The Nervous System

divided into two parts
1. the Peripheral Nervous System (PNS)
  1. in vertebrates this is composed of the nerves and ganglia
  2. transmits signals to and from the CNS as well as regulating movement and the internal environment
    1. afferent neurons transmit signals to the CNS
    2. efferent neurons transmit signals away from the CNS
    3. cranial nerves originate in the brain and generally terminate in the organs in the head or upper body
    4. spinal nerve originate from the spine and extend to parts of the body below the head
  3. two functional components of the PNS
    1. Motor system
      1. is voluntary and controls the movement of skeletal muscles
    2. autonomic nervous system
      1. is involuntary and regulates the internal environment as well in voluntary muscle contractions such as peristalsis
2. the Central Nervous System (CNS)
  1. in vertebrates this is composed of the brain and spinal cord
    1. the spinal cord sends signals from the brain to the PNS
      1. it also mediates reflex reactions such as the knee jerk reflex
        reflexes occur independently of the brain
    2. the brain and spinal cord are made up of:
      1. white matter: consists of myelinated axon bundles
      2. grey matter: consists of cells bodies and dendrites
      3. the ventricles of the brain and the central canal of the spinal cord are hollow and they both contain cerebrospinal fluid
        this is filtered from the blood and acts as a cushion for the brain and spinal cord
most multicellular organisms have a nervous system
1. except for
  1. sponges
  2. placozoans
  3. mesozoans
2. this can be a diffuse nerve net in the case of radially symmetrical organisms such as:
  1. Cnidarians
  2. ctenophores
3. most nervous systems consists of:
  1. a brain
  2. a central nerve cord or two cords running in parallel
  3. nerves radiating from the brain and central cord
Autonomic Nervous system: split into three divisions
1. sympathetic division
  2. fight or flight
  3. fight or flight
2. parasympathetic division
  1. have antagonistic effects on target organs
    1. gas exchange
    2. circulation
    3. hormone action
  2. rest and digest
  3. rest and digest
3. enteric division
  1. digestive tract
  2. pancreas
  3. gall bladder
  4. pancreas
  5. gallbladder

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The Nervous System

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	Created by yolajoy over 10 years ago