ANS- Anatomy and Functions of sympathetic and parasympathetic N.S.
Sympathetic N.S.
Preganglionic fibres originate from cell bodies in the grey matter of the lateral horn of the spinal
cord between the first thoracic segment down to the second or third lumbar segment (T1 to
L2/3). The so-called thoraco-lumbar outflow. These preganglionic fibres synapse with the post-
ganglionic neurones in the ganglia of the sympathetic chain. The ganglia form the sympathetic
chain arranged as two paravertebral chains. The post-ganglionic fibres leave the ganglia and join
the spinal nerves or visceral nerves to innervate the target organs.
Parasympathetic N.S.
Preganglionic fibres arise from the CNS from both the cranial (from brain stem) and sacral
nerves called craniosacral outflow. Cranial parasympathetic fibres arise from brainstem motor
nuclei of the 3rd, 7th, 9th, and 10th cranial nerves. Sacral outflow arises from the second, third,
and fourth sacral segments of the spinal cord. Fibres emerge from ventral rami of nerves S24
and form the pelvic splanchnic nerves.