Free nerve ending
Encyclopedia
A free nerve ending is an unspecialized, afferent nerve
ending, meaning it brings information from the body's periphery toward the brain. They function as cutaneous receptors and are essentially used by vertebrates to detect pain
.
or Pacinian corpuscle
s. They are the most common type of nerve
ending, and are most frequently found in the skin
. They mostly resemble the fine roots of a plant. They penetrate the epidermis and end in the stratum granulosum
. FNE infiltrate the middle layers of your smooth and hairy skin and they surrounds the hair follicles in your hairy skin.
). Thus, different free nerve endings work as thermoreceptors, cutaneous mechanoreceptors and nociceptors. In other words, they express polymodality
.
s (group III) and C (group IV) fibers end as free nerve endings.
Afferent nerve
In the nervous system, afferent neurons , carry nerve impulses from receptors or sense organs towards the central nervous system. This term can also be used to describe relative connections between structures. Afferent neurons communicate with specialized interneurons...
ending, meaning it brings information from the body's periphery toward the brain. They function as cutaneous receptors and are essentially used by vertebrates to detect pain
Nociception
Nociception is defined as "the neural processes of encoding and processing noxious stimuli." It is the afferent activity produced in the peripheral and central nervous system by stimuli that have the potential to damage tissue...
.
Structure
Free nerve endings are unencapsulated and have no complex sensory structures, unlike those found in Meissner'sMeissner's corpuscle
Meissner's corpuscles are a type of mechanoreceptor. They are a type of nerve ending in the skin that is responsible for sensitivity to light touch. In particular, they have highest sensitivity when sensing vibrations lower than 50 Hertz...
or Pacinian corpuscle
Pacinian corpuscle
Lamellar corpuscles or Pacinian corpuscles are one of the four major types of mechanoreceptor. They are nerve endings in the skin, responsible for sensitivity to vibration and pressure. Vibrational role may be used to detect surface, e.g., rough vs...
s. They are the most common type of nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
ending, and are most frequently found in the skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
. They mostly resemble the fine roots of a plant. They penetrate the epidermis and end in the stratum granulosum
Stratum granulosum
The stratum granulosum is a thin layer of cells in the epidermis. Keratinocytes migrating from the underlying stratum spinosum become known as granular cells in this layer...
. FNE infiltrate the middle layers of your smooth and hairy skin and they surrounds the hair follicles in your hairy skin.
Types
Free nerve ending have different rate of adaptation, stimulus modalities and fiber types.Rate of adaption
Different types of FNE can be rapidly adapting, intermediate adapting, or slowly adapting. Aδ fibres are fast-adapting, while C fibers are slowly adapting.Modality
Free nerve endings can detect temperature, mechanical stimuli (touch, pressure, stretch) or pain (nociceptionNociception
Nociception is defined as "the neural processes of encoding and processing noxious stimuli." It is the afferent activity produced in the peripheral and central nervous system by stimuli that have the potential to damage tissue...
). Thus, different free nerve endings work as thermoreceptors, cutaneous mechanoreceptors and nociceptors. In other words, they express polymodality
Polymodality
Polymodality is the feature of having multiple stimulus modalities. Examples includes free nerve endings....
.
Fiber types
The majority of Aδ (A delta) fiberA delta fiber
A delta fibers, or Aδ fibers, are a type of sensory fiber.They are associated with cold and pressure, and as nociceptors stimulation of them is interpreted as fast/first pain information....
s (group III) and C (group IV) fibers end as free nerve endings.
External links
- Nociception: Transduction. From the University of Utah.
- Textbook in Medical Physiology And Pathophysiology: Essentials and clinical problems. Copenhagen Medical Publishers. 1999 - 2000
- Somatosensory System from Dr. Daley of North Carolina Wesleyan College.