Your SlideShare is downloading. ×
Dorsal column pathway
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Dorsal column pathway

16,265
views

Published on

Published in: Health & Medicine, Technology

5 Comments
3 Likes
Statistics
Notes
  • Slide3...Layers of the skin are incorrect. The blue layer that is labeled 'dermis' is actually a part of the EPIDERMIS. The blue layer consists of the stratum basale (stratum germinativum), stratum spinosum, stratum granulosum, stratum lucidum--palms and soles, and stratum corneum...these layers are listed from the bottom to the top. The DERMIS contains blood vessels, nerve endings, sweat glands, oil glands, etc. I hope this clears things up a bit. Thank you.
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
  • excellent,,,
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
  • thank you very much
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
  • excellent
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
  • excellent
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
No Downloads
Views
Total Views
16,265
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
254
Comments
5
Likes
3
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. Dorsal column pathway DR SYED TOUSIF AHMED
  • 2. General Sensory Receptors Sensory pathways Spinocerebellar Pathway Posterior Column Pathways Anteriolatheral Pathways Posterior Tract Anterior Tract Fasciculus Cuneatus Fasciculus Gracilis Latheral Tract Anterior Tract Sensory Pathways
  • 3. Cutaneous sensory receptors Smooth skin (glaborous ) Hairy skin Free nerve endings The receptor location and its associated structure can alter the stimulus and influence the response Subcutis Dermis Epidermis Merkel disks detect steady pressure & are slowly adapting Free nerve endings around hair root can be either rapid or slowly adapting - depends on hair type Meissner’s corpuscles detect flutter & are rapidly adapting Pacinian corpuscles detect vibration & are very rapidly adapting Ruffini corpuscles detect steady pressure at higher threshold & are slowly adapting Free nerve endings in the skin are modality specific and can detect either pain or touch or pressure or temperature
  • 4. Tactile Sensations
    • arise by activation encapsulated mechanoreceptors
      • touch
      • pressure
      • vibration
    • arise by activation of free nerve endings
      • itch
      • tickle
  • 5. Touch
    • Crude touch
      • ability to perceive that something contacted skin
      • exact location, shape, size, or texture cannot be detected
    • Fine touch
      • provides specific information about location, shape, size, and texture of stimuli
  • 6. Proprioreceptors
    • Intrinsic knowledge of limb position is known as kinaesthesia.
    • Information is provided by sensory input from muscle spindles (Ia & II) and Golgi tendon organs.
    • These are mechanoreceptors and provide the CNS with information on muscle length, position and tension.
    • Muscle spindle group Ia afferent fibres are rapidly adapting (dynamic) and are sensitive to rapid changes in muscle length.
    • Muscle spindle group II afferent fibres are slowly adapting (static) and single the fixed length of the muscle.
  • 7. Joint Kinesthetic Receptors
    • located within and around articular capsules of synovial joints
    • perception of body movements
    • several types
      • free nerve endings and type II cutaneous mechanoreceptors
        • in capsules of joint and respond to pressure
      • small lamellated corpuscles
        • respond to acceleration and deceleration of joints during movement
      • articular ligaments contain receptors similar to tendon organs
        • adjust the contraction of adjacent muscles when excessive strain is placed on joint
  • 8. Two-Point Discrimination
  • 9. Processing at Receptor Level
    • Receptor must have specificity for stimulus activity
    • Stimulus must be applied to receptive field
    • Transduction must occur
    • Generator potential in 1 st order neuron must reach threshold
    • How is information about stimulus encoded?
    • Tonic receptors (slow adapting)
    • Phasic receptors (fast adapting)
    • Adaptation
  • 10.
    • Rapidly adapting cutaneous mechanoreceptors signal the onset and offset (phasic) of a stimulus and give rise to sensations such as vibration, touch, and movement
