What is the name of the action type for hormones that act on the same cell that produces it?
Activity Summary Learning Objectives
Background
Some hormones can act on many cell types, while others act on just one type. And, hormones regulate cells in different ways: some affect the very cells that make the hormone; other hormones regulate neighboring cells; still others regulate cells at a distance from where they are made. Hormones that regulate cells at a distance travel through the bloodstream. Consequently, these hormones come in contact with many different organs, tissues, and cell types. Yet, they only trigger a response when there is a functional receptor with a strong affinity for that hormone. Once the hormone binds to a receptor, cellular processes, such as changing which genes in a cell are active or triggering the production of a protein, are initiated. A target tissue's response to hormones is regulated by hormone concentration (there must be enough hormone to initiate a response), the number of receptors on the cell membrane, and the affinity the receptor and hormone have for each other. Hormone receptors are often large proteins with a specific structure, including a place for a hormone to attach (i.e., the binding site) and a part that produces chemicals that stimulate a cellular response. In addition to producing chemicals that stimulate a cell's response, target cells also often make substances that provide a feedback signal, which directs the cells producing a hormone to either increase or decrease the hormone level. Disease can result when hormone production is too high or low or when hormone receptors are blocked or nonfunctional. Leptin is a hormone produced by the body's fat tissue (adipocytes), and, typically, the amount made is proportional to the amount of fat tissue. Leptin helps regulate food intake and control how fats are distributed and stored in the body. Under normal circumstances, when a person's fat level drops, less leptin is produced. The part of the brain called the hypothalamus detects this decreased signal, and this decrease stimulates a person's desire to eat. Similarly, when the fat level returns to or exceeds a person's usual level, the leptin level rises. This increased signal reduces a person's desire to eat. One form of obesity in humans is due to a mutation in the gene responsible for leptin production. More common, however, is a mutation in the genes that encode for leptin receptors. In both cases, the amount of leptin available to body tissues is very different for people with a mutation than for those without it. So even after eating a full meal, people with these mutations can still feel hungry, making it easy to overeat and to gain weight. Mice that are unable to produce leptin become tremendously obese. Leptin injections cure this condition. This technique also works on those few people born with an inability to produce leptin. But since it is much more common to have a problem with the leptin receptor, most obese people do not lose significant amounts of weight when given leptin injections. In this activity, students make models that illustrate hormone-receptor systems. These models underscore the need for the hormone and receptor to be matched in order for them to be able to bind strongly to one another. The models also show how mutations interfere with the functioning of a hormone-receptor system. Key Terms endocrine system: A chemical communication system in the body that controls physiologic processes, such as growth, development, and appetite. hormones: Chemical messengers made by one type of cell that regulate the function of other types of cells (and sometimes the cell that made the hormone). Hormones have a specific structure that can bind to specific receptors, allowing for precise control of the cells they regulate. leptin: A hormone produced by fatty tissue (adipocytes) that acts on the brain, ultimately influencing appetite, body fat storage, and other physiologic processes. mutation: A change in a gene that alters the message carried by the gene. The gene product (often a protein) may be altered so that it functions differently or not at all. plasma membrane: The outer membrane of animal cells, made of a lipid bi-layer. It controls the movement of substances in and out of the cell. receptor: A molecule on the plasma membrane or inside a cell that binds to a specific substance, such as a hormone, and triggers a cellular response. For peptide hormones, receptors are in the plasma membrane. For steroid and thyroid hormones, the receptors are in the cytoplasm and nucleus. target tissue: A tissue with a receptor for a specific hormone that responds chemically to the hormone.
Write a possible outcome or consequence of the following mutations or conditions.
Write at least two strengths and two limitations of each model system.
Student Handout Questions
Web Sites NOVA scienceNOW Chipping Away at Leptin's Effects Hormones, Receptors, and Control Systems Leptin's Legacy Molecular Studies of Food Intake and Body Weight Books Biology Coloring Book The Concise Encyclopedia of the Human Body The "Hormones and Receptors" activity aligns with the following National Science Education Standards (see books.nap.edu/html/nses). Grades 5-8
Grades 9-12
Classroom Activity Author Developed by WGBH Educational Outreach staff. The Biology of Fat Learn how the body regulates weight by carefully controlling the storage and burning of fat and how a better understanding of these complex metabolic systems could lead researchers to treatments that curb obesity and improve public health. Available free from the Howard Hughes Medical Institute as four downloadable videos at www.hhmi.org/biointeractive/obesity/. What is the name of the hormones that act on the same cells that secrete them?Autocrine action: the hormone acts on the same cell that produced it.
What is the mode of action of hormones?There are two modes of hormonal action. A: Activation of cell-surface receptors and coupled second-messenger systems, with a variety of intracellular consequences. B: Entry of hormone into the target cell, binding to and activation of an intracellular (more...)
What allows a cell to respond to a hormone?Hormones cause cellular changes by binding to receptors on target cells. The number of receptors on a target cell can increase or decrease in response to hormone activity. Hormones can affect cells directly through intracellular hormone receptors or indirectly through plasma membrane hormone receptors.
What are the 3 types of hormone effects?There are three major types of hormones.. Protein hormones (or polypeptide hormones) are made of chains of amino acids. An example is ADH (antidiuretic hormone) which decreases blood pressure.. Steroid hormones are derived from lipids. ... . Amine hormones are derived from amino acids.. |