Autonomic Nervous System

Question 1

What is the structural difference between the somatic and autonomic nervous system?

Answer 1

The somatic nervous system has one ganglion: dorsal root ganglion

The autonomic nervous system has two ganglions: dorsal root ganglion and the autonomic ganglion

Question 2

Why does the autonomic nervous system need an extra ganglion?

Answer 2

To spread the signal more widely

Question 3

What are the two divisions of the autonomic nervous system?

Answer 3

Sympathetic
Parasympathetic

Question 4

What is the sympathetic nervous system responsible for?

Answer 4

Fight-or-flight

Question 5

What is the parasympathetic nervous system responsible for?

Answer 5

Rest and digest

Question 6

What neurotransmitter do sympathetic pathways use?

Answer 6

Acetylcholine neurotransmitter on the nicotinic receptor of the autonomic ganglionic

Norepinephrine neurotransmitter on the adrenergic receptor of target tissue

Question 7

What neurotransmitters do parasympathetic pathways use?

Answer 7

Acetylcholine neurotransmitter on the nicotinic receptor of the autonomic ganglionic

Acetylcholine neurotransmitter on the muscarinic receptor of target tissue

Question 8

What is the outflow for the sympathetic nervous system?

Answer 8

Thoracolumbar division (T1 to L2,3)

Question 9

Where is the lateral horn of the spinal cord found?

Answer 9

In spinal cord only between T1 and L2/3 aka thoracolumbar outflow

Question 10

What is the outflow of the parasympathetic nervous system?

Answer 10

Caniosacral outflow

Neurons begin at the cranial nerves (CN3, CN7, CN9, CN10) and the sacral spinal cord (S2–S4).

Question 11

What does the lateral horn contain?

Answer 11

Cell bodies of sympathetic neurons

Question 12

What are the two types of sympathetic ganglia?

Answer 12

Paravertebral ganglia
Prevertebral ganglia

Question 13

What are paravertebral ganglia?

Answer 13

The site where preganglionic fibers synapse with postganglionic neurons

Question 14

Where do paravertebral ganglia lie?

Answer 14

Anterior to the aorta and vertebral column

Occur on either side of the vertebral column from C-S5

Question 15

What do paravertebral ganglia form?

Answer 15

Two sympathetic trunks

Question 16

Where are prevertebral ganglia found?

Answer 16

Abdominal cavity around the origin of the major branches of the abdominal aorta.

Question 17

How do preganglionic fibres enter the sympathetic trunk?

Answer 17

After passing briefly through the anterior rami, preganglionic fibers enter the sympathetic trunk via white rami communicantes.

Question 18

What do postganglionic fibres do?

Answer 18

Approximately one preganglionic fiber synapses with at least thirty postganglionic fibers.

Question 19

What happens to post ganglionic fibres after synapsing?

Answer 19

Leave the ganglia through gray rami communicantes and travel through the anterior and posterior rami of the spinal nerves.

Question 20

Where do preganglionic nerve fibres synapse?

Answer 20

Paravertebral sympathetic chain ganglia or the prevertebral ganglia

Question 21

What is the sympathetic chain/trunk a mechanism for?

Answer 21

A mass distribution mechanism for sympathetic supply to all parts of the body

Question 22

What (white or grey) ramus communication is myelinated?

Answer 22

White ramus communication = myelinated

Grey ramus communication = unmyelinated

Question 23

What fibres do spinal nerves contain?

Answer 23

Post ganglionic sympathetic fibres as well as somatic fibres

Question 24

What do white ramus communication do?

Answer 24

The white ramus communicans carries preganglionic sympathetic fibers to the sympathetic chain.

Question 25

What do gray ramus communication do?

Answer 25

The gray ramus contains postganglionic sympathetic fibers rejoining the spinal nerve, going to the efector.

Question 26

What is the role of white matter?

Answer 26

Found in the deeper tissues of the brain, containing axons. Many axons are myelinated, giving the white matter its color. White matter helps conduct nerve signals and protect the axons.

Question 27

What is the role of grey matter?

Answer 27

Grey matter makes up the outer most layer of the brain. Mainly composed of neuronal cell bodies and unmyelinated axons. gets its grey tone from a high concentration of neuronal cell bodies

Question 28

Summarise the journey the sympathetic fibres go on

Answer 28

1. Sympathetic fibres originate in the lateral horn cells between spinal levels T1-L2/3. 2. They travel in the ventral root of the spinal nerve to the mixed spinal nerve (MSN). 3. They leave the MSN via a white ramus communication as preganglionic fibres to enter the sympathetic ganglion of the same vertebral level. 4. After synapsing in the sympathetic chain ganglion, they re-enter the spinal nerve via they grey ramus communication as post ganglionic fibres and are distributed via both dorsal and ventral rami of the spinal nerve. 5. The rami then go to supply skin and body wall structures such as arrector pili muscles, blood vessels and glands at that vertebral level (dermatome) with sympathetic input.

Question 29

If sympathetic fibres originate between T1-L2/3, how do parts of the body above and below T1-L2/3 receive sympathetic innervation?

Answer 29

Preganglionic fibres can travel up or down the sympathetic chain from between vertebral levels T1-L2/3 without synapsing there to then only synapse at the sympathetic ganglion levels higher or lower than T1-LW2/3 and enter the spinal nerve occurring at that level therefore all parts of the body receive sympathetic supply.

Question 30

What are the three options available in the sympathetic chain to the sympathetic fibres emerging from lateral horn cells?

Answer 30

1. Synapse in the chain at the same level 2. They can run up or down the chain and synapse at a different level 3. They can pass straight through the chain and synapse elsewhere eg in an autonomic nerve ganglion or plexus in the thorax or abdomen.

Question 31

What feature of the sympathetic chain allows mass activation?

Answer 31

Ability of the sympathetic preganglionic fibres to travel up or down the sympathetic chain

Question 32

What are splanchnic nerves?

Answer 32

Sympathetic preganglionic fibres which travel to supply organs

Question 33

What do splanchnic nerves to thoracic organs do? T1-T4

Answer 33

Synapse in the sympathetic chain and then run as postganglionic fibres to that organ.

Question 34

What do splanchnic nerves to abdominal organs do? T5-L2/3

Answer 34

Do not synapse in the sympathetic chain (just run through it) but pass as preganglionic fibres that synapse instead in prevertebral ganglia outwith the sympathetic chain and then run on from there as postganglionic fibres to supply the organ

Question 35

What do all postganglionic fibres of non-splanchnic nerves do?

Answer 35

Leave the sympathetic chain via grey ramus communication to jin the spinal nerve as the same vertebral level as the sympathetic ganglion in which they have synapsed

Question 36

What are the three main ganglia within the sympathetic chain?

Answer 36

Superior Middle Inferior

Question 37

What supplies the head and neck synapse?

Answer 37

Sympathetic fibres from T1-L2/3 supplying the head and neck synapse with the main ganglia from where postganglionic branches continue to the head and neck

Question 38

How can sympathetic fibres be stretched or damaged?

Answer 38

Along their course to the head and neck.

Question 39

What happens if sympathetic fibres are unilaterally distributed?

Answer 39

Produces a main symptom of Horner's syndrome: Partial ptosis - drooping of the eyelid Miosis - dropping of the eyelid Anhydrosis - decreased sweating

Question 40

Does the ANS consist of sensory fibres?

Answer 40

Yes

Question 41

Discuss sympathetic fibres

Answer 41

Short preganglionic Long postganglionic

Question 42

Discuss parasympathetic fibres

Answer 42

Long preganglionic Short postganglionic