(a) The central neural system (CNS) includes the brain and the spinal cord and is the – site of information processing and control. The PNS comprises of all the nerves of the body associated with the CNS (brain and spinal cord).
(b) Resting potential is the electrical potential difference across the resting plasma membrane. Here the outer surface of the axonal membrane is positively charged and inner surface is negatively charged and therefore is polarised.
The electrical potential difference across the plasma membrane, when the membrane is depolarised is called the action potential. Here the outer membrane is negatively charged and inner membrane is positively charged.
(c) Choroid layer is the middle layer of eye and is brownish black in colour. It is highly vascular and have pigments known as melanocytes which give colour to eye. Retina is the inner most and incomplete layer that extends up to ciliary body. The outer most layer of retina has two types of cells namely rods and cones.
