Division of nervous system - ANS

1. SUBMITTED BY,
NAJALA P

4.  The term autonomic nervous system (ANS) refers to
collections of motor neurons (ganglia) situated in the
head, neck, thorax, abdomen, and pelvis, and to the
axonal connections of these neurons.
 The autonomic nervous system functions to regulate the
body's unconscious actions
 The autonomic nervous system is a component of the
peripheral nervous system that regulates involuntary
physiological processes including heart rate, blood
pressure, respiration, digestion, and sexual arousal.
 It contains two anatomically distinct divisions
1. Sympathetic nervous system
2. Parasympathetic nervous system

5.  The sympathetic nervous system (SNS) and the parasympathetic
nervous system (PNS) contain both afferent and efferent fibers
that provide sensory input and motor output, respectively, to
the central nervous system.
 Generally, the SNS and PNS motor pathways consist of a two
neuron series:
i. a pre ganglionic neuron with a cell body in the CNS
ii. postganglionic neuron with a cell body in the periphery that
innervates target tissues.
 Activation of the SNS leads to a state of overall elevated
activity and attention: the “fight or flight” response. In this
process, blood pressure and heart rate increase,
glycogenolysis ensues, gastrointestinal peristalsis ceases.
 The SNS innervates nearly every living tissue in the body.

6.  The PNS promotes the “rest and digest” processes; heart rate
and blood pressure lower, gastrointestinal
peristalsis/digestion restarts, etc.
 The PNS innervates only the head, viscera, and external
genitalia, notably vacant in much of the musculoskeletal
system and skin, making it significantly smaller than the SNS
 Presynaptic neurons of both the SNS and PNS utilize
acetylcholine (ACh) as their neurotransmitter.
 Postsynaptic sympathetic neurons generally produce
norepinephrine (NE) as their effector transmitter to act upon
target tissues, while postsynaptic parasympathetic neurons
use ACh throughout

7.  The sympathetic nervous system connects the internal organs
to the brain by spinal nerves. When stimulated, these nerves
prepare the organism for stress by increasing the heart rate,
increasing blood flow to the muscles, and decreasing blood
flow to the skin.
 Sympathetic neurons have cell bodies located in the
intermediolateral columns, or lateral horns, of the spinal
cord.
 The sympathetic nervous system's primary process is to
stimulate the body's fight or flight response. It is, however,
constantly active at a basic level to maintain homeostasis.

8. There are two kinds of neurons involved in the transmission
of any signal through the sympathetic system:
1.pre-ganglionic and
2.post-ganglionic.
 The shorter pre ganglionic neurons originate in
the thoracolumbar of the spinal cord specifically
at T1 to L2~L3, and travel to a ganglion, often one of
the paravertebral ganglia, where they synapse with a
postganglionic neuron.
 From there, the long postganglionic neurons extend across
most of the body.

9.  The sympathetic nervous system consists of cells with bodies
in the lateral grey column from T1 to L2/3.
 These cell bodies are "GVE" (general visceral efferent)
neurons and are the preganglionic neurons. There are several
locations upon which preganglionic neurons can synapse for
their postganglionic neurons:
 Paravertebral ganglia of the sympathetic chain (these run on
either side of the vertebral bodies)
1. cervical ganglia
2. thoracic ganglia and rostral lumbar ganglia
3. caudal lumbar ganglia and sacral ganglia
 Prevertebral ganglia (celiac ganglion, aorticorenal ganglion,
superior mesenteric ganglion, inferior mesenteric ganglion)
 Chromaffin cells of the adrenal medulla (this is the one
exception to the two-neuron pathway rule: the synapse is
directly efferent onto the target cell bodies)

10. These ganglia provide the postganglionic neurons from which
innervation of target organs follows. Examples of splanchnic
(visceral) nerves are:
 Cervical cardiac nerves and thoracic visceral nerves, which
synapse in the sympathetic chain
 Thoracic splanchnic nerves (greater, lesser, least), which synapse
in the prevertebral ganglia
 Lumbar splanchnic nerves, which synapse in the prevertebral
ganglia
 Sacral splanchnic nerves, which synapse in the inferior
hypogastric plexus
 These all contain afferent (sensory) nerves as well, known as GVA
(general visceral afferent) neurons.

