Autonomic and Somatic Efferent Pathways | Animals | Pharmacology

This article will help you to differentiate between autonomic and somatic efferent pathways.

Difference # Autonomic:

1. Two neurons (pre and postganglionic) are arranged in series to supply smooth mus­cles and glands.

2. The autonomic nerves contain peripheral ganglia.

3. Preganglionic nerves are myelinated and postganglionic nerves are non-myelinated.

4. Some level of spontaneous activity of an organ is maintained even after nerve sec­tion.

5. Peripheral nerve plexuses are present.

6. Neurotransmitters are acetylcholine (in ganglia and parasympathetic neuro-effector junctions) and noradrenaline (at sym­pathetic neuro-effector junctions).

Difference # Somatic:

1. Single Moto neuron connects CNS to the skeletal muscles.

2. The somatic nerves contain no peripheral ganglia; the synapses are located entirely within the CNS.

3. Nerve fibres are myelinated.

4. Section of nerve causes paralysis and atrophy of the skeletal muscles.

5. Peripheral nerve plexuses are absent.

6. Neurotransmitter is acetylcholine at neuromuscular junctions.

The efferent segment of the ANS, is divided into two main components-the sympathetic or adrenergic or thoracolumbar outflow and the parasympathetic or cholinergic or craniosacral outflow. Another component of the ANS is enteric nervous system, consisting of intrinsic nerve plexuses of the GIT, which is closely intercon­nected with the sympathetic and parasympathetic systems.

The sympathetic and parasympathetic systems can function only after receiving the outputs from the CNS, whereas the enteric nervous system receives inputs from sympathetic and parasympathetic systems, but can act on its own to control the motor and secretory functions of the intestine without any output from the CNS.

The sympathetic and parasympathetic nerves consist of two neurons in series. The nerves, which connect CNS to the ganglia, are called preganglionic and those, which communicate ganglia to the organs, are postganglionic nerve fibres. Ganglia contains the nerve endings of the preganglionic fibres and cell bodies of the postganglionic fibers.

Generally, the sympathetic and parasympathetic nerves are func­tionally antagonistic to each other and both are received by most of the visceral organs. The net result of action depends upon the dominancy or number of their receptors present in an organ.