ascending & descending nerve tracts sanjaya adikari department of anatomy
TRANSCRIPT
Ascending &
Descending nerve tracts
Sanjaya AdikariDepartment of Anatomy
Control of the body by the brain
L
R
Contralateral representation
Contralateral = Opposite sideIpsilateral = Same side
Decussation = Crossing
Medulla
Sensory organs
LR Sensory
Medulla
Sensory organs
LR Sensory
Medulla
Effecter organs
LR Motor
Medulla
Effecter organs
MotorLR
Medulla
Sensory organs
Effecter organs
LR
Medulla
Thalamus
First order neuron
Second order neuron
Internal capsule
Third order neuron
Corona radiata
Ascending tracts
Medulla
Internal capsule
Sensory
Posterior surface
Upper medulla
Internal capsule
Upper motor neuron
Lower motor neuron(Final common pathway)
Descending tracts
Motor
Anterior surface
Lower medulla
Internal capsule
20%
Internal capsule
Corticobulbar
Corticospinal
L
Cranial nerves
Spinal nerves
LeftAscending tracts
White columns
Posterior white column
Lateral white column
Anterior white column
Anterior nerve root
Posterior nerve root
Lateral spinothalamic
Pain & temperature
Anterior spinothalamic
Crude touch & pressure
Medulla
Thalamus
First order neuron
Second order neuron
Internal capsule
Third order neuron
Pain & temperature
Crude touch & pressure
10
9
8
10
9
8
Crosses within one spinalsegment
Crosses within several spinalsegments
Fine touch, vibration,Conscious muscle & joint sense
Fasciculus gracilis
Fasciculus cuneatus
Medulla
Internal capsule
Muscle & joint sense to cerebellum
Anterior & posteriorspinocerebellar
Superior, middle & inferiorcerebellar peduncles
Left
Descending tracts
OlivospinalVestibulospinalTectospinal
RubrospinalLateral corticospinal
Anterior corticospinal
Left
Clinical Neuroanatomy by Richard S. Snell
Lemniscus
• This term is used for some ascending (sensory) nerve tracts in the upper part of
the medulla, pons and midbrain – Spinal lemniscus
combination of spinothalamic, spinotectal tracts
– Medial lemniscus
crossed posterior column fibers
– Lateral lemniscus
3rd neuron of auditory pathway
sensory motor
1 – All sensory and motor loss on contralateral side
1
R R
3
3 - Fine touch and vibration and motor weakness on the ipsilateral side, pain and
temperature loss on the contralateral side (Brown-Sequard)
2
2 – Fine touch and vibration loss on the ipsilateral side, pain and temperature and
motor weakness on the contralateral side
Thalamic
Mid-braintem
Unilateral cord lesion(Brown-Sequard)
Weakness (UMN)
Clinical Medicine by Kumar & Cleark’s
DA
B
Spinal cord lesions
C
Refer Clinical Medicine by Kumar & Cleark’s
A
A – Syringomyelia
A – Syringomyelia
Loss of pain and
temperature sense
without loss of fine touch.
Discontinuous sensory
loss
Loss of upper limb reflexes
Symptoms progress when
the cavity enlargesClinical Medicine by Kumar & Cleark’s
B
B – Poliomyelitis
C – Tabes dorsalis
C
Demyelination
C – Tabes dorsalis (of neurosyphilis)
Demyelination of dorsal roots
–Lightening pains, sensory ataxia,
reflex and sensory loss, muscle
wasting, charcot joints
–Argyll Robertson pupils
Sensory ataxia of tabes dorsalisThis is due to loss of proprioception
(position sense)
- stamping gait
- positive Romberg’s test
Argyll Robertson pupilsNo reaction to light. Constricts to
convergence
Lesion in the cerebral aqueduct
Anterior spinal artery occlusion
• Bilateral loss of motor function due to damage to corticospinal tracts and anterior gray horns
• Bilateral thermoanesthesia and analgesia due to damage to spinothalamic tracts
• Loss of bladder and bowel control due to damage to descending autonomic tracts
• Vibration, fine touch & position sense normal
Refer Clinical Medicine by Kumar & Cleark’s