SEM 1 - C - Somatic nervous system, A.N.S- para and sympathetic supply and ganglion

Question 1

Which root of the spinal nerve contains sensory neurons and which contains motor neurons?

Answer 1

The posterior (dorsal) rootlets and roots contain sensory neurones - this is the afferent pathway The anterior (ventral) rootlets and roots contain motor neurones - this is the efferent pathway

Question 2

The anterior and posterior roots join to form the spinal nerve. Where in the vertebrae is the spinal nerve found? The spinal cord has denticulate ligaments which are attached where? What are these ligaments function?

Answer 2

The spinal nerve can be found in the intervertebral foramen Denticulate ligaments are extensions of pia mater attaching between anterior and posterior nerve roots attaching to the dura mater It is thought that the denticulate ligaments function to suspend the spinal cord in the dural sac

Question 3

The spinal nerve splits to form dorsal and ventral rami What structures do each rami supply?

Answer 3

Dorsal rami supplies the posterior body wall and contains somatic motor, somatic sensory and sympathetic fibres Ventral rami supplies the anterior + lateral body wall and limbs and contains somatic motor, somatic sensory and sympathetic fibres

Question 4

We have talked about the somatic nervous system (body wall and limbs aka voluntary nervous sytem)), lets now talk about the autonomic nervous system (involuntary nervous system) What type of muscle does the ANS innervate? Is it under voluntary control? Which modalities does the ANS have?

Answer 4

ANS innervates smooth muscle and influences cardiac muscle. As it does not innervate skeletal muscle it is not under voluntary control ANS has sensory and motor fibres, as well as sympathetic and parasympathetic fibres

Question 5

What type of outflow is the parasympathetic division of the ANS? What type of outflow is the sympathetic division? What are the catchy phrases for each of parasympathetic and sympathetic?

Answer 5

Parasympathetic - craniosacral outflow - rest and digest Sympathetic - thoracolumbar outflow - fight or flight

Question 6

Which cranial nerves contain parasympathetics as one of their modalities? What are the ganglion at which these cranial nerves synapse before post ganglionic fibres reach the target organs/glands?

Answer 6

Cranial nerves III, VII, IX, X CN III - oculomotor nerve- ciliary ganglion CN VII - facial nerve - * pterygopalatine ganglion * submandibular ganglion CN IX - glossopharyngeal nerve - otic ganglion CN X - usually synapse almost directly onto the organ

Question 7

What structures does the oculomotor nerve innervate with its parasympathetics? What is the ganglion upon which it synapses again?

Answer 7

Oculomotor nerve synapses on ciliary ganglion Innervates the sphincter pupillae (muscle in the iris which causes pupil to constrict - eg in bright lights)

Question 8

State all the glands innervated by the parasympathetics travelling alongside the facial nerve? What structures does the facial nerve innervate with its parasympathetics via each ganglion? What is the ganglion upon which it synapses again?

Answer 8

Facial nerve via the * pterygopalatine ganglion - innervates lacrimal gland, nasal, palatine & pharygeal glands * submandibular ganglion - innervates submandibular & sublingual glands

Question 9

What structures does the glossopharyngeal nerve innervate with its parasympathetics? What is the ganglion upon which it synapses again?

Answer 9

Glossopharyngeal nerve - otic ganglion - paraympathetics to the parotid gland

Question 10

Up until what point in the abdominal cavity does the vagal nerve control innervation?

Answer 10

The vagal nerves provides visceral sensory and visceral motor fibres to the heart lungs and abdomen up until roughly the splenic flexure in the abdomen where the sacral roots of the ANS will take over parasympathetic supply

Question 11

What level does the vagus nerve pass through the diaphragm and alongside what? What three structures pass through the diaphragm at T12?

Answer 11

T8 - * inferior vena cava (8 letters) T10 - * oesophagus (10 letters), * vagus nerve (10 letters) T12 - * aortic hiatus (12 letters), * thoracic duct (12 letters), * azygous vein (the anomaly as only 10 letters)

Question 12

What are the sacral parasympathetic roots? What part of the body wall do they supply?

Answer 12

S2, 3, 4 There is no body wall supply Sacral roots supply distal abdomen (from splenic flexure) and the pelvic organs

Question 13

There is parasympathetic motor and sensory supply with the visceral sensory supply mostly coming from CN IX, X and sacral roots Basically the visceral motor is the parasympathetic supply to glands and organs, the visceral sensory is how we feel pain from the organs and the fibers travel with the parasympathetics at certain levels (gets tricky in the pelvis) Where do the cell bodies for sympathetic supply lie?

Answer 13

Cell bodies lie in the lateral horns of the spinal cord (grey matter) only from T1 to L2

Question 14

Although the sympathetic cell bodies only run in the lateral horns from T1 to L2, sympathetics are still needed beyond here ie the limbs - this is where the sympathetic chain comes into things The sympathetic chain is a linked group of paravertebral ganglia from cervical to sacral regions What do they right and left sympathetic chains merge to form inferiorly?

Answer 14

They merge to form the ganglion impar at roughly the sacrococcygeal junction

Question 15

The sympathetic chain communicates with both the spinal nerves and the prevertebral ganglia How does the sympathetic chain communicate with the spinal nerve?

Answer 15

Via connections known as rami communicantes (communicans)

Question 16

There are white and grey rami communicates, what is the difference?

