ANS Flashcards
What does the ANS control
Controls function of structures with smooth muscle, cardiac muscle, and certain glands
The ANS usually operates without conscious control EXEPT for when it uses
Emotion and memory
Where do sympathetic fibers originate
Lateral horn of T1-L3 “thoracolumbar division”
Where do parasympathetic fibers originate?
CN 3, 7, 9, 10 from the brainstem
S2-S4
“Craniosacral division”
The major brain structure receiving afferent information for the somatic ns is the ____________ and for the autonomic ns is the __________________
Thalamus
Hypothalamus
The major source of descending pathways for the somatic ns is __________and for the autonomic ns is ______________
Cerebral cortex
Hypothalamus
Efferent links between the CNS and viscera innervated by ANS involve how many neurons
2
What type of synapses are used for the ANS? What does this allow
Electrical synapse (gap junctions) Allows for steady and widespread contractions of visceral tissue (continuous and automatic)
Describe the myelination of the pre- and post- ganglionic ANS fibers
Pregang. Are lightly myelinated
Postgang. Are not myelinated
Describe the position of sympathetic and parasympathetic postganglionic cell bodies (in ganglia)
Sympathetic- cell bodies typically positioned close to spinal cord
Parasympathetic- cell bodies positioned close to effector
Describe sympathetic and parasympathetic pre/postganglionic fiber lengths
SYMPATHETIC short preganglionic long postganglionic
PARASYMPATHETIC long preganglionic short postganglionic
Describe the neurotransmitters released by sympathetic and parasympathetic nervous systems
SMPATHETIC ACh released at terminals of preganglionic fibers and NE released at terminals of postganglionic fibers
PARASYMPATHETIC ACh released at terminals of pre and postganglionic fibers
What receptors are found in the sympathetic and parasympathetic fibers
Ionotropic and metabotropic fibers
Function of the sympathetic nervous system
Increase activity during times of physical and emotional stress (exercise, emergency, excitement, and embarrassment)
Sympathetic NS triggers what reactions
• Pupil dilation and eyelid retraction
• Inhibition of salivation and lacrimation
• Stimulation of sweat glands
• Vasoconstriction of blood vessels to skin and gut
• Reroutes blood to muscles
• Piloerection
• Bronchodilation
• Increase in HR and cardiac output
• Reduction in neural output to digestive tract
• Inhibits digestion, inhibitions insulin release, inhibits intestinal motility and secretion
• Stimulation of hormone release
• From adrenal medulla: epinephrine and
norepinephrine
• From pancreas: glucagon
Preganglionic neurons extend from T1-L2/3 in the lateral horn of spinal gray matter to __________ and ____________
Head and thorax (via upper &mid thoracic fibers)
Abdominal organs, pelvic organs, and LE targets (via lower thoracic and upper lumbar fibers)
What different routes are take after sympathetic fibers exit SC via ventral rami
- To sympathetic trunk and synapse immediately w/ post gang. Neurons at same sc level
- Travel to sympathetic trunk and either ascend or descend to synapse in more cranial or caudal ganglia
- Go through trunk without synapse, to synapse later with postganglionic neurons in prevertebral ganglia
Preganglionic sympathetic diverge to synapse with multiple postganglionic fibers… this results in…
A single preganglionic fiber to have multiple target tissues (SNS can mass activate targets in response to stress)
Where are the targets for the postganglionic neurons of the SNS
To blood vessels and skin via gray communicating rami
To viscera via prevertebral ganglia
To lower extremities (sweat, vasoconstriction, and piloerection)
The main function of the parasympathetic NS is to
Increases activity during “rest and digest” periods to conserve energy use and build energy stores
The parasympathetic NS causes
Pupillary constriction
Activation of salivary an lacrimal glands
Slowing of HR
Bronchoconstriction
Vasodilation of vessels to intestines, rectum, bladder, and reproductive organs
Parasympathetic preganglionic neurons are found where? Where do they travel?
In the brainstem and sacral spinal cord and travel to the parasympathetic ganglia located close to the target muscles and glands
Parasympathetic Brainstem preganglionic nu
Edinger-westphal nu (3)
Superior and inferior salivary nu (7)
Nu. Ambiguous (9)
Dorsal motor nu of vagus n. (10)
Where are the sacral preganglionic nu
Lateral horns of S2-S4
Preganglionic Edinger-Westphal nu project to postganglionic neurons where?
