Sympathetic Nervous System

What does the ANS innervate?

cardiac muscle, smooth muscle, and glands

What part of the ANS has a short preganglionic fiber?

Sympathetic

What part of the ANS has a long postganglionic fiber?

Sympathetic

What part of the ANS has a long pregnaglionic fiber?

parasympathetic

What part of the ANS has a short postganglionic fiber?

Parasympathetic

What part of the ANS has diffuse/non localized activity?

Symapthetic NS

What part of the ANS is more precise in its activity?

Parasympathetic NS

General ANS wiring

3 neuron chain:

Central neuron

Preganglionic

Postganglionic

What type of fiber is the preganglionic fiber of the ANS

Type B myelinated

What type of fiber is the postganglionic fiber of the ANS?

Type C unmyelinated

Where is the central neuron of the ANS located?

Hypothalamus + runs to preganglionic fiber in spinal cord

What NT does the preganglionic fiber of the ANS release? Onto what receptor?

Ach onto nicotinic receptors

What NT does the postganglionic fiber of the parasympathetic nervous system release? Onto what receptors?

Releases Ach onto muscarinic receptors (M1-6)

What blocks both nictotinic and muscarinic receptors?

Atropine

What type of receptors are muscarinic receptors?What do they activate?

GPCRs, activates adenylate Cyclase

What NT does the postganglionic fiber of the symapthetic nervous system GENERALLY release? Onto what receptors?

Releases NE onto alpha 1 + 2, and beta 1 + 2 receptors

When does the symapthetic postganglionic fiber release norepinephrine?

When innervating a tissue that is also innervated by the parasympathetic nervous system

When does the sympathetic postganglionic fiber release Ach?

When the tissue is only innervated by the sympathetic system

What are the sweat glands of the body innervated by? What NT is released onto what receptor?

Sympathetic nervous system

Postganglionic fiber releases Ach onto M receptors of the sweat galnds

What are the sweat glands of palms and soles of feet innervated by? What NT is released and onto what receptor?

Sympathetic nervous system

Postganglionic fiber releases norepinephrine onto adrenergic receptors

What receptors are on the blood vessels of skin? What does increased sympathetic innervation do to these BVs?

Alpha 1

Vasoconstricts

What receptors are on the blood vessels of skeletal muscles? What does increased sympathetic innervation do to these BVS?

Beta 2

Vasodilate

What receptors are on the blood vessels of organs? What does increased sympathetic innervation do to these BVs?

alpha 1s

Vasoconstrict

What ways does the SNS dilate the blood vessels of skeletal muscle?

Releasing NE onto B2 receptor

Releasing Ach which produces NO, which dilates BVS

What would a sympathomimetic do to the eye?

Mydriasis

What are examples of direct sympathomimetics?

Phenylephrine

Aproclonidine

Phenylephrine MOA

alpha 1 agonist

Aproclonidine MOA

Alpha 2 agonist and weak alpha 1 agonist (with denervation hypersensitivity)

What are examples of indirect sympathomimetics?

selective Beta blocker

Non selective beta blocker

What is an example of a parasympathomimetic?

Pilocarpine

What does a parasympathomimetic do to the eye?

Miosis

Accomodation (in young eyes)

What was pilocarpine originally used for? What is it used for now?

Glaucoma Rx

Now is the new drop for presbyopia

What does a parasympatholytic do to the eye?

Mydriasis + cycloplegia (loss of accommodation)

What is cycloplegia?

paralysis of the ciliary muscle

Examples of parasympatholytics (are these better dilators or cycloplegics?)

Tropicamide: better dilator than cycloplegic

Cyclopentolate: better cycloplegic than dilator

Atropine: best dilator + cycloplegic

What is the dilator of choice?

Tropicamide

What are the 4 types/regions of sympathetic wiring?

1. Limbs and Body Wall

2. Thoracic Organs

3. Abdominal Organs

4. Head and Neck

What is the same with all 4 regions of symapthetic wiring?

They all start the same:

1. Preganglionic in interomediolateral cell column in lateral horn

2. Pregnaglionic passes through ventral root + leaves spinal nerve via white ramus to enter sympathetic trunk

Where are the cell bodies of the preganglionic sympathetic fibers going to the eye?

T1 + T2

Where are the cell bodies of the preganglionic sympathetic fibers going to the head + neck?

T1-T4

Where are the cell bodies of the preganglionic sympathetic fibers going to the heart and lungs?

T2- T6

Where are the cell bodies of the preganglionic sympathetic fibers going to abdominal organs?

T6-L2

Where are the cell bodies of the preganglionic sympathetic fibers going to the urinary system?

L1-L2/3

What is the sympathetic trunk?

Collection of ganglion connected by ascending and descending fibers

Where does the sympathetic trunk run?

Angle of mandible to sacral spinal cord

Another name for sympathetic trunk?

Paravertebral ganglion

How many sympathetic ganglia are there in the cervical region?

3: superior, middle, inferior

Despite having 3 sympathetic ganglia for 8 cervical spinal nerves, each spinal nerve has? WHat does this mean?

It's own grey ramus

Therefore the ganglia each have multiple grey rami coming off of it

Sympathetic Wiring of limbs and body wall

1. Enters Sympathetic trunk via white rami at levels T1-L2

2. Either synapses @ level it enters, or ascends/descends + synapses

3. Postganglionic fiber rejoins every spinal nerve via grey rami

Where in the sympathetic trunk do the pregnaglionic sympathetic fibers synapse?

At every level

Is there parasympathetic innervation to limbs + body wall?

NO, sympathetic onlyl

What do the sympathetic fibers of limbs + body wall innervate?

BVs of skin + skeletal muscle of limbs/body wall

Sweat glands/arector Pili

What are the muscles of body wall?

