Week 1 - G - Neuroanatomy 4 - Cranial nerve nuclei

Question 1

What are the twelve cranial nerves and where do they exit the central nervous system?

Answer 1

Olfactory nerve - forebrain Optic nerve - forebrain Oculomotor nerve - midbrain Trochlear nerve - midbrain Trigeminal nerve - pons Abducent, Facial, Vestibulocochlear nerve - pontomedullary junction Glossopharyngeal, Vagus nerve - medulla Spinal accessory nerve - arises in the cervical vertebrae Hypoglossal nerve - medulla

Question 2

What nerves are only sensory and no motor control?

Answer 2

Olfactory Optic Vestibulocochlear nerve

Question 3

Nerves exit the brainstem anteriorly apart from which cranial nerves? how do they exit?

Answer 3

Cranial nerve 4 - trochlear nerve exits the brainstem posteriorly Cranial nerve 8 - vestibulocochlear nerve exits the brainstem laterally

Question 4

As we have seen, some CN are purely motor, some purely sensory and some mixed. Motor components will be associated with motor nuclei, groups of efferent nerve cells that send their axons into the cranial nerve. Sensory components will be associated with sensory nuclei, groups of nerve cells upon which the sensory neurons of the cranial nerves synapse. Where is the soma of the sensory nerves found?

Answer 4

The soma of the sensory nerve cells will be found outside the CNS and axons will project into the CNS where they will synaspe

Question 5

What is the only sensory system that does not synapse in the thalamus before reaching the brain cortex

Answer 5

This would be olfaction

Question 6

What type of neurones are the oflactory neurones that project down into the cribiform plate of the ethmoid bone? (it has two neurites)

Answer 6

The olfactory neurones are bipolar neurones - the cell body gives off two neurites (dendrite + axon)

Question 7

The olfactory tracts travel from the olfactory bulbs to the primary olfactory area which is located where?

Answer 7

The primary olfactory cortex is located in the medial aspect of the temporal lobe known as the uncus

Question 8

The primary olfactory cortex is located in the medial aspect of the temporal lobe known as the uncus Where is the primary auditory cortex located?

Answer 8

The primary auditory cortex is located in the superior temporal gyrus

Question 9

What is the nucleus of the olfactory nerve then?

Answer 9

The nucleus of the olfactory nerve is known as the olfactory bulb located in the forebrain

Question 10

Label the diagram

Answer 10

Orange circle - superior colliculus Black circle -inferior colliculus Green circle - floor of the 4th ventricle Blue circle - Middle cerebellar peduncle

Question 11

What are the different modalities of the oculomotor nerve? What is the function of the oculomtor nerve?

Answer 11

Oculomtor nerve provides somatic motor supply and parasympathetic supply Somatic motor to levator palpebrae superioris, medial rectus, superior rectus, inferior rectus and inferior oblique Parasympathetic to the sphincter pupillae (constriction of the pupil) and the ciliary muscles of the ciliary body

Question 12

What are the oculomotor nerve nuclei? What level is the nuclei located?

Answer 12

Oculomotor nucleus - at the level of the superior colliculus is for the somatic motor control Edinger Westphal nucleus supplies the parasympathetics

Question 13

If there is damage to the oculomotor nucleus, what will happen to the eye?

Answer 13

Pupil will be dilated The eye will be facing down and out

Question 14

What nerve nuclei arises at the level of the inferior colliculus?

Answer 14

This would be the trochlear nucleus

Question 15

What is the modality of the trochlear nerve? Where does it exit the central nervous system? (ie where does the nerve arise on the brain) What does the trochlear nerve supply?

Answer 15

Somatic motor axons to the superior oblique muscle - moves eye down and out Trochlear nerve is the only nerve to exit the brainstem posteriorly (posterior aspect of midbrain)

Question 16

Which part of the brainstem are the oculomotor and trochlear nucleus located?

Answer 16

Oculomotor and trochlear nucleus are both located in the midbrain at the levels of the superior and inferior colliculus respectively

Question 17

What is the abducent nerve nucleus known as? What does the abducent nerve supply? and what action does this bring about? What are its modalities?

