Difference Between Free Nerve Endings and Encapsulated

The key difference between free nerve endings and encapsulated nerve endings is that free nerve endings do not have complex sensory structures while the encapsulated nerve endings have either a brush border encapsulation or fluid-filled sacs at the ends.

Nerve endings play an important role in the transmission of nerve impulses. More importantly, they are receptors. Mechanoreceptors have either free nerve endings or encapsulated nerve endings for their nerve impulse transmission. However, there is a difference between free nerve endings and encapsulated nerve endings in terms of their sensitivity, specificity and adaptability.

CONTENTS

1. Overview and Key Difference
2. What are Free Nerve Endings 
3. What are Encapsulated Nerve Endings 
4. Similarities Between Free Nerve Endings and Encapsulated Nerve Endings 
5. Side by Side Comparison – Free Nerve Endings vs Encapsulated Nerve Endings in Tabular Form
6. Summary

What are Free Nerve Endings?

Free nerve endings are the nerve endings that have no complex sensory structures. Furthermore, they are encapsulated free nerve endings. They are most commonly present in the skin and extend to the middle portion of the epidermis. The sensitivity of free nerve endings is high in comparison to the covered nerve endings. Thus, they are sensitive to pain, temperature, pressure, stretch and touch. However, during abrupt changes in stimulation, free nerve endings require more time for adaptation.

Figure 01: Free Nerve Ending

Among different mechanoreceptors found in the skin, Merkel’s disks contain free nerve endings. They are densely distributed in the fingertips and lips. Moreover, they respond to light touch.

What are Encapsulated Nerve Endings?

In contrast to free nerve endings, encapsulated nerve endings do not contain an open end for nerve transmission. Therefore, the sensitivity of encapsulated nerve endings is low in comparison to free nerve endings. Some mechanoreceptors have encapsulated nerve endings. Encapsulated nerve endings have brush borders that increase the specificity of nerve impulse transmission. They can also be fluid-filled sacs that can form encapsulations.

Figure 02: Free Nerve Endings vs Encapsulated Nerve Endings

Ruffini endings and Meissner’s corpuscles are mechanoreceptors that contain encapsulated nerve endings. Ruffini endings have low adaptability that can detect the stretch and deformations of skin and joints. They are important in providing grip for finger positions and movements.

Meissner’s corpuscles also have encapsulated nerve endings. They are mainly present in the upper dermis. However, they extend up to the epidermis as well. They are important in responding to stimuli, such as touch and pressure. Although they are slow to respond, their specificity is high.

What are the Similarities Between Free Nerve Endings and Encapsulated Nerve Endings?

• Both free nerve endings and encapsulated nerve endings transmit nerve impulses.
• They form mechanoreceptors in the skin.
• Both are sensitive to mechanical stimuli.

What is the Difference Between Free Nerve Endings and Encapsulated?

The key difference between free nerve endings and encapsulated nerve endings relies on the presence or absence of the encapsulation. Thus, free nerve endings do not have encapsulation while encapsulated nerve endings contain either a brush border encapsulation or fluid-filled sacs at the ends. Moreover, there is a difference between free nerve endings and encapsulated nerve endings in terms of their sensitivity, specificity and adaptability.

Summary – Free Nerve Endings vs Encapsulated

Nerve endings act as receptors for receiving signals. Nerve endings can be free or encapsulated. Free nerve endings lack encapsulation while encapsulated nerve endings have a brush border encapsulation or fluid-filled sacs at the ends. So, this is the key difference between free nerve endings and encapsulated. Moreover, free nerve endings are less specific, while encapsulated nerve endings are highly specific. However, free nerve endings are more sensitive than encapsulated nerve endings. In fact, free nerve endings are the commonest type of nerve endings that send signals to sensory neurons. Thus, this is the summary of free nerve endings and encapsulated.

Reference:

1. “Somatosensation” Boundless Biology, Lumen, Available here.
2. “36.2A: Somatosensory Receptors.” Biology LibreTexts, Libretexts, 9 Sept. 2019, Available here.

Image Courtesy:

1. “Blausen 0803 Skin FreeNerveEndings” By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia
2. “1401 Receptor Types” By OpenStax –  (CC BY 4.0) via Commons Wikimedia