Sensory system

Sensory system

1. SENSORY SYSTEM
DR. SNEHAL PALLOD
GUIDE-DR.GIRISH NANOTI

2. CENTRAL NERVOUS SYSTEM
integration / processing / modulating
stimulus
receptor neurone
motor / descending tracts
effector organ / response
PNS
transmission
lower motor neurone
sensory / ascending tracts
4
3
2
1

3. •Sensory information
• Exteroceptive information
• Proprioceptive information

4. sensory information
are received and carried by ascending tracts
•exteroceptive sensation
origin:- outside the body
e.g. temp, touch, light, sound, chemicals, mechanical
receptors:- surface layer of skin, mucosa
•proprioceptive sensation
origin:- within the body
e.g. muscles, joints, tendons
receptors – deeper layer of skin, tendons, joints, GTO, muscle
spindles, ligament
•Steriognosis , graphesthesia, and two point discrimination combind
( pc) and cortical sensation

6. sensory information
from the peripheral sensory endings
is conducted through the nervous system
by a series of neurones

7. information
•conscious sensation
–reach the cerebral cortex
•unconscious sensation
–reach to the areas other than cortex

8. spinal cord
•Grey matter
–mostly made up of cell bodies of neurone
•White matter
–composed of nerve fibres ( ascending and descending tracts )
embedded in neuroglial cells

9. nerve fibres
• enter the spinal cord through posterior nerve root
• after entering the spinal cord
sorted out and segregated into nerve bundles, tracts
( origin, function, termination )

10. ascending tracts
bundles of nerve fibres
linking
spinal cord with higher centres of the brain
convey information
from
soma / viscera to higher level of neuraxis

11. Ascending sensory pathway are organized
in three neuronal chain
- First order neurone
- Second order neurone
- Third order neurone

12. First order neurone
•cell body in posterior root ganglion
•peripheral process connects with sensory receptor
ending
•central process enter the spinal cord through the
posterior root
•synapse with second order neuron in spinal gray
matter

13. dorsal root
dorsal root
ganglion
spinal
nerve
dorsal
horn
FIRST ORDER NEURON

14. Second order neurone
•cell body in posterior gray column of spinal cord
•axon crosses the midline ( decussate )
•ascend & synapse with third order neuron in VPL
nucleus of thalamus

15. SECOND ORDER NEURON
• cross the mid line
• in front of central canal
1
st
2
nd

16. Third order neurone
•cell body in the thalamus( ventro lateral nucleus)
•give rise to projection fibres to the cerebral cortex,
postcentral gyrus ( sensory area )

17. ascending sensory pathway
( in general form )
from sensory endings
to
cerebral cortex
( note the three neurons chain )

18. sensory sensation
Three type
1.Superficial : pain ,temperature and superficial touch
carried by spinothalamic pathway(lateral)
2.Deep : crude touch ,joint position ,vibration carried
by dorsal coloumn
3.Cortical sensation : tactile localization, tactile
discrimination,tactile extiction,astereognosis,two
point discrimination and graphasthesia

19. Arrangements Of Sensory Fibers
•Posterior column : fibers from lower limb are placed
medially while fibers upper limbs are placed laterally
•Spinothalamic tract : just opposite to posterior
column
•In central cord lesion lateral spinothalamic tract is
affected 1
st
while posterior column sensations are
preserved this causes dissociative aneshesia

20. ascending tracts in spinal cord

21. Tracts & their functional components
•lateral spinothalamic tract
–pain, temperature
•anterior spinothalamic tract
–touch, pressure

22. •posterior white column
–conscious proprioceptive sense, discriminative
touch, vibratory sense
•spinocerebellar tract / cuneocerebellar
tract
–unconscious information from muscle, joints,
skin, subcutaneous tissues

23. sensation receptors pathways destination
Pain and temperature Free nerve endings Lateral STT
Spinal lemniscus
Postcentral
gyrus
Light touch and pressure Free nerve endings Anterior STT
Spinal lemniscus
Postcentral
gyrus
Discriminative touch,
vibratory sense,
conscious muscle joint sense
Meissner’s corpuscle,
pacinian corpuscles,
muscle spindles,
tendon organs
Fasciculus gracilis and cuneatus
Medial lemniscus
Postcentral
gyrus
Main somatosensory pathways

