Cranial Nerves Flashcards
Where are upper motor neurons found?
Usually in the cerebral cortex
Axons will project to lower motor neurons
Where are lower motor neurons found?
Usually located in the brainstem or spinal cord
What can happen if there is damage to upper motor neurons?
Paresis
Paralysis
Spastic paralysis
Exaggerated tendon reflexes
What can happens if there’s damage to lowers motor neurons?
Paresis / paralysis
Flaccid paralysis
Loss of tendon reflexes
Rapid muscle atrophy of affected muscles
Fasiculation - involuntary twitching of individual muscles
Describe the neuron order of the motor pathways
1st order - arises is cerebral cortex
2nd order - internuncial, grey column of spinal cord
3rd order - lower motor neuron in anterior grey column
What is the corticonuclear tract?
Motor pathway?
Arises mainly in the lateral aspect of the primary motor cortex
Synapses with cranial nuclei
Innervate most cranial nerve nuclei bilaterally
What receives unilateral innervation from the corticonuclear tract?
The facial nerve nuclei
Supplies the muscles of the lower quadrant of the face
Because facial messages come from both hemispheres not only the opposite side to which is moving
List the 12 cranial nerves
Olfactory Facial
Optic Vestibulocochlear
Oculomotor Glossopharyngeal
Trochlear Vagus
Trigeminal Accessory
Abducens Hypoglossal
What is the mnemonic for remembering the cranial nerves?
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Which of the cranial nerves are sensory?
Olfactory
Optic
Vestibulocochlear
Which of the cranial nerves are motor?
Oculomotor
Trochlear
Abducens
Accessory
Hypoglossal
Which of the cranial nerves are mixed?
(Both sensory and motor)
Trigeminal
Facial
Glossopharyngeal
Vagus
What is the mnemonic for remembering the function of the cranial nerves?
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What are the three ways cranial nerve fibres are named?
General vs Special
Somatic vs Visceral
Efferent vs Afferent
What do we know about general somatic efferents (GSE)?
Cell bodies in brainstem
Innervated skeletal muscle derived from somites
(3, 4, 6,12)
What do we know about special visceral efferents (SVE)?
Functionally identical to GSE
Cell bodies in brainstem
Innervated skeletal muscle derived from pharyngeal arches
(5,7,9,10,11)
What do we know about general visceral efferents (GVE)?
Cell bodies in the brainstem (parasympathetic)
Innervated smooth muscle or glands
(3,7,9,10)
What do we know about general somatic afferents (GSA)?
Cell bodies outside the CNS (ganglia)
From joint, tendon, skin, muscle
Pain, temperature, proprioception, touch and pressure
Innervated specific nuclei in the brainstem
(5,7,9,10)
What do we know about special somatic afferents (SSA)?
Similar to GSA
Transmit specialised sensory inputs (sight, hearing)
(2,8)
What do we know about special visceral afferents (SVA)?
Similar to SSA
Take info from chemoreceptors associated with viscera and senses (taste, smell)
(1,7,9,10)
What do we know about general visceral afferents (GVA)?
Receptors located in serous lining or smooth muscle of body viscera
Thirst, hunger, visceral pain, chemoreception
(7,9,10)
Describe the olfactory nerve
Sensory
Cell body in olfactory epithelium of nasal mucosa
No ganglion
Axons transmitted through cribiform plate of ethmoid bone to olfactory bulb
Postsynaptic fibres of 2nd order neurons form olfactory bulb
Fibres sent to autonomic centres and the limbic system
Sense of smell
Describe the optic nerve
Sensory
Cell bodies in retina (1st order)
Cell bodies in retinal ganglia (2nd order)
Myelinated 2nd order axons grouped together at the optic nerve
Leave the orbit via the optic canal
Terminate in the LGN and pretectal area of the midbrain
Cells of the LGN form geniculocarine tract
Travel to the primary visual cortex
Vision
What are the cranial nerves of the midbrain?
