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