Chapter 34 Information Flow and The Neuron

Chapter 34 Information Flow and The Neuron - Chapter 34...

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Chapter 34 Information Flow and The Neuron I. Cells of the Nervous System A. The neuron, or nerve cell, is the basic unit of communication in all nervous systems. B. Three classes of neurons work together: 1 Sensory neurons are receptors for specific sensory stimuli. 2 Interneurons in the brain and spinal cord integrate input and output signals. 3 Motor neurons send information from integrator to muscle or gland cells (effectors). C. Neuroglial cells physically support and protect the neurons in various ways. II. Functional Zones of the Neuron A. A neuron has three basic parts: 1 The cell body contains the nucleus and metabolic machinery for protein synthesis. 2 Dendrites are numerous, usually short extensions that receive stimuli (input zones). 3 An axon is usually a single, rather long extension that transmits impulses to other cells (output zones). B. There are variations of these features depending on the particular neuron described. III. Neural Messages A. Membrane Excitability 1 A neuron at rest maintains a steady voltage difference across its plasma membrane. a. The inside is more negatively charged than the outside. b. This is called the resting membrane potential. 2 When a neuron receives signals, an abrupt, temporary reversal—the inside becomes more positive—in the polarity is generated (an action potential). 3 Any membrane that can produce action potentials is said to show membrane excitability. B. Neurons “At Rest” 1 The resting membrane potential is the result of three factors: a. The concentrations of potassium, sodium ions, and other charged molecules are not the same on the two sides of the plasma membrane. b. Channel proteins spanning the membrane influence the diffusion of specific types of ions.
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Chapter 34 Information Flow and The Neuron - Chapter 34...

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