Divisions of the Nervous system

• Nervous system


  A body-wide system of nerve cells that collects information from the world, processes this information, and then takes action by directing bodily organs and muscles through the transmission of electrochemical messages
• Nervous system


  • Broken down into two parts: the central nervous system (CNS) and the peripheral nervous system (PNS)
• Central nervous system (CNS)


  Provides complex processing and contains the brain (where conscious and unconscious processing happens) and the spinal cord (receives and transmits information to/from the brain and body, can perform basic motor reflexes)
• Peripheral nervous system (PNS)

  A body-wide network of messenger neurons that collect sense impressions and deliver instructions to the body from the CNS
• Components of the PNS

  • Sensory (afferent) neurons (deliver information to the CNS)
  • Motor (efferent) neurons (transmit information away from the CNS)
• Somatic nervous system (SNS)


  Controls skeletal muscles, a voluntary system under conscious control
• Autonomic nervous system (ANS)


  Controls internal organs and glands, an involuntary system not under conscious control
• Branches of the ANS


  • Sympathetic (activates in stress response, increases bodily activities)
  • Parasympathetic (activates in rest, decreases bodily activities)
• Homeostasis


  The process by which the internal environment is maintained, involving a balance between the sympathetic and parasympathetic systems
• The gut contains about 100 million nerve cells, about as many as in a cat's brain