24. Tracts and their course in detail

25. Lateral spinothalamic tract
pain and thermal impulses
( input from free nerve endings, thermal receptors )
•transmitted to spinal cord in delta A and C fibres
•central process enters the spinal cord through posterior
nerve root, proceed to the tip of the dorsal gray column

26. •The central process of 1
st
order neuron synapse with cell body
of 2
nd
order neuron in substantia gelatinosa of posterior gray
column of the spinal cord
•The axon of 2
nd
order neuron cross to the opposite side
in the anterior gray and white commissure and ascend in
contralateral white column as lateral spinothalamic tract
•End by synapsing with 3
rd
order neuron in the ventral
posterolateral nucleus of thalamus
•Axon of the 3
rd
order neuron passes through the posterior
limb of internal capsule and corona radiata to reach the
postcentral gyrus of cerebral cortex ( area 3, 1 and 2 )

27. pain and temperature
pathways

28. Clinical application
destruction of LSTT
•loss of
–pain and thermal sensation
–on the contralateral side
–below the level of the lesion
patient will not
respond to pinprick
recognize hot and cold

29. Anterior spinothalamic tract
light touch and pressure impulses
( input from free nerve endings, Merkel’s tactile disks )
•First order neuron
–dorsal root ganglion( all level )
•Second order neuron
–in the dorsal horn, cross to the opposite side (decussate)
–ascend in the contralateral ventral column as ASTT
–end in VPL nucleus of thalamus
•Third order neuron
–in the VPL nucleus of thalamus
–project to cerebral cortex ( area 3, 1 and 2 )

30. Touch and Pressure Pathway

31. Clinical application
destruction of ASTT
loss of touch and pressure sense
–below the level of lesion
–on the contralateral side of the body

32. Fasciculus gracilis and fasciculus cuneatus
discriminative touch, vibratory sense and conscious
muscle joint sense
( inputs from pacinian corpuscles, Messiner’s corpuscles,
joint receptors, muscle spindles and Golgi tendon organs )
•axon of 1
st
order neuron enter the spinal cord
•passes directly to the posterior white column of the
same side ( without synapsing )

33. •long ascending fibres travel upward in the posterior
column of the same side as fasciculus gracilis and
fasciculus cuneatus
–( FG – carrying fibres from lower thoracic, lumbar and sacral regions /
including lower limbs )
–( FC - only in thoracic and cervical segments / including upper limb fibres )
•synapse on the 2
nd
order neuron in the nucleus
gracilis and cuneatus of medulla oblongata of the
same side.

34. lower 6 thoracic segments
lumbar segments
sacral segments
cervical segments
upper 6 thoracic segments
fasciculus gracilis
fasciculus cuneatus
[ nucleus G & C ]
in medulla
G
C

35. •axons of 2
nd
order neuron
“ internal arcuate fibres ” cross the median plane
( sensory decussation )
•ascend as medial lemniscus
through medulla oblongata, pons, and midbrain
•synapse on the 3
rd
order neuron in ventral posteriolateral nucleus of
thalamus
•axon of 3
rd
order neuron leaves and passes through the internal capsule,
corona radiata to reach the postcentral gyrus of cerebral cortex area 3, 1
and 2 )

36. pathways for
conscious proprioception
discriminative touch
vibratory sense

37. Clinical application
destruction of
fasciculus gracilia and cuneatus
•loss of muscle joint sense,
position sense, vibration sense
and tactile discrimination
•on the same side
•below the level of the lesion
(extremely rare to have a lesion of the spinal cord to
be localized as to affect one sensory tract only )

38. Posterior & Anterior Spinocerebellar Tract
•transmit unconscious proprioceptive information to
the cerebellum
•receive input from muscle spindles, GTOs and pressure
receptors
•involved in coordination of posture and movement of
individual muscles of the lower limb

39. First order neuron
•in dorsal root ganglion
•axons end in nucleus dorsalis of Clarke
Second order neuron
•cell body in nucleus dorsalis of Clarke
•give rise to axons ascending to the cerebellum of the
same side
( anterior – crossed & uncrossed fibres / posterior – uncrossed fibres)

