ANS Flashcards
(48 cards)
ANS General
Controls the body’s involuntary activities. Motor system for visceral organs, blood vessels, and secretory glands.
Oversees the body’s response to immediate lie- threatening challenges and the body’s vital maintenance needs (in: cardiovascular, GI, thermal homeostasis.
Nerves
Bundles of axons of nerve cell, or neuron.
Axon
a nerve fiber; a long projection off o a nerve cell, or neuron.
Ganglia
cluster of nerve cell bodies in peripheral nervous system. synapse depot for nerves.
Afferent
an axon that carries sensory info from periphery to the CNS.`
Efferent
axon that carries motor info from the CNS to the periphery.
Neurotransmitter
endogenous chemicals that relay an action potential from one nerve, across a synapse to a target nerve or organ.
Synapse
a synpatic cleft or space between the presynaptic and postsynaptic endings/effector organ, where the action potential is carried by neurotransmitters.
ANs Anesthesia Concern
Pulmonary, cardio, thermal, endocrine, and GI
Organization of ANS (General)
Preganglionic neuron (1st neuron between cns& ganglia)
- located in hypothalamus, brain stem or spinal cord
- projects to an autonomic ganglia
- Thinly myleinated axon
- ALL release acetylcholine onto nicotinic receptors.
Postganglionic Neurons (2nd neuron goes from ganglia to the effector organ) - unmyelinated axon
ANS Subsystems
Sympathetic Nervous System
- Fight or Flight
- amplification response
Parasympathetic Nervous System
- Rest and Digest
- discrete and narrowly targeted response
Ganglia Difference
Sympathetic Pathway
- close to the spinal cord
- short preganglionic fibers.
- long postganlionic fibers
Parasympathetic Pathway
- ganglia close to/ or in effector organ.
- long preganglionic fibers
- short postganglionic fibers
What is the first neural response?
Acetylcholine
Basal Rate
PsNS and SNS both are “on” at the same time: tone, allows for quick shifting from one to the other, fine control.
Predominant PsNS tone: cilliary muscle, Iris,SA node, GI tract, uterus, bladder, salivary glands.
Predominant SNS: arteriole, veins, sweat glands
Basal Rate
- Most organs have dual innervation (accelerator & brake).
- some patients have exagerrated effects. one or the other
2nd Messenger in ANS
- interaction of neurotransmitters with postsynaptic receptors results in signal transduction.
- in adrenergic (sympathetic) system, trasduction is mediated by G protein, which then regulates adenylyl cyclase, and phospholipase C to generate 2nd meengers and / or directly modulate various ion channels.
SYN 3 types of nerve fibers
- Grouped as paired sympathetic chains (2 sets)
- Various unpaired distal plexuses (group of nerves)
- terminal or collateral ganglia near the target.
largest segment comes from the Thoracic
What is a Plexuses
A bundle of nerves
SNS response to internal or external challenges
- fight or flight
- increase heart rate, arterial pressure, and cardiac output; dilate the bronchial tree; and shunt blood away from intestine and other viscera to voluntary muscles.
PsNS nervous input
Acts primarily to conserve energy and maintain organ function and to support vegetative processes.
What Happens in Horner Syndrome?
Stellate ganglion blockage with local anesthetic blocks the sympathetic fibers coursing to the ipsilateral head and neck.
This is characterized by ptosis, miosis, enopthalmos, and anhydrosis on the affected side.
3 paths axons can take
- enter the sympathetic chain via the white ramus and synapse there
- enters the sympathtic chain via the white ramus and ascend or descend a few segments before synpasing.
- enter via the white ramus and exit the chain without synpasing, but continue on to an outlying collateral ganglion.
Fight or Flight
Increased: BP, HR, and contractility, blood flow to skeletal muscles, blood glucose (via liver stimulation), mental activity (increased cortisol), metabolic rate, coagulation.
SNS: nerve/ synapse outside the CNS
- Paravertebral: 22 paired ganglia: sympathetic chain running along the and left side of the spinal column.
- Prevertebral: Unpaired ganglia, ganglia are in abdomen and pelvis.
- collateral: terminal ganglia, few ganglia, located near organs they innervate.
- Sympathetic preganglionic neurons can “meet up with’ their respective postganglionic partners.