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311DCh48 - Ch 48 pg 1011-1063 Neurons nerve cells Nerves...

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Ch. 48 pg. 1011-1063 Neurons – nerve cells; Nerves - bundles of fiberlike extensions of neurons Central nervous system (CNS) – brain and spinal cord Ganglia – segmentally arranged clusters of neurons Sensory neurons – transmit information from sensors that detect external stimuli and internal conditions Interneuron’s – integrate (analyze and interpret) sensory input, taking into account the immediate context as well as what has happened in the past Motor Neurons – motor output leaves CNS Effector cells – muscle cells or endocrine cells Reflexes – body’s automatic responses to stimuli Dendrites – highly branched extensions that receive signals from other neurons Axon – longer extension that transmits signals to other cells which may be neurons or effector cells Axon Hillock – conical region of an axon; signals travel down the axon are generated here Myelin sheath – axons are enclosed by a layer; Synaptic terminal – axon divides into several branches Synapse – site of communication between a synaptic terminal and another cell; information is passed from transmitting neuron (presynaptic cell) to the receiving cell (postsynaptic cell) by means of chemical messengers called neurotransmitters Glia – supporting cells that are essential for the structural integrity of the nervous system and for the normal functioning of neurons; outnumber neurons; do much more than hold neurons together Astrocytes – provide structural support for neurons and regulate the extracellular concentrations of ions and neurotransmitters; induce the formation of tight junctions between cells that line the capillaries in the brain and spinal cord Blood brain barrier – restricts passage of most substances into the CNS allowing the extracellular chemical environment of the CNS to be tightly controlled Radial glia – form tracks along which newly formed neurons migrate from the neural tube, the structure that gives rise to the CNS; can act as stem cells, generating neurons and other glia; multipotent Oligodendrocytes (CNS) & Schwann Cells (PNS) – glia that form the myelin sheaths around the axons of many vertebrate neurons; neurons become myelinated when Schwann or Oligodendrocytes grow around axons wrapping them in layers of membrane; myelin provides electrical insulation of the axon Membrane potential – voltage difference across plasma membrane Resting potential – membrane potential of a neuron that is not transmitting signals Equilibrium potential – magnitude of the membrane voltage at equilibrium; given by Nerst equation Gated ion channels – open or close in response to one of three kinds of stimuli Stretch gated ion channels – found in cells that sense stretch and open when the membrane is mechanically deformed
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