Chemical Signals in Animals

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

Chemical CommunicationBriefly 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”?

p. 1055

Endocrine Function is often Controlled by Negative Feedback

If the thyroid gland isremoved from a mammal,continued survival dependson replacement of thyroidhormones, T3 and T4.It is not necessary toreplace Calcitonin.Explain….

Describe the body functions typically coordinated by endocrine communication.

See also p. 1065

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?

Overview of the Transmembrane Electrochemical Potential

How does the Na-K pumpcontribute to thepotential?

Why is the cell membrane described as “polarized”?

p. 1009

Amplification in Signal

Transduction

p. 1075

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 ActionFirst 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 CommunicationAll multicellular

animals utilize neurosecretory cells for internal chemical signaling

Many so-called Many so-called endocrine glands endocrine glands contain neuro-contain neuro-secretory cells,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.

See p. 1061

Integration of Intercellular Communication

… … and brain cells may and brain cells may secrete hormones.secrete hormones.

Describe the structural and functional connections between the anterior pituitary and the hypothalamus.

p. 1070

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.

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Growth w/o metamorphosis