sympathetic root

Examples of sympathetic root in the following topics:

• Parasympathetic (Craniosacral) Division

  • Each has three roots entering the ganglion (motor, sympathetic, and sensory roots) and a variable number of exiting branches.
  • The motor root carries presynaptic parasympathetic nerve fibers (general visceral efferent fibers) that terminate in the ganglion by creating a synapse for the postsynaptic fibers traveling to target organs.
  • The sympathetic root carries postsynaptic sympathetic fibers (general visceral efferent fibers) that traverse the ganglion without creating a synapse.
  • The sensory root carries general sensory fibers (general somatic afferent fibers) that also do not create a synapse in the ganglion.
  • Because of its location, the parasympathetic system is commonly referred to as having craniosacral outflow, in contrast to the sympathetic nervous system, which is said to have thoracolumbar outflow.

• Autonomic Ganglia

  • The two main categories are: sympathetic ganglia and parasympathetic ganglia.
  • A dorsal root ganglion (or spinal ganglion) is a nodule on a dorsal root of the spine that contains the cell bodies of nerve cells (neurons) that carry signals from the sensory organs towards the appropriate integration center.
  • The axons of dorsal root ganglion neurons are known as afferents.
  • Sympathetic ganglia are the ganglia of the sympathetic nervous system.
  • Sympathetic ganglia are the tissue from which neuroblastoma tumors arise.

• Function and Physiology of the Spinal Nerves

  • The phrenic nerve arises from nerve roots C3, C4, and C5.
  • The sympathetic division typically functions in actions that need quick responses.
  • The functions of the parasympathetic and sympathetic nervous systems are detailed.
  • This diagram indicates the formation of a typical spinal nerve from the dorsal and ventral roots.
  • Numbers indicate the types of nerve fibers: 1 somatic efferent, 2 somatic afferent, 3–5 sympathetic efferent, 6–7 sympathetic afferent.

• Sympathetic Nervous System

  • Sympathetic ganglia are the ganglia of the sympathetic nervous system that initiate fight-or-flight, stress-mediated responses.
  • The sympathetic ganglia are the ganglia of the sympathetic nervous system (the red lines in the diagram below).
  • This response is also known as the sympathetico-adrenal response because the pre-ganglionic sympathetic fibers that end in the adrenal medulla—like all sympathetic fibers—secrete acetylcholine.
  • Sympathetic ganglia are the tissue from which neuroblastoma tumours arise.
  • This intercostal nerve shows the sympathetic ganglion at the top left.

• Divisions of the Autonomic Nervous System

  • The autonomic nervous system (ANS) contains two subdivisions: the parasympathetic (PSNS) and sympathetic (SNS) nervous systems.
  • Sympathetic and parasympathetic divisions typically function in opposition to each other.
  • The sympathetic division typically functions in actions requiring quick responses.
  • Many think of sympathetic as fight or flight and parasympathetic as rest and digest or feed and breed.
  • Distinguish between the parasympathetic and sympathetic subsystems of the autonomic nervous system

• Cervical Plexus

  • There is anastomosis with the accessory nerve, hypoglossal nerve, and sympathetic trunk.
  • There are two additional branches that are formed by the posterior roots of the spinal nerves:

• Autonomic Interactions

  • The sympathetic and parasympathetic autonomic nervous systems cooperatively modulate internal physiology to maintain homeostasis.
  • Sympathetic and parasympathetic divisions typically function in opposition to each other.
  • The sympathetic division typically functions in actions requiring quick responses.
  • Consider sympathetic as fight or flight and parasympathetic as rest and digest or feed and breed.
  • Some typical actions of the sympathetic and parasympathetic systems are listed below.

• Sympathetic Responses

  • The sympathetic division of the autonomic nervous system maintains internal organ homeostasis and initiates the stress response.
  • Alongside the other two components of the autonomic nervous system, the sympathetic nervous system aids in the control of most of the body's internal organs.
  • The sympathetic nervous system is responsible for regulating many homeostatic mechanisms in living organisms.
  • Some evolutionary theorists suggest that the sympathetic nervous system operated in early organisms to maintain survival since the sympathetic nervous system is responsible for priming the body for action.
  • One example of this priming is in the moments before waking, in which sympathetic outflow spontaneously increases in preparation for activity.

• Overview of the Spinal Nerves

  • Each spinal nerve is formed by the combination of nerve fibers from the dorsal and ventral roots of the spinal cord.
  • The dorsal roots carry afferent sensory axons, while the ventral roots carry efferent motor axons.
  • The first and second, and sometimes the third and fourth, lumbar nerves are each connected with the lumbar part of the sympathetic trunk by a white ramus communicans.
  • Its anterior root helps form the coccygeal plexus.
  • Spinal nerves arise from a combination of nerve fibers from the dorsal and ventral roots of the spinal cord.

• Preganglionic Neurons

  • Sympathetic preganglionic fibers tend to be shorter than parasympathetic preganglionic fibers because sympathetic ganglia are often closer to the spinal cord while parasympathetic preganglionic fibers tend to project to and synapse with the postganglionic fiber close to the target organ.
  • The sympathetic division has thoracolumbar outflow, meaning that the neurons begin at the thoracic and lumbar (T1–L2) portions of the spinal cord.
  • The sympathetic division (thoracolumbar outflow) consists of cell bodies in the lateral horn of the spinal cord (intermediolateral cell columns) from T1 to L2.
  • Whereas in the parasympathetic division there is a divergence factor of roughly 1:4, in the sympathetic division there can be a divergence of up to 1:20.
  • The site of synapse formation and this divergence for both the sympathetic and parasympathetic preganglionic neurons does, however, occur within ganglia situated within the peripheral nervous system.