the autonomic nervous system

• Somatic nervous system


  Consists of somatic motor neurons that innervate the skeletal muscles of the body

  
• Somatic motor neurons


  When stimulated, cause skeletal muscles to contract
• Somatic nervous system


  Usually operates under voluntary (conscious) control
• Autonomic nervous system (ANS)


  Regulates cardiac muscle, smooth muscle, and glands
• Autonomic motor neurons


  Regulate visceral activities by either increasing (exciting) or decreasing (inhibiting) ongoing activities in their effector tissues
• Autonomic nervous system


  • Often functions to some extent even if nerve supply is damaged
  • Operates without conscious control
• Autonomic nervous system


  Consists of two main divisions: sympathetic nervous system and parasympathetic nervous system
• Dual innervation


  Most organs receive nerves from both the sympathetic and parasympathetic divisions
• Sympathetic nervous system


  Promotes the fight-or-flight response, which prepares the body for emergency situations
• Parasympathetic nervous system


  Enhances rest-and-digest activities, which conserve and restore body energy during times of rest or digesting a meal
• Enteric nervous system (ENS)


  Consists of millions of neurons in plexuses that extend most of the length of the gastrointestinal tract
• Autonomic motor pathways


  1. Consist of two motor neurons in series

  2. Preganglionic neuron has cell body in CNS, axon extends to autonomic ganglion

  3. Postganglionic neuron has cell body in autonomic ganglion, axon extends to visceral effector
• Preganglionic neurons


  • In sympathetic division, have cell bodies in lateral horns of spinal cord
  • In parasympathetic division, have cell bodies in brainstem and sacral spinal cord

  
• Somatic motor neurons release only acetylcholine (ACh) as their neurotransmitter
• Autonomic motor neurons release either acetylcholine (ACh) or norepinephrine (NE)
• The somatic nervous system and autonomic nervous system differ in structure and function

  
• Input and output components of the autonomic nervous system

  • Interoceptors (main input)
  • Visceral effectors (main output)

  
• Autonomic nervous system


  • Has two motor neurons in each motor pathway
  • Preganglionic neuron synapses with postganglionic neuron
• Anatomical components of the somatic and autonomic nervous systems

  • Sensory input
  • Control of motor output
  • Motor neuron pathway
  • Neurotransmitters and hormones
  • Effectors
  • Responses

  
• Sympathetic preganglionic axons are shorter, as the sympathetic ganglia are near the spinal cord. Parasympathetic preganglionic axons are longer, as the terminal ganglia are located close to or within the visceral organs.
• Parasympathetic division has terminal (intramural) ganglia located close to or within the visceral organs. Sympathetic division has sympathetic trunk ganglia and prevertebral ganglia.
• Sympathetic preganglionic neuron axons

  • May synapse with postganglionic neurons in the ganglion it first reaches
  • May ascend or descend to a higher or lower ganglion before synapsing
  • May continue through the sympathetic trunk ganglion to end at a prevertebral ganglion
  • May pass through the sympathetic trunk ganglion and a prevertebral ganglion to the adrenal medullae
• A single sympathetic preganglionic fiber has many axon collaterals and may synapse with 20 or more postganglionic neurons, allowing widespread sympathetic responses
• Parasympathetic preganglionic axons pass to terminal ganglia near or within a visceral effector, usually synapsing with only 4-5 postganglionic neurons supplying a single effector, allowing localized parasympathetic responses
• Autonomic plexuses


  • Tangled networks of both sympathetic and parasympathetic axons, often along major arteries
  • Contain sympathetic ganglia and autonomic neurons
• Lic


  Unspecified term
• Periarterial


  Around an artery
• Nerve


  Part of the nervous system that transmits signals

  
• Posterior horn


  Part of the spinal cord
• Visceral effector: heart


  Part of the body that is innervated by the autonomic nervous system
• Carotid artery


  Major artery in the neck
• Visceral effectors


  • Eyes
  • Lacrimal glands
  • Salivary glands
  • Pineal gland
  • Nasal mucosa
  • Sweat glands
  • Blood vessels
  • Arrector pili muscles of skin of face
• Posterior root


  Part of a spinal nerve
• Ganglion


  Cluster of nerve cell bodies
• Anterior root


  Part of a spinal nerve
• Prevertebral ganglion


  Ganglion located in front of the vertebral column
• Celiac ganglion


  Prevertebral ganglion located near the celiac artery
• Chromaffin cell


  Cell that secretes hormones
• Adrenal cortex


  Outer layer of the adrenal gland
• Adrenal medulla


  Inner layer of the adrenal gland