What is the Difference Between Somatic and Visceral Reflex

The main difference between somatic and visceral reflex is that the somatic reflex occurs in skeletal muscles whereas, the visceral reflex occurs in soft tissue organs. Furthermore, the somatic nervous system produces somatic reflexes while autonomic nervous system produces visceral reflexes.  

Somatic and visceral reflex are two types of reflex arcs or nerve circuits produced by the different systems of the peripheral nervous system. Both types of reflexes are important for the coordination between the central nervous system and the effector organ. 

Key Areas Covered 

1. What is Somatic Reflex
     – Definition, Features, Types
2. What is Visceral Reflex
     – Definition, Features, Types
3. What are the Similarities Between Somatic and Visceral Reflex
     – Outline of Common features
4. What is the Difference Between Somatic and Visceral Reflex
     – Comparison of Key Differences

Key Terms 

Autonomic Nervous System, Skeletal Muscles, Smooth Muscle Contractions, Somatic Nervous System, Somatic Reflex, Visceral Reflex 

What is Somatic Reflex 

Somatic reflex is the reflex of the somatic nervous system, which produces unconscious motor responses in skeletal muscles. Here, it uses alpha motor neurons, which control the voluntary muscular movements. Below are some examples of somatic reflexes. 

• Stretch reflex – it is responsible for the stretch of the skeletal muscles. It is a type of monosynaptic reflex; therefore, it is rapid. 
• Flexor reflex – it is responsible for the pulling out of the body parts in response to a hot stove. It is a polysynaptic reflex.  
  

  Figure 1: Somatic Reflex

• Crossed-extensor reflex – responsible for the strong withdrawal reflexes in response to sharp objects. 

What is Visceral Reflex 

Visceral reflex is the reflex arc of the autonomic nervous system which produces a glandular or non-skeletal muscular response in internal organs like the heart, blood vessels, organs in the gastrointestinal tract, etc.  

Figure 2: Visceral and Somatic Efferent Pathways

Some examples of visceral reflexes are sneezing, coughing, swallowing, vomiting, dilation of the pupil, contraction of smooth muscles of the hollow organs in different organ systems. 

Similarities Between Somatic and Visceral Reflex 

• Somatic and visceral reflex are two types of reflex arcs or nerve circuits which coordinate the function of different effector organs. 
• Both reflexes start from the spinal cord. Therefore, both types of reflexes occur before the information reaches the brain.  
• Generally, they use the efferent pathway for their output while they receive sensory signals through the afferent pathway. 
• Also, the five components of each reflex arc are the sensory receptor, sensory neuron, integration center, motor neuron, and effector target. 
• Besides, both produce a rapid, involuntary, and predictable response in response to a specific stimulus. 

Difference Between Somatic and Visceral Reflex 

Definition 

Somatic reflex refers to a reflex induced by stimulation of somatic sensory nerve endings while the visceral reflex refers to a reflex mediated by autonomic nerves and initiated in the viscera. Thus, this is the fundamental difference between somatic and visceral reflex.

Type of Nervous System 

Another difference between somatic and visceral reflex is that the somatic nervous system produces somatic reflex while the autonomic nervous system produces visceral reflex. 

Effector Organ 

The main difference between somatic and visceral reflex is that the somatic reflex innervates skeletal muscles while the visceral reflex innervates soft tissue organs. 

Function 

Furthermore, the somatic reflexes contract skeletal muscles while the visceral reflexes are responsible for the contractions of the digestive system and reproductive system, dilation of the pupil, defecating and vomiting. 

Role 

Moreover, the somatic reflexes protect the body from injuries while the visceral reflexes carry out the functions of the internal organs.  Hence, this is another difference between somatic and visceral reflex.

Conclusion 

Somatic reflex is the nerve circuit of the somatic nervous system. It is responsible for the contraction of skeletal muscles. On the other hand, the visceral reflex is the nerve circuit of the autonomic nervous system. It is responsible for the contraction of smooth muscles and organs inside the body. Therefore, the main difference between somatic and visceral reflex is the type of effector organ.

References:

1. “Anatomy and Physiology.” Introduction to Sociology – 1st Canadian Edition, BCcampus, 6 Mar. 2013, Available Here

Image Courtesy:

1. “Imgnotraçat arc reflex eng” By MartaAguayo – Own work (CC BY-SA 3.0) via Commons Wikimedia  
2. “1505 Comparison of Somatic and Visceral Reflexes” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia