1. Somatosensory Pathways
Lecture No 7

2. Ability to Determine Stimulus
Precisely where on the body a specific stimulus originated depends on the projection of information from the thalamus to the primary sensory cortex
Sensory Homunculus

3. 3 Major Somatic Sensory Pathways
The dorsal( posterior) column pathway
The anterolateral pathway
The spinocerebellar pathway

4. Posterior Column Pathway
Carries sensations of highly localized (“fine”) touch, pressure, vibration, and proprioception
Figure 15–5a

5. The Anterolateral Pathway
Provides sensations of “light” touch, pain, and temperature
Ascend within the anterior or lateral spinothalamic tracts:
the anterior spinothalamic tracts carry light touch
The lateral spinothalamic tracts carry pain and temperature sensations

6. Strong Visceral Pain aka Referred pain
An individual can feel pain in uninjured part of body when pain actually originates at another location
Sensations arriving at segment of spinal cord can stimulate interneurons that are part of anterolateral pathway
Activity in interneurons leads to stimulation of primary sensory cortex, so an individual feels pain in specific part of body surface:

7. The Spinocerebellar Pathway
Cerebellum receives proprioceptive information about position of skeletal muscles, tendons, and joints
Figure 15–7

8. Thank you