Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
CHAPTER 45 CHEMICAL SIGNALS IN ANIMALS I. An Introduction to Regulatory Systems The activities of the various specialized parts of an animal are coordinated by the two major systems of internal communication: the nervous system and the endocrine system. - The nervous system is involved with high-speed messages. - The endocrine system is slower and involves the production, release, and movement of chemical messages. (provides a longer lasting responce) Endocrine glands = Ductless glands that secrete hormones into the body fluids for distribution throughout the body (via the blood) Exocrine glands = Secrete chemicals, such as sweat, mucus, and digestive enzymes, into ducts which convey the products to the appropriate locations As we learn more about the regulatory processes of animals, it becomes increasingly clear that the endocrine system and the nervous system are interrelated; homeostasis depends heavily on their overlap. A. The endocrine system and the nervous system are structurally, chemically, and functionally related Many endocrine organs and tissues contain specialized nerve cells called neurosecretory cells that secrete hormones. Several chemicals serve both as hormones of the endocrine system and as signals in the nervous system. - Norepinephrine functions as both an adrenal hormone and as a neurotransmitter. The regulation of several physiological processes involves structural and functional overlap between the two systems. Positive and negative feedback regulate mechanisms of both systems. II. Chemical Signals and Their Mode of Action Chemical signals operate at virtually all levels of organization - Intracellular (within cells) - Cell to cell - Tissue to tissue - Organ to organ (this is level that was considered the subject of classic endocrinology, with hormones acting as the chemical signals) - Organism to organism (includes pheromones, chemical signals that function between organisms of the same species; classified according to function e.g., mate attractant, territorial marker, alarm substance). Compounds called local regulators operate at the cell to cell and tissue to tissue levels of organization. A. A variety of local regulators affect neighboring target cells Examples of local regulators include the following: - Histamine (involved with various immune and regulatory responses; - Interleukins (involve with various immune responses; - Retinoic acid (involved with vertebrate development; - Nitric oxide (NO) - NO released by endothelial cells of blood vessels makes the adjacent smooth muscle cells relax, dilating the vessel. - NO released by white blood cells kills certain cancer cells and bacteria in the body fluids. Growth factors = Peptides and proteins that regulate the behavior of cells in growing and developing tissues - Must be present in the extracellular environment for certain cell types to grow and develop normally. Prostaglandins
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/05/2008 for the course BIO G 006 taught by Professor Macneill,a. during the Spring '08 term at Cornell.

Page1 / 5


This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online