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![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](https://image.slidesharecdn.com/sensorysystem-171220190401/75/Sensory-system-34-2048.jpg)
Uploaded byDr Praman Kushwah
Sensory system
This document summarizes the key components of the human sensory system. It describes how sensory information is received by receptors, transmitted through neurons in the peripheral and central nervous systems, and integrated and processed in the brain. Specifically, it discusses: 1) The pathways for different sensory modalities from receptors to the spinal cord and brain, including pain/temperature, touch, and proprioception. 2) The ascending tracts that transmit sensory information from the spinal cord to the brain, such as the lateral spinothalamic, anterior spinothalamic, and posterior columns. 3) Common lesions that affect sensory pathways and how they impact sensation, such as hemisection of the spinal cord or damage to
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Sensory system
- 1. SENSORY SYSTEM DR. SNEHALPALLOD 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 receivedand 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 theperipheral 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 • Greymatter – 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 • enterthe 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 ofnerve fibres linking spinal cord with higher centres of the brain convey information from soma / viscera to higher level of neuraxis
- 11. Ascending sensory pathwayare 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.
- 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 1st 2nd
- 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 SensoryFibers • 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 1st while posterior column sensations are preserved this causes dissociative aneshesia
- 20. ascending tracts inspinal cord
- 21. Tracts & theirfunctional components • lateral spinothalamic tract – pain, temperature • anterior spinothalamic tract – touch, pressure
- 22. • posterior whitecolumn – conscious proprioceptive sense, discriminative touch, vibratory sense • spinocerebellar tract / cuneocerebellar tract – unconscious information from muscle, joints, skin, subcutaneous tissues
- 23. sensation receptors pathwaysdestination 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 theircourse in detail
- 25. Lateral spinothalamic tract painand 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 centralprocess of 1st order neuron synapse with cell body of 2nd order neuron in substantia gelatinosa of posterior gray column of the spinal cord • The axon of 2nd 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 3rd order neuron in the ventral posterolateral nucleus of thalamus • Axon of the 3rd 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.
- 28. Clinical application destruction ofLSTT • 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 lighttouch 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 PressurePathway
- 31. Clinical application destruction ofASTT loss of touch and pressure sense – below the level of lesion – on the contralateral side of the body
- 32. Fasciculus gracilis andfasciculus 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 1st order neuron enter the spinal cord • passes directly to the posterior white column of the same side ( without synapsing )
- 33. • long ascendingfibres 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 2nd order neuron in the nucleus gracilis and cuneatus of medulla oblongata of the same side.
- 34. lower 6 thoracicsegments lumbar segments sacral segments cervical segments upper 6 thoracic segments fasciculus gracilis fasciculus cuneatus [ nucleus G & C ] in medulla G C
- 35. • axons of2nd order neuron “ internal arcuate fibres ” cross the median plane ( sensory decussation ) • ascend as medial lemniscus through medulla oblongata, pons, and midbrain • synapse on the 3rd order neuron in ventral posteriolateral nucleus of thalamus • axon of 3rd 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 discriminativetouch vibratory sense
- 37. Clinical application destruction of fasciculusgracilia 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 & AnteriorSpinocerebellar 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 sensepathways 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.
- 43. clinical application • reliefof pain posterior rhizotomy (posterior root) cordotomy (lateral STT) • Injury hemisection of spinal cord • diseases tabes dorsalis / syringomyelia / vascular
- 45. FRONT: UPPER BODY TESTPOINT: 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 TestPonits 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 TestPonits 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 - OphthalmicDivision of Trigeminal Nerve (Upper Face) V2 - Maxillary Division of Trigeminal Nerve (Mid Face) V3 - Mandibular Division of Trigeminal Nerve (Lower Face)
- 51. Lesions and sensorysystem involvement
- 52. BRAIN STEM SYNDROME: lossof 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 ofall 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 withreduced 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 isdivided 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.
- 58. Complete Transaction OfSpinal 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 areaffected. 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 thespinal cord ( Brown Sequard’s syndrome ) • Dorsal column damage • Lateral column damage • Anterolateral column damage • Damage to local cord segment and nerve roots
- 61.
- 62. below the levelof 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.
- 64. CENTRAL CORD SYNDROME Mostcommon 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 toneurosyphilis,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 COLUMNDISEASE 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 Bladderatony 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.
- 71.
- 72. VASCULAR SYNDROMES OFSPINAL 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 painand 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 Lossof proprioception and vibratory sense. Pain and temperature is preserved. Absence of motor deficit.
- 75. CONUS MEDULLARIS SYNDROME Contributesto 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.
- 77. CAUDA EQUINA SYNDROME • Beginsat 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.