Neuroanatomy Exam 2 - Touch Pathways 1

What structure makes up the dorsal column from T6 and below?

fasciculus gracilis

What structure makes up the dorsal column from above T6?

fasciculus gracilis
fasciculus cuneatus

True/False
The medial lemniscus is found in each brainstem region.

true

What is the orientation of the medial lemniscus in the midbrain?

vertical

What is the orientation of the medial lemniscus in the pons?

horizontal

What is the orientation of the medial lemniscus in the medulla?

vertical

What information does the dorsal column medial lemniscus pathway carry?

discriminative touch information from the BODY

What does discriminative touch include?

pressure
vibration
proprioception

What are some of the characteristics of the receptors of the DCML pathway?

- high # sensory units
- small receptive fields
- better localization
- high degree of sensation in fingers, mouth

For a stimulus to reach consciousness, the signal needs to reach the _______

cortex

Crude awareness may be possible if the signal reaches the ________, but a meaningful awareness and any ability to discriminate the stimulus requires that the signal reaches the _________

thalamus, cortex

What does high fidelity do?

provide accurate information about the location of stimulation; a somatotopic map is created

How many neurons are in this pathway?

3 neurons

First order projects from where to where

peripheral receptor to brainstem

Second order projects from where to where

brainstem to thalamus

Third order projects from where to where

thalamus to cerebral hemispheres

Where does the 1st neuron begin?

begins in the peripheral receptor

Where is the cell body of the 1st neuron?

cell body in DRG

Where does the 1st neuron travel?

ascend in fasciculus gracilis (T6 and below) or fasciculus cuneatus (above T6)

Where does the 1st neuron synapse?

nucleus gracilis or cuneatus in lower medulla

Where is the cell body of the 2nd neuron?

in nucleus gracilis or cuneatus

Where does the 2nd neuron ascend?

in contra medial lemniscus

Where does the 2nd neuron synapse?

VPL in thalamus

Where is the cell body for the 3rd neuron?

VPL of thalamus

Where does the 3rd neuron pass?

pass through internal capsule (posterior limb)

Where does the 3rd neuron project to?

primary somatosensory cortex in parietal lobe

Where in the brain does the pathway cross?

lower medulla

What happens if you cut sensory path before it crosses?

signs and symptoms will be ipsilateral

What happen if you cut sensory pathway after it crosses?

signs and symptoms contralateral to lesion