60. (i) Name the parts labelled 1, 2 and 3. (Type in the parts separated by commas. Leave no spaces around the commas.)   61. (ii) State the main functions of the parts labelled 1 and 2.   62. (iii) How are the brain cells arranged in the part labelled '1'?   63. (iv) What is the structural and functional unit of the nervous system?   64. (v) Name the fluid that surrounds the brain. State its function.