Difference Between Somatic and Autonomic Nervous System

Somatic vs Autonomic Nervous System

The nervous system lets organisms feel the glory of life, and it functions through signal transferring throughout the body to control its movements and other activities. The nervous system is composed of central processing unit/s (brain and spinal cord) called Central Nervous System and the Peripheral Nervous system. Somatic and autonomic nervous systems are the two main components of the peripheral nervous system based on the capability to manage the movements of the muscles voluntarily. This article reviews the most important and interesting differences exhibited between somatic and autonomic nervous systems.

Somatic Nervous System

Somatic nervous system (SONS) is also known as the Voluntary nervous system. The SONS is capable of managing the movements of the skeletal muscles voluntarily. There are efferent nerves present in the SONS to stimulate muscle contractions. All the voluntary movements in the skeletal muscles are controlled by the SONS. However, the reflex arcs are not controlled by this system. It is important to consider the pathway of the nerve signals where those begin at upper motor neurons in the precentral gyrus. The initial stimulus from the precentral gyrus (acetylcholine) is transmitted through the upper motor neuron and corticospinal tract. Then, it proceeds down through axons and finally reaches the skeletal muscle at the neuromuscular junction. At this junction, the release of acetylcholine from the terminal knobs of the axon takes place and nicotinic acetylcholine receptors of skeletal muscles relay the stimulus to contract the whole muscle. Acetylcholine is termed as an excitatory neurotransmitter, which is present in both vertebrates and invertebrates. However, the invertebrates sometimes have inhibitory neurotransmitters in their somatic nervous system. Despite the ability to move the skeletal muscles very smoothly through the SONS, the reflex arc is an involuntary neural circuit that controls the skeletal muscles.

Autonomic Nervous System

Autonomic nervous system (ANS) is also known as the visceral or involuntary nervous system that controls the most essential muscular movements to sustain the life of an animal. Contraction of cardiac muscles to beat the all-important heart, most parts of the digestive tract, regulation of respiratory function, maintenance of the size of pupil, and sexual stimulation are some of the major functions governed by the ANS. Despite the fact that ANS regulates involuntary actions, respiration can be controlled with some consciousness. Based on the function of the ANS, there are two main subsystems known as afferent (sensory) and efferent (motor). The presence of both excitatory and inhibitory synapses regulates the proper functionality of the ANS in the body of animals. Sympathetic and Parasympathetic nervous systems are the two main functional modules in the ANS. The sympathetic module is important for ‘fight or flight’ activity, as it promotes a very high blood supply to the skeletal muscles, increases heart rate, and inhibits peristalsis and digestion. The parasympathetic nervous system promotes the ‘rest and digest’ phenomenon; dilation of blood vessels to the digestive tract is one of the things managed by this subsystem.


What is the difference between Somatic and Autonomic Nervous System?

• SONS can be voluntarily manageable while ANS is involuntary.

• ANS accounts for more muscular movements than SONS would govern.

• Functions of ANS are more complex compared to SONS signalling pathways.

• In vertebrates, SONS involves excitatory neurotransmitters while ANS has both excitatory and inhibitory neurotransmitters.

• ANS acts on smooth muscles, cardiac muscles, and glands whereas SONS acts always on skeletal muscles.

• SONS needs only one efferent neuron while ANS should have two efferent neurons and ganglia to transmit a signal.