Board Review- CNS + Autonomic Anatomy
--Lateral ventricle Foramen of Munro Third Ventricle aqueduct of Sylvius Fourth Ventricle
Foramen of Luschka or Magendie cisterns subarachnoid space arachnoid granulations -->
--Cisterns: Perimesencephalic cisterns (interpeduncular,
quadrigeminal, and ambient), prepontine, Cisterna Magna, and
--Made in Choroid plexus of lateral (occipital and temporal [but
not frontal!]), third, and fourth ventricles.
--Total volume is ~150cc, made at ~20cc/hr
--subdural from bridging veins, Epidural from mid meningeal artery, SAH from aneurysms
--DA from substantia nigra pars compacta in ventral midbrain
--ACh from nucleus basalis of Meynert (affected in Alzheimers) in basal forebrain.
--NE from locus ceruleus (rostral pons)
--5HT from Raphe nucleus (in midbrain/pons/medulla)
--Midbrain has nuclei of CN 3,4
Pons has nuclei of CN 5,6,7,8
Medulla has nuclei of CN 9,10,11,12.
CN2 – optic n to optic chiasm to optic tract (wraps around midbrain) synapses at LGN to optic radiations
(superior loop is parietal, inferior loop [Meyer’s] is temporal) synapses at visual cortex
CN3- nucleus in midbrain, pass through red nucleus, exits ventrally in interpeduncular fosssa, travels
between PCA and SCA and along the PComm, through cavernous sinus, exits through Sup. Orbital
Fissure and then divides into superior (innervates sup. rectus, levator palpebrae) and inferior divisions
(medial / inf. recti/ inf. oblique, and presynaptic parasympathetics to ciliary ganglia).
CN4- nucleus in midbrain. Decussates and exits dorsally at level of inf. colliculi, travels forward on the
under surface of the tentorium cerebelli, and enters cavernous sinus.
CN6- nucleus in pons. Exits at cerebellopontine angle, ascend upwards in subarachnoid space (longest
course) between pons and clivus and enters Dorello’s canal into cavernous sinus.
CN5- nucleus in pons. 2 roots: motor and sensory and 3 division (V1-3)
Motor: Pons exits anteriorly passes over Meckel’s cave foramen ovale joins with V3 to form
mandibular nerve to supply the muscles of mastication
Sensory: Main sensory ganglion = semilunar or gasserian ganglion, which is in Meckel’s cave, projects to
pons (spinal trigeminal tract), synapse in pons then project to VPM of thalamus
V1 travels through the cavernous sinus and exits through superior orbital fissure
V2 travels through the cavernous sinus and exits through foramen rotundum
V3 (see motor root above)
CN7- Starts in pons, fibers wrap around CN6 nucleus [facial colliculus] then exits ventrolaterally at CP
angle and enters internal auditory meatus. Important branches: branch to stapedius then chorda
tympani (taste) branches off right before CN7 exits the stylomastoid foramen. Posterior auricular
branches off right after the exit.
CN1 cribiform plate (ethmoid bone)
CN2 optic canal
CN3,4,V1,6 superior orbital fissure
CNV2 foramen rotundum
CNV3 foramen ovale
CN7,8 internal auditory meatus, 7 continues on to exit through stylomastoid foramen
CN9, 10,11 jugular foramen
CN12 hypoglossal canal
-- If lesion is after CN7 exits skull (red
line), the pt will have only facial
weakness. If lesion is between chorda
tympani and br to stapedius (green
line), then the pt will have facial
weakness + loss of taste. If lesion is
between br to stapedius and internal
auditory meatus (purple line), then the
patient will have facial weakness + loss
of taste + hyperacusis.
-- The CNs that innervate contralateral structures: CN4 and the superior rectus subnucleus of CN3
-- CNs with parasympathetics:
CN3: Edinger Westphal nucleus ciliary ganglion papillary constrictor
CN7: superior salivatory nucleus [2 branches]
1. greater petrosal nerve pterygopalatine ganglion lacrimal glands
2. chorda tympani + lingual n submandibular ganglion sublingual and submandibular
CN9: inferior salivatory nucleus tympanic nerve +lesser petrosal nerve otic ganglion parotid
CN10: dorsal motor nucleus of CN10 ganglia near within or near organs (heart, gut, etc)
--The facial colliculus consists of CN6 nucleus + fibers from CN7 and is on the floor of fourth ventricle.
--Olfaction does not go through the thalamus
-- Mammilothalamic tract/ fornix inputs to anterior
nuclei of thalamus (from mammillary bodies).
-- Ventral Lateral motor
Medial geniculate hearing
Lateral geniculate vision
Anterior limbic system
Ventral Posterolateral somatosensory
Pulvinar behavioral orientation to stimuli
Medial dorsal limbic pathways, relay to frontal
From Blumenfeld Intralaminar nuclei consciousness/ alertness
Centromedian nuclei motor relay to basal ganglia
Reticular nuclei regulates other thalamic nuclei
--Septal nuclei receive input from fornix.
