endocrine glands contain neuro-secretory 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.

18. Integration of Intercellular Communication
p. 1070
… and brain cells may secrete hormones.
Describe the structural and functional connections between the anterior pituitary and the hypothalamus.

19. 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