12.  Sympathetic nervous system arise from near the middle of the
spinal cord in the interomediolateral nucleus of lateral grey
column, beginning at the first thoracic vertebra of the
vertebral column and are thought to extend to the second or
third lumbar vertebra.
 Because its cells begin in the thoracolumbar divisions-the
thoracic and lumbar regions of the spinal cord-the
sympathetic nervous system is said to have a thoracolumbar
outflow
 Structures in the brain, spinal cord and peripheral nervous
system support the function of the sympathetic nervous
system

13.  Receptors in internal organs of the chest and abdomen collect
information from the body and send it up to the brain
through the spinal cord and cranial nerves.
 The hypothalamus, a brain structure important for regulating
homeostasis, receives signals from the body and tunes the
activity of the autonomic nervous system in response.

14.  The sympathetic nervous system is responsible for up- and down-
regulating many homeostatic mechanisms in living organisms.
 Fibers from the SNS innervate tissues in almost every organ system,
providing at least some regulation of functions as diverse as pupil
diameter, gut motility, and urinary system output and function.
 It is perhaps best known for mediating the neuronal and hormonal stress
response commonly known as the fight-or-flight response.
 This response is also known as sympatho-adrenal response of the body

15.  as the preganglionic sympathetic fibers that end in the adrenal
medulla secrete acetylcholine, which activates the great
secretion of adrenaline (epinephrine) and to a lesser extent
noradrenaline (norepinephrine) from it.
 Therefore, this response that acts primarily on
the cardiovascular system is mediated directly via impulses
transmitted through the sympathetic nervous system and
indirectly via catecholamines secreted from the adrenal
medulla.
 The sympathetic nervous system is responsible for priming the
body for action, particularly in situations threatening survival.
 Sympathetic nervous system stimulation causes
vasoconstriction of most blood vessels, including many of
those in the skin, the digestive tract, and the kidneys. The
sympathetic nervous system doesn't destress the body once
the tree is felled or the danger has passed.

16. ORGAN EFFECTS
Eye Dilates
Heart Increases rate and force of contraction
Lungs Dilates bronchioles via circulating adrenaline
Blood vessels Dilate in skeletal muscle
Digestive system Constricts in gastrointestinal organs
Sweat glands
Activates sudomotor function and sweat
secretion
Digestive tract Inhibits peristalsis
Kidney Increases renin secretion
Ductus deferens Promotes emission prior to ejaculation
Examples of sympathetic system action on various organs[

17.  The sympathetic nervous system becomes overactive in a
number of diseases, according to a review in the
journal Autonomic Neuroscience. These include
cardiovascular diseases like ischemic heart disease,
chronic heart failure and hypertension
 A boost of sympathetic signaling raises the blood pressure
and enhances tone in smooth muscles, which may cause
hypertension.
 Beyond cardiovascular ailments, sympathetic dysfunction has
been associated with kidney disease, type II diabetes, obesity,
metabolic syndrome and even Parkinson's disease.

18.  Sympathetic dysfunction also underlies mental
health conditions such as anxiety, depression and chronic
stress, an article in Forbes reported.
 In short bursts, the body's physical stress response can be
useful and grant an energizing boost of mental focus. If
prolonged, however, the stress signals whizzing through the
body wreak havoc.
 Besides maintaining a mental feeling of constant stress, the
extra epinephrine and cortisol damage blood vessels,
increase blood pressure and promote a buildup of fat.

19.  The parasympathetic system is responsible for stimulation of
"rest-and-digest" or "feed and breed" activities that occur
when the body is at rest, especially after
eating,including sexual arousal ,Salivation
, lacrimation(tears), urination, digestion, and defecation.
 Its action is described as being complementary to that of
the sympathetic nervous system, which is responsible for
stimulating activities associated with the fight-or-flight
response.

20.  Nerve fibres of the parasympathetic nervous system arise
from the central nervous system. Specific nerves include
several cranial nerves, specifically oculomotor nerve,facial
nerve, glassopharyngeal nerve and the vagus nerve.
 Three spinal nerves in the sacrum(S2-4), Commonly referred
to as pelvic splanchnic nerves, also act as parasympathetic
nerves.
 Owing to its location , the parasympathetic system is
commonly referred to as having craniosacral outflow

22.  The parasympatheic nerves are autonomic or visceral
branches of the peripheral nervous system.
 Parasympathetic nerve supply arises through three primary
areas:
 1.certain cranial nerves in the cranium, namely preganglionic
parasympathetic nerve arises from specific nuclei in CNS
 2.The vagus nerve does not participate in these cranialganglia
as most of its parasympathetic fibres are destined for broad
array of gangliaon or near thoracic viscera and abdominal
viscera.
 3.the pelvic splanchnic efferent preganglionic nerve cell
bodies reside in the lateral gray horn of the spinal cord at the
T12-L1 vertebral levels, and their axons exit the vertebral
column as S2-S4 spinal nerves through the sacral foramina.

