Transcript 1. dia - Semmelweis University

Neuronal architecture of the
spinal cord: prorioceptive and
nociceptive (withdrawal)
reflex arcs
Viktória Vereczki M.D., PhD.
Department of Anatomy, Histology and
Embryology
Semmelweis University
Gross anatomy of spinal cord
•45 cm lon
from the atlas to L1L2
•Maximal volumes:
Intumescentia
cervicalis: 38mm
Intumescentia
lumbalis: 35 mm
Gross anatomy of spinal cord
Gross anatomy of spinal cord
Spinal ganglion
Pseudounipolar neurons in
the spinal ganglion (HE)
Neuronal architecture of spinal cord
C3
C6
Cervical nerves 1-8
C3
Thoracic nerves
1-12
C6
Th6
Th6
Lumbar nerves 1-5
L3
L3
S2
Sacral nerves 1-5
Coccygeal nerve 1
n. L3
n. S2
S2
Neuronal architecture of spinal cord
White matter
•Dorsal funiculus
cervical segment
•Ventral funiculus
•Lateral funiculus
•Anterior fissure
•Dorsal median sulcus
•Dorsal septum
thoracic segment
•Sulcus dorsolateralis:Radices dorsales
•Sulcus ventrolateralis:radices ventrales
•Ventral white comissure
•Dorsolateral tract of Lissauer
sacral segment
White matter:
Dorsolateral tract
of Lissauer
White matter:
Ascending pathways:
Descending pathways:
White matter:
Fasciculus proprius: proriospinal fibers
Neuronal architecture of spinal cord- gray matter
•Posterior gray column
dorsal horn( viscerosensory
(enteroception) and somatic sensory neurons)
•Anterior gray column
ventral horn(somatomotor neurons)
•Lateral gray column( only at thoracic segments)
horn (visceromotor neurons)
lateral
Neuronal architecture of spinal cord- gray matter
Rexed laminae of spinal cord
( at the level of Th10)
1. Dorsal nucleus of Clarke-Stilling
2. Proper nucleus of dorsal comumn
Neuron types: 1. radicular
2. funicular
3. internuncial
4. interneurons: f.i. Renshaw cells
3. Substantia gelatinosa (Rolandi)
4. Marginal zona
5.Intermediolateral cell column
6. Intermediomedial cell collumn
7. Motor neurons of ventral horn
Laminae of Rexed
Afferent fibers, terminating here
Efferent fibers , originating here
lamina I. –marginal zone
Marginal neurons (Waldeyer-neurons):
pain - and temperature sensory
neurons, visceral afferents, from brain
stem: monoaminoergic descending
fibers
Tr. spinothalamicus
Dorsolateral tract of Lissauer
lamina II. -substantia gelatinosa
(Rolandi)
From the skin nociceptive fibers:
unmyelinated os myelinated, from
brain stem: monoaminoergic
descending fibers
The unmyelinated axons of substantia
gelatinosa cels ascend or descend for up
to four segments of the spinal cord; their
branches synapse within the dorsal horn
lamina III-IV. nucleus proprius
columnae dorsalis
Mechanoreceptors of skin
Spinothalamic tract
lamina V-VI.
Transmitting touch , pain and visceral
signals
Spinothalamic tract
Fibers associating within the spinal cord
lamina VII. -nucleus dorsalis seu
nucleus thoracicus (Clarke-Stilling
nucleus)
Th1-L3:cornu laterale:
• nucleus intermediolateralis
• nucleus intermediomedialis
sacral part:
Proprioceptive and epicritic sensation
of the skin of the lower part of the body
-internuntial neurons among the
descending pathways and
motoneurons, Renshaw cells
Dorsal spinocerebellar tract (Flechsig)
lamina VIII.
-comissural nucleus of
Lenhossek
crossing fiber in the comisssura alba
lamina IX.
