CH 7 part 1

What does the Primary Somatosensory Cortex (PSC) do?

Conscious perception of sensation from contralateral side of the body

What is Broca's area for PSC?

Areas 3, 1, 2

Lesion at PSC affects what?

Sensory deficits in contralateral side of body

What are the 2 parts of the Somatosensory Association Cortex?

Parietal Association Cortex and Secondary Somatosensory Area

Where is Parietal Association Cortex located?

Posterior to Primary Somatosensory Cortex

What is Broca's area for Parietal Association Cortex?

Area 5, 7

Where is Secondary Somatosensory Area located?

Superior margin of Sylvian Fissure called PARIETAL OPERCULUM

What is Parietal Association Cortex and Secondary Somatosensory Area involved in?

Higher order sensory processing

Lesions in Secondary Somatosensory Area affects what?

Deficits in higher order sensory processing

What is Somatic Sensation?

Conscious perception of Proprioception, Touch, Vibration, Pain, and Temp

What are the 2 main sensory pathways?

• Dorsal (Posterior) Column Pathways

• Anterolateral Pathway (Spinothalamic Tract)

What does Dorsal Column Pathway Convey?

Vibration, Jt Position (Proprioception), Fine/Discriminative Touch

Dorsal Column Pathway is AKA

Dorsal Column Medal Leminscus Pathway (DCML)

What does Anterolateral/Spinothalamic Pathway Convey?

Pain, Temp, Crude Touch

What is Pain?

An unpleasant sensory or emotional experience associated w or resembling that w actual or potential tissue

Dorsal Column and Anterolateral Pathway is a ___ neuron pathway?

3 Neuron

Sensory neuron fibers are classified by what?

Fiber diameter

What type of axons transmit sensory information faster than smaller diameter, unmyelinated axons?

Larger Diameter, Myelinated Axons

Sensory Neuron Fiber Types: What does A-Alpha and A-Beta pick up

• Dorsal Column Pathway

  • Propriception, Vibration, Superficial/Deep Touch

Sensory Neuron Fiber Types: What does A-8 (Gamma) and C fibers Pick up?

• Anterolateral/Spinothalamic Pathway

  • Pain, Temp, Itch

What is a Dorsal Root Ganglion (DRG)?

Cell Bodies

DRG axons bifurcate to produce what 2 long processes?

1. Carries sensory information in FROM periphery

2. Carries sensory information INTO the spinal cord through the dorsal root

Dorsal Column Pathway: Define Touch, how can you discriminate it? What else?

• Well localized

• Can be discriminative between 2 closely spaced points touching the skin

• Graduations of Intensity

Dorsal Column Pathway: Axon Structure

Large Diameter and Myelinated

Dorsal Column Pathway: What does the First Neuron (Primary Sensory Neuron) carry info INTO and TO? Ip

• INTO ipsilateral dorsal column (Fasciculus Gracilis/Cuneatus)

• Ascends TO inferior medulla

Dorsal Column Pathway: What does the Primary Sensory Neuron synapse at?

Synapse at Nucleus Gracilis or Cuneatus in the inferior medulla

Dorsal Column Pathway: Where do some axons collaterally synapse for the Primary Sensory Neuron?

On interneurons or motor neurons in gray matter of SC

Dorsal Column Pathway: Is Dorsal Column Pathway somatotopically organized?

YAASSS

Dorsal Column Pathway: What information does Fasciculus Gracilis ("Thin") carry?

Info from legs and lower trunk (T7-12)

Dorsal Column Pathway: What information does Fasciculus Cuneatus ("Wedge") carry?

Info from arms, neck and upper trunk (T1-T6)

Dorsal Column Pathway: For the Second Neuron, the decussation is AKA?

Internal Arcuate Fibers (at Inferior Medulla)

Dorsal Column Pathway: For the Second Neuron, these fibers then travel up to the thalamus and become known as what?

Medial Lemniscus

Dorsal Column Pathway: Where do Secondary Neurons synapse?

Ventral Posterior Lateral Nucleus (Thalamus)

Dorsal Column Pathway: Where does Third Neuron travel after passing thru Ventral Posterior Lateral Nucleus?

TO the Posterior limb of the Internal capsule

Dorsal Column Pathway: How does the Third Neuron reach the Internal Capsule?

Somatosensory Radiations (Medial to Corticospinal Tract)

Dorsal Column Pathway: After reaching the Internal Capsule, where does the Third Neuron ascend?

TO Primary Somatosensory Cortex (POST Central Gyrus)

Spinothalamic Tract: What type of function does it have?

Protective

Spinothalamic Tract: Axon Structure

• Small diameter

• Unmyelinated and Myelinated Axons

Spinothalamic Tract: What are the 3 pathways of the Spinothalamic Tract?

• Spinothalamic (Conscious)

• Spinoreticiular

• Spinomesencephalic

Spinothalamic Tract: Where does the First Neuron (Primary Sensory Neuron) carry info INTO?

Dorsal horn of SC

Spinothalamic Tract: Where do some First Neuron axons ascend or descend?

A level to enter Lissauer's tract before entering gray matter at the dorsal root entry zone

Spinothalamic Tract: What does the First Neuron Synapse in?

Dorsal Horn (Laminae 1 and 5)

Spinothalamic Tract: Does the Second Neuron cross over IMMEDIATELY to the opposite side of SC?

NOOOOOOOOOOOOOOO

Spinothalamic Tract: How many spinal segments does it take for Second Neuron to ascend in the Anterior Commissure to cross over to other side of SC?

~ 2-3 Spinal Segments

Spinothalamic Tract: After ascending to Anterior Commissure to cross over to other side of SC, what happens to the Secondary Neuron?

Enters the Anterolateral Pathway (Spinothalamic Tract)

Spinothalamic Tract: After the Second Neuron enter the Anterolateral Pathway, what does it synapse w?

Ventral Posterior Lateral Nucleus (Thalamus)

Spinothalamic Tract: In the Second Neuron, there are also axons that synapse where?

Intralaminal Thalamic and Medial Thalamic Nuclei which project diffusely to entire cerebral cortex

What is the Intralaminar Thalamic and Medial Thalamic Nuclei involved in?

Arousal and Behavioral aspect of pain

Spinothalamic Tract: After passing through the Ventral Posterior Lateral Nucleus, where does the Their Neuron pass through? And how does it do it?

Posterior limb of internal capsule (via Somatosensory Radiations)

Spinothalamic Tract: After passing through the Internal Capsule, where does the Third Neuron Ascend?

Primary Somatosensory Cortex (POST Central Gyrus)

Summary Spinothalamic Tract: At every spinal level, how does the Secondary Neuron carry info to Spinothalamic Tract?

Climbs up a few segments in the anterior commissure to cross over to the other side of the SC to then enter the spinothalamic tract

Summary Spinothalamic Tract: What info is in the Spinothalamic Tract? How many segments below?

• Pain, Temp, and Crude Touch from opposite side of body...

• Beginning a few (2-3) segments below that SC

Example Spinothalamic Tract: What info is carried in the L Spinothalamic Tract at the C4 SC Level?

Right-sided pain, temperature and crude touch beginning a few segments below the C4 SC level (from ~C6-C7 and below)

Example Spinothalamic Tract: What info is carried in the R Spinothalamic tract at the T8 SC Level?

L Sided pain, temp, and crude touch beginning a few segments below the T8 level (From T10-T11 and below)

Is Spinothalamic Tract Somatotopically Organized?

YASSSS