Autonomic Nervous System Flashcards
Which CN neurons transmit viscerosensory information?
9 and 10
What are the 2 types of viscerosensory receptors?
- Nociceptors
2. Physiologic
What type of stimuli do nociceptors respond to?
stimuli that have the potential to damage tissue or to stimuli resulting from the presence of damaged tissue.
Why is visceral pain often described as diffuse and difficult to localize?
Because receptor density is low and receptive fields are correspondingly large.
What type of stimuli do physiologic receptors respond to?
innocuous stimuli monitoring the functions of visceral structures on a continuing basis. (help to maintain homeostasis)
What are the two pathways in the viscerosensory and visceromotor systems?
- Sympathetic
2. Parasympathetic
In the viscerosensory system, what type of information does the sympathetic nervous system convey?
Information originating from nociceptors
In the viscerosensory system, what type of information does the parasympathetic nervous system convey?
Information originating from physiologic receptors
Where do viscerosensory fibers originate from?
structures that receive GVE input from the same spinal level as the one it is entering.
What type of visceral activity that enters the spinal cord reach the level of consciousness?
only information related to pain
What are the target areas of the viscerosensory system?
- Reticular Formation
2. Nucleus of Solitary Tract
What is the reticular formation made up of?
Diffuse and ill-defined collection of nuclei interspersed among all the more compact and named structures of the brainstem.
Where does the reticular formation project to?
Hyothalamus and thalamus, ultimately projects to broad areas of cortex (mostly frontal lobe).
What type of information reaches the reticular formation?
Sympathetic and Parasympathetic viscerosensory information.
What is the job of the reticulothalamic/thalamocortical pathway?
To “alert” or “activate” the cerebral cortex as a whole and constitute one important part of the ascending reticular activating system.
Where is the Nucleus of the Solitary Tract located?
Medulla
What type of information does the Nucleus of the Solitary Tract receive?
Parasympathetic viscerosensory information
Where does information from the Nucleus of the Solitary tract project to?
Several brainstem nuclei that are involved in pharyngeal and laryngeal reflexes and the central regulation of respiratory, cardiovascular, and GI fxns.
What is referred pain?
Where noxious stimuli originate in a visceral structure and are perceived as pain arising from a somatic structure. Mechanism is thought to involve a convergence of somatic and visceral information onto pools of dorsal horn neurons
What are the target tissues of the Visceromotor system?
- Cardiac Muscle (SA node)
- Smooth Muscle (blood vessels and hollow viscera)
- Glandular Epithelium (skin, hollow, and solid viscera)
What type of influence do the sympathetic and parasympathetic divisions have on target tissues?
Overlapping and anatagonist influences on target tissues located in body cavities and some structure of the head.
What does the sympathetic division of the visceromotor system innervate?
Target tissues of body wall and extremities, adrenal medulla, and most arterial blood vessels.
What are the 2 neurons involved in the pathway from Brainstem/Spinal Cord–> Target Tissues?
- Preganglionic Neuron
2. Postganglionic Neuron
Where is the cell body and axon of the preganglionic neuron?
Cell Body- CNS
Myelinated axon projects to an autonomic ganglion
Where is the cell body and axon of the postganglionic neuron?
Cell Body- Autonomic ganglion
Unmyelinated axon projects to target tissue
Where do the preganglionic neurons in the sympathetic division of visceromotor system synapse?
On chromaffin cells of adrenal medulla
Describe the synapse with target tissues of the terminal branches of postganglionic neurons.
- Postganglionic neurons have swellings containing neurotransmitter vesicles along their length, giving them a beaded appearance.
- Neurotransmitter released acts on effector cells up to 100mm away. Therefore exerting a diffuse control over target tissues.
What are the functions of the visceromotor system?
- Control of visceral functions- regulation of cardiovascular, respiratory, digestive, urinary, and reproductive organs.
- Adaptive responses to stimuli- light, temperature, stress.
Where does the sympathetic outflow in the visceromotor system originate?
Thoracolumbar area- T1-L2 (Intermediolatearl Cell Column of Lateral Horn)
How is the pathway of the sympathetic division different from parasympathetic in visceromotor system?
Generally have short preganglionic fibers and long post ganglionic fibers.
Where are the cell bodies and axons of the preganglionic neurons in the sympathetic division of the visceromotor system?
Cell bodies: Interomedial cell column of the lateral horn of T1-L2.
Axons: exit through ventral roots and enter sympathetic trunk via white communicating rami
Where are the 3 places the preganglionic neuron in the sympathetic division of the visceromotor system can synapse?
- In a paravertebral ganglion either at the same or different level.
- Pass through a paravertebral ganglion to form a splanchnic nerve
- Pass through a paravertebral ganglion to synapse directly on a chromaffin cell of adrenal medulla.
What is the adrenal medulla?
An endocrine gland that secretes both epinephrine and norepinephrine into circulation
How are the cell bodies of the postganglionic neurons in the sympathetic division of the visceromotor system grouped?
