Autonomic Nervous System Flashcards
What does the somatic component of the nervous system do?
collects:
- sensory information including tactile, pain, and thermal sensation
- proprioception from external environment
propagates motor impulses to skeletal muscles
What does the visceral (autonomic) component of the nervous system do?
- gathers sensory info such as pressure and stretch from internal milieu
- distributes motor impulses to glands, smooth muscles, and cardiac muscles
What is the motor part of the somatic nervous system composed of?
a single neuron that connects CNS (either the motor nuclei of cranial nerves or the anterior horns of the spinal cord) to the skeletal muscles
What is the motor part of the autonomic nervous system composed of?
2 neurons that synapse at autonomic ganglia, and connect the CNS (either parasympathetic nuclei of cranial nerves III, VII, IX and X - or lateral horns of spinal cord) to target organs
What are the 2 divisions of the motor component of the autonomic nervous system?
sympathetic division
parasympathetic division
What does the sympathetic division of the autonomic nervous system do?
- prepares body for emergencies (flight or flight), increasing heart beat and respiratory rate, constricting peripheral blood vessels, and increasing blood pressure
- changes distribution pattern of blood in body (ie. blood will be rerouted from skin and intestine to skeletal muscles)
- suppresses peristaltic movements of gastrointestinal tract, and constricts sphincters
What does the parasympathetic division of the autonomic nervous system do?
- stores energy (rest and response)
- usually activated after meal and reduces heart beat, increases gastrointestinal tract and endocrine gaand secretion, and dilates sphincters of gastrointestinal tract and urinary system
- causes sleepiness
Sympathetic Nervous System
What is the sympathetic division composed of?
- centers
- ganglia
- efferent fibers
Sympathetic Nervous System
What do efferent fibers do?
connect centers and ganglia to target organs
Sympathetic Nervous System
What are the preganglionic (motor) neurons of this system?
- reside in lateral horn of spinal cord segemnts T1-L2
- axons of these neurons form efferent (motor) fibers that travel along with the ventral root of the corresponding spinal nerve
Sympathetic Nervous System
What are white ramus communicans?
efferent (motor) fibers after emerging through the intervertebral foramen, and entering the sympathetic trunk
Sympathetic Nervous System
4 routes that preganglionic fibers may take.
- They may synapse with the postganglionic neurons in the sympathetic trunk ganglia at the same level. The axons of postganglionic neurons either return to the corresponding spinal nerve as gray ramus communicans to be distributed to the body wall or directly target the thoracic viscera. Those postganglionic fibers traveling with the spinal nerve target the smooth muscles and glands of the body wall skin. Those postganglionic fibers targeting the thoracic viscera arise from Tl to T4 ganglia and are usually named after their primary targets such as cardiac and esophageal nerves.
- They may ascend to higher levels or descend to lower levels along with the sympathetic trunk and synapse with the postganglionic neurons at that level. The postganglionic fibers then either enter the spinal nerve as gray ramus communicans to be distributed to the upper and lower limbs or directly target the head and neck viscera.
- Some of these preganglionic fibers bypass the sympathetic
trunk ganglia without synapsing and form splanchnic nerves including greater, lesser, least, and lumbar splanchnic nerves. The splanchnic nerves enter the abdomen and synapse with the postganglionic neurons in prevertebral ganglia
such as celiac, superior mesenteric and inferior mesenteric ganglia. The postganglionic fibers then target the abdominal or pelvic viscera. It’s worth mentioning that the sacral splanchnic nerves are exceptionally postganglionic fibers and directly target some of the pelvic viscera. - There are also some preganglionic fibers that bypass the sympathetic trunk ganglia without synapsing and supply the suprarenal (adrenal) medulla, thus the suprarenal medulla cells act as the postganglionic neurons.
Sympathetic Nervous System
What are gray ramus communicans?
axons of postganglionic neurons may return to the corresponding spinal nerve as gray ramus communicans (otherwise they are distributed to the body wall or directly target the thoracic viscera)
Sympathetic Nervous System
What are the 4 types of splanchnic nerves?
- greater
- lesser
- least
- lumbar
Sympathetic Nervous System
What are splanchnic formed by?
formed by preganglionic fibers, if these fibers bypass sympathetic trunk ganglia without synapsing
Sympathetic Nervous System
What are the 3 types of prevertebral ganglia?
- celiac
- superior mesenteric
- inferior mesenteric
Sympathetic Nervous System
What are sacral splanchnic nerves?
exceptionally postganglionic fibers that directly target some of the pelvic viscera
Sympathetic Nervous System
What is the sympathetic trunk (chain) formed by?
ascending and descending sympathetic fibers and the associated ganglia (paraverterbal ganglia)
Parasympathetic Nervous System
What is the parasympathetic division composed of?