Answer 17

Known as abducens nucleus Supplies the lateral rectus - brings about abduction of the eye It is a somatic motor nerve

Question 18

Where is the abducent nerve nucleus located?

Answer 18

The abudcent nerve nucleus is located in the caudal aspect of the pons

Question 19

What is the final motor cranial nerve? (not a mixed one) What muscles does it supply? WHat extrinsic muscle of the tongue does it not supply and what supplies this? What modality is this nerve?

Answer 19

The hypoglossal nerve Supplies the intrinsic muscles of the tongue and the genioglossus, styloglossus, hyoglossus Doesnt supply the palatoglossus which is supplied by the vagus nerve hypoglossal nerve is somatic motor

Question 20

Hypoglossal nucleus extends over a very long distance as it a long column of cells What part of the brainstem does it extend through?

Answer 20

Extends over most of the medulla of the brainstem

Question 21

Note how III, IV, VI and XII emerge close to the midline: reflects the location of their nuclei Run through again the nucleus and where the nucleus are located (which part of brainstem) and what muscles/modalities the nerves are

Answer 21

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Question 22

Spinal accessory nerve has two components - the cranial accessory and spinal accessory components Were do nuclei for both the components arise?

Answer 22

Spinal accessory nuclei - anterior horns of the spinal cord segments C1-C5 Cranial accessory nuclei - the nucleus ambiguus located in the medulla

Question 23

How does the spinal root of the accessory nerve exit and enter the cranial cavity? Where is it that the cranial and spinal roots come into contact?

Answer 23

Spinal root comes up through the foramen magnum and curves round to exit the cranial cavity via the jugular foramen The cranial and spinal roots only come into contact as they exit via the jugular foramen and then the cranial accessory root joins with the vagus nerve

Question 24

What modality is the spinal accessory nerve and what muscles are supplied?

Answer 24

It is somatic motor Supplies the sternocleidomastoid and trapezius muscles

Question 25

What are the mixed cranial nerves? What are their foramen of the skull? Where do they arise in the brain? (exit the central nervous system)

Answer 25

* Trigeminal nerve - arises at the pons Ophthalmic - Superior orbital fissure Maxillary - Foramen rotundu m Mandibular - Foramen ovale * Facial nerve - arises at the pontomedullary junction - Internal acoutic meatus through facial canal to stylomastoid foramen * Glossophyangeal nerve - arises at the medulla - Jugular foramen * Vagus nerve - at the medulla - jugular foramen

Question 26

What are the functions of the trigeminal nerve? Which nerve carries what innervation to the anterior 2/3rds of the tongue from CN V?

Answer 26

Motor to the muscles of mastication Sensory supply to the skin over the face Sensory to the anterior 2/3rds of the tongue via the lingual nerve - branch of the mandibular division of the trigeminal nerve

Question 27

What muscle in the ear attached to the malleus does the trigeminal nerve supply?

Answer 27

Tensor tympani - supplied by mandibular division of trigeminal nerve

Question 28

The sensory nucleus of the trigeminal forms a long column of neurons that stretches from the midbrain down to the upper 2 segments of the cervical spinal cord. It has 3 parts, separated by function. What are the three sensory nuclei?

Answer 28

Mesencephalic nucleus Pontine trigeminal nucleus Spinal nucleus

Question 29

What sensory information do the three nucleus provide?

Answer 29

Mesencephalic nucleus - proprioception from chewing muscles Pontine trigeminal nucleus - Fine (discriminative) touch and vibration Spinal nucleus - pain and temperature

Question 30

What is the only site in the CNS where the cell bodies of primary afferents live inside the CNS?

Answer 30

This is the mesencephalic nucleus - proprioception from chewing muscles

Question 31

State again what the trigeminal nuclei that span the brainstem are? Which nuclei is the motor nucleus of the trigeminal nerve located beside? What are the functions of the nuclei? What nerve branch of the trigeminal nerve supplies sensory innervation to the anterior 2/3rds of the tongue?

