Done by:

Tymaa Al-zaben & Amin Al-ajalouni

** Hello SERTONIN!

note:: the slide included within the sheet but make sure back to slide for pictures

SLIDE 3

The Autonomic Nervous System

Function : Regulate activity of smooth muscle, cardiac muscle

& certain glands .

Structures involved :

1- general visceral afferent neurons (GVA)

2- general visceral efferent neurons (GVE)

3-integration center within the brain "control center in hypothalamus and

other system such as limbic system"

Receives input from limbic system and other regions of the cerebrum.

SLIDE4

Autonomic versus Somatic NS Somatic nervous system

Afferent : consciously perceived sensations.

Effectors : excitation of skeletal muscle.

Efferent : one neuron from CNS, cell body either in anterior horn of spinal

cord in spinal nerve OR motor nuclei of cranial nerve axon exit directly

toward effectors organ( Skeletal muscles).

Autonomic nervous system

Afferent : unconsciously perceived visceral sensations.

Effectors : involuntary inhibition or excitation of smooth muscle, cardiac

muscle or glandular secretion.

Efferent : two neurons needed to connect CNS to organ .

preganglionic "cell body in CNS" and its axon exit toward target which is

postganglionic neurons and its axon exit toward effectors.

SLIDE 5

Autonomic versus Somatic NS • Notice that the ANS pathway is a 2 neuron pathway

while the Somatic NS only contains one neuron.

** The major Neurotransmitter is ACh, exception in sympathetic-post ganglionic

neuron which is Epinephrine.

SLIDE 6

Comparison of Somatic and Autonomic Nervous Systems

please back to slide to read the table SLIDE 7

Basic Anatomy of Motor ANS Preganglionic neuron

cell body inside brain or spinal cord

axon is myelinated type B fiber that extends to autonomic ganglion

neurotransmitter :ACh

Postganglionic neuron

cell body lies outside the CNS in an autonomic ganglion

axon is unmyelinated type C fiber that terminates in a visceral

effectors

neurotransmitter :ACh+ epinephrine

SLIDE 8

Divisions of the ANS

2 major divisions

1-Sympathetic (thoracolumbar) division

*preganglionic cell bodies in thoracic and first 2 lumbar

segments of spinal cord "anteriomedial cell column in lateral horn of spinal

cord" and it is the only area where the preganglion of sympathetic is present.

2-Parasympathetic (craniosacral) division

** two part 1- cranial part 2- spinal part ((sacral region))

preganglionic cell bodies in nuclei of 4 cranial nerves and the sacral

spinal cord (S2-S4) and same area of sympathetic "anteriolateral horn" exit

with spinal nerve .

## Both sympathetic &parasympathetic Dual((double )) innervated different

organ "viscera " :

we mean in dual innervations ; same organ innervated by sympathetic and

parasympathetic^^opposite action ^^.

-one speeds up organ and one slows down organ

*Sympathetic NS increases heart rate

* Parasympathetic NS decreases heart rate

SLIDE 9

Sympathetic Division

application to that ...

*sympathetic innervate more structures and more organs than

parasympathetic .

*so parasympathetic is more specific in action than sympathetic

that is why parasympathetic for normal physiological situation and opposite

to it sympathetic in emergence situation ..

• A single sympathetic preganglionic fiber has many axon collaterals

and may synapse with 20 or more postganglionic neurons.

• The postganglionic axons typically terminate in several visceral

effectors and therefore the effects of sympathetic stimulation are

more widespread than the effects of parasympathetic stimulation.

SLIDE 10

Structure of the Sympathetic Division

Autonomic ganglion

preganglion

post ganglion

Sympathetic

shorter Longer -Near to CNS &direct parallel to vertebral column

parasympathetic

longer Shorter -connection near the wall of organ its self

Thoracolumbar division

• Preganglionic neurons originate from the thoracic and

lumbar levels of the spinal cord (T1‐L2)

IN The lateral horn (intermediolateral column (IML))

Sympathetic ganglia: post ganglion present outside CNS in autonomic

ganglia "sympathetic ganglia"

**types of sympathetic ganglion:

1) Paravertebral ganglia:

we are talk about Sympathetic trunk (vertebral chain) ganglia which direct

parallel to vertebral column.

2)Prevertebral (collateral) ganglia:

present in abdominopelvic region, or organs innervated by sympathetic NS in

abdomen &pelvis where the post ganglion present there.

example :

'note that the name of them referral to the name of major branches of

abdomen aorta' .

celiac, superior mesenteric, inferior mesenteric, aorticorenal

**SO preganglionic in spinal cord 'thoracic region' and postganglionic either in

sympathetic trunk or preverbal column.