Intercostal

Abdominal muscles

Trapezius

Sympathetic Wiring of thoracic organs pathway

1. Preganglionic enters sympathetic trunk @T2- T6 + ascends to 3 cervical ganglion + upper 4 thoracic ganglion + synapses here

2. Postganglionic fibers leave as cardiopulmonary splanchinic nerves to heart and bronchi

THEY DO NOT jump on spinal nerves

Superior cardiac splanchic nerve location + innervation

Superior cervical ganglia

Innervates heart

Middle cardiac splanchnic nerve location + innervation

Middle cervical ganglia

Innervates the heart

Inferior cardiac splanchnic nerve location + innervation

Inferior cervical ganglia + T1 (potential T2 as well) [aka stellate ganglion]

Heart

Which splanchnic nerve is most important for innervating the heart?

Inferior cardiac splanchnic

stellate ganglion

inferior cervical ganglion + 1st thoracic ganglion fuses to form this

Pulmonary splanchnic nerves location + innervation

T2-T5

Innervate the lungs

Stimulating B1 receptors does what to the heart?

Increases HR + force of contraction

What does atrial fibrillation do to ejection?

Decreases it

What does ventricular fibrillation do to ejection?

NO ejection

B2 receptor stimulation does what do the bronchi?

Bronchodilate

Sympathetic Wiring of abdominal organs pathway

1. Preganglionic fibers from T6-L2 enters sympathetic trunk + passes through WITHOUt synapsing

2. Leaves trunk near aorta as thoracic/abdominal splanchnic nerves

3. Run to ganglia in anterior aorta + synapse

The cardiopulmonary splanchnic nerves are what kind of fiber?

Postganglionic (unmyelinated C)

The thoracic/abdominal splanchnic nerves are what kind of fiber?

Preganglionic (myelinated B)

What are the 3 thoracic/abdominal splanchnic nerves?

greater thoracic splanchnic

lesser thoracic splanchnic

least thoracic splanchnic

Where does the greater thoracic/abdominal splanchnic nerve synapse?

Synapses in celiac ganglion

What does the postganglionic fiber from the celiac ganglion innervate?

Esophagus

Stomach

Duodenum of small intestine

Where does the lesser thoracic/abdominal splanchnic nerve synapse?

Superior Mesenteric ganglion

What does the post gang fiber from the superior mesenteric ganglion innervate?

Small intestine: Jejunum/ileum

Large intestine: up to transverse colon/splenic flexure

Where does the lowest thoracic/abdominal splanchnic nerve synapse?

Inferior mesenteric ganglion

What does the post gang fiber from the inferior mesenteric ganglion innervate?

Large intestine after splenic flexure (descending + sigmoid + rectum)

Pelvic organs

Sympathetic Wiring to head + neck pathway

1. Fibers from T1-T4 enter sympathetic trunk + ascend to superior cervical ganglion

2. Synapse in superior cervical ganglion + postgang fiber leaves to innervate effector

Sympathetic innervation to the eye pathway

1. Pregnaglionic cell body in T1 + T2

2. Enters sympathetic trunk + ascends to superior cervical ganglion

3. Synapse in superior cervical ganglion

4. Postganglionic fibers jump on common carotid + follows both internal + external carotids to effectors

Where does the sympathetic fibers to the eye run when ascending to superior cervical ganglion?

Over the lung and under the subclavian artery

Common carotid dissection usually affects which sympathetic fiber?

Preganglionic

Sympathetic fibers on the external carotid innervate?

Sweat glands of face

Sympathetic fibers on internal carotid innervate?

Iris

Mullers muscle

BVs of head + orbit

Pathway of sympathetic fibers on internal carotid

1. Fibers on internal carotid

2. Jump on CN III + V1 in cavernous sinus

3. Follows CN III to mullers (lid elevation)

4. Follows CN V1 in two paths

A. V1-> nasociliary n—> long + short ciliary nerves —> dilator of iris

B. V1 —> lacrimal n. —> blood vessels of lacrimal gland

Damage to sympathetic fibers of external carotid only would cause

Facial anhydrosis

What is oculosympathetic paresis? What can be damaged

Damage to the SNS of head + eye

Occurs with damage to ANY of the following:

Central

Preganglionic

Postganglionic

Symptoms of oculosympathetic paresis? Why?

Ptosis (muller muscle inhibition)

Miosis (dilator inhibition)

Anhyrdosis (sweat gland inhibition)

Heterchromia (inhibits melanin production)

Oculosympathetic paresis is also called?

Horners

When does horners cause heterchromia?

If it is congenital + in someone with dark eyes

Why does horners only cause heterchromia in someone with dark eyes?

because it inhibits melanin production, blue eyes already have limited/no melanin, so you wouldn't see a difference

Dark eyes have a lot of melanin, so you would notice the difference

What causes damage to central neuron in horners? Extras?

Stroke/inflammation

Will have CNS involvement

What are causes of preganglionic lesion in horners? What should you ask about?

Pancoast tumor

Metastatic breast cancer

Neck injury (carotid dissection)

ASk about neck pain

What are causes of postganglionic lesion in Horners? Symptoms/check?

Internal carotid aneurysm before or in cavernous sinus

Symptoms: cluster headaches + migraines

Check: CNs of cavernous sinus, especially CN VI

What kind of cell is used in the somatosensory system?

Unipolar

What are the fibers of the somatosensory system called?

Central and peripheral fibers

Sympathetic nervous system releases what onto the adrenal medulla? What does this cause?

Ach onto nicotinic receptors

Causes the adrenal medulla to release epi + norepinephrine into blood

How does the adrenal medulla release epinephrine into blood?

Releases epi + norepinephrine into medullary vein, which dumps into vena cava + heart, heart pumps it everywhere