Autonomic Nervous System Flashcards
What is the ANS?
involuntary/visceral motor system (plus BVs, sweat glands)
What is the purpose of the ANS?
maintaining homeostasis and survival
The ANS innervates everything except
CNS tissue and skeletal muscle
What are the 3 divisions of the ANS?
SNS, PSNS, and enteric NS
SNS and PSNS innervate
most but not all tissues
T/F SNS and PSNS innervate the same places within an organ
False; they target different places within the organ
T/F SNS and PSNS are working antagonistically and in competition
False;
The ENS innervates the
GIT
ENS comprises its own
sensory, motor, and interneurons
The ENS has what type of reflexes?
intrinsic/enteric that do not require the brain or spinal cord
T/F the ENS is part of the PSNS
False; it is anatomically and functionally independent
SNS nerves come from the
thoracolumbar: thoracic and upper lumbar spinal cord; none are cervical or sacral in origin
PSNS nerves come from the
craniosacral: brainstem (cranial), and sacral parts of the spinal cord
T/F SNS and PSNS nerves arise from the length of the spinal cord
False; SNS: thoracolumbar, PSNS: craniosacral, no ANS pathways from the cervical or lumbar enlargements
Where in the spinal cord are there no SNS or PSNS pathways originating?
cervical and lumbar enlargements
Sympathetic ganglia are generally
more distant from organs
Parasympathetic ganglia are generally
closer to or within organs
What are the two categories of sympathetic ganglia?
2x Paravertebral (sympathetic chain) and 1x prevertebral (midline)
Paravertebral ganglia are located
sympathetic chain; bilateral on each side of the vertebral column
Prevertebral ganglia are located
one set, down midline
Sympathetic preganglionic axons are (long/short)
short
Sympathetic postganglionic axons are (long/short)
long
Parasympathetic preganglionic axons are (long/short)
long
Parasympathetic postganglionic axons are (long/short)
short
Preganglionic axons are generally
lightly myelinated/unmyelinated
Postganglionic axons are generally
all unmyelinated
T/F somatic/voluntary motor nerves have no ganglia
True
SNS and PSNS can only be truly differentiated by
anatomy; the location of where the preganglionic neurons originate (SNS: thoracolumbar vs PSNS: cervico-sacral)
Nicotinic receptors are
LGICs
Muscarinic receptors are
GPCRs
In the SNS, preganglionic ______ acts on _____ receptors on the ganglia
ACh; nicotinic
In the SNS, postganglionic ______ acts on _______ receptors while _______ acts on _______ receptors in ______
NA acts on a- & b-aRs; ACh acts on muscarinic receptors in sweat and adrenal glands
In the PSNS, preganglionic _______ acts on _______ receptors
ACh, nicotinic
In the PSNS, postganglionic _____ acts on _______ receptors
ACh, muscarinic
In the somatic NS, preganglionic _______ acts on ______ receptors on the _______
ACh, nicotinic, alpha motor neuron
In the somatic NS, postganglionic ______ acts on ______ receptors on the _______
ACh, nicotinic, muscle
What are non-classical transmitters?
Non-cholinergic and non-noradrenergic transmitters in the ANS
What are examples of non-classical ANS NTs?
ATP, NO, neuropeptides (eg substance P, neuropeptide Y)
T/F glutamate and GABA are also used as primary NTs in the peripheral NS/ANS
False; they are the primary NTs of the CNS
How do nerve terminals in the ANS differ from somatic NMJs?
there are no easily visible terminals; instead, there is more than one transmitter release site per axon (varicosities)
What are extra-junctional receptors?
expressed remotely from the synapse
Preganglionic neurons of the SNS originate from where in the spinal cord?
