CNS Unit 6 Ascending Systems Flashcards
In the Spinal Cord, the Fasciculus Cuneatus and Fasciculus Gracilis are part of which Ascending Tract? What are their functions?
Both of these structures are collectively called the Posterior/Dorsal Column Medial Lemniscal
- The Fasciculus Gracilis carries LE information from the periphery up to the brain
- The Fasciculus Cuneatus carries UE information from the periphery to the brain
What are the different Ascending Tracts?
- Posterior/Dorsal Column Medial Lemniscal
- Anterolateral System:
–Spinothalamic *
–Spinoreticular
–Spinomesencephalic - Ventral and Rostral Spinocerebellar
- Dorsal Spinocerebellar and Cuneocerebellar
What are the Main Ascending Long Tracts of the Nervous System? What is their function? What is the name (and level) of decussation?
- Posterior/Dorsal Medial Lemniscal Pathway
–Function: Vibration, Joint position, Fine touch
–Name/Level of Decussation: Internal Arcuate Fibers (Lower Medulla) - Anterolateral Pathway
–Function: Pain, Temp., Crude touch
–Name/Level of Decussation: Anterior Commissure (Spinal Cord)
With Sensory Reception in the PNS, what do Merkel’s Receptors sense?
2-Point Discrimination
With Sensory Reception in the PNS, what do Pacinian receptors sense?
Vibration
With Sensory Reception in the PNS, what do Bare Nerve ending/Free nerve endings sense?
Pain and Temperature
With Sensory Reception in the PNS, what do Corpuscle of Ruffini endings sense?
Stretch of the skin
What is the function of Meissner’s Corpuscles of the DCML?
Discriminative touch
What is the function of Merkel’s Disc of the DCML?
Pressure
With different Nerve Fiber types, which one travels the fastest?
A-Alpha (Group 1), these are bigger and myelinated
With different Nerve Fiber types, which one travels the slowest?
C (Group 4), these are smaller and not myelinated
In the Thalamus, what are the Main Nuclear Divisions?
- Anterior Nuclear Group
- Medial Nuclear Group (Mediodorsal Nucleus)
- Lateral Nuclear Group
- Intralaminar Nuclei (This divides the medial and lateral nuclear group)
- Midline Thalamic Group
- Thalamic Reticular Nucleus (The thin sheet the envelopes the lateral aspect of the thalamus)
What are the Major functions of the Thalamus?
- Integration and relay of sensory information
- Integration and relay of motor control information from cerebellum and basal ganglia to the motor cortex
- Gating of passage of sensory and motor information
- Transmit states of consciousness from brainstem to cortex
With the Main Categories of Thalamic Nuclei, what are the 2 different Relay Nuclei and their roles??
They relay information
Specific Relay Nuclei
- Projections to the primary sensory and motor areas
- Nuclei mainly in the lateral thalamus
- VPL (Ventral Posterior Lateral), PM, LGN (Lateral Geniculate Nucleus), MGN (Medial Geniculate Nucleus), anterior nucleus
Widely Projecting (Nonspecific Nuclei)
Tends to be more Medial Dorsal
- Projections to large regions of association involved in behavioral orientation towards stimuli
- Pulvinar, MD (Mediodorsal Nucleus)
With the Main Categories of Thalamic Nuclei, Where does the Intralaminar Nuclei lie and whats its function?
- Lies within the Internal Medullary Lamina
- Main inputs and outputs with the basal ganglia
With the Main Categories of Thalamic Nuclei, What is the Reticular Nucleus and its function?
- This is a thin sheet lateral to thalamus and medial to internal capsule
- DOES NOT project to the cortex, Inputs and Outputs within the thalamus
What is the Reciprocal Connection with the Ventral Anterior (VA) with the Cortex?
VA is connected with the Frontal Cortex
What is the Reciprocal Connection with Lateral Dorsal (LD) and the Anterior Nuclear Group (Ant.) with the cortex?
LD and Ant. are connected with the Cingulate Gyrus
What is the Reciprocal Connection with Ventral Lateral (VL) with the cortex?
VL is connected with Motor and Premotor Cortex
What is the Reciprocal Connection with Ventral Posterior Lateral (VPL) and Ventral Posterior Medial (VPM) with the cortex?
VPL and VPM are connected with the Somatosensory cortex
What is the Reciprocal Connection with Mediodorsal Nucleus (MD) with the cortex?
MD is connected with the Prefrontal Cortex
What is the Reciprocal Connection with Intralaminar Nucleus (IN) with cortex?
IN is connected with widespread cortical regions of the cortex
What is the Reciprocal Connection with the Lateral Geniculate Nucleus (LGN) with the cortex?
LGN is connected with the Visual Cortex
What is the Reciprocal Connection with the Medial Geniculate Nucleus (MGN) with the cortex?
The MGN is connected with the Auditory Cortex
What is the 1st order neuron of the DCML pathway?
- The receptor (Vibration, proprioception, light tough) enters the dorsal root.
- Which then enters the Ipsilateral posterior/dorsal column
(Fasciculus Gracilis- below T6-LE
Fasciculus cuneatus- above T6-UE) - This then travels up the spinal cord to the Closed Caudal/lower Medulla and here we see the first synapse from:
–Nucleus Gracilis (T6 and below) or
–Nucleus Cuneatus (T6 and above)
What is the 2nd order neuron of the DCML pathway?
Once synapse occurs in the Nucleus Gracilis or Cuneatus
- Axons cross to the contralateral side via the Internal Arcuate Fibers (In Caudal/lower Medulla)
- Information then travels in the Medial Lemniscus
- This then synapses with the Ventral Posterior Lateral (VPL) of the Thalamus
What is the 3rd order neuron of the DCML pathway?
- This starts in the Ventral Posterior Lateral (VPL) in the thalamus
- This then travels through the posterior limb of the Internal capsule
- Then its Final Synapse is in the appropriate area of the homunculus in the somatosensory cortex, UE lateral and LE medial
What is the 1st order neuron of the Lateral Spinothalamic Tract pathway?
- The receptor (Pain, Temp, crude touch) enter the dorsal root
- This then synapses immediately in the gray matter of the spinal cord, this occurs in the:
–Marginal Zone/Rexed’s Laminae I
–Neck of Dorsal Horn/Rexed’s Laminae V
–Some collaterals ascend and descend in Lissauer’s tract
What is the 2nd order neuron of the Lateral Spinothalamic Tract pathway?
- This starts in the dorsal horn and cross to contralateral side via the Anterior/Ventral Commissure
- This info then travels in the Anterolateral spinothalamic tract
Once it reaches above the Medulla the tract is called Spinal Lemniscus - This then synapses in the Thalamus in the:
–VPL nucleus: A pain (acute/sharp pain)
or
–Intralaminar and Mediodorsal Nuclei: C pain (Chronic pain)
What is the 3rd order neuron of the Lateral Spinothalamic Tract pathway?
- This starts in the Thalamus:
–VPL nucleus: A pain (acute/sharp pain)
or
–Intralaminar and Mediodorsal Nuclei: C pain (Chronic pain) - This then travels to the Cerebral Cortex
–A pain through the internal capsule to somatosensory area
–C pain though limbic cortex and somatosensory cortex
What is the Tract of Lissauer?
What would be affected with a lesion?
This is formed by the A-delta fibers: Pain and Temp.
- The fibers ascend and descend 2 or 3 levels of the spinal cord (Ipsilateral)
- They decussate in the white matter of the spinal cord behind the anterior median fissure
- A lesion will affect the contralateral side - 2 or 3 segments down and the ipsilateral side at the level of damage