–motor nuclei of ventral horn
Aα-motoneurons
Aγ- motoneutons
lamina X.-substantia grisea centralis
-tr.corticospinalis, tr. Reticulospinalis
-preganglionic sympathetic neurons
-preganglionaris parasympathicus
neurons
Additional nuclei of lamina IX.:
Cervical segment:
1. Phrenic nucleus (C3-C5): Phrenic nerve
Bronislaw
Onuf-Onufrowicz
(1863-1928)
2. spinal accessory nucleus (C1-C5): spinal root of accessory nerve
innervating sternocleidomastoid adn trapezius muscle
S2 segment:
3. nucleus Onuf (motor nucleus of pudendal nerve: urinary and fecal continence,
innervating ischiocavernosus, bulbospongiosus muscles and pelvic floor
4. Lateral central nucleus
Gray matter:
1.:
Cajal-Ag impregnation
II.
lamina
Gray matter: 2.:
VII. lamina
X. lamina
Schematic representation of motor neurons
1.
2. 4.
6.3.
5.
1. Nucleus retrodorsolateralis: kis ujjizmok
2. Nucleus dorsolateralis: alkar és kéz izmai
3. Dorsalisan: hajlító izmok
4. N. ventromedialis et dorsomedialis:tarkóés hátizmok, bordaközi és hasizmok
5. N. ventrolateralis: vállöv és felkar izmai
6. Ventralisan: feszítő izmok
Spinal nerve
Ramus posterior
Ramus meningeus
Ramus communicans griseus
Ramus anterior
Plexuses
Ramus communicans albus
Typical arrangement of the spinal nerves
Reflexes of the spinal cord
1. Proprioceptive, monosynaptic reflex
Reflexes of the spinal cord
1. Proprioceptive, monosynaptic reflex
1. Receptor :
Annulospiral endings of neuromuscular spindle
2. Afferent nerve: 1st neuron from spinal
2.
ganglion
Iα type sensory fibere its collaterals terminate on
the same segment’s motoneuron, and more
caudal segments’ inhibiting neurons
1.
3.
4.
5.
3. Central connections:
monosynaptic
4. Efferent nerve: 2nd neuron
Aα motoneuron innervating its own extrafusal
fibers
5. Effector:
Its own muscle fiber
6. Additional connections:
a., reciprok inhibition
b., gamma-loop
1. Proprioceptive, monosynaptic reflex
6. Additional connections :
a., reciprok inhibition
b., gamma-loop
specific inhibitory
neuron
Antagonist muscle group is inhibited
1. Proprioceptive, monosynaptic reflex
6. Additional connections :
a., reciprok inhibition
b., gamma-loop
1.
gamma-loop
4.
1.Descending axon
(pl. tr. reticulospinalis, tr.
vestibulospinalis)
2.
5.
3.
2. Aγ neuron (innervation intrafusal
fibers)
3. Neuromuscular spindle:
anulospiral receptor
4. Iα sensory neuron‘s fiber for the
muscle spindle
Function:
Regulating muscle tone
5.Aα motoneuron (innervation of
the extrafusal musclefiber)
Clinical importance of monosynaptic reflexes:
Clinical tendon jerks
DIMINISHED
Lesion of „lower motoneurons”
EXAGGERATED
(trauma, degeneration,
demyelination disorder,
infections, impairment of blood
supply, tumors)
Lesion of „upper
motoneurons” -
Flaccid paralysis of
affected muscles:
segmantal localization
lack of inhibitory
pathways results in
spastic palsy
Examples:
patella-reflex L2-4, biceps-reflex C5-6, triceps-reflex
C6-7, gastrocnemius-reflex S1-2
Reflexes of the spinal cord
2. Polysynaptic, nociceptive (withdrawal) reflex arc
Reflexes of the spinal cord
2. Polysynaptic, nociceptíve (withdrawal) reflex arc
1. Receptor:
Nociceptors in skin , mucosa
2. Afferent nerve: 1st neuron from spinal
ganglion
Aδ, C rostok (Lissauer –zone)
3. Central connections: 2nd or
3rd neuron:
Interneurons, funicular neurons: among many segments,
Renshaw-inhibition
4. Efferent nerve : at least the 3rd neuron
Aα motoneuron
5.Effector:
Flexor muscles of the same side , and extensor muscles of
the opposite side
Examples:
abdominal-reflex, cremasteric-reflex, cornea-reflex.
2. Polysynaptic, nociceptíve (withdrawal) reflex arc
2.
3.
1.
4.
5.