Lecture17 - Lecture 22: The Nervous System Chapter 48...

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Lecture 22: The Nervous System Chapter 48
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neuron - a nerve cell; the fundamental unit of the nervous system, having structure and properties that allow it to conduct signals by taking advantage of electrical charge across its cell membrane nerve - a ropelike bundle of neuron fibers tightly wrapped in connective tissue
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central nervous system (CNS) - brain and spinal cord in vertebrates peripheral nervous system (PNS) - sensory and motor neurons that connect the central nervous system
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sensory neurons - transmit information from sensors to the CNS interneurons - analyze and interpret the sensory input motor neurons - conveys output of interneurons from CNS to effector cell (i.e., muscle or endocrine cell) Stages of information processing
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Stages of information processing: the example of the knee-jerk reflex reflex = automatic response to a stimulus mediated by the spinal cord or lower brain
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Neuron structure
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Glial cells - supporting cells that are essential for the structural integrity of the nervous system and for the normal function of neurons astrocytes (CNS) - regulate extracellular ion and neurotransmitter concentrations; facillitate transfer of neurotransmitter through synapse; dilate blood vessels near active neurons; induce formation blood-brain barrier radial glia - form tracks for neuron migration from neural tube during development Schwann cells (CNS) - form myelin sheaths around axons of many neurons
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membrane potential = voltage (difference in concentration of electrons between the inner and outer portions) across the plasma membrane resting potential - membrane potential across a resting neuron (one that isn’t transmitting signals); all membrane potentials (resting or not) depend on ion gradients that exist across the membrane Energy must be expended to establish and maintain gradients
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Sodium potassium pump: cells expel three sodium ions and take in two potassium ions in an ATP- dependent manner for each cycle this energetic process helps to establish/maintain the difference in sodium and potassium across the membrane
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source of resting potential (using simplified artificial systems): for potassium: -add potassium chloride to both sides of the beaker (more on left) -chambers separated by a membrane selectively permeable to potassium only -potassium rushes down its concentration gradient, leaving negatively charged chloride ions behind in the inner chamber, resulting in a buildup of negative charge -negative charge keeps potassium from exiting and draws positive potassium ions in
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This note was uploaded on 11/24/2011 for the course BIOLOGY 110 taught by Professor Bentz during the Spring '09 term at Drexel.

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Lecture17 - Lecture 22: The Nervous System Chapter 48...

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