( 4c ) Sympathetic Nervous System

" Fight Or Flight "

Here sympathetic neurons are the lines in Blue

how many neurons are there?

3

= ALL part of sympathetic nervous system ( fight or flight )

Anatomy wise

Do the sympathetic neurons come from a DIFFERENT place in the central nervous system?

Yes!

Where do they come from?

Thoracolumbar

Thoracolumbar

means

• Thoracic Region ( chest )

  AND

• Lumbar Region ( abdominal )

MIDDLE of the SPINAL CORD

Parasympathetic was either

• Cranial region

  OR

• Sacral region

Sympathetic is

• Thoracic region

  AND

• Lumbar region

= MIDDLE of SPINAL CORD

They are anatomically

SEPARATED

Which of these neurons Fires Action potential during fight or flight mode?

ALL OF THEM DO !!!

→ at the SAME TIME

So when you go into fight or flight

→ ALL cylinders are firing action potential

= get BODYWIDE fight or flight response

this can be called

Generalized Sympathetic Discharge

note: generalized means it involves many things!

Generalized Sympathetic Discharge

as when you go into fight or flight mode

you get a

BODY-WIDE fight or flight response ( generalized )

→ ALL sympathetic neurons are firing action potentials AT ONCE!!

in CONTRAST parasympathetic

response is

a little more fine-tuned ( selective )

example:

You can fire a little more parasympathetic response in one area compared to another area

While in sympathetic the response is

Simultaneously ALL firing at once!!

( not selective )

Let’s look at the upper one first

What’s the legnth of the preganglionic neuron here?

( long or short )

Quite Short !!

opposite to parasympathetic where it was really long!

So

This short pregangilonic neuron

→ synapses at a ganglion that’s

only about an inch away from the spinal cord

= VERY CLOSE to SPINAL CORD

What is this specific Ganglion Called?

Sympathetic Ganglion Chain

What’s something related to the Sympathetic Nervous System in this spinal cord pic?

Synaptic Ganglion Chain

• it’s literally about an inch away from the spinal cord

Spinal Cord

• Since we’re currently talking about Autonomic Neurons

It’s cell bodies are in which horn?

The Lateral Horn

( side )

All it’s axons that are LEAVING goes out what root?

Ventral Root

( everything that leaves goes out the ventral side )

Notice:

It’s synapses literally an INCH AWAY from the SPINAL CORD

at the ● Symapathetic Ganglion Chain

Called a chain because:

There’s a chain of them!

If the PREganglionic ( first ) neuron is short

what’s the length of the POSTganlionic ( second ) neuron here?

LONG !!

Let’s look at the bottom one now

At the SAME TIME the top set is working

Is the bottom set working too?

Yes!

In the bottom set

Preganglionic neuron goes THROUGH

the sympathetic ganglion chain

BUT DOESN’T STOP THERE

the axon keeps on going!

It Synapses FURTHER AWAY at the

Collateral Ganglion

( another type of ganglion )

Where do we usually see the Collateral Ganglion ?

• Abdominal Cavities

• Pelvic Cavities

= where the preganglionic neuron doesn’t synapse at the sympathetic ganglion chain → keeps on going and synapses further away

Look at #3

• Preganglionic neuron comes out

→ goes THROUGH the sympathetic ganglion chain but doesn’t stop there

→ axon keeps on going to collateral ganglion!

review pic for next card

Sympathetic are Thoracic and Lumbar

But Notice something different in the BOTTOM area?

𖧋𖧋𖧋𖧋𖧋= sympathetic ganglion chain

● = synapse

it goes THROUGH the sympathetic ganglion chain

→ keeps on going an synapses over there ( collateral ganglions )

Notice:

The organs involved in this are

• Abdominal

  AND

• Pelvic

Regions

Besides from where the ganglion is

The top set and bottom set are

the SAME

Their ONLY difference is

Where the ganglion is

• right outside or further away

How are they the same?

BOTH the top and bottom line HAVE a

Preganglionic ( first ) Neuron that’s Cholinergic

review: what does Cholinergic refer to?

Acetylcholine ( Ach )

So both of their cholinergic preganglionic neurons release

Acetylcholine ( Ach )

What’s the type of cholinergic receptor does the acetylcholine bind to?

Nicotonic receptors

( remember: anytime acetylcholine’s involved it’s gonna be nicotinic receptor EXCEPT for parasympathetic on your final organ → muscarinic )

Remember:

Anytime acetylcholine’s involved it’s gonna be nicotinic receptor

EXCEPT for

Parasympathetic on your final organ → muscarinic

The preganglionic ( first ) neuron is = cholinergic

How about the postganglionic ( second ) neuron?

The postganglionic neuron is Adrenergic

Cholinergic talks about acetylcholine

While

Adrenergic talks about

DIFFERENT MOLECULES

Adrenergic

what are the 2 Adrenergic Molecules?

• Epinephrine

• Norepinephrine

Memory Hint for

Adrenergic

think:

Adrenaline

when someone says “fight or flight”

you’d usually think of adrenaline!

Adrenergic “Adrenaline”

So sympathetic postganglionic “fight or flight” neurons are releasing

Adrenergic molecules

( think adrenaline )

Epinephrine is commonly abbreviated as

epi = the common one!

E = only in textbooks

( in medicine they use “epi” )

What do Epi-pens inject someone with?

( when they have allergic reaction )

Epinephrine

norepinephrine is commonly abbreviated as

NE

Epinephrine is the SAME thing as

Adrenaline !!

= just different NAMES

Where the name “adrenaline” come from

One scientist found it in

Adrenal Gland tissue

= called it Adrenaline

Where did the name “epinephrine” come from

An EARLIER scientist also found it there!

Epinephrine means “on kidney”

Which name does the USA use?

Epinephrine

Norepinephrine

Which name does the UK and Europe use?

Adrenaline

Noradrenaline

Epinephrine and Adrenaline are synonyms

meaning

They are the SAME THING!!

just called different names

So in the Sympathetic postganglionic ( second ) neuron is adrenergic

meaning

it’ll RELEASE ONE of those adrenergeric molecules!

• Epinephrine

• Norepinephrine

which ONE does it release?

Norepinephrine ( NE )

Norepinephrine is the

neurotransmitter released from the sympathetic postganglionic neuron

Compare and Contrast Pic

of

• Somatic Nervous System

• Autonomic Nervous System

  • parasympathetic division

  • sympathetic division

Somatic Nervous System ( ONE motor neuron )

→ release acetylcholine ( Ach )

= Binds to nicotinic acetylcholine receptors ( N-AChR )

Parasympathetic Nervous System

→ releases acetylcholine ( Ach )

Binds to nicotinic acetylcholine receptors ( N-AChR ) on second neuron

• Excites second neuron

  → also releases acetylcholine ( Ach )

Binds to MUSCURINIC acetylcholine receptors ( M-AChR ) !!!!

side by side we can easily see the receptor differences here

Sympathetic Nervous System

→ releases acetylcholine ( Ach )

Binds to nicotinic acetylcholine receptors ( N-AChR ) on second neuron

→ Second neuron RELEASES NOREPINEPHRINE ( NE )