40. muscle joint sense pathways
to cerebellum

41. •Spinotectal tract
–passes pain, thermal, tactile information to superior
colliculus for spinovisual reflexes
•cross the median plane
•synapse in the superior colliculus
•integrate visual and somatic sensory information
( it brings about the movement of eye and head
towards the source of information )
•Spinoreticular tract
–uncrossed fibres, synapse with neurones of reticular
formation
(important role in influencing level of consciousness)
•Spino-olivary tract

42. spinotectal tract
spinoreticular tract
spino-oloivary tract

43. clinical application
•relief of pain
posterior rhizotomy (posterior root)
cordotomy (lateral STT)
•Injury
hemisection of spinal cord
•diseases
tabes dorsalis / syringomyelia / vascular

45. FRONT:
UPPER BODY TEST POINT:
C2: OCCIPITAL PROTUBERANCE
C3: SUPRACLAVICULAR FOSSA
C4: ACROMIOCLAVICULAR JOINT
C5:LATERAL ANTICUBITAL FOSSA
C6:THUMB
C7:MIDDLE FINGER
C8:LITTLE FINGER
T!: MEDIAL ANTICUBITAL FOSSA
T2:APEX OF AXILLA
LOWER BODY TEST POINT:
L1: UPPER ANTERIOR THIGH
L2:MID ANTERIOR THIGH
L3:MEDIAL FEMORAL
CONDYLE
L4:MEDIAL MALLEOLUS
L5: DORSUM OF THE THIRD
MTP JOINT
S1: LATERAL HEEL
S2:POPLITEAL FOSSA
S3:ISCHIAL TUBEROSITY
S5:PERIANAL AREA

46. Upper Body Test Ponits
C2 - Occipital Protuberance
C3 - Supraclavicular Fossa
C4 - Acromioclavicular Joint
C5 - Lateral Antecubital Fossa
C6 - Thumb
C7 - Middle Finger
C8 - Little Finger
T1 - Medial Antecubital Fossa
T2 - Apex of Axilla
Lower Body Test Points
L1 - Upper Anterior Thigh
L2 - Mid Anterior Thigh
L3 - Medial Femoral Condyle
L4 - Medial Malleolus
L5 - Dorsum 3rd MTP Joint
S1 - Lateral Heel
S2 - Popliteal Fossa
S3 - Ischial Tuberosity
S5 - Perianal Area

47. Upper Body Test Ponits
C2 - Occipital Protuberance
C3 - Supraclavicular Fossa
C4 - Acromioclavicular Joint
C5 - Lateral Antecubital Fossa
C6 - Thumb
C7 - Middle Finger
C8 - Little Finger
T1 - Medial Antecubital Fossa
T2 - Apex of Axilla

48. V1 - Ophthalmic Division of Trigeminal
Nerve (Upper Face)
V2 - Maxillary Division of Trigeminal Nerve
(Mid Face)
V3 - Mandibular Division of Trigeminal
Nerve (Lower Face)

51. Lesions and sensory system
involvement

52. BRAIN STEM SYNDROME:
loss of pain ,touch and
temperature on same
side of the face and
opposite side of the body
due to involvement of
trigeminal tract and
nucleus and lateral
spinothalamic tract

53. THALAMIC SYNDROME:
loss of all type of
sensation of opposite
side of the body and
position sense more
affected than other
type of sensation.
There may be
spontaneous pain and
discomfort

54. PARIETAL LOBE SYNDROME:
A) loss of tactile localization
b) loss of tactile discrimination
C)tactile extinction
D)astereognosis
E)two point discrimination: finger pulp, lips,
palm, sole,dorsum of the foot ,back

55. HYSTERICAL:
A)complete hemianaesthesia with reduced
hearing vision taste smell ,reduced vibration,
only over one half of the skull.
B)sharply defined sensory loss not confined to
the distribution of the root or cutaneous
nerve
C)postural sense is rarely affected.

56. •It is divided into complete and incomplete
cord syndromes.
•INCOMPLETE CORD SYNDROMES.
•Brown sequards syndrome.
•Central cord syndrome.
•Anterior cord syndrome.
•Posterior cord syndrome.
•Conus medullaris syndrome.
•Cauda equina syndrome.

57. COMPLETE CORD TRANSECTION

58. Complete Transaction Of Spinal Cord
CAUSES-
Trauma
Metastatic carcinoma
Multiple sclerosis
Spinal epidural haematoma
Autoimmune disorders
Post vaccinial syndromes.
All ascending tracts from below and descending
tracts from above are interrupted.
Affects motor sensory and autonomic functions.

