Cerebellum Light micrograph of a crosssection through the cortex surface and medulla core of a lobe of a human cerebellum part of the brain It is highly folded with fissures white lines between its ridges lobules The cortex has a molecular layer orange which mainly consists of nerve fibre networks Beneath this is a layer of Purkinje nerve cells not seen here This lies over a granular layer red of nerve cells Beneath the cortex is the medulla black This contains white matter which consists of large nerve fibres axons The cerebellum controls body posture coordinates muscle movement balance Magnification x at mm size