Grouped into discrete ganglia that are located at some distance from the target tissue.
- Cell bodies in paravertebral ganglion
- Cell bodies in prevertebral ganglion.
When the cell bodies are in the paravertebral ganglion, what are the 2 pathways of the axons.
Axon exits through gray communicating ramus (spinal nerve)–>target tissues of head, body wall, and extremities.
Axon exits as carotid, cardiac, or pulmonary nerve–> target tissues of head and thorax.
When the cell bodies are in the prevertebral ganglion, what is the pathway of the axon?
Splanchnic nerve–>cell body–>axon contributes to formation of perivascular plexus (follows arterial supply of viscera)–> target tissues of abdomen and pelvis
What are the 2 types of ganglia in the sympathetic division of the visceromotor system?
- Paravertebral
2. Prevertebral
Describe the paravertebral ganglia in the sympathetic division of the visceromotor system.
From 2 parallel cords that extend the full length of vertebral column
-connected to spinal cords via white or gray communicating rami
Describe the prevertebral ganglia in the sympathetic division of the visceromotor system.
- Associated with abdominal aorta
- Celiac, Aorticorenal, Superior Mesenteric, Inferior Mesenteric
Describe the branching pattern of the preganglionic neurons
Branch into the periphery and synapse on many postganglionic neurons
-Diffuse and widespread
Where do postganglionic neurons receive input from?
- Many preganglionic neurons
- Lots of input, lots of output.
What neurotransmitters are used when the preganglionic neurons synapse onto the postganglionic neuron in the sympathetic division of the visceromotor system?
Aetylcholine (+Neuropeptides)
What receptors are used when the preganglionic neurons synapse onto the postganglionic neuron in the sympathetic division of the visceromotor system?
Cholinergic-Nicotinic
Ionotropic, evoking fast excitatory postsynaptic potentials
What neurotransmitters are used when the postganglionic neurons synapse on the target tissues in the sympathetic division of the visceromotor system?
- Norepinephrine (except AcH at most sweat glands)
What receptors are used when the postganglionic neurons synapse on the target tissues in the sympathetic division of the visceromotor system?
Adrenergic
Metabotropic, evoking slow excitatory or inhibitory post synaptic potentials
What is the function of the Beta 1 receptors?
Excitatory effects on cardiac muscle.
What is the function of Beta 2 receptors?
Inhibitory effects on smooth muscle
What is the function of the Sympathetic Division of the Visceromotor System?
- Mobilization of resources for intensive activity (aka flight or fight response)
- On going, selective control of viscera
What are the actions of the “flight or fight response”
- Increases: HR, BP, Bloow flow, BG level, sweating, and pupil diameter.
- Decreases: gut motility, digestive gland secretion, blood flow to abdomin or viscera.
- Stimulation of adrenal medulla to enhance response to stress.
What is Complex Regional Pain syndrome?
characterized by chronic, continuous, intense pain in one of the extremities, possibly due to abnormal connections between sympathetic postganglionic neurons and nociceptive dorsal root ganglion neurons following a tissue or nerve injury.
Where does the parasympathetic division of the visceromotor system originate?
Craniosacral Region
Cranio- CN 3, 7, 9, 10
Sacral- S2-S4 (Sacral Parasympathetic Nucleus)
How is the pathway of the parasympathetic division different from sympathetic in visceromotor system?
Generally have long preganglionic fibers and short postganglionic fibers.
Where are the cell bodies and axons of the CRANIAL preganglionic neurons in the parasympathetic division of the visceromotor system?
Cell Bodies: Nuclei of CN 3, 7, 9, 10
Axons: Exit brainstem as branches of those CNs
Where are the cell bodies and axons of the SACRAL preganglionic neurons in the parasympathetic division of the visceromotor system?
Cell bodies: Sacral parasympathetic nucleus of S2-S4
Axon: Exits SC through ventral roots and forms pelvic nerves
In the parasympathetic division of the visceromotor system, how are the post ganglionic neurons divided?
- Selected Cranial (3, 7, 9)
2. CN 10 and Sacral
Where are the cell bodies and axons of the Selected Cranial post ganglionic neurons in the parasympathetic division of the visceromotor system?
Cell Bodies: discrete ganglia associated with each CN
Axons: Travel with branches of CN V and innervate some target tissues of the head
Where are the cell bodies and axons of CN 10 and Sacral post ganglionic neurons in the parasympathetic division of the visceromotor system?
Cell Bodies: Terminal Ganglia
Axons: located in target tissue and innervate target tissues of the body cavities.
Where are the ganglia of the parasympathetic division of the visceromotor system located?
- Selected Cranial: Head, CN 3, 7, 9, 10.
2. Terminal: located in or on the wall of the target organ
Where do post ganglionic neurons receive input from?
