chapter 3

• The Autonomic Nervous System (ANS) is largely independent (autonomous) and its activities are not under direct conscious control
• The ANS is concerned primarily with visceral functions such as cardiac output, blood flow to various organs, and digestion, which are necessary for life
• Both the Autonomic Nervous System and the Somatic Nervous System have afferent (sensory) inputs that provide information regarding the internal and external environments and modify motor output through reflex arcs of varying size and complexity
• In the Nervous System, chemical transmission occurs between nerve cells and between nerve cells and their effector cells through the release of small amounts of transmitter substances from the nerve terminals into the synaptic cleft
• Anatomy of the Autonomic Nervous System:

  • Sympathetic Nervous System:
  • Sympathetic Outflow is thoraco-lumbar
  • Location of the Preganglionic Neuron (PN) is near to the Spinal Cord
  • Length of PN is shorter
  • Location of Ganglion is near the Spinal Cord
  • Length of Postganglionic Neuron is longer
  • Neurotransmitter at Ganglion is Acetylcholine
  • Neurotransmitter at Postganglionic Neuron is Norepinephrine
  • Parasympathetic Nervous System:
  • Parasympathetic Outflow is cranio-sacral (C III, VII, IX, X)
  • Location of the Preganglionic Neuron (PN) is near to the Spinal Cord
• • Length of PN is longer
  • Location of Ganglion is far from Spinal Cord
  • Length of Postganglionic Neuron is shorter
  • Neurotransmitter at Ganglion is Acetylcholine
  • Neurotransmitter at Postganglionic Neuron is Acetylcholine
• Chemical Signaling Between Cells:

  • Hormones are secreted by specialized endocrine cells into the bloodstream, where they travel throughout the body, exerting effects on broadly distributed target cells
  • Local mediators include histamine and prostaglandin
  • Neurotransmitters