S03/4 Ascending Tracts

Spinothalamic Tract
1. Receptor Modalities
  1. Pain
  2. Temperature
  3. Crude touch
  4. Pressure
  5. Itch
  6. Tickle
  7. Sexual Sensation
2. Receptors
  1. Free Nerve Endings
    1. Lateral Tract
    2. Pain
    3. Temperature
  2. Merkel's Disk and Ruffini's Endings
    1. Anterior Tract
    2. Touch
3. Tract of Lissauer
  1. Primary neuron goes up/down a few spinal segments before synapsing
4. http://youtu.be/QpoEh9VQ7so
5. Primary neuron
  1. Synapses at the substantia gelatinosa in the dorsal horn after travelling in the Tract of Lissauer
  2. Secondary neuron
    1. Decussates and travels in the anterior or lateral spinothalamic tracts to the medulla, where the two tracts join to the spinal lemniscus. The neuron then ascends to the VPL of thalamus and synapses.
    2. Tertiary neuron
      1. Arises from the thalamus and travels via the internal capsule to the sensory cortex
Spinocerebellar Tract
1. Sensory Modalities
  1. Unconscious proprioception
  2. Receptors
    1. Muscle Spindles
    2. Golgi Tendon Organs
    3. Joint capsules
  3. http://youtu.be/cGxyJosd-pw
  4. Clarke's column
    1. Column in the dorsal horn
    2. C8-L3
  5. Ipsilateral 2 neurone pathway
  6. Primary neuron
    1. Anterior; cell body in DRG, synapses at Clarke's column
    2. Posterior; cell body in DRG, synapses at Clarke's column
    3. Secondary neuron
      1. Anterior; travels up to Pons in dorsal spinocerebellar tract, out of Pons via Inferior Cerebellar Peduncle, and into cerebellar cortex
      2. Posterior; travels up to Midbrain in dorsal spinocerebellar tract, out of Midbrain via Superior Cerebellar Peduncle and crosses over cerebellum to synapse in the cerebellar cortex
  7. 2 tracts, posterior and anterior
Dorsal Columns
1. Receptor Modalities
  1. Fine Touch
  2. 2-point discrimination
  3. Proprioception
  4. Vibration
2. Receptors
  1. Meissner's Corpuscle, Merkel's endings, Ruffini's endings and Pacinian Corpuscle
    1. Vibration
    2. Fine touch
    3. Vibration
  2. Muscle Spindle and GTO
    1. Proprioception
3. http://youtu.be/70Kg4uPem4U
4. Primary neuron
  1. If from lower limb = gracilis, if from upper limb = cuneatus, travel in the dorsal column to the cuneate and gracilis nuclei of the medulla
  2. Secondary neuron
    1. Decussate in the Medulla and continue upwards in the medal lemniscus to synapse at the VPL in the thalamus
    2. Tertiary neuron
      1. Arises from the thalamus and travels via the internal capsule to the sensory cortex
Trigeminothalamic Tract
1. http://youtu.be/0kftFO3nAyY
2. Receptor Modalities
  1. Pain, touch and temperature from neck, head and face
3. Receptor
  1. Free nerve ending
4. Pain
  1. Primary Neuron
    1. Travels through trigeminal ganglion and down to the Medulla, synapsing at the spinal nucleus
    2. Secondary neuron
      1. Travels in the trigeminal lemniscus to the VPM (ventral posteromedial nucleus) of the thalamus, where it synapses
      2. Tertiary neuron
        VPM via internal capsule to cerebral cortex
5. Touch
  1. Primary Neuron
    1. Travels through trigeminal ganglion and down to the Pons, synapsing at the Chief Sensory Nucleus
6. Temperature
  1. Primary Neuron
    1. Travels through trigeminal ganglion and down to the midbrain, synapsing at the Mesencephalic nucleus
    2. Secondary Neuron
Spinal Cord White Matter
1. Cervical
  1. Oval shape
  2. Prominant dorsal horns
    1. Extensive sensory input from upper limbs
  3. Prominent ventral horns
    1. Extensive motor output from the upper limbs
2. Gracile Fasciculus
  1. Carries info from the lower limb (below T3)
3. Cuneate fasciculus
  1. Carries info from the upper limb (T3 and above)
4. Thoracic
  1. Small ventral horns
  2. Lateral horns
    1. Preganglionic sympathetic motor
5. Lumbar
  1. Prominent dorsal horns
    1. Extensive sensory input from lower limbs
  2. Prominent ventral horns
    1. Extensive motor output to lower limbs
  3. Little white matter
6. Sacral
  1. Small and round
  2. Lateral horn from S2-S4
  3. Mostly grey matter
Neurons and Receptors
1. 3 Neurone System
  1. Primary Neuron
    1. Cell body in DRG
  2. Secondary Neuron
    1. Decussates
  3. Tertiary Neuron
    1. Thalamus (VPL) to cortex
2. Receptors
  1. Exteroreceptors
    1. Found on body surfaces (external environment)
  2. Interoreceptors
    1. Internal receptors (viscera and internal environment)
  3. Proprioceptors
    1. Muscles
      1. Respond to changes in muscle length and tension
Clinical Correlations
1. Subacute combined degeneration
  1. Vitamin B12 deficiency (pernicious anaemia)
  2. Affects
    1. Dorsal Columns
    2. Spinocerebellar tracts
    3. Corticospinal tracts
2. Syringomyelia
  1. Fluid collection in the spinal canal
    1. Syrinx
  2. Affects
    1. Spinothalamic tract
    2. Upper limb and upper chest sensory loss
3. Brown-Sequad Syndrome
  1. Trauma causing damage to half of the cord (hemisection)
    1. Problems with the dorsal columns on the same side of the cord
    2. Impaired spinothalamic on the other side (pain and temp.)
    3. Paralysis of leg on same side
    4. Loss of all modalities at level of lesion
4. Syphilis (Tabis dorsalis)
  1. Impairs dorsal columns

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S03/4 Ascending Tracts

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	Created by chris.brees over 10 years ago