ABSTRACT
Stimuli that give rise to different sensory modalities such as touch, pressure, pain and temperature are carried to the somatosensory cortex in afferent pathways consisting of three neurons. The primary afferent neuron carries an action potential from a sensory receptor to the dorsal horn of the spinal cord or the medulla oblongata. The secondary neuron carries the action potential further from the dorsal horn to the thalamus. The tertiary or third-order neuron carries the action potential from the thalamus to the somatosensory cortex. See Figure 14.1.
