Lecture 9: Somatosensory Pathways Part 1 Flashcards
What information does the PCML and trigeminothalamic pathway transmit?
Discriminative Touch
Pressure
Vibration
Proprioception
What is two point discrimination?
Ability to discriminate between two stimuli simultaneously
What areas would have high density of tactile receptors?
Digits
Perioral region
What areas would have low density of tactile receptors?
Back
Small receptive fields have ____ receptor density.
Large receptive fields have ____ receptor density.
Small receptive fields have HIGH receptor density.
Large receptive fields have LOW receptor density.
What type of axons are primary afferent fibers?
Sensory
Where do primary afferent fibers have their cell bodies?
Dorsal Root Ganglion
In the PCML pathway, where do primary afferent fibers enter the spinal cord?
Medial division of posterior root
In the PCML pathway, where do primary afferent fibers travel after entering the spinal cord via the posterior root?
Posterior Columns: Fasciculus Gracilis and Cuneatus
Where is Fasciculus Gracilis found (both generally in the SC and in an SC cross section)?
Found in whole spinal cord but receives input from sacral Region to T6 (located medially)
Where is Fasciculus Cuneatus found (both generally in the SC and in an SC cross section)?
T6 and above (located laterally)
Which fibers are found more medially?
Sacral and the more rostral you go, the more lateral those fibers are found
What supplies the posterior columns?
Posterior Spinal Artery
If the PCML pathway is affected from a spinal cord lesion, what can happen?
Ipsilateral reduction or loss of discriminative, positional, and vibratory tactile sensations
Will happen at and below level of injury
What is sensory ataxia?
Loss of muscle tendon reflex and proprioceptive losses from extremities due to lack of sensory input
Can lead to difficulty walking and wide based stance
In the PCML pathway, where are 2nd order neurons found?
Gracile and Cuneate Nuclei in the posterior medulla
Where are the gracile and cuneate nuclei receiving their input from?
First order neurons (primary afferents) from ipsilateral dorsal root ganglion
What are internal arcuate fibers?
After synapsing at the gracile and cuneate nuclei, they are the fibers that cross anteromedially in the medulla
What is medial lemniscus?
The new name of the fibers after they cross at the medulla until they terminate
In the medial lemniscus, where do the upper and lower extremity fibers now reside after the rotation in the pons?
Upper: Medial
Lower: Lateral
Where does the medial lemniscus terminate?
Ventral Posterolateral Nucleus of the Thalamus
What supplies the medial lemniscus?
Anterior Spinal Artery
What supplies the Ventral Posterolateral Nucleus of the Thalamus?
Thalamogeniculate Branches of Posterior Cerebral Artery
From the Ventral Posterolateral Nucleus of the Thalamus, where do the third order neurons go to?
Primary and Secondary Somatosensory Cortices
