10- Anatomy Of The Ans

Question 1

What is the difference between the S and P ANS

Answer 1

Parasympathetic 
Localised
Conserves body energy
• Sympathetic
MASS RESPONSE - everything is activated in the fight-flight response Mobilises body energies for increased activity

Question 2

Where are ganglia found in the S and P ANS

Answer 2

Sympathetic = SHORT preganglionic fibre
Ganglia are found in the SYMPATHETIC TRUNK which is closer to the spinal cord than the organ/viscera being innervated
The connection between all the ganglia allows a generalised response
• Parasympathetic = LONG preganglionic fibre
Found close to or even in the organ/viscera they innervate

Question 3

What makes up the SNS

Answer 3

TWO sympathetic trunks
Nerve plexuses (e.g. cardiac plexus - dense innervation of sympathetic fibres)
Subsidiary ganglia - there are some specialist ganglia that are little bit further out in the body

Question 4

What does the SNS innervate

Answer 4

Sweat Glands - usually the parasympathetic has the localised function but the exception is the sweat glands (makes sense because when you’re in fight-flight mode you’ll sweat a lot)
Arrector pili muscle of hair follicles - your hair stands on end when you’re scared
Muscular walls of blood vessels
Heart, lungs, abdominal and pelvic viscera

Question 5

Which direction does the white and grey Ramus go

Answer 5

WHITE ramus = fibres go TOWARDS the ganglion

GREY ramus = fibres COMING FROM the ganglion

Question 6

Describe the route of the SNS preganglionic neurone

Answer 6

Preganglionic neurons are in the lateral column grey matter of spinal cord T1 to L3
o
• The fibres emerge from the spinal cord via the ventral root of the spinal nerve
• Passes through the ventral ramus to the white rami communicantes to the sympathetic ganglion
• Connection between the ventral ramus and the sympathetic ganglion is via:
WHITE ramus = fibres go TOWARDS the ganglion
GREY ramus = fibres COMING FROM the ganglion

Question 7

Which 3 routed out of the dorsal ramus can the s preganglionic fibre take

Answer 7

SIMPLEST: the preganglionic fibre synapses in that sympathetic ganglion staight away. The postganglionic fibre then goes out to the spinal nerve via the GREY ramus communicantes at the same level and then it goes out to the viscera
The fibre can come into the sympathetic ganglion and then go up or down the sympathetic chain and synapse in any of the other ganglia so the postganglionic neurons are then distributed at the level of that ganglion
The third option is to go straight through the ganglion without synapsing and then to synapse in one of the subsidiary ganglia which are a little bit further out such as the coeliac ganglion and the superior mesenteric ganglion

Question 8

Where are the sympathetic ganglia located

Answer 8

Ganglia by REGION:
Cervical = 3
o Thoracic = 11 or 12
Lumbar = 4 or 5
o Pelvis=4or5
• NOTE: preganglionic fibres do NOT come out in the cervical region
• Sympathetic fibres pass from the spinal nerves to the sympathetic trunk via the white ramus communicantes

Question 9

Give some examples of plexuses

Answer 9

Around the pharynx 
Cardiac plexus
Thyroid plexus 
Pulmonary plexus 
Around the thoracic aorta 
Splanchnic nerves

Question 10

What are the 3 splanchnic nerves

Answer 10

Greater
Follow the thoracic aorta supply
Pierces the diaphragm and enters the abdomen plexus around great blood vessels supplying the gut
• Lesser
Pierces the diaphragm and enters the abdomen plexus around the aorta
• Least
Pierces the diaphragm and enters the abdomen plexus around the gut