--Hippocampal formation receives input from the
Septal nuclei entorhinal cortex
--Fornix connects the hippocampus to the septal nuclei
(precommisural fornix) and mamillary bodies (post
--Perforant pathway connects the entorhinal cortex to the
Adapted from www.wikipedia.com
Striatum = Caudate + Putamen
Lentiform nucleus = Putamen + Globus pallidus
-- Major input to BG is from the cortex (to striatum)
-- Major output from BG to the thalamus is Gpi
(Ventral anterior nuc of thalamus specifically)
-- STN is excitatory to Gpi
-- Caudate is lateral to the lateral ventricles.
Nature Reviews Neuroscience 7, 464-476 (June 2006)
--Contains 3 layers: granule cell [innermost and most cell dense], Purkinje cell layer, and molecular layer
[outermost]. Granule cells receive the inputs. Purkinje cells are outputs. Molecular layer has granule
cells, Purkinje cell dendrites, and interneurons (basket and stellate cells).
--Input to cerebellum comes from climbing fibers or mossy fibers. Climbing fibers come only from
contralateral inferior olivary nucleus. The wrap around the cell body and dendrites of Purkinjes. Each
climbing fiber will supply ~10 Purkinje cells but each Purkinje cell has only 1 climbing fiber input.
Climbing fibers are excitatory on Purkinjes. Mossy fibers synapse onto granule cells which then
bifurcate into parallel fibers (run perpendicular the dendrites of Purkinje), which synapse onto the
dendrites of Purkinje cells. Purkinje cells are inhibitory on the deep cerebellar nuclei.
--Basket and stellate cells are in the molecular layer and receive excitatory input from parallel fibers and
cause inhibition of adjacent Purkinje cells. Golgi (in granule layer) cells also receive excitatory input
from parallel fibers and provide inhibition of granule cells. [see pages 660,661 in Blumenfeld]
-- Cerebellar cortex and peduncle lesions always produce ipsilateral findings because of “double
crossing.” First decussation is in superior cerebellar peduncle. The next decussation is in the
corticospinal tract. Superior cerebellar peduncle mainly carries output from the cerebellum, the middle
and inferior mainly carry inputs.
-- Purkinje cells carry the output of the cerebellum to the deep cerebellar nuclei (DEGF = dentate,
emboliform, globose, fastigial), primarily through the Superior Cerebellar Peduncle.
-- inferior olive supplies climbing fibers (only source of climbing fibers). The others enter cerebellum
through mossy fibers.
-- Stellate cells inhibit Purkinje cells.
-- Dentate nuclei send projections to VL nucleus of thalamus.
-- Climbing fibers originating in the left inferior olivary nucleus travel through the inferior cerebellar
peduncle to synapse with their cerebellar targets
-- Layer 4 is the primary input layer from the thalamus. Layer 5, 6 are primary output layers. 5 goes to
non cortical areas, 6 goes to the thalamus. 1 has dendrites, 2 and 3 have afferent and efferent
connections between other cortex.
Sympathetics arise cell bodies in intermediolateral cell columns of spinal cord from T1 to L3,
Parasympathetics from CN3,7,9,10 and S2-4. Both use nACh for preganglionic synapses. Sympathetics
use norepinephrine at end organs (except for mACh for sweat glands), parasympathetics use mACh.
-- Third order sympathetics (to the eye): neuron cell bodies are in superior cervical ganglion. First order
is from hypothalamospinal tract intermediolateral cell column super cervical ganglion
cavernous sinus Muller’s muscle + iris. Depending on lesion location, can get a partial Horner’s
because branches that innervate sweat glands come off more proximally.
Bowel / Bladder
Detrusor is innervated by parasympathetics. Bladder
dome and internal urethral sphincter are innervated
by sympathetics. External urethral sphincter is
striated muscle (voluntary). When bladder is full
(wall is stretched), afferents sends info up to cortex.
Frontal micturition inhibiting area / pontine
micturition centers activate the voiding reflex
(detrusor reflex). Sympathetics (T11-L1) are
inhibited and parasympathetics (S2-S4 Onuf’s
nucleus) are activated causing the bladder wall to
contract and the sphincters to relax. Lesion to the
cortex cause incontinence. Lesions to the spinal cord
(above S2-4, acutely) cause an atonic bladder
(urinary retention, bladder distension, overflow
incontinence). Chronic spinal cord lesions cause a
hyperreflexic (spastic) bladder urinary frequency
and urge incontinence due to detrusor sphincter
dyssynergia. Lesions to the peripheral nerves or S2-
S4 cause a flaccid areflexic bladder leading to
--Detrusor wall muscle is innervated by
--epithalamus = posterior dorsal segment of the diencephalon. It includes the habenula + pineal gland.
The habenula projects to the interpeduncular nucleus in the midbrain. It connects the limbic system to
other parts of the brain.
--Area postrema, which is one of 8 circumventricular organs. Rest are: posterior pituitary, median
eminence, vascular organ of lamina terminalis, subfornical organ, pineal gland, subcommisural organ,
--Central Tegmental Tract. Palatal tremor is localized to Guillain - Mollaret’s Triangle, which consists of
dentate nucleus, contralateral red nucleus, and contralateral inferior olivary nucleus.
Sup Cerebellar Peduncle Red Nucleus
Central tegmental tract
Inf Cerebellar Peduncle Inf Olivary Nucleus
[All images from Blumenfeld, except for Papez circuit diagram, from wikipedia.com and BG circuits from
Nature Reviews Neuroscience 7, 464-476 (June 2006)]