Illustration of a cross-section through a healthy human brain. The large arching structure at centre is the corpus callosum, which facilitates communication between the hemispheres. The smaller curved structure is the fornix, which passes signals to the hypothalamus from the hippocampus. At bottom right is the cerebellum, which controls voluntary muscular movement and maintains posture and balance. To the left of the cerebellum is the brainstem, which controls subconscious functions such as breathing and the regulation of heart rate, and also connects the brain to the spinal cord.