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bio notes - Animal Tissues and Organ Systems Chapter 25...

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Animal Tissues and Organ Systems Chapter 25 Most extracellular fluid is interstitial fluid , which fills spaces between cells and tissues. Homeostasis is a state in which the internal environment is being maintained within a range that cells can tolerate. o Sensory receptors, integrators, and effectors are in charge of it. 1. Sensory Receptors: cells or cell parts that detect stimuli, which are specific forms of energy 2. Integrator: a central command post that receives and processes information about stimuli. (ex: the brain) 3. Integrators issues signals to EFFECTORS: muscles, glands, or both—that carry out suitable responses to the stimulation. Feedback mechanisms are major homeostatic controls over what goes on in cells and the multicelled body o Negative Feedback Mechanisms: an activity changes a specific condition in the internal environment, and when the condition changes past a certain point, a response changes. o Positive Feedback Mechanisms: they spark a chain of events that intensify change from an original condition. Positive feedback is usually associated with instability in a system Chapter 29 Epithelial Tissue Epithelium is a sheet-like tissue of cells with little extracellular material between them. One side is exposed to environment or body fluid, the other side is glued to another tissue o Most epithelial cells have flattened, cuboidal, or columnar shape o Function in absorption, secrection, and some are ciliated.
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o Those that function in absorption have microvilli: fingerlike projections that increase area across which substances are absorbed. o Simple epithelium has one layer of cells; Stratified has 2 or more Gland Cells: only epithelial tissue has these; they produce and secrete substances that function outside the cell In most animals, secretory cells are clustered inside glands: organs that secrete substances onto the skin or into a body cavity. o Exocrine Glands: ducts or tubes that deliver secretions onto a free epithelial surface (secretions include mucus, saliva, tears, milk, digestive enzymes, earwax) o Endocrine Glands: no ducts. They secrete hormones directly into interstitial fluid Cell junctions connect adjoining cells in most tissues o Tight Junctions are rows of proteins that seal epithelial cell membranes together—prevents fluid from seeping b/w spaces b/w cells o Adhering Junctions: hold cells together at distinct spots. Tissues that stretch have these (skin) o Gap Junctions: permit ions and small molecules to pass freely from the cytoplasm of one cell to another. In tissues in which cells perform coordinated action Connective Tissue Connective tissues are the body’s most abundant and widely distributed tissues. o
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This note was uploaded on 04/25/2011 for the course BIOL 101 taught by Professor Hogan during the Spring '08 term at UNC.

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bio notes - Animal Tissues and Organ Systems Chapter 25...

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