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ASCENDING PATHWAYS
Alvin B. Vibar, M.D.
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CASE:
A 25 y/o male fell to the ground hitting his
lower back against the gutter when his
motorbike skidded on the wet road. When he
tried to get up, he was unable to move his right
leg. He was brought to the hospital and upon
examination, he could NOT FEEL PAINon
the left side up to the level of the umbilicus.He could NOT FEELthe VIBRATIONof
the tuning fork on his right foot.
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GENERAL SENSES Light Touch
Pressure
Pain
Temperature
Proprioception
-Vibration sense
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Tactile senseawareness and precise location of verydelicate mechanical stimuli
Includes:
Two point senseability to distinguish stimulation by one or two points applied to the skin
Fine touch / Stereognosisability to recognize objects by touchalone
Graphesthesia- abilityto recognize numbers or letters drawn on theskin
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Pressure= deep touch
Involves stimuli applied to
subcutaneous structures;firmly pressingon the skin
with a blunt object and by
squeezing subcutaneous
structures
Pain
Fast painsharp,pricking and well localized
Slow paindull, burningtype and diffuse
Temperature
Hot
Cold
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Proprioception
Position / Posture senseawareness of the positionof parts of the body; tested by passively moving a limb or oneof its parts to a certain position and having the subject movethe opposite limb to the same position
Motion senseawarenessof active or passivemovements of the parts of the body; tested by passivelyflexing and extending individual fingers and toes, hand and
foot, forearm and leg etc. with eyes closed, the subject shouldbe able to recognize the direction, speed and range of the
movement
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Sensory information is detected by specific receptors that aresensitive to stimuli arising from both outside and within ourbodies
EXTERORECEPTORS external world; respond to pain,
temperature, touch, vibration and pressure
ENTERORECEPTORS - within the body
PROPRIOCEPTORS within the body and signal awareness ofbody position and movement in space
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Receptors
Mechanoreceptors
touch, pressure and
proprioception
Nocireceptorspain
Thermoreceptorswarm
/ cold
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Review: General Sensation
Receptors
Touch
Meissners corpuscles , Merkels disc ,
Hair follicle endings , Golgi Mazzoni
PressurePacinian corpuscles
PainFree nerve endings
TemperatureCold - Krause end bulb
Hot Ruffinis corpuscles
ProprioceptionTendon and Muscle spindles
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Review: Spinal Cord
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3 Columns in the White Matter
Posterior funiculus
Lateral funiculus
Anterior funiculus
Each column is subdivided into tracts.
These tracts are:
Ascending tract
Descending tract
Intersegmental tracts
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Parts of the Gray Matter
Posterior horn
Lateral horn
Anterior horn
The cell bodies in the gray substance are grouped into
clusters of nuclei of laminae.
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Laminae of Rexed - groupings
Laminae I VI located in theposterior horn
Lamina VII located at thelateral horn
Laminae VIII and IX located at the
anterior horn Lamina X gray substance
surrounding the central canal
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Spinal cord with laminae of Rexed
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ASCENDING TRACTS
Location Origin DestinationANTERIOR COLUMN
Ventral Spinothalamic med. to ant. nerve roots Free nerve endings for Post-central gyruslight touch & pressure
Spino-olivary junction of ant. & lat. Cutaneous & proprio- Infr. Olivary nuclei
white columns ceptive organs LATERAL COLUMN
Dorsal Spinocerebellar periphery of lat. white Muscle spindles, tendon Cerebellar cortex
column organs, joint receptors
Ventral Spinocerebellar periphery of lat. white Muscle spindles, tendon Cerebellar cortex
column organs, joint receptors Lat. Spinothalamic med. to Ventral Spino- Free nerve endings for Post-central gyrus
cerebellar tract pain & temperature
Spinotectal ant. to Lat. Spinothalamic Midbrain TectumPOSTERIOR COLUMN
Fasciculus gracilis beside dorsomedian sulcus Meissners, Pacinian, Post-central gyrus
muscle spindles,
tendon organs
Fasciculus cuneatus between Fasc. Gracilis & Meissners, Pacinian, Post-central gyrus
post. gray column muscle spindles, tendon organs
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Review:Dermatomes Area of the skin supplied by the
somatosensory fibers from a singlespinal nerve ; useful in localizing thelevels of lesions
C2 back of head C5 tip of shoulder
C6 thumb C7 middle finger C8 small finger T4 T5 nipple T10 umbilicus L1 inguinal L4 L5 big toe S1 small toe S5 perineum
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REMEMBER: Rule number 1
Sensory information can either be
CONSCIOUS and make us aware of the
sensation or on a NONCONSCIOUS level
and serve to adjust the movement or
function of our body
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REMEMBER: Rule number 2
Sensory information is bundled according to MODALITY
MECHANICAL STIMULI discriminative touch,pressure, vibration and proprioception Posterior Column
Medial Lemniscus
NOCICEPTIVE STIMULI pain and temperatureAnterolateral System
PROPRIOCEPTION conveyed to the Cerebellum
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Ascending Tracts