Answer 31

Mesencephalic nucleus - proprioception from chewing muscles Pontine trigeminal nucleus - fine touch and vibration Spinal nucleus - pain and temperature Motor nucleus is medial to the pontine trigeminal nucleus Lingual nerve branch of the mandibular nerve supplies sensation to the anterior 2/3rds of the tongue

Question 32

The spinal nucleus of the trigeminal nerve merges with the upper horn of the spinal cord Is the fasciculus gracilis or cuneatus medial in the dorsal column of the spinal cord? Which recieves info from the lower and which from the upper limb?

Answer 32

Fasciculus gracilis (lower limb) is medial to the fasciculus cuneatus (upper limb)

Question 33

What are the modalities of the facial nerve? (4 modalities) What is innervated by the modalities?

Answer 33

Motor innervation to the muscles of facial expression and the stapedius Parasympathetics to the submandibular and sublingual salivary glands and the lacrimal gland Special sensory (taste) to the anterior 2/3rds of the tongue via the chorda tympani branch Technically also provides somatosensory to the ear

Question 34

What are the modalities of the glossopharyngeal nerve? (4 modalities)

Answer 34

Somatic sensory to the oropharynx Special sensory (taste) to the posterior 1/3rd of the tongue Somatic motor to stylopharyngeus muscle Parasympathetic to the parotid gland

Question 35

What are the modalities of the vagus nerve? (4)

Answer 35

Sensory to the pharynx and abdominal viscera Motor to the muscles of the larynx/pharynx Special sensory (taste) to the epiglottis Parasympathetics to ganglia in thoracic and abomindal viscera

Question 36

Name the 4 nuclei of the facial nerve?

Answer 36

Facial motor nucleus Superior salivatory nucleus Solitary nucleus Spinal nucleus of trigeminal nerve

Question 37

What are the 4 nuclei of the facial nerve function?

Answer 37

1. The facial mtoor nucleus to msucles of facial expression and stapedium 2. Superior salivatory nucleus for the parasympathetics to the gland 3. Solitary nucleus - for taste to anterior 2/3rds of the tongue 4. Spinal nucleus of trigeminal nerve-somatosensation 2 ear

Question 38

Which nuclus of the facial nerve gives off a tract which arches around the abducent nerve nucleus?

Answer 38

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Question 39

What are the 4 nuclei of the glossopharyngel nerve? The IXth nerve has no real nucleus to itself. Instead it shares nuclei with VII and X.

Answer 39

1. Solitary nucleus - taste to posterior 1/3rd of the tongue 2. Spinal trigeminal nucleus - small amount of somatosensation to the ear 3. Inferior salivatory nucleus - parotid gland parasympathetics 4. Nucleus ambiguus - motor to stylopharnyngeus

Question 40

Where are the glossopharyngeal nucleus located?

Answer 40

They are located in the upper medulla

Question 41

What are the 4 vagus nerve nuclei? Where are the nuclei found?

Answer 41

1. Dorsal motor nucleus - parasympathetics 2. Solitary nucleus - tiny taste from epiglottis 3. Spinal trigeminal nucleus - somatosensation for ear 4. Nucleus ambiguus - motor pharynx and larynx In the upper medulla

Question 42

Several nuclei in the brainstem are shared by more than one cranial nerve: Name the nuclei shared by CN VII,IX and X and the function

Answer 42

Solitary nucleus - CN VII, CNIX, CN X - supplies taste to tongue and epiglottis Superior and inferior salivatory nucleus - CN VII, CNIX - parasympahetics to major salivary glands Nucleus ambiguus - CN IX and X - motor for stylopharyngeus (CN IX) and motor to laryngopharynx

Question 43

What other nerve shares the nucleus ambiguus nucleus apart from CN IX and X?

Answer 43

Cranial root of CN XI has the nucleus ambiguus

Question 44

List all the cranial nerve and their nuclei List at what region of the brain they are

Answer 44

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Question 45

The solitary nucleus extends in a V shape from upper to lower medulla What sensations does this nucleus carry out?

