question_answer 2)

Compare the following (a) Central Neural System (CNS) and Peripheral Neural System (PNS) (b) Resting potential and action potential (c) Choroid and retina  

Answer:

Comparison between Central Neural System (CNS) and Peripheral Neural System (PNS) The 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). The nerve fibres of the PNS are of two types (i) Afferent fibres (ii) Efferent fibres (b) Comparison between Resting Potential and Action Potential The electrical potential difference across the resting plasma membrane A is called the resting potential. The electrical potential difference across the plasma membrane at the site A is called the action potential, which is in fact termed as a nerve impulse. (c) Comparison between Choroid and Retina The middle layer of eye ball which contains many blood vessels and looks bluish in colour is known as choroid. The choroid layer is thin over the posterior two-thirds of the eye ball, but it becomes thick in the anterior part to form the ciliary body. The ciliary body itself continues forward to form a pigmented and opaque structure called the iris. Retina is the inner layer of eye ball and it contains three layers of cell from inside to outside, i.e., ganglion cells, bipolar cells and photoreceptor cells. There are two types of photoreceptor cells, namely, rods and cones. These cells contain the light-sensitive proteins called the photopigments.