The cerebellum is at the back of the head, at the bottom of the brain: tucked under the back of the cerebral hemispheres and behind the brainstem, in the posterior cranial fossa of the skull. [1]
The 3D brain needs JavaScript. The text below still says where the cerebellum is and what it does.
Slice
Opens cut by a side (sagittal) slice through the cerebellum. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
In the posterior cranial fossa, the deep hollow at the back of the base of the skull. [1]
It looks like a separate structure attached to the bottom of the brain, tucked underneath the cerebral hemispheres, and is separated from them by a sheet of tough dura mater, the cerebellar tentorium (tentorium cerebelli). The cerebrum lies above that sheet, the cerebellum below it. [1][2]
It sits on the back (posterior) surface of the brainstem. [3]
A single structure on the midline with two cerebellar hemispheres, joined by a narrow middle zone, the vermis. [1]
What it does
It does not start movements; it contributes to coordination, precision and accurate timing, combining input from the spinal cord’s sensory systems and other parts of the brain to fine-tune motor activity. [1]
It compares what the cerebrum commanded with sensory feedback about what actually happened. When the motor cortex starts walking, for example, feedback from muscles and joints lets the cerebellum check and adjust the movement. [3]
It also plays a role in cognitive functions such as attention and language, and in regulating fear and pleasure responses, though its movement roles are the most solidly established. [1]
It contains more neurons than the rest of the brain combined, mostly tiny granule cells, yet takes up only about 10% of the brain’s volume. [1]
Connections
Three paired cerebellar peduncles connect it to the rest of the nervous system, and all of its connections with other parts of the brain travel through the pons. [1]
Superior cerebellar peduncle: mainly output, carrying fibres via the thalamus to the cerebral cortex. [1]
Middle cerebellar peduncle: input from the pons, mainly from the pontine nuclei. [1]
Inferior cerebellar peduncle: input from the vestibular nuclei, the spinal cord and the tegmentum. [1]
Inside it
The surface is a thin, continuous layer of cortex folded like an accordion into fine parallel grooves; its key neurons are Purkinje cells and granule cells. [1]
The white matter inside is called the arbor vitae (“tree of life”) for its branching look in cross-section, and holds four deep cerebellar nuclei of grey matter. [1]
Other names
Latin for “little brain”: a diminutive of cerebrum. Plural: cerebella or cerebellums. [1]
Size
About 10% of total brain volume, while holding more neurons than the rest of the brain. [1]
On this model the cerebellum measures about 56 mm front to back, 53 mm top to bottom and 106 mm side to side (the box it fits in, not its volume). [4]
Centre of the cerebellum compared with the centre of the brainstem: 33 mm further back, 5 mm lower; 33 mm apart in a straight line. [4]
Centre of the cerebellum compared with the centre of the left occipital lobe: 27 mm further forward, 30 mm lower, 18 mm closer to the midline; 44 mm apart in a straight line. [4]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.