Corpus callosum is found in the brain of

Which nervous system can increase the rate of heart beat?

Statement-$I$: Fibres of the tracts are covered with the myelin sheath,which constitute the outer part of the cerebral hemisphere.
Statement-$II$: The hypothalamus contains a number of centres which control body temperature,urge for eating and drinking. In the light of the above statements,choose the most appropriate answer from the options given below:

Which structure consists of tracts of myelinated nerve fibres?

Assertion: Cerebellum has additional space for many more neurons.
Reason: Cerebellum has a very convoluted surface.

Cerebrospinal fluid $(CSF)$ is produced by