Ciliary muscles for pupillary constriction
Preganglionic neurons from the superior and inferior salivary nuclei project where?
Salivary and lacrimal glands
Preganglionic neurons from nu ambiguous project to postganglionic neurons where?
Cardiac muscles for slowing HR
Preganglionic neurons from the dorsal motor nu of the vagus nerve project to postganglionic neurons where?
Thorax and abdomen for glandular secretion
Cardiac muscle for slowing HR
Lungs for bronchoconstriction
Gut for increased motility and digestion
Sacral preganglionic nuclei project from the lateral horns of S2-S4 to postganglionic neurons where?
Colon for vasodilation
Rectum for vasodilation
Bladder for muscle contraction
Reproductive organs for vasodilation
Most structures are innervated by sympathetic and parasympathetic ns except for
These are innervated by (sympathetic/parasympathetic) only.
Sweat glands
Erector pili muscles
Most blood vessels
Adrenal medulla
Sympathetic innervation only
What structure regulates the amount of parasympathetic/sympathetic input on a target organ
Hypothalamus
Why do sympathetic responses are longer lasting than parasympathetic responses
Divergence of preganglionic neurons
Longer unmyelinated postganglionic neurons
Slower inactivation of NE in the synapse
Presence of NE and E from adrenal medulla in blood
Acccelerated parasympathetic responses can be activated during _____________
Paradoxical fear
Define paradoxical fear
Fear without a way to “win”
Accepting the outcome
List the structures that control ANS function
Hypothalamus Brainstem nu Amygdala (and other limbic structures) Medial prefrontal cortex Insular cortex
ANS control is regulated by
Barorectptors
Chemoreceptors
Osmoreceptors
Thermoreceptors
Afferent input from sympathetic and parasympathetic structures serves what functions:
Feedback input via solitary nu for local autonomic reflex (modulates visceral motor activity)
Inform higher integrative centers for more complex patterns of stimulation that may signal danger and/or may require more multi system control
The medullary reticular formation performs ________ control on SNS and PSNS preganglionic neurons
Modulatory
The dorsal horn and intermediate zone of spinal gray matter perform project neurons (bilaterally, ipsilaterally, or contralaterally) to the solitary nu
Ipsilaterally
Solitary nu project where to eventually impact SNS and PSNS preganglionic neurons
To parabrachial nucleus
Medullary reticular formation
And directly to SNS/PSNS preganglionic neurons (reflex)
How does information get to the hypothalamus to control SNS/PSNS preganglionic neurons?
Baro/chemo/thermo/osmo- receptors > dorsal root ganglion > dorsal horn and intermediate zone of grey matter > solitary nu > parabrachial nu ( to hypothalamus) and > thalamus >cortex > amygdala > hypothalamus > preganglionic neurons
Explain referred pain
Some of the 2nd order neurons in the dorsal horn that receive visceral sensory input are part of the anterolateral system > since these neurons are also in charge of relaying input about superficial pain, visceral pain often gets perceived as cutaneous pain
> travels to VPL of thalamus then to insular cortex for integration
Where is visceral input integrated with input from other sensory modalities and from higher cognitive centers (central autonomic network)
Insular cortex
Medial prefrontal cortex
Hypothalamus
Hippocampal formation and amygdala
What is considered the primary visceral motor area
Insular cortex
What is considered the primary visceral motor area
Medial prefrontal cortex
What part of the central autonomic network compares input to biological set points (controls blood flow, regulates metabolism, regulates reproductive activity, and coordinates responses to threatening conditions)
Hypothalamus
What nervous system is the largest and most complex system of the ANS
Enteric system
The enteric system exerts control of gastrointestinal system through neuronal system embedded in the lining of GI organs to do what functions?
Peristalsis
Segmentation
Hormone secretion (gastrin and secretin)
The enteric ns utilizes more than 30 neurotransmitters (nicknamed second brain), how much of the body’s serotonin is found in the gut? How about dopamine?
90% of the body’s serotonin
50% of the body’s dopamine
The gut is modulated by sympathetic and parasympathetic ns but also has _________________________________ that operate independently of SNS and PSNS control
An extensive system of nerve cells in its wall
