NERVOUS SYSTEMS

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CHAPTER 48 NERVOUS SYSTEMS
Section A An Overview Of Nervous Systems
Dr. Hesham Sharaf
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Nervous system
Central N.S.
Peripheral N.S.
(CNS) composed of Brain Spinal cord is
responsible for integration
(PNS) composed of peripheral nerves
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Nervous systems perform three overlapping
functions (sensory input, integration and motor
output)
Fig. 48.1, Page 1023
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Networks of neurons build connections to form
nervous systems

• Neuron Structure and Synapses ????????? ???????.
• The neuron (nerve cell) is the structural and
  functional unit of the nervous system.
• Nerve impulses are conducted along a neuron.
• Dentrite ? cell body ? axon hillock ? axon
• Some axons are protected by a myelin sheath.
• Axon endings are called synaptic terminals.
• They contain neurotransmitters ???????? ???????
  
  which conduct a signal across a synapse.
• Synapse is the junction between a presynaptic
  and postsynaptic neuron.
• Presynaptic cell is the transmitting cell.
• Postsynaptic cell is the target cell.

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?????? ?????
????? ??????
Fig. 48.2, Page 1023
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• Sensory receptors ?????????? ??????
  
  a responsive to external and internal
  stimuli.
• Such sensory input is conveyed to integration
  centers (CNS) in which the input is interpreted
  and associated with a response.
• Sensory neuron ?????? ?????? receives
  information from the sensory receptor (e.g. eye)
  and passes it to the motor neuron.
• Motor output is the conduction ????? of signals
  from integration centers (CNS) to effector cells
  (e.g. muscular cells).
• Effector (motor) neuron carries out the bodys
  response to a stimulus.
• Interneuron ?????? ??????? ??????? intermediate
  cell between the sensory and motor neuron (exists
  in spinal cord ????? ??????)