Answer 16

White rami communicantes are myelinated and only exist from T1 to L2 as the sympathetic output from spinal nerve to sympathetic chain Grey rami communicantes are unmyelinated and exist from all levels of the sympathetic chain - these carry fibres from the chain to the spinal nerve

Question 17

Are white or grey rami fibres preganglionic?

Answer 17

White rami communicantes are preganglionic fibres as they carry fibres from the spinal to synapse in the sympathetic chain Grey rami communcantes are postganglionic as the fibres have synapse in the ganglion and travel back from chain to spinal nerve

Question 18

Sympathetic fibres can pass from the lateral horns into a spinal nerve then into the sympathetic chain via a white ramus communicans. From there they can either go to a local plexus or use the chain to ascend or descend to structures outwith the thorax/abdomen Once the sought after spinal level has been reached what will happen for supplying this region?

Answer 18

The sympathetic fibres will travel along grey rami communicantes to re-enter the spinal nerve and supply that region

Question 19

Remember for structures outwith the T1 to L2 vertebral level that require sympathetics, the sympathetic fibres must enter the sympathetic chain via white rami communicans between T1 to L2 (only exist between these levels) and then travel back via grey rami communicans Do sympathetics supply the posterior body wall travel via the ventral or dorsal ramus?

Answer 19

Posterior body wall - dorsal ramus Anterolateral body wall - ventral ramus

Question 20

What structures are actually innervated by the sympathetics in the body wall?

Answer 20

Arrector pili muscle (smooth muscle) - piloerection Sweat glands Blood vessels (smooth muscle of blood vessels - causes constriction)

Question 21

What do sympathetic fibres form plexi (plexuses) on, to allow the fibres to reach their target organs?

Answer 21

The sympathetic fibres will form plexi on arterial vessels to allow the fibres to reach their target organs

Question 22

There are four main courses taken by presynaptic sympathetic fibres within the sympathetic trunks (chain) Describe the four main courses?

Answer 22

1. Ascending and then synapsing - usually when going to supply the head 2. Synapsing at level of entry - when supplying the thoracic/trunk region 3. Descending and then synapsing - usually when supplying eg the lower limb 4. Passing through the sympathetic trunk without synapsing to enter an abdominopelvic splanchnic nerve - this occurs only for the innervation of abdominopelvic viscera

Question 23

When the sympathetic fibers Pass through the sympathetic trunk without synapsing to enter an abdominopelvic splanchnic nerve - this occurs only for the innervation of abdominopelvic viscera, WHERE DOES THE SYNAPSE OCCUR?

Answer 23

The synapse will occur where the sympathetic fibres form a plexus around an artery heading to the target organ of the abdominopelvic area ( tis plexus is also known as the prevertebral ganglia)

Question 24

Which organ is it where the the sympaethtic fibres actually synapse almost directly onto the organ?

Answer 24

This would be the adrenal medulla

Question 25

Can somatic nerves or visceral nerves localise pain well?

Answer 25

Somatic nerves can localise pain very well as they are nerves supplying body wall structurees Visceral nerves supply deep structures and therefore pain is not localised well

Question 26

It extends from T1 to L2, and contains the autonomic motor neurons that give rise to the preganglionic fibers of the sympathetic nervous system, (preganglionic sympathetic general visceral efferents)? What is this column that makes up the lateral horns known as?

Answer 26

The intermediolateral nucleus (IML) - lateral horns of grey matter - this is the column which extends from T1 to L2

Question 27

Which vertebral levels do sympathetic fibres for the upper limb, thoracic viscera, head and neck originate from? Which vertebral levels do sympathetic fibres for the body wall and abdominal viscera originate from? Which vertebral levels do sympathetic fibres for the lower limb and pelvic viscera originate from?

Answer 27

Upper limb/ head and neck/ thoracic viscera - T1-T6 Body wall and abdominal viscera - T7-T11 Lower limb/Pelvic viscera - T11-L2

Question 28

Pain from the viscera is carried into the sympathetic chain, then travelling along a GRC back into the spinal nerve and therefore thee body interprets the pain as coming from the spinal nerve, not from the viscera Pain from an internal organ is expressed as pain from the body wall itself What do the general visceral afferent fibres usually accompany in the abdomen?

Answer 28

General visceral afferent fibres usually accompany sympathetic fibres in the abdomen

Question 29

Answer 29

General visceral afferents in the pelvis depend on the ‘pain line’ This is an imaginary line drawn across organs in contact with the peritoneum vs those that are not GVA from structures above the pain line/structures in contact with the periotneum follow sympathetic fibres GVA from structures below the pain line follow parasympathetic fibres - S2-4 dermatomal distribution

Question 30

Sympathetic and parasympathetic often integrated to allow control E.g. the heart Heart beat is spontaneous but modified by the actions of the autonomic nervous system * Which nerve helps with parasympathetic modification of the heart beat? * Which nerves help with sympathetic modification of the heart beat? * Do the fibres synapse intrinsic (at heart) or extrinsic?

Answer 30

Parasympathetics - Vagus nerve (ganglion for synapse is intrinsic here) Sympathetics - T1 to T5/6 spinal levels - Cervical and Superior Thoracic Paravertebral Ganglia (synpase is in the sympathetic chain)

Question 31

ENS is not visible to the naked eye The ENS works independently and with the ANS to control movements of the GI tract Has motor and sensory componenets Where does the enteric nervous system form plexuses?

Answer 31

ENS forms plexuses in the walls of the GI system