PNB 2264 Lecture Notes - Lecture 18: Reticular Formation, Midbrain Tectum, Superior Colliculus
16 Aug 2018
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Spinal cord ascending (afferent) and descending (efferent) tracts. Discovered through lesions (damage) and loss of function. Major sensory tract conscious perception of cutaneous stimulation (stroking the skin) Convergence less precise spatial information: touch, pain, temp, pressure, tickle and itch. 3 neurons in sequence: 1st (dorsal ganglion) project to skin; synapse on inter neuron 2nd cell bodies. Contralateral ascension 3rd cell body in thalamus sensory cortex lesions no interruption due to collateral fibers ipsilateral (same side) contralateral (other side) Clinical example left side cord damage loss of pain and temp sensation below that point form right side of body (contralateral) Dorsal-column/medial lemniscal tracts internal, pressure, vibration, proprioception, two-point discrimination. Divided into fasciculus gracilis (bottom) and cuneatus (top) 1st (dorsal root ganglion) ascent ipsilaterally 2nd in medulla (gracilis and cuneatus nuclei) ascent through lemniscus 3rd thalamus sensory cortex. Fasciculus fasciculus gracilis: sensory input below the mid-thoracic area fasciculus cuneatus, above the mid-thoracic area.