Intermediolateral cell column (between the dorsal and ventral horns)
Sympathetic ganglia are essential for
integrating and coordination of sympathetic control between organs and tissues
Paravertebral ganglia innervate
vasoconstrictor neurons
Prevertebral ganglia innervate
non-vascular smooth muscle (eg airways, repro tract)
SNS postganglionic neurons originate from
paravertebral and prevertebral ganglia
What is divergence?
one preganglionic SNS neuron can activate up to 200 ganglion neurons - this is a mechanism for coordinating EFFECTS in many tissues at once
What is convergence?
prevertebral ganglion neurons have more dendrites and receive more signals, integrating them from multiple inputs (including ENS) to decide what the response should be
Adrenal medulla cells are innervated by
sympathetic preganglionic neurons (ACh, N)
What is the sympathoadrenal system?
SNS preganglionic neurons innervate adrenal medulla cells (ACh, N) to release NA and A into the circulation (FoF response)
T/F the SNS is only activated for the FoF response
False; it is essential for normal living eg adjustments of blood pressure, temperature changes, digestive changes, positional changes
T/F SNS activation is an all or none response
False; FoF is an extreme situation where the response is coordinated, but individual cells/tissues/organs are normally precisely and independently activated
Where are the preganglionic cranial PSNS nuclei located?
in the midbrain (EW), upper medulla (salivatory), and in the middle medulla (DMN of vagus, Nuc Amb)
What are the 3 PSNS cranial nuclei?
EW nucleus; Salivatory nuclei; Dorsal motor nucleus of vagus and nucleus ambiguus
The Edinger-Westphal nucleus projects to
to ciliary ganglion to control sphincter pupillae and ciliary muscle
The Salivatory nuclei project to
submandibular, sphenopalatine, and otic ganglia to control lacrimal, salivary, sublingual, nasal, and palatine glands
The Dorsal Motor Nucleus of Vagus and Nucleus Ambiguus project to
microganglia near and on outer surface of thoracic and abdominal organs to control numerous visceral functions
Sacral PSNS preganglionic neurons originate from
cluster of neurons (S1-S5) in the interomediolateral column
Sacral PSNS preganglionic neurons project from the spinal cord to
pelvic ganglia/pelvic plexus/inferior hypogastric plexus via pelvic splanchnic nerves
Extensions of the pelvic plexus lie
close to or within pelvic organs; axons can be long and susceptible to injury
T/F pelvic ganglia contain PS neurons only
False; it is a mixed ganglia containing parasympathetic and sympathetic neurons
Compared to sympathetic ganglia, pelvic ganglia act as
relay stations; there is little integration and few or no dendrites
What is different about transmission in the SNS vs PSNS?
PSNS is restricted to purely synapses whereas the SNS can use synapses but also the bloodstream via hormones produced in the adrenal medulla
T/F the PSNS is purely rest-and-digest in function
False; can be activated under many situations and some functions are not related to a rest-and-digest situation e.g. bladder control and reproductive organs; it does things all the time on more subtle ways
Visceral afferent neurons (sensory) provide input to
local interneurons and projection neurons in spinal and brainstem circuits
Most autonomic reflexes involve the _________ rather than only the _________
the brain (supraspinal reflex); spinal cord (spinal reflex)
The major integrative centre for autonomic function is the
Nucleus Tractus Solitarius (NTS) in the medulla
The NTS contains
second-order sensory neurons that receive input from visceral afferents
The NTS receives input from
primary visceral afferents
The NTS distributes information either to ___________ or ___________
local spinal reflexes (feedback) or higher centres (more complex responses)
Information from the NTS projected to local reflexes
feedback on local reflexes that control organ/tissue function
Information from the NTS projected to higher centres
provides information to drive more complex responses (coordinated behaviour: visceral, somatic, endocrine; emotion)
The _________ is the centre of autonomic control, specifically the ___________
hypothalamus; paraventricular nucleus (PVN)
The hypothalamus (and PVN) receives input from
sensory pathways (visceral, olfactory, etc.), intrinsic sensory structures (osmoreceptors), circulating hormones (angII), accessing via circumventricular organs
The most important brain region for coordination of autonomic output is
the hypothalamus, especially the paraventricular nucleus
How does the hypothalamus handle autonomic inputs and outputs?
it compares the situation (inputs) to biological set points, and if deviation is detected it adjust (outputs) behaviour and autonomic function