59. SENSORY
all sensations are affected.
Pin prick test is very valuable.
Sensory level is usually 2
segments below the level of
lesion.
Segmental paresthesia occur
at the level of lesion.

60. Hemisection of the spinal cord
( Brown Sequard’s syndrome )
•Dorsal column damage
•Lateral column damage
•Anterolateral column damage
•Damage to local cord segment and nerve roots

61. spinal cord hemisection

62. below the level of lesion
on the side of lesion
lateral column damage
• UMNL
dorsal column damage
• loss of position sense
• loss of vibratory sense
• loss of tactile discrimination
anterolateral system damage
• loss of sensation of pain and
temperature on the side opposite
the lesion
local segment
side of lesion
Dorsal Root
• irritate
• destruction
Ventral root
• flaccid paralysis

63. CENTRAL CORD SYNDROME

64. CENTRAL CORD SYNDROME
Most common cause is syringomyelia.
others hyperextension injuries of neck,intramedullary
tumours,trauma.
Associated with chiari type 1 and 2.and dandy walker
malformation.
SENSORY
Pain and temperature are affected.
Touch and proprioception are preserved.
Dissociative anaesthesia.
Shawl like distribution of sensory loss.
MOTOR.
Upper limb weakness >lowerlimb

66. •Other features;
–Horners syndrome
–Kyphoscoliosis
–. Sacral sparing
–Neuropathic arthropathy of shoulder and elbow
joint
–Prognosis is fair.

67. Occurs due to neurosyphilis,diabetes mellitus
Usually occurs 10 to 20 yrs after infection
SENSORY
Impaired position and vibration sense in LL
Tactile and postural hallucinations can occur.
Numbness or paresthesia are frequent complaints..
Sensory ataxia.
Positive rhomberg sign.
POSTERIOR COLUMN SYNDROME

68. POSTERO LATERAL COLUMN DISEASE
CAUSES;
VITB12 DEFICIENCY
AIDS
HTLV ASSOCIATED
MYELOPATHY.
CERVICAL SPONDYLOSIS
Paresthesia in feet
Loss of proprioception and
vibration in legs
Sensory ataxia

69. positive rhomberg sign
Bladder atony
Corticospinal tract
involvement;spasticity,hyperreflexia ,bilateral
Babinski sign.
Aids:associated dementia and spastic bladder is
present
HTLV associated myelopathy;slowly progressive
paraparesis increase in csf igG with antibodies
to HTLV1.

70. SPINAL ARTERY

71. ANTERIOR CORD SYNDROME

72. VASCULAR SYNDROMES OF SPINAL
CORD
Mostly occurs due to anterior spinal artery.
conus medullaris is frequently involved.lies
opposite to vertebral bodies T12 and L1.
Neck pain of sudden onset.
MOTOR
Flaccid and areflexic paraplegia

73. SENSORY
Loss of pain and temperature.
Preservation of positon and vibration.
AUTONOMIC
urinary incontinence.
Spinal cord infarction usually occurs in T1 to T4
segment.and L1
Occurs due to syphilitic arteritis ,aortic
dissection,atherosclerosis of aorta,SLE
,AIDS,AV malformation

74. POST SPINAL ARTERY
SYNDROME
UNCOMMON
Loss of proprioception and
vibratory sense.
Pain and temperature is
preserved.
Absence of motor deficit.

75. CONUS MEDULLARIS SYNDROME
Contributes to 25%spinal cord injuries.
Lies opposite to vertebral bodies of T12 and L1.
Caused by flexion distraction injuries and burst
fractures.
Both UMN and LMN deficits occur.
Development of neurogenic bladder.

76. CAUDA EQUINA SYNDROME

77. CAUDA EQUINA SYNDROME
•
Begins at L2 disk space distal to
conus medullaris.
MOTOR
Flaccid lower extremities.
Knee and ankle jerk absent.
SENSORY-
Asymmetrical sensory loss
Saddle anaesthesia
Loss of sensation around
perineum,anus,genitals.
AUTONOMIC-
Loss of bladder and bowel function.
Urinary retention.
Occurs due to acute disk herniation
epidural haematoma,tumour

78. Polyneuropathy:
symmetrical glove
stocking anesthesia
( distal part is more
affected)

79. THANK YOU