23.  The oculomotor nerve is responsible for a
number of parasympathetic functions related to
the eye.
 There are two motors that are part of the
oculomotor nerve known as the somatic motor
and visceral motor.
 The somatic motor is responsible for moving the
eye in precise motions and for keeping the eye
fixated on an object. The visceral motor helps
constrict the pupil.

24.  The parasympathetic aspect of the facial nerve controls secretion
of the sublingual and submandibular salivary glands, the lacrimal
gland, and the glands associated with the nasal cavity. This nerve
controls secretions of saliva and mucus in the mouth and nose,
respectively.
 These nerves go to the parotid salivary glands that provide extra
saliva to the tongue and beyond.
 The glossopharyngeal nerve has parasympathetic fibers that
innervate the parotid salivary gland.
 Vagus nerve An estimated 75 percent of all parasympathetic
nerve fibers in the body come from this nerve. This nerve has
branches in many key organs, including the stomach,
kidneys, liver, pancreas, gallbladder, bladder, anal sphincter,
vagina, and penis

25.  The vagus trunks then join with preaortic sympathetic
ganglion around the aorta to disperse with the blood vessels
and sympathetic nerves throughout the abdomen.
 The vagus contribution of parasympathetic continues down
the gut tube until the end of the midgut.
 The pelvic splanchnic nerves, S2-4, work in tandem to
innervate the pelvic viscera.
 The visceral tissues in the pelvis that the parasympathetic
nerve pathway controls include those of the urinary bladder,
ureters, urinary sphincter, anal sphincter, uterus, prostate,
glands, vagina, and penis

26.  Unconsciously, the parasympathetic will cause
peristaltic movements of the ureters and intestines,
moving urine from the kidneys into the bladder and
food down the intestinal tract and, upon necessity, the
parasympathetic will assist in excreting urine from the
bladder or defecation.
 Also, parasympathetic stimulation of the internal anal
sphincter will relax this muscle to allow defecation.
There are other skeletal muscles involved with these
processes but the parasympathetic plays a huge role in
continence and bowel retention.

27.  Salivation: As part of its rest-and-digest function, the PSNS
stimulates production of saliva, which contains enzymes to help
your food digest.
 Lacrimation: Lacrimation is a fancy word for making tears. Tears
keep your eyes lubricated, preserving their delicate tissues.
 Urination: The PSNS contracts the bladder, which squeezes it so
urine can come out.
 Digestion: The PSNS stimulates the release of saliva to promote
digestion. It also enacts peristalsis, or the movement of the
stomach and intestines, to digest food as well as release bile for
the body to digest fats.
 Defecation: The PSNS constricts the sphincters in the intestine
and moves digested food material down the digestive tract so a
person can have a bowel movement

28.  The vagus nerve plays a crucial role in heart rate regulation
by modulating the response of sinoatrial node; vagal tone can
be quantified by investigating heart rate modulation induced
by vagal tone changes.
 In sexual activity,In males, the cavernous nerves from
the prostatic plexus stimulate smooth muscles in the fibrous
trabeculae of the coiled helicine arteries of penis to relax and
allow blood to fill the two corpora cavernosa and the corpus
spongiosumof the penis, making it rigid to prepare for sexual
activity.

31.  Autonomic dysfunction develops when the nerves
of the ANS are damaged. This condition is
called autonomic neuropathy or dysautonomia.
Autonomic dysfunction can range from mild to
life-threatening. It can affect part of the ANS or
the entire ANS.
 Sometimes the conditions that cause problems
are temporary and reversible. Others are chronic,
or long term, and may continue to worsen over
time.
 Diabetes and Parkinson’s disease are two
examples of chronic conditions that can lead to
autonomic dysfunction.

32.  Dizziness and fainting upon standing up,
or orthostatic hypotension
 an inability to alter heart rate with exercise, or
exercise intolerance
 sweating abnormalities, which could alternate
between sweating too much and not sweating
enough
 digestive difficulties, such as a loss of
appetite, bloating, diarrhea, constipation,
or difficulty swallowing
 urinary problems, such as difficulty starting
urination, incontinence, and incomplete emptying
of the bladder

33.  sexual problems in men, such as difficulty
with ejaculation or maintaining an erection
 sexual problems in women, such as vaginal
dryness or difficulty having an orgasm
 vision problems, such as blurry vision or an
inability of the pupils to react to light quickly