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Department of Anatomy
Neural pathways
MUDr. Marek Joukal, Ph.D.
SPINAL REFLEX – proprioceptive
Proprioceptive receptor – muscle spindle
Register protraction and shortening of the muscles
Fibrous cover – in the muscle (extrafusal muscular fibres)
Inside modified muscular fibers – intrafusal
I: sensory, motor – γ motoneurons
Sensory fibers – protraction of the muscle – information carried to α motoneurons in ncl. motorii
α motoneurons – contraction of the muscle (extrafusal fibers)
Gama loop (regulation of muscular tonus):
γ motoneurons – activation via RF
Contraction of the muscle spindle – subsequent reaction of sensory fibers
SPINAL REFLEX – exteroceptive
1st neurons
ganglion spinale, psudounipolar neurons
receptor – nerve endings in skin
2nd neurons
interneurons in spinal cord (reflex centre)
3rd neurons
α motoneuron
effector – striated muscle
OPTIC PATHWAY
retina
RADIX LATERALIS (80-90% fibers)
1st neuron
rods, cones
2nd neuron
bipolar cells
3rd neuron
multipolar cells (nervus opticus)
4th neuron
corpus geniculatum laterale
Area 17, 18, 19
Horizontal cells in retina
connect and inhibit rods and cones
Amacrine cells in retina
inhibit ganglionic cells
Retinotopic organization
Fibers from appropriate parts of retina
Terminate in specific regions of
corpus geniculatum lat. + cortex
RADIX MEDIALIS (10-20% fibers)
Colliculus sup. – optico-motor reflexes
efferent pathways tr. tectospinalis
Area praetectalis – pupilar reflexes
Hypothalamus –tr. retino-hypothalam. (ncl. suprachiasmat)
cirkadian rhytmes
Pulvinar thalami – feedback circuits to the cortex
Ncl. interstitialis (Cajal) – FLM
eye coordination
Substantia nigra
PUPILAR REFLEX
miosis
mydriasis
m. sphincter pupilae – parasympathicus
m. dilatator pupilae – sympaticus
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1st neuron
ganglion spirale cochlae (pars cochlearis n. VIII)
2nd neuron
ncl. cochlearis dorsalis
(ncl. cochlearis ventralis – corpus trapezoideum)
3rd neuron
ncl. colliculi inf.
4th neuron
corpus geniculatum mediale
(radiatio acustica capsulae internae)
Gyri temporales transversi (area 41, 42)
Auditory pathway
VESTIBULAR PATHWAY
1st neurons – ggl. vestibulares n. VIII. (meatus acusticus int.)
tr. vestibulo-cerebellaris directus
balance, posture, head and eye movements
2nd neurons – ncll. vestibulares (sup., inf., med., lat.)
Effer. pathways:
tr. vestibulo-cerebellaris indirectus
FLM – vestibulo-oculo-motor reflex
tr. vestibulo-spinalis (ncll. motorii)
3rd neurons – thalamus (tr. vestibulo-thalamicus)
Cortex cerebri
Sensory, motor regions, lobus insulae (to realize the movements,
vertigo…..)
1st neuron
regio olfactoria
(axons - nn.olfactorii)
2nd neurons
bulbus olfactorius (mitral cells)
tr. olfactorius - stria olfactoria med. + lat. +
intermedia
Cortex cerebri
interm.-piriform region (around area cribrosa ant.)
lat.-entorhinal region (uncus g. parahippocamp.)
med. - amygdalar complex
3rd neurons thalamus – orbitofrontal cortex
OLFACTORY PATHWAY
1st neuron – pseudounipolar neurons
ggl. geniculi n. VII (chorda tympani) 2/3 tongue
(n. petrosus major)
ggl. n. IX – posterior 1/3 tongue
ggl. n. X – around epiglottis
2nd neuron
ncl. gustatorius
3rd neuron
thalamus (ncl. VPM)
Cortex cerebri
area 43 (operculum frontale), insula
GUSTATORY PATHWAY
SOMATOSENSORY PATHWAY (protopatic, anterolateral system)
1st neuron
pseudounipolar neurons in ganglion spinale
2nd neuron
ncl. proprius
(axons are crossed on appropriate spinal segment)
tractus spino-thalamicus ant. (skin sensitivity, sensory infromation
about pain)
tractus spino-thalamicus lat. (temperature, affective aspects of
pain)
3rd neuron
thalamus (ncl. VPL)
Gyrus postcentralis area 3,2,1,
Information via spinal nerves – temperature, pain
SOMATOSENSORY PATHWAY (protopatic, trigeminal system)
1st neuron
pseudounipol. neurons in cranial nerves ggl
(V, VII, IX, X)
2nd neuron
ncl. tr. spinalis n. trigemini
tractus trigemino-thalamicus
3rd neuron
thalamus (ncl. VPM)
Gyrus postcentralis area 3,2,1,
Information via cranial nerves – temperature, pain
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SOMATOSENSROY PATHWAY (epicritic, posterior column, lemniscal system)
Information via spinal nerves – soft touch – discriminative sensation
1st neuron: pseudounipolar neurons in ganglion spinale
central branches – tractus spino-bulbaris
(fasciculus gracilis + cuneatus)
2nd neuron: ncl. gracilis + ncl. cuneatus med.
