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)
Review the primary functions for each region of the brain as shown on the attached image
Review the primary functions for each region of the brain as shown on the attached image
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
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
what is the posterior column-medial lemniscus (DCML) responsible for sensing?
- PROPRIOCEPTION
- VIBRATION
- FINE TOUCH (two-point discrimination)
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
Study and understand the relationship in sizes for each section of this sensory homunculus. Board questions will ask you which is bigger etc.
Study and understand the relationship in sizes for each section of this sensory homunculus. Board questions will ask you which is bigger etc.
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
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.
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.
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
Study and understand the chart comparing the somatosenory pathways
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
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.
syringomyelia:
- Formation of a “_____” (tube) in spinal cord _____ matter, causing enlargement of _____ _____
- Often occurs in _____ cervical cord
- Associated with _____-_____ malformation*
- Associated with _____ syndrome*
- Loss of _____ and _____ ___-laterally
- Affects _____ commisure
- _____ discrimination, _____, and _____ are normal
syringomyelia: ***buzzword = showl or cape***
- Formation of a “syrinx” (tube) in spinal cord white matter, causing enlargement of central canal
- Often occurs in lower cervical cord
- Associated with Arnold-chiari malformation*
- Associated with horner syndrome*
- Loss of pain and temperature bilaterally
- Affects white commisure
- Tactile discrimination, vibration, and proprioception are normal
Central Cord syndrome:
- Typically a _____ injury.
- Injury preferentially involves _____ portion of spinal cord
- causes _____ strength
- _____ pain and temp sensation *mostly in _____ extremities*
- Typically with _____ due to _____ limbs being medial and _____ limbs being lateral
- _____ and _____ usually preserved
Central Cord syndrome:
*** •Typically a hyperextension injury!!!!!! ***
- Injury preferentially involves central portion of spinal cord
- causes decreased strength
- Decreased pain and temp sensation *mostly in upper extremities*
- Typically with sparing due to upper limbs being medial and lower limbs being lateral
- Vibration and proprioception usually preserved
Brown-sequard syndrome:
- _____ of the spinal cord
- loss of pain and temp sensation _____ side of body below lesion
- loss of discriminative touch and proprioception on the _____ side of the body
- paralysis on _____ body below the lesion
Brown-sequard syndrome:
- Hemisection of the spinal cord (trauma, tumors, disc protrusion etc.)
- loss of pain and temp sensation contralateral side of body below lesion
- loss of discriminative touch and proprioception on the ipsilateral side of the body
- paralysis on ipsilateral body below the lesion
Tabes Dorsalis:
- Condition caused by _____ _____
- Causes _____ of dorsal columns and roots.
- Typically affects lower _____ and _____ regions
- Impairs _____ and _____ and leads to sensory _____
- Patients have _____ _____ pupils
- Positive _____ and no deep tendon reflexes
Tabes Dorsalis:
Condition caused by tertiary syphilis
Causes demyelination of dorsal columns and roots.
Typically affects lower thoracic and lumbosacral regions
Impairs sensation and proprioception and leads to sensory ataxia (cant sense or feel legs = poor coordination)
Patients have Argyll Robertson pupils
(small pupils that constrict to accommodation but pupils will not react to light)
Positive Romberg and no deep tendon reflexes
Blood flow review:
Understand where the main arteries are in the spinal canal and what would happen if they had any problems
Blood flow review:
Understand where the main arteries are in the spinal canal and what would happen if they had any problems
Anterior spinal artery syndrome:
- Infarction of anterior spinal artery
- Loss of _____ and _____ below the level of the lesion
- Spares most _____, _____, and _____ touch
- _____ due to corticospinal tracts
Anterior spinal artery syndrome:
- Infarction of anterior spinal artery
- Loss of pain and temperature below the level of the lesion
- Spares most proprioception, vibration, and fine touch
- Paralysis due to corticospinal tracts
Match the syndrome with the correct portion of spinal cord on the attached image:
- Anterior cord syndrome
- Brown-Sequard syndrome
- Central cord syndrome
- Complete spinal cord injury
- Posterior cord syndrome
Match the syndrome with the correct portion of spinal cord on the attached image:
- Anterior cord syndrome
- Brown-Sequard syndrome
- Central cord syndrome
- Complete spinal cord injury
- Posterior cord syndrome
