Exam 1: Somatosensory Pathways; DCML and Anterolateral Flashcards
The 2 main somatosensory pathways are?
Posterior column-medial lemniscus (DCML) consisting of the fasciculus gracilis and fasciculus cuneatus
and
Anterolateral pathways (Spinothalamic)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/689/776/a_image_thumb.png?1453271941)
Review the primary functions for each region of the brain as shown on the attached image
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/690/299/q_image_thumb.png?1453272128)
Review the primary functions for each region of the brain as shown on the attached image
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/690/299/a_image_thumb.png?1453272050)
Neuron Organization overview:
- Ascending tracts consists of multiple neurons entering the spinal cord and traveling to primary somatosensory cortex
- First-order → Sensory neurons, cell body located in _____ _____ (posterior root)
- Second-order → Give rise to axons that _____ and travel to a higher level of CNS
- Third-order → typically located in _____ and extends to the sensory region of the cortex
Neuron Organization overview:
- Ascending tracts consists of multiple neurons entering the spinal cord and traveling to primary somatosensory cortex
- First-order → Sensory neurons, cell body located in spinal ganglion (posterior root)
- Second-order → Give rise to axons that decussate and travel to a higher level of CNS
- Third-order → typically located in Thalamus and extends to the sensory region of the cortex
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/691/656/a_image_thumb.png?1453272520)
Name the two fasciculi the posterior column-medial lemniscus (DCML) is made of and what they carry sensory signal for.
- Gracile fasciculus (medial): Lower trunk and lower extremities
- Cuneate fasciculus (lateral): Upper trunk and upper extremities
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/691/850/a_image_thumb.png?1453272719)
what is the posterior column-medial lemniscus (DCML) responsible for sensing?
- PROPRIOCEPTION
- VIBRATION
- FINE TOUCH (two-point discrimination)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/692/002/a_image_thumb.png?1453272769)
Neurons of Posterior column-medial lemniscus (DCML):
• 1st order neuron: enter spinal cord _____ and give off ascending and descending branches.
These neurons ascend and synapse in the nuclei _____ and _____ in medulla oblongata
- 2nd order neuron: begin at synapse in medulla and decussate as _____ _____ _____ and then ascend as the _____ _____ these end as a synapse on the _____ of thalamus
- 3rd order neuron: leaves _____ thalamus through _____ _____ and _____ _____ to reach post-central gyrus of cerebral cortex
Neurons of Posterior column-medial lemniscus (DCML):
• 1st order neuron: enter spinal cord ipsiilaterally and give off ascending and descending branches.
These neurons ascend and synapse in the nuclei gracilis and cuneatus in medulla oblongata
- 2nd order neuron: begin at synapse in medulla and decussate as internal arcuate fibers and then ascend as the medial lemniscus these end as a synapse on the VPL of thalamus
- 3rd order neuron: leaves VPL thalamus through internal capsule and corona radiate to reach post-central gyrus of cerebral cortex
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/692/113/a_image_thumb.png?1453273368)
Study and understand the relationship in sizes for each section of this sensory homunculus. Board questions will ask you which is bigger etc.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/693/387/q_image_thumb.png?1453273613)
Study and understand the relationship in sizes for each section of this sensory homunculus. Board questions will ask you which is bigger etc.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/693/387/a_image_thumb.png?1453273604)
what are the anterolateral pathways (spinothalamic tract) anterior** and **lateral sensory tracts responsible for sensing?
Which of those senses are from the anterior spinothalamic tract?
Which of those senses are from the lateral spinothalamic tract?
• anterolateral pathways = PAIN, TEMPERATURE, CRUDE TOUCH
anterior spinothalamic tract = CRUDE TOUCH
lateral spinothalamic tract = PAIN, TEMPERATURE
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/693/328/a_image_thumb.png?1453273418)
Neurons of Anterior spinothalamic tract (crude touch):
- 1st order neuron: enter spinal cord through _____ _____ _____. Travel _____ segments contributing to posterolateral tract of _____, synapse in substansia gelatinosa in _____ gray column
- 2nd order neuron: begin at synapse and decussate in the _____ gray and white _____ within _____ segments* of spinal cord and ascend as anterior spinothalamic tract, joins lateral spinothalamic tract and spinotectal tract and forms _____ _____. They then synapse at _____ of _____ (Crude touch)
- 3rd order neuron: begin at _____ pass through posterior limb of _____ _____ and _____ _____ and reach primary somatosensory cortex.
