Download Anatomy Lecture 2 – Cranial Nerves

Cranial Nerve
Function
Skull Exit
I: Olfactory
Sensory
II: Optic
III: Oculomotor
Sensory
Motor
IV: Trochlear
Motor
V: Trigeminal
Both
VI: Abducens
Motor
VII: Facial
Both
Cribiform Plate
(Crista Gallae)
Optic Canal
Superior
Orbital Fissure
Superior
Orbital Fissure
SOF,
Rotundum,
Ovale
Superior
Orbital Fissure
Internal
Auditory
Foramen
VIII:
Vestibulocochlear
Sensory
IX:
Glossopharyngeal
X: Vagus
Both
XI: Accessory
XII: Hypoglossal
Cranial
Motor Nuclei
-
Target Muscle
S/P
--
-
Oculomotor
Nucleus
Trochlear
Nucleus
Trigeminal
V3 Nucleus
-Ciliary Muscles
of Iris
Superior
Oblique
Opthalmic,
Maxillary,
Mandibular
Lateral Rectus
P
Lacrimal
Gland, Mucous
Membranes
Submandibula
r, Sublingual
Glands
--
P
Parotid Gland
P
Thoracic and
Abdominal
Viscera
Trapezius
Sternocleidom
astoid
P
Abducens
Nucleus
Facial
Nucleus
Internal
Auditory
Foramen
Jugular
Foramen
Jugular
Foramen
-
Motor
Jugular
Foramen
Accessory
Nucleus
Motor
Hypoglossal
Canal
Hypoglossal
Nucleus
Both
Nucleus
Ambiguous
Nucleus
Ambiguous
P=Parasympathetic
S=Sympathetic
Brainstem:
 Midbrain: contains nuclei for CNIII
 Pons: contains nuclei for CNIV, CN V, and CN VI
 Medulla Oblongata: contains nuclei for CN VII, CN IX, CN X, CN XII.
 Spinal Nucleus is homologous to the Lamina I/II
 Pontine Nucleus is homologous to the Nucleus Gracilis/Cuneatus
TRACTS:

Spino-Thalamic Tract (Sensory – Pain and Temperature)
-






o 1st Order Neuron: Dorsal Root Ganglion
o 2nd Order Neuron: Lamina I/II
o Decussates
o 3rd Order Neuron: VPL of Thalamus
o Project to appropriate region of Sensory Homunculus
Spino-Cerebellar Tract (Sensory – Touch, Vibration, Proprioception)
o 1st Order: Doral Root Ganglion
o 2nd Order: Nucleus Gracillis/Cuneatus in Brainstem
o Decussate
o 3rd Order: VPL of Thalamus
o Project to appropriate region of Sensory Homunculus
Spinal Efferent Pathway: (Cortico-Spinal Tract) (Motor)
o Upper Motor Neurons: Cell bodies are located in the appropriate
region of the motor homunculus in the Pre-Central Gyrus.
o Axons of UMN pass through the Internal Capsul
o Most decussate
o Follow Cortico-Spinal Tract
o Synapse on the Lower Motor Neurons in Lamina IX of the Spinal Cord
o Axons of LMN exit through the ventral root and travel within either
dorsal or ventral primary rami to their targets.
Efferent Pathway to Orofacial Region: *** (Motor)
o Upper Motor Neurons: Cell bodies are located in the orofacial region
of the somatotopic map in the motor homunculus.
o Axons of UMN descend through the internal capsul
o Decussate
o Diverges from Cortico-Spinal Tract in the brainstem
o Synapse on the Lower Motor Neurons in the motor nuclei of the
brainstem.
o Axons of LMN in each cranial nucleus exit the CNS in their cranial
nerves to their targets
Trigeminal System Tract: (Sensory)
o 1st Order: Trigeminal Ganglion
o Split into three branches: Opthalmic, Maxillary, Mandibular
o Terminate on naked endings in the skin.
Orofacial Pain Pathway (Sensory)
o 1st Order: Trigeminal Ganglion
o 2nd Order: Spinal Nucleus
o Decussate
o 3rd Order: VPM of Thalamus
o Project to appropriate region of the Sensory Cortex
Orofacial Touch Pathway (Sensory)
o 1st Order: Trigeminal Ganglion
o 2nd Order: Pontine Nucleus
o Decussate
o 3rd Order: VPM of Thalamus
o Project to appropriate region of the Sensory Cortex
Cranial Motor Nuclei:
 CN III, CN IV, CN VI: Do not synapse on LMN’s in the nucleus because they
are involved in bilateral, highly coordinated muscle movements of the eye.
 CN XI: Cell bodies of LMNs are located in the Lamina IX in the in the upper 45 Cervical levels of the spinal cord
Lesions to Upper and Lower Motor Neurons:
 Upper Motor Neurons: If damage is to the axons before the decussation, this
results in paralysis of the associated muscles on the contralateral side.
o Regeneration? No
 Spinal Cord: If damage is to the spinal cord, the paralysis will be on the
ipsilateral side
o Regeneration? No
 Lower Motor Neurons: Damage results in ipsilateral flaccidity and
weakness.
o Regeneration? Possibly.
AUTONOMIC NERVOUS SYSTEM:







