Somatosensory Pathways Lecture No 7

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

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

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

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:

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

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