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Difference Between Somatic and Autonomic Nervous System

Somatic-vs-Autonomic

The nervous system is one of the most critical systems of the body. It picks up the signals from organs and generates a suitable action. The nervous system is classified into the central nervous system (CNS) and peripheral nervous system (PNS). The central nervous system comprises the brain and the spinal cord. At the same time, the peripheral nervous system consists of all nerves and neuromuscular junctions involved in the exchange of signals. Somatic and autonomic nervous systems are further branches of the peripheral nervous system. It may sound complicated, but here’s everything you need to know about the difference between somatic and autonomic nervous systems.

Comparison Table

CharacteristicSNSANS
DefinitionControls
voluntary functions
Controls
involuntary functions
TypesNo further typesSympathetic
& parasympathetic
MovementVoluntaryInvoluntary
Muscle TypeSkeletal musclesSmooth and
cardiac muscles
NeurotransmittersExcitatoryExcitatory & inhibitory
ComplexityLess complexMore complex
ExamplesSkeletal muscle movementStomach, heart, pupil

What is Peripheral Nervous System?

The peripheral nervous system consists of all nerves and nerve branches arising from the brain and spinal cord. The nerves coming out of the brain are called cranial nerves. In contrast, those branching from the spinal cord are spinal nerves. These nerves transport information to and from the central nervous system to other body parts. Neurons are the fundamental unit of the nervous system, including the sensory, motor, and mixed neurons. They send, receive, and transmit signals across the body. The cell body (soma) of the neuron makes sure everything is working fine. The dendrites receive signals, and the axon transmits signals to other neurons. The exchange of information takes place in the form of nerve impulses between neurons.

The somatic and autonomic nervous systems are divisions of the peripheral nervous system.

Somatic Nervous System

The somatic nervous system is the voluntary nervous system. It is involved in the voluntary action of the muscles signals. It manages the skeletal muscles voluntarily. The somatic nervous system contains the efferent and the afferent nerves involved in the to and fro transport of information. The afferent nerves pick up the signals, and the efferent nerves direct the muscles. It also contributes to the input of the senses. The somatic nervous system controls the information when any of your senses are used for an action.

Acetylcholine is an excitatory neurotransmitter, also working as an autocrine hormone, that stimulates movements in the somatic nervous system. It releases from the axon and acts on the acetylcholine receptors in the muscles for contraction. The signals from the neurotransmitters are set through the upper motor neuron to the skeletal muscle through the axons. The somatic nervous system also comprises the somatic reflex arc (knee reflex).

Autonomic Nervous System

As opposed to the somatic nervous system, the autonomic nervous system manages the involuntary actions of your body. The involuntary actions of the autonomic nervous system include heart beating, digestive system muscle movement, contraction, dilation of the eye pupil, etc. Acetylcholine acts as an inhibitory neurotransmitter and slows down or inhibits various movements.

Autonomic-Nervous-System

The sympathetic and parasympathetic nervous systems are further branches of the autonomic nervous system. The sympathetic nervous system is also known as the “fight or flight” response of the body to stress conditions. Nevertheless, the parasympathetic nervous system brings the body back to normal. It is more active during the state of rest, like sleeping.

Similarities Between Somatic and Autonomic Nervous Systems

  • The somatic and autonomic nervous systems are divisions of the peripheral nervous system.
  • They comprise cranial and spinal nerves arising from the brain and spinal cord, respectively.
  • They have afferent and efferent nerves that help in the transmission of signals.
  • Both systems contribute to muscle movements in the body.
  • They receive, transmit and send signals in the form of nerve impulses through neurotransmitters.
  • They are mainly found in vertebrates, and not in invertebrates.

Differences Between Somatic and Autonomic Nervous Systems

Definition

Somatic Nervous System

It is the part of the peripheral nervous system that deals with voluntary muscle functions in the body.

Autonomic Nervous System

Whereas the autonomic nervous system regulates the involuntary movement of the tissues and organs.

Movement

Somatic Nervous System

The somatic nervous system manages voluntary muscle functions. It also comprises the somatic reflex.

Autonomic Nervous System

As opposed to the somatic nervous system, the autonomic nervous system manages involuntary reflexes and movements.

Type of Muscle

Somatic Nervous System

The involved muscles are one of the most significant differences between the somatic and autonomic nervous systems. The somatic nervous system acts on skeletal muscles to provide voluntary movement.

Autonomic Nervous System

On the other hand, the autonomic nervous system acts on cardiac and smooth muscles.

Neurotransmitters

neurotransmitters

Somatic Nervous System

The somatic Nervous System involves excitatory neurotransmitters to produce voluntary action.

Autonomic Nervous System

Whereas excitatory and inhibitory neurotransmitters are both involved in the autonomic nervous system.

Complexity

Somatic Nervous System

The functions of the somatic nervous system are not as complex as the autonomic nervous system.

Autonomic Nervous System

In contrast, the autonomic nervous system functions are complex because of sympathetic and parasympathetic pathways.

Examples

Somatic Nervous System

The somatic nervous system majorly helps in the movement of skeletal muscles.

Autonomic Nervous System

However, the autonomic nervous system regulates smooth muscle and cardiac function apart from pupil dilation and contraction, and respiratory function partially.

The Bottom Line

The somatic and autonomic nervous systems are divisions of the peripheral nervous system. The peripheral nervous system comprises nerves and neuromuscular junctions. It is responsible for transmitting signals throughout the body. The somatic nervous system regulates voluntary muscle function. Alternatively, the autonomic nervous system manages involuntary muscle function. Skeletal muscle movement is an example of the somatic nervous system, while the autonomic nervous system controls heart and stomach muscle function.

FAQs

What is the weight of the brain?

The human brain weighs around three pounds. The weight and size of the brain reduce as we grow.

What is some autonomic reflex vs somatic reflex examples?

Cardiac muscles and smooth muscles are examples of autonomic reflexes, whereas the knee reflex occurs by somatic reflexes.

What is the somatic nervous system function?

The function of the somatic nervous system is to ensure proper management of voluntary muscle functions in the body, like the skeletal system.

What is the opposite of the autonomic nervous system?

The opposite of the autonomic nervous system is the somatic nervous system. It regulates movement and muscle while the autonomic nervous system controls internal organs.

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