tractus bulbo-thalamicus
axons (fibrae arcuatae int. crossed – decussatio
lemniscorum)
lemniscus medialis
3rd neuron
thalamus (ncl. VPL)
Gyrus postcentralis area 3,2,1,
SOMATOSENSORY PATHWAY (epicritic, trigeminal system)
Information via cranial nerves – soft touch – discriminative sensation
1st neuron:
pseudounipolar neurons in ggl V, VII, IX, X
2nd neuron: ncl. sensorius principalis n. V
axons are crossed – lemniscus trigeminalis
3rd neuron
thalamus (ncl. VPM)
Gyrus postcentralis area 3,2,1,
SOMATOSENSORY PATHWAY (PROPRIOCEPTION)
Information via spinal nerves – from locomotor app. LE + trunk
1st neuron:
pseudounip. neurons in ganglion spinale
2nd neuron: ncl. thoracicus (C8 – L3)
tr. spino-cerebellaris ant. + post.
cerebellum – information processing
tractus cerebello-thalamicus
thalamus
ncl. ventrales laterales (VL)
Gyrus frontalis + praecentralis
(praemotor and motor cortex)
SOMATOSENSORY PATHWAY (PROPRIOCEPTION)
Information via spinal nerves – locomotor app. UE
1st neuron:
pseudounip. neurons in ganglion spinale
cent. branches – fasciculus cuneatus (lat)
2nd neuron: ncl. cuneatus lat.
tr. cuneo-cerebellaris
cerebellum - information processing
tractus cerebello-thalamicus
thalamus
ncl. ventrales laterales (VL)
Gyrus frontalis + praecentralis
(praemotor and motor cortex)
SOMATOSENSORY PATHWAY - PROPRIOCEPTION
Information via cranial nerves – V, VII, IX, X (muscles derived from branchial arches)
1st neuron:
pseudounipolar neurons in ncl. tractus mesencephalicus n. V
central branches – tractus trigenino-cerebellaris
cerebellum – information processing
tractus cerebello-thalamicus
thalamus
ncl. ventrales laterales (VL)
Gyrus frontalis + praecentralis (praemotor and motor cortex)
MOTOR PATHWAY - PYRAMIDAL
fylogen. young, strongly myelinated, voluntary
Descendent from cortex cerebri to motor ncll.
Tractus cortico- spinalis
from cortex cerebri, decussatio pyramiduum (medulla oblongata)
ncll. motorii medullae spinalis
Tractus cortico- nuclearis
ncll. motorii cranial nerves
(in somato and branchiomotor zone)
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MOTOR PATHWAY - EXTRAPYRAMIDAL (involuntary)
reflex motion, automated movements,
Control circuits of voluntary motion (affect speed,
preciseness)
Connections of BG – processing motor circuits
Tr. reticulo-spinalis – facilitatory + inhibitory system of
motion
Tr. rubro-spinalis – muscular tonus of UE flexors
Tr. tecto-spinalis – optic and acustic-motor reflexes
Tr. vestibulo-spinalis – affect postural muscles
References
Dubový, P., Jančálek, R.: Základy neuroanatomie a nervových drah I. Masarykova univerzita Brno, 2013
Dokládal, M., Páč, L.: Anatomie člověka III. Masarykova univerzita v Brně, 1995.
Čihák, R.: Anatomie 3. Praha, Grada, 2001, 2004
Sobotta, J.: Atlas of Human Anatomy Vol1 –2 Munich, Urban und Schwarzenberg, 1993
Páč, L., Vargová, L., Čuta, M. : Anatomie pro antropology III. Nadace universitas, Akademické nakladatelství
CERM. Masarykova univerzita 2013.
Wiliams, P. & Warvick, R.: Gray´s Anatomy, 37 ed, Churhill Livingstone, 1996
Netter, F.:Atlas of Human Anatomy, 4th ed., Elseviesr, USA, 2006