Receives synaptic input from only one or a few preganglionic neurons (more focused than sympathetic)
What neurotransmitters are used when the preganglionic neuron synapses on the post ganglionic neuron in the parasympathetic division of the visceromotor system?
Acetylcholine (+Neuropeptides)
What receptors are used when the preganglionic neuron synapses on the post ganglionic neuron in the parasympathetic division of the visceromotor system?
Cholinergic-Nicotinic
What neurotransmitters are used when the post ganglionic neuron synapses on the target tissue in the parasympathetic division of the visceromotor system?
Acetylcholine (+Neuropeptides)
What receptors are used when the post ganglionic neuron synapses on the target tissue in the parasympathetic division of the visceromotor system?
Cholinergic-Muscarinic
Metabotropic. Evokes slow excitatory or inhibitory post synaptic potentials.
What is the functional role of the M1 receptor?
Excitatory effects on smooth muscle and glandular tissue
What is the functional role of the M2 receptor?
Inhibitory effects on smooth muscle and cardiac muscle.
What is the function of the parasympathetic division of the visceromotor system?
- Promotion of restorative processes
2. On-going, selective control of viscera.
Describe the organization of the enteric division of the visceromotor system.
- Walls of GI tract
- Motor+Sensory+ Interneurons in 2 interconnected plexuses.
- Independent of CNS, has both sympathetic and parasympathetic input.
What is the function of the enteric division of the visceromotory system?
Controls the cooridnated contraction and relaxation of intestinal smooth muscle and regulates secretion and blood flow.
What 3 structures are associated with regulation of ANS?
- Hypothalamus
- Nucleus of Solitary Tract
- Reticular Formation
What is responsible for the regulation of ANS?
Central Autonomic Network
What is the Central Autonomic Network?
- interconnected set of structures in the forebrain and brainstem.
- integrates sensory input, and input from higher CNS centers involved in cognition and complex behavioral functions.
- coordinates visceral motor, endocrine, and somatic motor outflow.
What is the role of hypothalamus in Central Autonomic Network?
-Highest integrator of autonomic and endocrine functions.
What is the role of Nucleus of Solitary Tract in Central Autonomic Network?
- most important brainstem structure coordinating autonomic functions.
Where is the nucleus of the solitary tract located and how is it divided?
Location: Medulla
Organization: Divided into caudal (visceral) nucleus and rostral (gustatory) nucleus.
What kind of information does the nucleus of the solitary tract receive?
GVE and SVE (related to taste).
Where do the axons of the visceral nucleus project to?
- Preganglionic neurons in brainstem/SC (sensory/motor reflexes)
- Autonomic centers in reticular formation (cardiac, respiratory centers)
- Higher integrative centers in the hypothalamus and amygdaloid.
What is the reticular formation?
- diffuse and ill-defined collection of nuclei interspersed among brainstem.
- autonomic centers organize the efferent activities of specific pools of primary visceral motor neurons.
Where does the reticular formation get its input from?
Sympathetic and Parasympathetic viscerosensory information.
Where does the reticular formation project to?
- preganglionic neurons in the brainstem/SC
2. Hypothalamus
What are 2 examples of visceral reflexes?
- Cardiovascular- Baroreceptor Reflex
2. Urinary Bladder- Micturition
What is the function of the baroreceptor reflex?
maintains BP within normal ranges in response to sudden postural changes.
Describe what happens during the baroreceptor reflex when a pt stands up and there is a reduction in BP.
- Decrease in discharge of Baroreceptors in carotid and aortic sinuses.–> Increase sympathetic, decrease parasympathetic outflow of cardiac system–> Increase in HR, SV, and TPR–>Increase in BP
What is orthostatic hypotension.
Severe drop in BP when an individual assumes an upright position due to failure of baroreceptor reflex.
What is the function of Micturition?
the neural control of bladder function involves the coordination of relevant autonomic, somatic motor, and cognitive faculties that inhibit or promote urination.
During bladder filling, what is the discharge of mechanoreceptors in bladder?
low
During bladder filling, describe what low discharge of mechanoreceptors causes.
- Increase sympathetic outflow to internal urethral sphincter ( contraction of sphincter)
- inhibition parasympathetic outflow to bladder wall (relaxed wall)
- Tonic activity of sacral somatic motor neurons to external urethral sphincter ( contraction of external urethral sphincter)
-All leads to urine storage
When the bladder is full, what is the discharge of mechanoreceptors in bladder?
increases to a threshold level
When the bladder is full, describe what high discharge of mechanoreceptors causes.
- decrease sympathetic outflow to internal urethral sphincter ( relaxation of sphincter)
- increase parasympathetic outflow to bladder wall (contraction of wall)
- inhibition of sacral somatic motor neurons to external urethral sphincter ( relaxation of external urethral sphincter)
What is autonomic dysreflexia
syndrome characterized by abrupt onset of excessively high BP in persons with SCI due to loss of supraspinal control of sympathetic and sacral parasympathetic system, precipitated by a noxious stimulus below the level of SCI.
