Ascending & Descending pathways

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9 Terms

1
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Three ascending tracts in spinal cord

  1. Spinocerebellar

  2. Spinothalmic

  3. Leminiscal

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Spinocerebellar

  • Convey information about propioception from muscle/tendon.

  • Propioceptors provided information on body position on the same side of the body

    1st order neuron: Sensory neuron cell bodies in DRG

    2nd: In dorsal horn of spinal cord neuron & synapses at Cerebellum

<ul><li><p>Convey information about propioception from muscle/tendon.</p></li><li><p>Propioceptors provided information on body position on the same side of the body</p><p></p><p><span style="color: yellow">1st order neuron:</span>  Sensory neuron cell bodies in DRG</p><p><span style="color: yellow">2nd:</span> In dorsal horn of spinal cord neuron &amp; synapses at Cerebellum</p><p></p></li></ul><img src="https://knowt-user-attachments.s3.amazonaws.com/c0b616c1-5edc-48cf-b110-f7e42fb978b3.png" data-width="100%" data-align="center"><p></p>
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Specific/Lemniscal

  • Touch/vibration and proprioception crossover in medulla

  • Carry discriminatory sensation from skin (touch, pressure) and propioception

1st order neuron: Sensory neuron cell bodies in DRG

2nd order neuron: Medulla- these neurons decussate in medulla

3rd order neuron: Thalamus (projects to primary somatosensory area of cortex on opposite side of the brain

<ul><li><p>Touch/vibration and proprioception crossover in medulla</p></li><li><p>Carry discriminatory sensation from skin (touch, pressure) and propioception</p></li></ul><p></p><p><span style="color: yellow">1st order neuron:</span>  Sensory neuron cell bodies in DRG</p><p><span style="color: yellow">2nd order neuron:</span> Medulla- these neurons decussate in medulla</p><p><span style="color: yellow">3rd order neuron:</span> Thalamus (projects to primary somatosensory area of cortex on opposite side of the brain</p><p></p><img src="https://knowt-user-attachments.s3.amazonaws.com/f040d6ae-a613-4d99-877b-b0e222bc5ef2.png" data-width="100%" data-align="center"><p></p><p></p>
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Spinothalamic/Non-Specific

  • Carries information on pain and temperature and deep pressure

  • Pathways crossover in spinal cord

1st order neuron: Sensory neuron cell bodies in DRG

2nd order neuron: Dorsal horn of spinal cord’s axons decussate

3rd order neuron: Thalamus projects information to primary somatosensory area of cortex

<ul><li><p>Carries information on pain and temperature and deep pressure</p></li><li><p>Pathways crossover in spinal cord</p></li></ul><p></p><p><span style="color: yellow">1st order neuron:</span>  Sensory neuron cell bodies in DRG</p><p><span style="color: yellow">2nd order neuron:</span> Dorsal horn of spinal cord’s axons decussate</p><p><span style="color: yellow">3rd order neuron:</span> Thalamus projects information to primary somatosensory area of cortex</p><p></p><img src="https://knowt-user-attachments.s3.amazonaws.com/3e470a51-d999-49e5-9d48-a5e5417b1b1b.png" data-width="100%" data-align="center"><p></p>
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Descending pathways in spinal cord

  • Pyramidal (aka corticospinal tracts)

    • Direct: Descends without synapsing

  • Rubrospinal (aka extrapyrimidal tract)

    • Indirect: multineuronal pathways

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What is Pyramidal (aka corticospinal tracts) for

Regulate fast and fine skulled movement

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What is Rubrospinal (aka extrapyrimidal tract) for

Regulate balance, posture, coarse limb movement, head and neck, eye movement

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Pyramidal (aka corticospinal tracts)

  • Control voluntary and conscious movements on the opposite side of the body

  • Decussate in either medulla or spinal cord

  • Synapse either directly on spinal motor neuron or on an interneuron (more often) that connects to motor neuron.

<ul><li><p>Control voluntary and conscious movements on the opposite side of the body</p></li><li><p>Decussate in either medulla or spinal cord</p></li><li><p>Synapse either directly on spinal motor neuron or on an interneuron (more often) that connects to motor neuron.</p></li></ul><img src="https://knowt-user-attachments.s3.amazonaws.com/0e030a16-e5c8-4eaa-abef-ef0bb6bb5a0c.png" data-width="100%" data-align="center"><p></p>
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Rubrospinal (aka extrapyrimidal tract)

  • Controls unconscious, voluntary muscles controlling posture and balance

  • Always multi-synaptic

  • Arise in brain stem nuclei (e.g., red nucleus)

  • Decussate in brain stem (medulla)

  • Moderated by pyramidal neurons

<ul><li><p>Controls unconscious, voluntary muscles controlling posture and balance </p></li><li><p>Always multi-synaptic </p></li><li><p>Arise in brain stem nuclei (e.g., red nucleus)</p></li><li><p>Decussate in brain stem (medulla)</p></li><li><p>Moderated by pyramidal neurons</p></li></ul><img src="https://knowt-user-attachments.s3.amazonaws.com/cc95996d-05cb-4e20-9254-79199d233795.png" data-width="100%" data-align="center"><p></p>