SLIDE 11

Pathway from Spinal Cord to Sympathetic Trunk Ganglia:

• Preganglionic axons → anterior root of a spinal nerve → white ramus

→ sympathetic trunk ganglion.

**cell body of Preganglion in lateral horn of S.C exit S.C with ventral root of

spinal nerve & unit with ventral root ..

**spinal nerve exit by intervertebral foramen, outside vertebral column gives

branch:

Dorsal ,ventral, rami communicant(white +gray)

White rami communicantes transmitted fiber of Preganglion neuron outside

S.C toward sympathetic trunk.

• White rami communicantes: structures containing

sympathetic preganglionic axons that connect the anterior ramus

of the spinal nerve with the ganglia of the sympathetic trunk.

SLIDE 12

Fate of Preganglionic Neurons in Sympathetic Trunk

What will happen to pre ganglion fiber ??

Options :

1. Synapse in the post sympathetic ganglion of sympathetic trunk at the same

level (at level of entry).

2. Ascend up or descend in the sympathetic trunk and then synapse with

postganglionic neouron in ganglia (above) or (below) ..

to serve structure above\below thoracic ; we know that the pre ganglion of

sympathetic present only in thoracic and upper lumber so we need to provide

another structure ..

3. Continue, without synapsing, through the sympathetic trunk

ganglion to end at a prevertebral ganglion(anterior to abdomen aorta)

and synapse with post in it .

Innervating viscera in the abdominopelvic cavity

exit Via abdominopelvic splanchnic nerves ' above

diaphragm '

4. Pass through the sympathetic trunk ganglion and a prevertebral ganglion

and then to the adrenal medulla 'the cells of medulla serve as post ganglionic'.

SLIDE 13

Organization of Sympathetic Trunk Ganglia

Two sympathetic trunks along the vertebral column(both side)

Each sympathetic trunk ganglia has: 3 cervical(sup,mid,inf),11or12 thoracic,

4 or 5 lumbar, 4 or 5 pelvic and both trunks end caudally in one joint

ganglion (ganglion impar) بلتقوا مع بعض بالنهاية وبشكلوا

Postganglionic neurons from

the superior cervical ganglion ‐head and heart.

the middle cervical ganglion and the inferior cervical ganglion ‐heart.

Thoracic sympathetic trunk‐ heart(upper part of thoracic)

, lungs, and bronchi.

so keep in your minde

HEAD== Upper Cervical

HEART==Mid & Inf Cervical & Upper part of Thoracic

SLIDE 14

Pathways from Sympathetic Trunk Ganglia to Visceral Effects

The axons for the sympathetic nervous system are 4:

1-spinal 2-cephalic periarterial 3-sympathetic nerves 4-splanchnic nerves

The territory of the sympathetic nervous system:

All viscera

Blood vessels

Erector pili muscles

Which means that the sympathetic nervous system needs to reach all over the

body (somatic regions)

*Unlike the parasympathetic which only reaches the viscera

Which also means that the easiest way to reach all somatic areas is by the spinal

nerves

So the spinal nerves will carry with their (somatic afferents and efferents)post

ganglionic sympathetic fibers

The cephalic periarterial nerves will go the head and neck regions

The sympathetic nerves are considered direct postganglionic nerves from the

sympathetic trunk that will go to the viscera of thoracic or cervical region

And the splanchnic like we said contain preganglionic fibers that will go toward

the prevertebral ganglion .

SLIDE 15

THE SPINAL NERVES:

Gray ramus: Axons of some postganglionic neurons leave

the sympathetic trunk by entering a short pathway called a gray ramus

and merge with the anterior ramus of a spinal nerve .

Blood vessels (vasomotion), arrector mm. (pilomotion), and

sweat glands (sudomotion) ..

Gray rami communicantes: structures containing

sympathetic postganglionic axons that connect the ganglia

of the sympathetic trunk to spinal nerves.

Like we already mentioned that the spinal nerves intermediolateral cell columen

will give preganglionic sympathetic fibers which will go to the spinal never then

to the sympathetic trunk via the white communicants, after it reaches the trunk

it will synapse with the ganglia there and the postganglionic fibers from the

ganglia will go back again to the spinal nerves via the gray communicants, which

will then innervate all the somatic regions via the spinal nerves.

SLIDE 16

CEPHALIC PERIARTERIAL NERVES:

Some sympathetic preganglionicneurons that enter the sympathetic trunk

ascend to the superior cervical ganglion where they synapse

with postganglionic neurons Some of these leave the

sympathetic trunk by forming cephalic arterial nerves.

Serve visceral effectors in the skin of the face and head and iris (dilator)

Like we know we don’t have spinal nerves in the head region, we only have

cranial nerves

And we also don’t have white or gray communicants in head region

So how will we get sympathetic innervation to the head region?

