A delta fiber
Encyclopedia
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.
They are thinly myelin
ated, so conduct signals more rapidly than unmyelinated C fibers, but more slowly than other, more thickly myelinated "A" class fibers.
The fibers terminate at Rexed lamina I.
ated axons with a moderate conduction velocity, or speed of travel of a nerve signal (2 to 30 m/s). These nerve
fibers are associated with acute (sharp) pain and therefore constitute the afferent
portion of the reflex arc
that results in "pulling away" from noxious stimuli (e.g. yanking hand away from hot stove). A certain proportion of Aδ fibers are also associated with sensations of temperature
(also known as 'cold receptors' in mammals) and pressure
. Slowly-conducting, unmyelinated C fibers, by contrast, carry slow, burning pain.
Like other sensory fibers, the Aδ fiber is an extension of a pseudounipolar neuron
with its cell body located in a dorsal root ganglion
or trigeminal ganglion. Within the spinal cord
, afferent nociceptor fibers synapse
at or near the spinal cord level where they enter.
They are associated with cold and pressure, and as nociceptors stimulation of them is interpreted as fast/first pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
information.
They are thinly myelin
Myelin
Myelin is a dielectric material that forms a layer, the myelin sheath, usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. Myelin is an outgrowth of a type of glial cell. The production of the myelin sheath is called myelination...
ated, so conduct signals more rapidly than unmyelinated C fibers, but more slowly than other, more thickly myelinated "A" class fibers.
The fibers terminate at Rexed lamina I.
Structure
They are thin, myelinMyelin
Myelin is a dielectric material that forms a layer, the myelin sheath, usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. Myelin is an outgrowth of a type of glial cell. The production of the myelin sheath is called myelination...
ated axons with a moderate conduction velocity, or speed of travel of a nerve signal (2 to 30 m/s). These 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...
fibers are associated with acute (sharp) pain and therefore constitute the afferent
Afferent
Afferent is an anatomical term with the following meanings:*Conveying towards a center, for example the afferent arterioles conveying blood towards the Bowman's capsule in the Kidney. Opposite to Efferent.*Something that so conducts, see Afferent nerve fiber...
portion of the reflex arc
Reflex arc
A reflex arc is a neural pathway that controls an action reflex. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord...
that results in "pulling away" from noxious stimuli (e.g. yanking hand away from hot stove). A certain proportion of Aδ fibers are also associated with sensations of temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
(also known as 'cold receptors' in mammals) and pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
. Slowly-conducting, unmyelinated C fibers, by contrast, carry slow, burning pain.
Like other sensory fibers, the Aδ fiber is an extension of a pseudounipolar neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
with its cell body located in a dorsal root ganglion
Dorsal root ganglion
In anatomy and neuroscience, a dorsal root ganglion is a nodule on a dorsal root that contains cell bodies of neurons in afferent spinal nerves.-Unique unipolar structure:...
or trigeminal ganglion. Within the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
, afferent nociceptor fibers synapse
Synapse
In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell...
at or near the spinal cord level where they enter.