    • Slowly adapting mechanoreceptors continuously signal (tonic) the intensity of the stimulus and give rise to the sensation of pressure.
    • Cutaneous receptors with small receptive fields are involved in fine spatial discrimination, whereas receptors with larger receptive fields are less spatially precise.
    • Overlap of receptive fields allows lateral inhibition to occur in the ascending pathways and increase sensory acuity.
    Cutaneous mechanoreceptors
  • 11. Somatosensory system receptor classification
  • 12. First-Order Neuron
    • Sensory neuron delivers information to CNS
    • Cell body is located in dorsal root ganglion
    • Synapses with interneurons in CNS
  • 13. Second-Order Neuron
    • Usually interneurons receiving information from first order neurons
    • Axons cross to opposite sides of body
      • Decussation
    • May be located in the spinal cord or brain stem
  • 14. Third-Order Neuron
    • Located in thalamus
    • Carries information to cerebrum
    • Synapses with neurons of the primary sensory cortex
  • 15. Ascending Pathways to Brain
    • What type of information do the neurons carry?
    • 3 chains of successive neurons to brain
      • 1 st order neurons
        • Where is cell body?
        • Conduct impulses from cutaneous receptors and proprioceptors
        • Synapse w/ 2 nd order
      • 2 nd order neurons
        • Cell bodies in dorsal horn or in medullary nuclei
        • Transmit impulses to thalamus or cerebellum; synapse
      • 3 rd order neurons
        • In thalamus
        • Where do they conduct information to?
        • No 3 rd order neurons in cerebellum
  • 16.
    • First order neurons
      • Sensory neurons that deliver sensory information to the CNS
    • Second order neurons
      • First order neurons synapse on these in the brain or spinal cord
    • Third order neurons
      • Found in the thalamus
      • Second order neurons synapse on these
    • Only 1% of incoming sensory impulses actually reach the cerebrum.
    First, second, and third order neurons The Organization of Sensory Pathways
  • 17. Posterior Column Pathway
    • Carries sensations of highly localized (fine) touch, pressure, vibration, proprioception
    • Spinal Tracts Involved:
      • Left/right fasciculus gracilis
      • Left/right fasciculus cuneatus
  • 18. Peripheral nerves system
  • 19. Sensory Pathways and Ascending Tracts in the Spinal Cord
  • 20. dorsal cloumn pathway
  • 21. Dorsal column pathway
  • 22. Dorsal-column leminiscal pathway
    • Principally conveys tactile discrimination, vibratory and position senses (A  ,large fibres).
    • 1st order sensory neurones run on the same side & synapse with 2nd order neurones in the dorsal column nuclei .
    • 2nd order neurones integrate the input and their axons cross to the opposite side. These ascend through the medial leminiscus
    • Further integration in the thalamus & 3rd order neurones project to the cortex.
  • 23. The Posterior Column Pathway and the Spinothalamic Tracts The area of sensory cortex devoted to a body region is relative to the number of sensory receptors.
  • 24. Dorsal column pathway Large sensory nerves: Touch, vibration, two-point discrimination, proprioception Primary somatosensory cortex (S1) in parietal lobe Thalamus Medulla Medial lemniscus Spinal cord Dorsal column Dorsal column nuclei
  • 25. Dorsal column damage dorsal column pathway Left spinal cord injury
    • Loss of sense of:
    • touch
    • proprioception
    • vibration
    • in left leg
  • 26. Dorsal column damage
    • Sensory ataxia
    • Patient staggers; cannot perceive position or movement of legs
    • Visual clues help movement
  • 27. Central Pathways
  • 28. 3.3 Spinocerebellar pathway
    • Carries unconscious proprioception signals
    • Receptors in muscles & joints
    • 1 st neuron: enters spinal cord through dorsal root
    • 2 nd neuron: ascends to cerebellum
    • No 3 rd neuron to cortex, hence unconscious
  • 29.
    • Coding in the sensory system could theoretically follow:
      • The labeled-line principle in which each receptor responds to a limited range of stimuli and sends a direct line to the brain.
      • 2 . Across-fiber pattern in which each receptor responds to a wider range of stimuli and contributes to the perception of each of them.
  • 30. THANK YOU

×