Ascending pathways

Question 1

Describe the Dorsal column-medial lemniscus pathway.

Answer 1

Under the stimulus of touch, proprioception, and pressure.
1st order neuron:
input is conducted from the surface- to the dorsal ganglion to the dorsal root of the spinal cord.
It then enters the Posterior Funiculus (fasciculus gracilus or cuneatus).
continues on the axon until it reaches the medulla

2nd:
in the medulla, the 1st order terminates and gives rise to the 2nd order neuron (either the cutaneous or gracilis nucleus) that decussates prior to entering the medial lemniscus.
Continues to ascend in the medial lemniscus, past the medulla, and past the mesencephalon into the thalamus.

3rd:
The thalamus gives rise to the 3rd order neuron that carries the information/stimulus to the primary somatosensory cortex (postcentral gyrus)

Question 2

Describe the somatotopic organization in the DCML.

Answer 2

In the spinal cord: Fasciculus gracilis- lower body, Fasciculus cutaneus upper.
The somatotopic organization in the DCML pathway is such that sensory information from the lower parts of the body is transmitted to more medial regions of the brain, while sensory information from the upper parts of the body is transmitted to more lateral regions of the brain.

Question 3

Describe the columnar organization of the cerebral cortex and how efferent projections work.

Answer 3

levels:
2-3- Project other cortical areas, such as the motor.
4- input from thalamus becomes conscious
5- brainstem, spinal cord, basal ganglia
6- thalamus

Question 4

Describe the anterolateral pathway.

Answer 4

Usually pain and temperature
1st
many collaterals of axons
spreads to different regions of the brain

2nd
gives rise to the Ipsilateral anterolateral Tract and ascending fiber in the lissaurers tract.
Contralateral tract: the axon decussates over several segments within the spinal cord
In the medulla collaterals (spinoreticular fibers) attach to the reticular formation.
Mesencephalon: Gives rise to spinomesencephalic fibres and attaches onto superior colliculus via spinotectactal fibres.

3rd
in the thalamus the intralaminar thalamic nucleus (spinorecticular).
Spinothalamic to the VPL and P
relayed to different regions in the brain such as emotions and waking up.

Question 5

what are the functional properties of the Spinothalamic system?

Answer 5

provides for a less precise, less well-localized, more emotion
The affective component of the pain experience is due to the divergent projections of the spinothalamic system, especially those into the reticular formation, intralaminar thalamic nuclei, and limbic system

Question 6

What does the anterolateral pathway sense?

Answer 6

Pain, Temperature, Crude touch, pressure.