Neurons of Anterior spinothalamic tract (crude touch)
• 1st order neuron: enter spinal cord through posterior root ganglion. Travel 1-3 segments contributing to posterolateral tract of Lissauer, synapse in substansia gelatinosa in posterior gray column
- 2nd order neuron: begin at synapse and decussate in the anterior gray and white commisures within several segments* of spinal cord and ascend as anterior spinothalamic tract, joins lateral spinothalamic tract and spinotectal tract and forms spinal lemniscus. They then synapse at VPL of thalamus ( Crude touch)
- 3rd order neuron: begin at VPL pass through posterior limb of internal capsule and corona radiate and reach primary somatosensory cortex.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/693/524/a_image_thumb.png?1453275665)
Neurons of Lateral spinothalamic tract (pain and temp):
- 1st order neuron: enter spinal cord from _____ _____ _____ and enter posterior gray column. → divide into ascending and descending branches → form posterolateral tract of _____. Synapse at _____ gray column including substansia gelatinosa
- 2nd order neuron: begin at synapse and decussate in the _____ gray and white _____ within _____ segments* of spinal cord and ascend as lateral spinothalamic tract, joins anterior spinothalamic tract and spinotectal tract and forms _____ _____. They then synapse at _____ of _____ (pain and temp)
- 3rd order neuron: begin at _____ pass through posterior limb of _____ _____ and _____ _____ and reach primary somatosensory cortex.
Neurons of Lateral spinothalamic tract (pain and temp)
• 1st order neuron: enter spinal cord from posterior root ganglion and enter posterior gray column. → divide into ascending and descending branches → form posterolateral tract of Lissauer. Synapse at posterior gray column including substansia gelatinosa
- 2nd order neuron: begin at synapse and decussate in the anterior gray and white commisures within one segments* of spinal cord and ascend as lateral spinothalamic tract, joins anterior spinothalamic tract and spinotectal tract and forms spinal lemniscus. They then synapse at VPL of thalamus (pain and temp)
- 3rd order neuron: begin at VPL pass through posterior limb of internal capsule and corona radiate and reach primary somatosensory cortex.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/693/863/a_image_thumb.png?1453275679)
The anterior spinothalamic neurons enter the spinal cord through the posterior root within _____ segments
while the
lateral spinothalamic neurons enter the spinal cord through the posterior root within _____ segments
The anterior spinothalamic neurons enter the spinal cord through the posterior root within 1 - 3 segments
while the
lateral spinothalamic neurons enter the spinal cord through the posterior root within 1 segments
*These are board questions
Study and understand the chart comparing the somatosenory pathways.
Try filling in the blanks for practice
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/695/320/q_image_thumb.png?1453276346)
Study and understand the chart comparing the somatosenory pathways
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/695/320/a_image_thumb.png?1453276039)
Understand when and where axons area added laterally instead of added medially.
Understand when and where axons area added laterally instead of added medially.
*opposite of (? missed what was said)
**as you go up they get added laterally
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/695/615/a_image_thumb.png?1453276726)
Central modulation of pain:
- Pain modulation involves _____ horn, _____, _____, and _____
- Goal is to inhibit pain transmission in _____ horn
Central modulation of pain:
- Pain modulation involves dorsal horn, hypothalamus, amygdala, and cortex
- Goal is to inhibit pain transmission in dorsal horn
Gate Control theory:
- Sensory inputs from non-_____ A-β fibers
- Periaqueductal gray matter receives input from _____, _____, and _____
- Uses _____ _____ _____ (RVM)
Contains serotonin (5-HT) containing neurons in _____ nuclei
RVM also sends inputs mediated by _____ _____ to locus ceruleus which contains _____ projections.
Gate Control theory:
- Sensory inputs from non-pain A-β fibers
- Periaqueductal gray matter receives input from amygdala, hypothalamus, and cortex
- Uses Rostal Ventral Medulla (RVM)
Contains serotonin (5-HT) containing neurons in raphe nuclei
RVM also sends inputs mediated by substance P to locus ceruleus which contains NE projections.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/176/695/753/a_image_thumb.png?1453276903)