parasympathetic system

Examples of parasympathetic system in the following topics:

• Parasympathetic Responses

  • The parasympathetic nervous system regulates organ and gland function during rest and is considered a slowly activated, dampening system.
  • The parasympathetic nervous system (PSNS, or occasionally PNS) is one of the two main divisions of the autonomic nervous system (ANS) (shown in ).
  • The sympathetic nervous system can be considered a quick response, mobilizing system; and the parasympathetic a more slowly activated dampening system.
  • The parasympathetic nervous system may also be known as the parasympathetic division.
  • The parasympathetic nervous system, shown in blue, is a division of the autonomic nervous system.

• Parasympathetic (Craniosacral) Division

  • Parasympathetic ganglia are the autonomic ganglia of the parasympathetic nervous system which lie near or within the organs they innervate.
  • Parasympathetic ganglia are the autonomic ganglia of the parasympathetic nervous system, blue fibers).
  • Because of its location, the parasympathetic system is commonly referred to as having "craniosacral outflow," which stands in contrast to the sympathetic nervous system, which is said to have "thoracolumbar outflow."
  • The parasympathetic nervous system, shown in blue, is a division of the autonomic nervous system.
  • Describe features of the parasympathetic division of the autonomic nervous system

• Autonomic Interactions

  • The sympathetic and parasympathetic autonomic nervous systems cooperatively modulate internal physiology to maintain homeostasis.
  • Example processes that are modulated by the sympathetic and parasympathetic systems and are not easily labeled as "fight" or "rest" include the maintenance of blood pressure when standing and the maintenance of regular heart rhythms.
  • Some typical actions of the sympathetic and parasympathetic systems are listed below.
  • In the autonomic nervous system, preganglionic neurons connect the CNS to the ganglion.
  • Describe the interactions between the sympathetic and parasympathetic divisions of the autonomic nervous system

• Divisions of the Autonomic Nervous System

  • The autonomic nervous system (ANS) contains two subdivisions; the parasympathetic (PSNS) and sympathetic (SNS) nervous systems.
  • The autonomic nervous system (ANS) is classically divided into two subsystems (see : the parasympathetic nervous system (PSNS) and sympathetic nervous system (SNS).
  • The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.
  • Sympathetic and parasympathetic divisions typically function in opposition to each other.
  • Distinguish between the parasympathetic and sympathetic subsystems of the autonomic nervous system

• Preganglionic Neurons

  • In the autonomic nervous system (ANS), nerve fibers that connect the central nervous system to ganglia are known as preganglionic fibers.
  • In the autonomic nervous system (ANS), fibers from the central nervous system to the ganglion are known as preganglionic fibers.
  • All preganglionic fibers, whether they are in the sympathetic nervous system (SNS) or in the parasympathetic nervous system (PSNS), are cholinergic - that is, these fibers use acetylcholine as their neurotransmitter - and are myelinated.
  • 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 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.

• Autonomic Reflexes

  • The autonomic nervous system (ANS or visceral nervous system or involuntary nervous system) is the part of the peripheral nervous system that acts as a control system.
  • The ANS is classically divided into two subsystems: the parasympathetic nervous system (PSNS) and sympathetic nervous system (SNS) which operate independently in some functions and interact co-operatively in others.
  • An older simplification of the sympathetic and parasympathetic nervous systems as "excitatory" and "inhibitory" was overturned due to the many exceptions found.
  • A more modern characterization used is that the sympathetic nervous system is a "quick response mobilising system" and the parasympathetic is a "more slowly activated dampening system"; but even this also has exceptions, such as in sexual arousal and orgasm where both play a role.
  • The enteric nervous system is also sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

• Autonomic Nervous System (ANS)

  • The autonomic nervous system (ANS or visceral nervous system or involuntary nervous system) is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness and controls visceral functions .
  • It is classically divided into two subsystems: the parasympathetic nervous system (PSNS) and sympathetic nervous system (SNS).
  • The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.
  • The effect of parasympathetic stimulation is to increase activity in the entire enteric nervous system The proximal half of the nervous system is innervated from the cranial parasympathetic nerve fibers via the vagal nerve.
  • The distal half is innervated via the Sacral Parasympathetic nerves.

• Autonomic Ganglia

  • In the peripheral nervous system, afferents refer to the axons that relay sensory information into the central nervous system (i.e. the brain and the spinal cord).
  • Sympathetic ganglia are the ganglia of the sympathetic nervous system.
  • Parasympathetic ganglia are the autonomic ganglia of the parasympathetic nervous system.
  • Efferent parasympathetic nerve signals are carried from the central nervous system to their targets by a system of two neurons.
  • Parasympathetic ganglia of the head (red circles) help supply all parasympathetic innervation to the head and neck.

• Postganglionic Neurons

  • In the parasympathetic division, they are cholinergic and use acetylcholine as their neurotransmitter.
  • The parasympathetic fibers: The axons of presynaptic parasympathetic neurons are usually long: They extend from the CNS into a ganglion that is either very close to or embedded in their target organ.
  • As a result, the postsynaptic parasympathetic nerve fibers are very short.
  • In the cranium, preganglionic fibers (Cranial nerves III, VII, and IX) usually arise from specific nuclei in the Central Nervous System (CNS) and synapse at one of four parasympathetic ganglia: ciliary, pterygopalatine, otic, or submandibular.
  • The parasympathetic nervous system uses acetylcholine (ACh) as its chief neurotransmitter, although peptides (such as cholecystokinin) may act on the PSNS as a neurotransmitter.

• Vagus (X) Nerve

  • The vagus nerve (cranial nerve X) is responsible for parasympathetic output to the heart and visceral organs.
  • Besides output to the various organs in the body, the vagus nerve conveys sensory information about the state of the body's organs to the central nervous system. 
  • The dorsal nucleus of vagus nerve: Sends parasympathetic output to the viscera, especially the intestines.
  • The nucleus ambiguus: Sends parasympathetic output to the heart (slowing it down).
  • Parasympathetic innervation of the heart is partially controlled by the vagus nerve and is shared by the thoracic ganglia.