Dorsal / Posterior Column
Position sense
2 pt discrimination
Fine, discriminative
Stereognosis
Vibration sense
Spinothalamic tract
ASTT touch / P
LSTT pain & temp
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REMEMBER:
Somatosensory pathwaysconsist of three neurons:
Number 1in the sensory ganglia
Number 2 in the spinal cord or brainstem
Number 3in the thalamus
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Pain and Temperature Pathway
using the LSTT
Free nerve endingsDorsal root ganglion
Postero-lateral funiculusPosterior horn
Laminae V VIILateral spinothalamic tract
VPLN of the thalamusPrimary somatosensory
area ( Broadmanns area 3,1,2)
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Pain and Temperature Pathway
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Medial Lemniscus Pathway
Axons enter the SC and pass directly
to ipsilateral posterior column (caudal fibers below T6 enterFasciculus gracilis and rostral fibersabove T6 enter Fasciculus cuneatusto ascend)
Terminate in Nucleus gracilis andNucleus cuneatus
Axons of secondary nuclei cross themidline as Internal arcuate fibersand form the Medial Lemniscus
Terminates in the VPLN of thalamus
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Discriminative Touch and Pressure
ReceptorsDorsal root ganglionCuneate
fasciculus and Gracile fasciculusCuneate andGracile nucleiMedial lemniscusVPLN of
the thalamusPrimary Somatosensory cortex
( BA 3, 1, 2 )
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Discriminative Touch and Pressure
Pathway
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Somatotopic
distribution of fibers
in the Posterior
Column Medial
Lemniscus system
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Slide 7.31
Sensory and Motor Areas of the
Cerebral Cortex
Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 7.14
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Proprioception Pathway
Receptors
Muscle spindles
Tendon spindles
Conscious proprioception
= fibers each the cerebrum
Unconscious proprioception= fibers each the cerebellum
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Receptors
Dorsal root ganglion
Posterior columnCuneate and gracile
fasciclesCuneate and gracile nuclei
Medial lemniscus
VPLN of the thalamus
BA 3, 1, 2
Conscious Proprioception Pathway
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CASE:
A 25 y/o male fell to the ground hitting his
lower back against the gutter when his
motorbike skidded on the wet road. When he
tried to get up, he was unable to move his rightleg. He was brought to the hospital and upon
examination, he could NOT FEEL PAINon
the left side up to the level of the umbilicus.He could NOT FEELthe VIBRATIONof
the tuning fork on his right foot.
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Brown-Sequard
s syndrome
Spinal Cord Hemisection
Features:
Contralateral loss of pain & temperature
Ipsilateral loss of proprioception
Ipsilateral manifestations of upper and
lower motor neuron lesions
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Dermatomes Area of the skin supplied by the
somatosensory fibers from a singlespinal nerve ; useful in localizing thelevels of lesions
C2 back of head C5 tip of shoulder C6 thumb C7 middle finger C8 small finger T4 T5 nipple T10 umbilicus L1 inguinal L4 L5 big toe S1 small toe S5 perineum
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Spinal Cord lesions:
Syringomyeliaprogressive cavitation around thecentral canal; loss of pain & temperature sensations inhands & forearm ( common in cervical)
Tabes Dorsaliscaused by neurosyphilis; dorsalroot involvement with secondary degeneration ofdorsal columns ( loss of vibration and position sense)
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Disorders of the Sensory System
Anesthesialoss of sensitivity to pain in all /part of the body
Hypoesthesiaan abnormally reduced
sensitivity to touch Hyperesthesiaan abnormally heightened
sensitivity of part of the body
Paresthesiaan abnormal or unexplainedtingling, pricking or burning sensation on theskin
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Somatic Sensory arising from Face
Trigeminal Gasserian or Semilunar
ganglion
3 divisions:
Opthalmic
Maxillary Mandibular
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Trigeminal Nerve
P i d T t P th
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Pain and Temperature Pathway -
Face
Receptors N1 ( Gasserian / Semilunar Ganglion)
N2 ( Nucleus of Trigemino Spinal tract )
N3 (Ventral Postero Medial nucleus of Thalamus)
- Post central gyrus ( B.A. 3,1,2)
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Touch and Pressure Pathway - Face
Receptors N1 ( Gasserian / Semilunar Ganglion)
N2 ( Main sensory nucleus )
N3 (Ventral Postero Medial nucleus of Thalamus)
- Post central gyrus ( B.A. 3,1,2)
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Proprioception Pathway - Face
Receptors N1 ( Mesencephalic nucleus)
N2 ( Main Sensory nucleus)
N3 (Ventral Postero Medial nucleus ofThalamus)
- Post central gyrus ( B.A. 3,1,2)
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Pain and Temperature Pathway
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Trigeminal Neuralgia (Tic Douloureux)
Episodes of sharp, stabbing painthat radiates over
the areas innervated by sensory branches of the
maxillary or mandibular divisions of CN V
Triggered by moving the mandible, smiling or
yawning, or by cutaneous stimulation
May becaused by pressure on or interruption of
the blood supply of the trigeminal ganglion
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THANK YOU.
in due time we
shall reap
.
if we don
t lose
heart .