Answer 45

Taste and general visceral sensations

Question 46

What nerves supply special sense of taste?

Answer 46

Facial nerve via chorda tympani branch to anterior 2/3rds of the tongue Glossopharyngeal nerve to posterior 1/3rd of the tongue Vagus nerve to some tatse receptors in the epilglottis

Question 47

What tract is the motor input to the cranial nerves known as?

Answer 47

This is the corticobulbar tract

Question 48

The reticular formation is a network of loosely aggregated cells with cell bodies, axons and dendrites intermingling in the central core of the brainstem. It is distinct from the long pathways (like the medial lemniscus, or the corticospinal tract) and the specific distinct cell groups (like cranial nerve nuclei). In general, the reticular fibres located where cause extensor movements and the reticular fibres located where cause flexor movmements?

Answer 48

The reiticular fibres located in the pons cause extensor movements and inhibit flexor movememnts The reticular fibres located in the medulla facilitates flexor movements and inhibit extensor movements

Question 49

What is amytrophic lateral sclerosis? Does it cause UMN or LMN disease?

Answer 49

ALS is the main type of motor neuron disease It is a progressive UMN and LMN disease therefore produces symptoms of both It causes the loss of UMNs in the motor cortex and the anterior horn of the corn Weakness, fascicultions, atrophy

Question 50

What are the other types of motor neurone disease, what do they affect?

Answer 50

Progressive bulbar palsy - only affects cranial nerve 9-12 Porgressive muscular atrophy - affects the anterior horns only - no UMN signs Primary lateral sclerosis - UMN signs only

Question 51

What does the corticobulbar tract supply? What does a bulbar palsy affect? State the different types of MND again?

Answer 51

Corticobulbar tract - supplies the motor neurones of the cranial nerve (V,VII,X,XI,XII) Corticobulbar tract gives motor function of the non-oculomotor cranial nerves.

Question 52

What movmeents are never affected in MND and therefore separtes MND from mysathenia gravis? What is MG?

Answer 52

Eye movements are never affected in MND Myasthenia gravis is caused by autoantibodies to the post synapctic acetchycoloine channls leading to progessive fatiguiability The most commonly affected muscles are those of the eyes, face, and swallowing.

Question 53

What is the treatment option for MG and for MND?

Answer 53

MND - only medication treatment shown to have any effect is the anti-glutamatergic - riluzole MG - give anticholinesterases inhibitors - ie rivastigmine or pydrodstigmine

Question 54

What are the nuclei of the facial nerve?

Answer 54

Facial motor nucleus - motor for muscles of facial expression Superior salivatory nucleus - parasympathetics to both the sublingual and submandibular glands and lacrimal gland Solitary nucleus - taste for anterior 2/3rds of the tongue Spinal nucleus of trigeminal nerve - somatosensation to ear

Question 55

Many of the cortical inputs to the cranial nerves are bilateral Explain how this is different in the facial nerve?

Answer 55

The muscles of the upper face (forehead and around eyes) receive bilateral facial nerve innervation - the input to the facial nucleus is bilateral for the upper half of the face The muscles of the lower face (smiling etc) recieve contralateral innervation

Question 56

How will an UMN facial nerve lesion present? How will a LMN facial nerve lesion present?

Answer 56

UMN - will cause loss of function in the lower aspect of the face contralaterally Will have sensation to upper half of face due to the upper face having bilateral innervation and ipsilateral facial nerve isnt affetced LMN - will block both contralateral & ipsilateral innnervation - loss of function to upper and lower halfs of face

Question 57

Where is the UMN of the cranial nerves? Where is the lower motor neuron?

Answer 57

UMN of the cranial nerves is from the primary motor cortex (precentral gyrus of posterior frontal lobe) to the cranial nerve nucleus Lower motor neuron is from cranial nerve nucleus to the strucutre it innervates

Question 58

Explain why patients with a right sided upper motor neuron facial nerve palsy are unable to smile but able to raise their eyebrowns on the left side? But a patient with a right sided lower motor neuron nerve palsy would be unable to smile or raise their eyebrowns on the left side

Answer 58

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