Side by side
| Compared | Cerebellum | Brainstem |
|---|---|---|
| Where it is | At the back of the head, under the occipital lobes and behind the pons and medulla, separated from the cerebrum above by a sheet of dura, the tentorium cerebelli. [2][4] | The stalk in front of the cerebellum: the midbrain at the top, the pons in the middle and the medulla oblongata at the bottom, continuing as the spinal cord at the foramen magnum. [1] |
| What it does | Coordinates movement and fine-tunes its timing and precision, and keeps balance and posture; it does not start movements, it adjusts them, and it takes part in learning motor skills. [2] | Carries the motor and sensory tracts between brain and body, holds the nuclei of cranial nerves III to XII and regulates breathing, heart rate and the sleep cycle. [1][5] |
| Connects with | Three pairs of cerebellar peduncles join it to the brainstem: the superior to the midbrain, the middle to the pons and the inferior to the medulla oblongata. [2][6][7][8] | Above, it joins the diencephalon (thalamus and hypothalamus); below, the spinal cord; the corticospinal tract runs down through all three of its sections. [1][9] |
| Size measured from the model | 56 mm front to back, 53 mm top to bottom, 106 mm side to side [3] | 46 mm front to back, 81 mm top to bottom, 42 mm side to side [3] |
Size is the box each part fits in on this one model (cerebellum; brainstem), not its volume. Real brains vary.
How far apart are they?
Measured from the model [3], from the cerebellum to the brainstem:
- Centre to centre: 33 mm in a straight line.
- The centre of the brainstem is 33 mm further forward, 5 mm higher and the same distance from the midline than the centre of the cerebellum.
- Nearest points of the two shapes: under 1 mm apart.
A “centre” here is the average position of the points on the part’s 3D surface, so for a curved part such as a C shape it can sit outside the part itself. The nearest-points figure is measured between the corners of the simplified meshes, so a gap of 2 or 3 mm or less is within the model’s coarseness: read it as “touching or nearly so”.
How to tell them apart
- The cerebellum is not part of the brainstem, though it is part of the hindbrain: the hindbrain is the pons, the medulla oblongata and the cerebellum together. [10][1]
- The fourth ventricle lies between them: the pons and medulla form its floor and the cerebellum its roof. [11]
- The cerebellum’s surface is packed with fine parallel folds (folia), with two hemispheres joined by the midline vermis; the brainstem is a smooth column by comparison. [2]