Oculomotor
Trochlear
Describe the GSE aspects of the Oculomotor nerve
Emerges from the midbrain
All extraocular skeletal muscles other than lateral recurs and superior oblique
Controls eye movement
Levator palpebrae superioris - elevates upper eyelid
From Oculomotor motor nucleus
Describe the GVE aspects of the Oculomotor nerve
Parasympathetic
Constricts pupil via sphincter pupillae and cillary muscles
From the Edinger-Westphal nucleus sympathetic fibres leave cillary ganglion with post ganglionic parasympathetic fibres
Terminate in cillary body
Pupillary light and accommodation reflex
Describe the Trochlear nerve
Motor
Emerges from the dorsal aspect of the brainstem
GSE
innervate superior oblique extraocular muscle
Abducts, depresses, medially rotates the eye
Cell bodies in Trochlear nucleus of midbrain
Only cranial nerve formed axons that cross the midline before they exit
What is the cranial nerve of the pons?
The trigeminal
Describe the GSA aspect of the trigeminal nerve
Protio major
3 divisions transmit sensations of touch, pressure, nociception, and thermal changes
V1 - opthalmic division
V2 - maxillary division
V3 - mandibular
The three sensory nuclei form a continuous column from C2 to the midbrain
What are the three sensory nuclei of the GSA fibres of the trigeminal nerve?
Spinal trigeminal nucleus
Principle sensory nucleus
Mesencephalon nucleus
What regions does the opthalmic division of the trigeminal supply?
Exists the superior orbital fissure
Upper eyelid
Forehead
Scalp
What regions does the maxillary division of the trigeminal supply?
Exits the foramen rotundum
Lower eyelid
Upper lip and teeth
Maxillary aspect of face
Lateral strip of temporal area
What regions does the madibular division of the trigeminal supply?
Exits the foramen ovale
Lower lip and teeth
Oral cavity
Skin over mandible
Lateral side of head rostral to ear
Describe the SVE of the trigeminal nerve
Portio minor
Bypasses trigeminal ganglion
Innervates muscles of mastication
And others
It has one motor nucleus
What muscles of mastication are innervated by SVE fibres of trigeminal?
Temporalis
Masseter
Medial pterygoid
Lateral pterygoid
What other muscles do SVE fibres of trigeminal innervate?
Mylohyoid
Ant belly of digastric
Tensor tympani
Tensor veli palantine
What are the cranial nerves of the pons medulla junction?
Abducens
Facial
Vestibulocochlear
Describe the Abducens nerve
Motor
GSE
Innervates the lateral rectus
Nucleus located in the pons
Facial axons loop around it forming a facial colliculus
Leaves the superior orbital fissure
Interneurons go to contralateral Oculomotor nucleus
Allows lateral and medial rectus muscles to work together
What are the five motor branches of the facial nerve?
Temporal
Zygomatic
Buccal
Mandibular
Cervical
Describe the SVE aspect of the facial nerve
Called the Branchial motor component
Cell bodies in facial motor nucleus
Innervates muscles of
Facial expression
Platysma
Stylohyoid
Stapedius
Post belly of digastric
Which fibres of the facial nerve are carried in the intermediate nerve?
GVE
SVA
GSA
GVA
Describe the GVA aspect of the facial nerve
Called secretomotor?
Innervation to lacrimal, sublingual and submandibular glands
Cell bodies in superior salivatory nucleus
Travel in nervus intermedius
Divide to become the greater petrosal and chorda tympani
Describe the SVA of the facial nerve
Innervation to the Ant 2/3 of the tongue (taste)
Cell bodies in the geniculate ganglion
Enters solitary tract
Terminates in the gustatory nucleus within the nucleus of the solitary tract
Describe the GSA aspect of the facial nerve
Fibres transmit info from external ear and external acoustic meatus
(Pain, touch, temperature)
Travel in nervus intermedius
Terminate in the spinal trigeminal tract
Describe the GVA aspect of the facial nerve
Cell bodies in the geniculate ganglion
Sensation from soft palate, nasal cavity, middle ear
Terminate in the spinal trigeminal tract
Describe the vestibulocochlear nerve
Two separate nerves enclosed in the same connective tissue sheath
Vestibular nerve
Cochlear nerve
Describe the vestibular nerve
Cell bodies in vestibular ganglion
Neurons project to vestibular nuclei of pons and medulla
Medial and inferior nuclei have connections with the cerebellum
Lateral nucleus sends axons ipsilaterally down the spinal cord to form the lateral vestibulospinal tract
Describe the cochlear nerve
Cell bodies in the spiral ganglion of the cochlea
Neurons project to cochlear nuclei of medulla
Cross midline to enter the superior olivary nucleus (medial geniculate nucleus of the thalamus)
Small number of axons leave the SON and provide innervation to stapedius
