13 - Cell Communication Chapter 16 Cells communicate all of...

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Cell Communication Chapter 16
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Cells communicate all of the time. Whether we are talking about unicellular organisms like yeast, or cells of a multicellular organism like yourself, individual cells send and receive a multitude of signals. A cell may produce a given signal (hormone, paracrine, etc) that must be detected by a target cell. The target cell, in order to respond, must contain receptor proteins for that particular signal. Signal transduction begins once that receptor is bound with its signal molecule and converts that information to a cellular response.
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Signal Molecules and Mechanisms
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Your book uses Insulin and glucagon as examples of hormone signals. But you have all sorts of hormones that work in your body. Gonadotropins (FSH and LH) control reproduction. These hormones are released from the anterior pituitary, travel through the body and have the gonads (testes and ovaries) as their target tissues. At the target tissues, these hormones stimulate the release of the sex hormones and are responsible for sperm production and egg maturation.
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One of the best examples of paracrine activation is with blood clotting and platelet plug formation. Recall that platelets are circulating in your bloodstream all of the time. When they come into contact with a vascular injury, they become activated (change shape, become sticky, degranulate and accumulate). All of these processes are controlled by paracrine secretions.
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The best example of neuronal activation is muscle contraction. The signal from the somatic motor system signals the muscle cell to contract. This pathway involves an electrical signal that is converted to a chemical signal (via neurotransmitter) back to an electrical signal that leads to an influx of calcium and the sliding filament theory.
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A good example of contact- dependent communication is with the immune system.
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Each cell responds to a limited set of signals. Without an appropriate receptor, a cell cannot and will not react to a signal.
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The same signal molecule may have very different effects on its target tissues depending on the receptors present. For example, acetylcholine is the neurotransmitter for the skeletal system, but also can influence cardiac muscle and salivary gland secretion.
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What kind of effects can a signal molecule have on a cell? Change shape, size Movement Metabolism Gene Expression A typical cell possess a collection of different receptors making the cell simultaneously sensitive to many extracellular signals.
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The integration of the extracellular signals allows a relatively small number of signal molecules, used in different combinations, to exert subtle and complex control over cell behavior.
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Each receptor is typically activated by only one type of signal and the receptor protein performs the primary transduction step.
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13 - Cell Communication Chapter 16 Cells communicate all of...

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