Spinal Nerves:
In rabbit there are 37 pairs of spinal nerves, while in frog there are 9 or 10 pairs of spinal- nerves.
In Human only 31 pairs of spinal- nerves are found. Each spinal nerve is mixed type and arises from the roots of the horns of gray matter of the spinal cord.
In dorsal root only afferent or sensory fibres and in ventral root efferent or motor fibres are found.
Both the roots after moving for distance in the spinal cord of vertebrates combine with each other and come out from the Inter verterbal for a men in the form of spinal nerves.
Spinal Nerves : The term spinal nerves generally refers to a mixed spinal nerve, which carries motor sensory and automatic signals between the spinal cord and the body. Humans have left - right pairs of spinal nerves corresponding to the segment of vertebral column.
Outside the vertebral column the nerve divides into branches.
Spinal nerves take their origin from spinal cord. All of them are mixed nerves having both sensory and motor fibres. The sensory fibres originate from the dorsal horn of the spinal cord. They carry information from organs to spinal cord. The motor fibres take their origin from the ventral horns of the spinal cord. These supply information required for the movement of the muscles.