Dorsal Column Medial Lemniscus Flashcards
What is the dorsal column medial lemniscus (DCML) system for?
Two point discrimination
Vibratory sense
Conscious muscle joint sense
What are the damn receptors involved in DCML system?
Meissner corpuscles
Pacinian corpuscles
Muscle spindles and tendon organs
Where is the cell body of the first order neuron located in the DCML system?
Dorsal root ganglion
Where does the first order neuron go?
The axon enter the dorsal white column ipsilaterally and divide into long ascending and short descending fibers.
What are ascending fibers and where do they go?
They synapse with internuncial neurons and in the anterior horn cells. Some of them ascend and form the fasciculi.
What are descending fibers?
They’re short and they give collateral branches that synapse with the internuncial neurons or the anterior horn cells.
What is the function of ascending and descending fibers?
Intersegmental reflexes
What is fasciculus gracilis?
They are the ascending fibers from sacral, lumbar and lower six thoracic spinal nerves.
They are present throughout the length of spinal cord.
It is medial to the fasciculus cuneatus.
What is fasciculus cuneatus?
They are ascending fibers from upper thoracic and cervical segments only.
It is lateral to the fasciculus gracilis.
What is the difference between fasciculi cuneatus and gracilis?
Fasciculus gracilis carry sensations from below the level of T6 while fasciculus cuneatus carry sensations from above T6. They both are separated by a septum.
Where is the second order neuron located?
Nuclei gracilis and cuneatus of medulla
Where does second synapse occur?
Ipsilaterally in the nuclei gracilis and cuneatus of medulla
What are the internal arcuate fibers?
The fibers from the nuclei cuneatus and gracilis decussate and ascend as medial lemniscus through brainstem.
Where does the decussation happens?
After the nuclei cuneatus and gracilis
Where does the third synapse occur?
Ventral posterolateral nucleus of the thalamus.
