16 nerves2007mod_nxpowerlite_

16 nerves2007mod_nxpowerlite_ - NERVES Peripheral nervous...

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NERVES Peripheral nervous system Dr. Kelly Selman (D2-32) September 26, 2007 Reading assignment: Ross 5 th : Chapter 12 (peripheral nerve) Chapter 15 (nerve endings)
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Nervous System Nervous system: a complex communication system made up of over 100 million neurons Each neuron has an average of more than 1000 interconnections with other neurons Properties of neurons Excitable Conductive (propagate impulses) Secretory Neurotransmitters at synapse Neurohormones (oxytocin and vasopressin) Trophic (nutritive) Neurons can regenerate but most can not divide
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Excitable: cells respond to changes in environment or stimuli by eliciting changes in electrical potential of their plasma membrane. Cells become depolarized (Na + influx, K + eflux). Conductile: modification of electrical potential may be propagated (conducted) throughout the cell. Propagation, called the action potential or nerve impulse, quickly travels long distances (2-3 ft).
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Neurons are secretory cells Neurotransmitters: released at synapse (acetylcholine, norepinephrine, serotonin, dopamine, nitric oxide) Synapse: region of specialized contact between nerve cells. Electrical signals from pre-synaptic cells are converted to chemical signals (release of neurotransmitters) that affect a change in a post-synaptic cell Neurohormones: (Antidiuretic hormone) Axon Dendrite Synapse
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Other properties of neurons…. Trophic (nutritive) If cut nerve to muscle the muscle atrophies Neurons are fully differentiated cells and usually do not divide. Exception: olfactory cells (bi-polar nerve cells) in the olfactory epithelium and neuroepithelial cells of taste buds Under some situations, neurons can regenerate but they can not divide
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Nervous system CNS (central nervous system) Brain and spinal cord PNS (peripheral nervous system) *** Nerve fibers Small aggregates of nerve cells (ganglia) Receptors (specialized nerve endings) Types of cells in PNS Neurons and Support cells Supports cells of PNS: Schwann cells and satellite cells (Both derived from neural crest cells and have external lamina)
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Neurons have 3 different functional regions Muscle Reception and integration of info. Receptor portion Dendrites Cell body (Soma or Perikaryon ) Axon Effector (Transmitter) portion Conductile portion Generation of action potential&conduction
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( Retina ) (Dorsal Root ganglion ) Multipolar Sensory neurons: convey impulses from receptors to CNS Motor neurons: convey impulses from CNS (ganglia) to effector organs Interneurons: form a communicating network between other neurons Different types of neurons
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Nerve fiber” has several definitions 1. Axon 2. Axon with all of its external coverings (including myelin sheath and Schwann cells) 3. Any process of nerve cell (axon or dendrite) 4. The whole organ (“nerve”), which is made of several different types of tissues
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Dendrites Receptor portion that is specialized to receive stimuli Dendrites
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16 nerves2007mod_nxpowerlite_ - NERVES Peripheral nervous...

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