- centers
- ganglia
- efferent fibers
Parasympathetic Nervous System
Where are the preganglionic (motor) neurons of this system?
in either the parasympathetic nuclei of the cranial nerves III, VII, IX, and X in the brainstem
or
in lateral horn of spinal cord segements S2-S4
Parasympathetic Nervous System
In which 4 ganglia are the postganglionic parasympathetic neurons in the head located in?
- ciliary ganglion
- pterygopalatine ganglion
- submandibular ganglion
- otic ganglion
Parasympathetic Nervous System
What is the ciliary ganglion?
- associated with CN III
- gives rise to postganglionic fibers that target ciliary muscle and sphincter pupil
Parasympathetic Nervous System
What is the pterygopalatine ganglion?
- associated with CN VII
- its postganglionic fibers mainly target lacrimal gland
Parasympathetic Nervous System
What is the submandibular ganglion?
- associated with CN VII
- its postganglionic fibers regulate secretion of submandibular and sublingual glands
Parasympathetic Nervous System
What is the otic ganglion?
- associated with CN IX
- its postganglionic fibers regulate secretion of parotid gland
Parasympathetic Nervous System
What do preganglionic parasympathetic fibers of CN X synapse with?
parasympathetic (visceral) ganglia located close or within the wall of the target organs
- short postganglionic fibers arising from these ganglia supply thoracic and part of the abdominal viscera
Parasympathetic Nervous System
What are pelvic splanchnic nerves?
preganglionic parasympathetic fibers that arise from lateral horn of spinal cord segments S2-S4
Parasympathetic Nervous System
Where do the pelvic splanchnic nerves enter?
enters pelvis via sacral nerves, and innervate the distal part of the gastrointestinal tract and pelvic viscera
Autonomic Sensory Neurons
Where are autonomic sensory neurons founds?
in dorsal root ganglia of spinal nerves, or sensory ganglia of cranial nerves VII, IX, and X
Autonomic Sensory Neurons
What do peripheral fibers of autonomic sensory neurons do?
collect sensory info concerning stretch, chemical stimulation, and hypoxia from glands and smooth muscles
Autonomic Sensory Neurons
Where are the central fibers of the autonomic sensory neurons within the dorsal root ganglia
they enter the posterior horn of the spinal cord and contribute to the spinothalamic tract
Autonomic Sensory Neurons
Where are the central fibers of the autonomic sensory neurons within the sensory ganglia of cranial nerves VII, IX, and X?
they enter the sensory nuclei of the brainstem and from there travel to the thalamus
Enteric System
What is the enteric system?
subdivision of ANS
Enteric System
What does the enteric system consist if?
motor and sensory neurons that form a local neuronal circuit in the wall of the alimentary canal
Enteric System
How are the motor and sensory neurons organized?
into 2 interconnected plexuses (myentric and submucosal) between layers of the alimentary canal
Enteric System
What does the enteric system regulate?
alimentary canal activities including glandular secretion, motility (peristalsis), and blood flow
Enteric System
How is the enteric system connected to the ANS and CNS?
this system receives input from motor part of ANS, but generally acts independent of CNS
Autonomic Plexuses
What are autonomic plexuses?
nervous networks formed by sympathetic and parasympathetic fibers, along with afferent autonomic fibers
Autonomic Plexuses
What is the cardiac plexus?
autonomic plexus in the thoracic region named after the target organ - heart
Autonomic Plexuses
What is the pulmonary plexus
autonomic plexus in the thoracic region named after the target organ - lungs
Autonomic Plexuses
What are autonomic plexuses in the abdomen associated with?
autonomic ganglia that serve as synapse site for preganglionic sympathetic fibers
Autonomic Plexuses
Where are abdominal autonomic plexuses?
surround abdominal aorta branches, and use these brances as a guide to distribute to target organs
Autonomic Plexuses
What are the 3 types of abdominal autonomic plexuses?
- celiac plexus
- superior mesenteric plexus
- inferior mesenteric plexus
named after the aorta branches (arteries) they surround
Autonomic Plexuses
What forms the superior hypogastric plexus?
parts of the outflow of the 3 types of abdominal autonomic plexuses (celiac, super mesenteric, inferior mesenteric)
Autonomic Plexuses
Where is the superior hypogastric plexus formed?
in front of the bifurcation of aorta
Autonomic Plexuses
What are inferior hypogastric nerves?
bifurcation of aorta splits into right and left bundles known as the inferior hypogastric nerves
Autonomic Plexuses
What forms the inferior hypogastric plexus?
inferior hypogastric nerves descending into the pelvis, and along with autonomic fibers in the pelvic region
