cranial nerves & integrated systems Flashcards
list the 12 pairs of cranial nerves and their location
I: olfactory –> telencephalon (cerebrum)
II: optic –> diencephalon
III: oculomotor –> mesencephalon
IV: trochlear
V: trigeminal --> rhombencephalon VI: abducens VII: facial VIII: vestibulocochlear IX: glossopharyngeal X: vagus XI: accessory XII: hypoglossal
compare the spinal and cranial nerves
- SIMILARITIES
both peripheral nerves (excluding CN II, which is part of CNS) - LOCATION OF MOTOR/SENSORY NUCLEI
cranial motor nuclei —> medial brain stem
cranial sensory nuclei —> lateral brain stem
spinal motor nuclei —> ventral horn of grey matter
spinal sensory nuclei —> dorsal horn of grey matter - COMPONENT FIBRES
cranial can be heterogenous
spinal always a mix of motor and sensory (excluding C1 which is purely motor) - SPECIAL SENSES
cranial nerves can innervate special senses (smell, vision, taste, hearing, balance) - PRESENCE OF GANGLIA
cranial: sensory ganglia of the head contain perikarya of (pseudo)unipolar sensory nerves
spinal: dorsal root ganglia contain perikarya of (pseudo)unipolar sensory nerves - PRESENCE OF AUTONOMIC NERVES
cranial: only parasympathetic ganglia (CN III, VII, IX, X)
spinal: parasympathetic nerves in sacral and sympathetic in thoraco-lumbar regions
define the different types of AFFERENT fibres found in cranial nerves
- GENERAL SOMATIC AFFERENT (GSA):
- touch, pain, temperature, itch
- similar to info carried in dorsal roots of the spinal cord
- e.g. CN V - SPECIAL SOMATIC AFFERENT (SSA):
- vision hearing and balance
- e.g. CN II, VIII - GENERAL VISCERAL AFFERENT (GVA):
- sensory feedback from organs or glands
- pain, stretch
- e.g. CN IX, X - SPECIAL VESCERAL AFFERENT (SVA):
- sensor feedback from organs of chemical sensing
- taste, oflaction
- e.g. CN I, VII, IX, X
define the different types of EFFERENT fibres found in cranial nerves
- GENERAL SOMATIC EFFERENT (GSE):
- fibres that innervate muscles of head and neck
- e.g. CN III, IV, VI, XII - GENERAL VISCERAL EFFERENT (GVE):
- fibres that belong to the autonomic nervous system and supply parasympathetic ganglia
- smooth muscle around blood vessels and glands
- e.g. CN III, VII, IX & X - SPECIAL VISCERAL EFFERENT (SVE):
- innervate muscles of pharyngeal arches/branchial efferents
- e.g. CN V, VII, IX, X & XI
what is the sulcus limitans?
sulcus limitans divides the altar (sensory) and basal plates (motor) in the spinal cord and brain stem
spreading of sulcus limitans during development:
- –> in spinal cord, pushes basal plate/motor neurons venrally & altar plate/sensory neurons dorsally
- –> in brain stem, pushes basal plate/motor neurons medially & altar plate/sensory neurons laterally
which four cranial nerves contain parasympathetic fibres?
how can these fibres be classified?
where do these parasympathetic fibres synapse?
oculomotor (III), facial (VII), glossopharyngeal (IX), and vagus (X) nerves contain parasympathetic fibres
these fibres are classified as general visceral efferent (GVE) fibres
oculomotor (III) synapses onto the ciliary ganglion
facial (VII) synapses onto the pterygopalatine ganglion and submandibular ganglion —> terminates at superior salivatory nucleus
glossopharyngeal (IX) synapses onto otic ganglion —> terminates at inferior salivatory nucleus
vagus (X) terminates at the dorsal motor nucleus of vagus
oculomotor nerve (CN III):
- –> fibre type?
- –> orignation & synapses?
- –> innervations & functions?
oculomotor nerve contains both GSE and GVE
originates in the midbrain –> passes through superior orbital fissure —> synapses to ciliary ganglion
innervates:
- 4/6 of extraocular muscles
- levator palpeprae superior (upper eyelid)
- ciliary muscle and sphincter pupilae (intrinsic eye muscles –> pupillary constriction in response to light)
pupillary light reflex
- bright light enters ONLY ONE pupil
- optic nerve and optic tract transport the light signal
- collaterals from the optic tract synapse on neurones of the pretectal area
- pretectal fibres cross contralaterally at the posterior commissure
- neurones of the pretectal area project bilaterally to the
Edinger-Westphal nuclei of the oculomotor nerve - parasympathetic oculomotor fibres from the Edinger-
Westphal nuclei innervate the sphincter pupillae muscle - constriction of both pupils
what are the results of an uncul herneation?
uncus = anterior end of parahippocampul gyrus
an uncal herniation can put pressure on:
- the 3rd cranial nerve —> pupil dilates
- the posterior cerebral artery (ischemia of the ipsilateral primary visual cortex)
furthermore, the tentorium can put pressure on the midbrain
—> lesion of pyramidal and sensory pathways
what are the results of oculomotor nerve palsy
results in paralysis of muscles innervated by CN III
- downward and outward gaze of affected eye
- dilated pupil of affected eye
- ptosis (drooping eyelid) of affected eye
- diplopia (double vision)
trochlear nerve (CN IV):
- –> fibre type?
- –> orignation & synapses?
- –> innervations & functions?
trochlear nerve contains GSE fibres
only nerve that originates from dorsal midbrain —> passes through superior orbital fissure —> tendon of muscle passes through a pulley called the trochlea
innervates:
- superior oblique muscle —> moves eye down and out
what are the results of a trochlea nerve lesion?
gaze deviates upward and inward of affected eye
inability to rotate eye infero-laterally
diplopia (double vision)
abducens nerve (CN VI):
- –> fibre type?
- –> orignation & synapses?
- –> innervations & functions?
abducens nerve contains GSE fibres
originates from the anterior border of the pons and medulla oblongata —> passes through superior orbital fissure
innervates:
- lateral rectus muscle —> abducts eye
what are the results of a abducens nerve lesion?
gaze deviates inward
inability to abduct eye
trigeminal nerve (CN V):
- –> fibre type?
- –> orignation & synapses?
- –> innervations & functions?
trigeminal nerve contains GSA fibres and SVE/BE fibres
originates from pons —> synapses on trigeminal/semilunar ganglion (located on middle of cranial fossa)
V1: OPTHALMIC NERVE
- passes through superior orbital fissure
- only sensory fibres
- supplies the skin of the forehead, eyelids, eyebrow, & nose
- supplies the eye (pain sensation)
V2: MAXILLARY NERVE
- passes through foramen torundum
- only sensory fibes
- supplies the skin of the middle face, teeth of upper jaw, and maxillary sinus
V3: MANDIBULAR NERVE
- passes through oval foramen
- both sensory and motor
- sensory supply to skin of lower face, teeth of lower jaw, and tongue (not taste)
- motor supply to muscles of mastication
CN 5 also mediates jaw-jerk reflex
sensory relay is to the VPM of the thalamus