The superior cervical ganglion will receive efferent sympathetic fibers thro white

communicants and it will synapse in the ganglia, then the postganglionic fibers

will leave as the cephalic periarterial (around blood vessesl) (they will use the

arteries like the carotid and form plexuses around them) nerves after they

become close with their target they will jump from being close to arteries

(periarterial) to the cranial nerves, ex:deep petrosal nerves which was considered

cephalic periarterial nerve until it reached pterygoid canal and joined the great

petrosal and formed the nerve of pterygoid canal

SLIDE 17

THE SYMPATHETIC NERVES:

Some axons of the postganglionic neurons leave the trunk by forming

sympathetic nerves (Cardiopulmonary splanchnic nerves)

Innervate the heart and lungs.

Serves all viscera above diaphragm tqreebn (in thoracic region and cervical) (like

heart lungs….)

It is formed in this pattern

Preganglionic sympathetic fibers going to the sympathetic trunk via white

communicants then synapsing with any ganglia in the trunk either at same level

or not, then those postganglionic fibers will leave as the sympathetic nerves

A student asked: how will the superior cervical innervate the heart?? Doctors

answer: 3adi it descends down to the heart but before reaching the heart it

forms a plexus (cardiac plexus)

SLIDE 18

SPLANCHNIC NERVES:

# Some sympathetic preganglionic axons pass through the sympathetic trunk

without terminating in it. Beyond the trunk they form nerves called splanchnic

nerves which extend to prevertebral ganglia

1. T5‐T9 or T10‐ Greater splanchnic nerve

2. T10‐T11‐ Lesser splanchnic nerve

3. T12‐ least splanchnic nerve

4. L1‐L4‐ Lumbar splanchnic nerve

They leave the sympathetic trunk as preganglionic fibers!!! Which means they

don’t synapse in the sympathetic ganglias (important to remember) and they

will go toward the prevertebral ganglia

They are from t5-t12 but sometimes we can say we have lumbar splanchnic

nerves too

We have greater splanchnic nerves, lesser splanchnic never, least splanchnic

nerves which all originate above the diaphragm and penetrate the diaphragm

down to the abdomen mainly from the cruras of diaphragm so they can reach the

prevertebral ganglia

SLIDE 20

Splanchnic Nerves to the Adrenal Medulla

Some sympathetic preganglionic axons pass, without synapsing, through the

smpathetic trunk, greater splanchnic nerves and celiac ganglion into the adrenl

medulla (modified sympathetic ganglia).

Release hormones into blood

• 80% epinephrine, 20% norepinephrine.

But also put in mind that not all splanchnic nerves will terminate in the

prevertebral ganglia, some of them may continue to the adrenal glands (medulla)

and synapse there to help secrete epinephrine and norepinephrine

SLIDE 19

THE PREVERTEBRAL GANGLIA:

We have 4 ganglias : celiac, aorticorenal, superior mesenteric, inferior

mesenteric

All of theseganglias receive preganglionic fibers from splanchnic nerves then

synapse and give postganglionic fibers to the abdominopelvic organs

Note: all viscera is supplied by what we call plexuses which contains sympathetic

and parasympathetic fibers like (thoracic, cranial)

SLIDE 22

AFFERENT SYMPATHETIC FIBERS:

Viscera → sympathetic ganglion → white rami communicants → spinal nerve →

dorsal root ganglion → spinal cord

Theres a lil different between somatic and autonomic afferents, the autonomic

afferents perception is lower than somatic perception, less sensitivity, less in

number, and less receptors.

Mainly they are end nerves neurons and they carry a lot of modalities

These afferent fibers will go back the same way they came as simple as that but

when they reach the nerve level they will go to the dorsal root ganglia of spinal

cord and this is why we have what is called referral pain when we have visceral

damage because of the meeting between visceral afferents and somatic afferents

in the dorsal root ganglia

So the visceral referral pain depends on the entrance into the spinal cord so if a

sympathetic afferent of an organ entered at the level of t3-t5 the referral pain

will be mostly in dermatomes innervated by t3-t5

SLIDE 21

ORGANS INNERVATED BY SYMPATHETIC SYSTEM:

Structures innervated by each spinal nerve

sweat glands, arrector pili mm., blood vessels to skin & skeletal mm.

Thoracic & cranial plexuses supply:

heart, lungs,esophagus & thoracic blood vessels.

plexus around carotid artery to head structures.

Splanchnic nerves to prevertebral ganglia supply:

GI tract from stomach to rectum, urinary & reproductive organs.

Sorry for any mistakes

"Difficult Roads often leads to beautiful destinations"

THE END <3