It carries pain, temperature and crude touch from the body. Its fibres cross the midline in the spinal cord, then climb through the medulla, pons and midbrain to the thalamus, which relays them to the postcentral gyrus, the primary somatosensory cortex. [1][2]
A tract has no shape of its own in this atlas; lit: the parts it runs through, in order.
The 3D brain needs JavaScript. The steps below still say where the spinothalamic tract runs, in order.
The brain starts seen from the left, a little from the front and below, so the brainstem the fibres climb and the gyrus they reach behind the central sulcus both show. Step through lights one step at a time, about 1.2 s each, bottom to top; tap a step below to light it alone. Drag to turn, pinch or scroll to zoom. Step through is off because your device asks for reduced motion; tap each step instead.
Each step lights the whole part, not the narrow course of the fibres inside it. At the first step the atlas has only the top of the spinal cord, drawn as its thin central canal, so the dorsal horn and the crossing are not drawn; the thalamus is lit whole, though the fibres end in one nucleus of it. [3][1]
The route, in 6 steps
Pain, temperature and crude-touch fibres, whose cell bodies sit in the dorsal root ganglia, enter the spinal cord through the dorsal roots. They may run up or down a segment or two in the dorsolateral tract of Lissauer, then synapse on second-order neurons in the grey matter of the dorsal horn. [1][2]Where is the spinal cord?
Crossing in the spinal cord: the second-order axons cross the midline in the anterior white commissure, within one or two segments of where the fibres came in, and climb the opposite side of the cord in its anterolateral white matter, as the lateral spinothalamic tract (pain and temperature) and the anterior spinothalamic tract (crude touch and pressure). So from the cord upward, each side carries pain and temperature from the opposite half of the body. The atlas has no shape for the crossing, so it is not marked. [1][2]
Already crossed, the fibres climb through the outer (lateral) part of the medulla without a synapse. On the way through the brainstem some fibres of the anterolateral system leave for the reticular formation (the spinoreticular fibres), which is concerned with arousal. [1][4]Where is the medulla oblongata?
The tract runs on up through the tegmentum of the pons, its back part, behind the basilar part where the corticospinal tract runs down. [1][5]Where is the pons?
In the midbrain the fibres run up the side of the tegmentum, close to the medial lemniscus. Some anterolateral fibres end here instead, in the periaqueductal grey and the superior colliculus (the spinomesencephalic fibres). [4][1]Where is the midbrain?
The tract ends in the thalamus, mainly in its ventral posterolateral (VPL) nucleus, the same relay the dorsal column pathway uses. The third-order neurons start here. [1][6]Where is the thalamus?
The third-order axons climb through the posterior limb of the internal capsule to the primary somatosensory cortex of the postcentral gyrus, which maps the opposite half of the body: the leg near the midline at the top, the hand and face lower down the side. [1][7][2]Where is the postcentral gyrus?
How it differs from the dorsal column–medial lemniscus pathway: the spinothalamic tract carries pain, temperature and crude touch, and its second-order fibres cross in the spinal cord, within a segment or two of where they enter; the dorsal column pathway carries fine touch, vibration and limb position, and crosses only in the medulla. Both relay in the ventral posterolateral nucleus of the thalamus and end in the postcentral gyrus. [1][8][2]Where does the dorsal column–medial lemniscus pathway run?
It has two divisions: the lateral spinothalamic tract carries pain and temperature, the anterior spinothalamic tract crude touch and pressure. [1]
It is a chain of three neurons: dorsal root ganglion to dorsal horn, dorsal horn to thalamus, thalamus to cortex. [1][2]
It is the main tract of the anterolateral system, which also holds the spinoreticular and spinomesencephalic fibres that end in the brainstem rather than the thalamus. [4]
Pain and temperature from the face take a parallel route through the trigeminal nerve to a neighbouring relay, the ventral posteromedial (VPM) nucleus of the thalamus. [6][4]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); it has no shape for tracts, so a pathway is shown by the parts it runs through.