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 If the thyroid gland is removed from a mammal, continued survival depends on replacement of thyroid hormones, T 3 and T 4. It is not necessary to replace Calcitonin. Explain…. Describe the body functions typically coordinated by endocrine communication.

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?

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): 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): 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): 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?

For Practice: Biological Signal Transduction If this is the second messenger, where is the first messenger? What do protein kinases do? What are the two general ways that a cell may respond to an extracellular chemical message (one that cannot enter the cell)? What are the chemical characteristics of the signal molecule? … of the receptor?

Identify the: 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? …more practice

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. Ca 2+ 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 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.

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