Sympathetic and Parasympathetic systems are motor only
Preganglionic Neurons: Cell bodies inside of the CNS
Postganglionic Neurons: Cell bodies inside of the PNS
Input for both systems is from the hypothalamus.
Sympathetic and Parasympathetic divisions can be distinguished by the
location of Preganglionic Cell Bodies:
o Parasympathetic: Cranial/Sacral
o Sympathetic: Thoraco/Lumbar
Autonomic Targets:
o Salivary Glands
 Parotid
 Submandibular
 Sublingual
o Mucous Glands of Nose and Oropharynx
o Orbital Structures:
 Lacrimal Gland
 Sphincter and Ciliary Muscles of the Iris (parasympathetic)
 Dilator Muscle of Iris (Sympathetic)
 Superior Tarsal Muscle (Sympathetic)
o Blood Vessels (Sympathetic)
o Sweat Glands
Sympathetic Tract: (MOTOR)
o Pre-Ganglionic Neurons: Lamina VII (intermediolateral horn) at
T1/T2
Myelinated axons exit via ventral root
Enter Sympathetic Chain via White Rami Communicantes
Axons course up the sympathetic chain to Superior Cervical Ganglion
Synapse on the Post-Ganglionic Neurons at the Superior Cervical
Ganglion
o Post-Ganglionic Neurons follows blood vessels to their targets.
Horner’s Syndrome:
o Caused by disruption of the sympathetic supply.
o It can result from:
 Pancoast tumor in the apex of the lung
 Compression of cervical or thoracic sympathetic chain on the
affected side.
o Symptoms:
 (Pseudo)ptosis: Partial drooping of the eye due to paralysis of
the superior tarsal muscle.
 Miosis: Constricted pupil due to inactivation of the dilator
muscle.
 Enophthalmos: Sunken eye due to inactivation of Mueller’s
muscle.
 Anhidrosis: Reduced sweat production
 Flushing of face due to dilation of blood vessels.
Cranial Nerves with Parasympathetic Function:
o CN III (Oculomotor):
o CN VII (Facial):
o CN IX (Glossopharyngeal):
o CN X (Vagus):
Parasympathetic Pathway: Sphincter Muscle of the Eye
o Pre-Ganglionic Neuron: Nucleus of Edinger-Westphal
o Exit: CN III
o Post-Ganglionic Neuron: Ciliary Ganglion
Parasympathetic Pathway: Lacrimal, Submansibular, Sublingual Salivary
Glands
o Pre-Ganglionic Neuron: Superior Salivary Nucleus
o Exit: CN VII
o Post-Ganglionic Neuron: Pterygopalatine & Submandibular
Parasympathetic Pathway: The Parotid
o Pre-Ganglionic Neuron: Inferior Salivary Nucleus
o Exit: CN IX
o Post-Ganglionic Neuron: Otic Ganglion
Parasympathetic Pathway: Viscera of Thorax and Abdomen
o Pre-Ganglionic Neuron: Dorsal Motor Nucleus
o Exit: CN X
o Post-Ganglionic Neuron: discussed later
o
o
o
o





