The dorsal column nuclei are a pair of nuclei in the dorsal columns of the

dorsal column–medial lemniscus pathway The dorsal column–medial lemniscus pathway (DCML) (also known as the posterior column-medial lemniscus pathway (PCML) is the major sensory pathway of the central nervous system that conveys sensations of fine touch, vibration, two-point dis ...

(DCML) in the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

. The name refers collectively to the cuneate nucleus and gracile nucleus, which are situated at the lower end of the

medulla oblongata The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involun ...

. Both nuclei contain

second-order neuron Second-order may refer to: Mathematics * Second order approximation, an approximation that includes quadratic terms * Second-order arithmetic, an axiomatization allowing quantification of sets of numbers * Second-order differential equation, a d ...

s of the DCML, which convey fine touch and

proprioceptive Proprioception ( ) is the sense of self-movement, force, and body position. Proprioception is mediated by proprioceptors, a type of sensory receptor, located within muscles, tendons, and joints. Most animals possess multiple subtypes of propri ...

information from the body to the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

via the

thalamus The thalamus (: thalami; from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter on the lateral wall of the third ventricle forming the wikt:dorsal, dorsal part of the diencephalon (a division of ...

Structure

Nerve pathways

The dorsal column nuclei each have an associated

nerve tract A nerve tract is a bundle of nerve fibers (axons) connecting Nucleus (neuroanatomy), nuclei of the central nervous system. In the peripheral nervous system, this is known as a nerve fascicle, and has associated nervous tissue, connective tissue. T ...

in the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

, the gracile fasciculus and the cuneate fasciculus, together forming the dorsal columns. Both dorsal column nuclei contain synapses from afferent nerve fibers that have travelled in the spinal cord. They then send on second-order

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

s of the dorsal column–medial lemniscal pathway. Neurons of the dorsal column nuclei eventually reach the

midbrain The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum. It is functionally associated with vision, hearing, mo ...

and the

. They send

axon An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, ...

s that form the internal arcuate fibers. These cross over at the sensory decussation to form the

medial lemniscus The medial lemniscus, also known as Reil's band or Reil's ribbon (for German anatomist Johann Christian Reil), is a large ascending bundle of heavily myelinated axons that decussate in the brainstem The brainstem (or brain stem) is the pos ...

. They then

synapse In the nervous system, a synapse is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending o ...

with third-order neurons of the thalamus.

Nuclei

The major nuclei are the cuneate nucleus and gracile nucleus. These are present at the bottom of the

Gracile nucleus

The gracile nucleus is medial to the cuneate nucleus. Its neurons receive afferent input from

dorsal root ganglia A dorsal root ganglion (or spinal ganglion; also known as a posterior root ganglion) is a cluster of neurons (a ganglion) in a dorsal root of a spinal nerve. The cell bodies of sensory neurons known as first-order neurons are located in the dors ...

sensory neuron Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded receptor potentials. This process is called sensory transduc ...

s of the lower

torso The torso or trunk is an anatomical terminology, anatomical term for the central part, or the core (anatomy), core, of the body (biology), body of many animals (including human beings), from which the head, neck, limb (anatomy), limbs, tail an ...

and the lower limbs. The gracile nucleus and gracile fasciculus carry epicritic,

kinesthetic Proprioception ( ) is the sense of self-movement, force, and body position. Proprioception is mediated by proprioceptors, a type of sensory receptor, located within muscles, tendons, and joints. Most animals possess multiple subtypes of propri ...

, and conscious

information from the lower part of the body (below the level of T6 in the spinal cord). Because of the large population of neurons in the gracile nucleus they give rise to a raised area called the gracile tubercle on the posterior side of the closed medulla at the floor of the

fourth ventricle The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ...

Cuneate nucleus

The cuneate nucleus is lateral to the gracile nucleus. It carries the same type of information, but from the upper body and the upper limbs (except the

face The face is the front of the head that features the eyes, nose and mouth, and through which animals express many of their emotions. The face is crucial for human identity, and damage such as scarring or developmental deformities may affect th ...

, which is carried by the principal sensory nucleus of trigeminal nerve). The cuneate nucleus is wedge-shaped and located in the closed part of the medulla. It lies lateral to the gracile nucleus and medial to the spinal trigeminal nucleus in the medulla. The large number of neurons found there give rise to the cuneate tubercle seen on viewing the posterior aspect of the medulla on the side of the

Function

The dorsal column nuclei help to carry fine touch and

information from the body to the

. The gracile nucleus carries information from the lower

and the lower limbs. The cuneate nucleus carries information from the upper body and the upper limbs.

Clinical significance

The dorsal column nuclei may degenerate during

ageing Ageing (or aging in American English) is the process of becoming older until death. The term refers mainly to humans, many other animals, and fungi; whereas for example, bacteria, perennial plants and some simple animals are potentially biol ...

, although evidence for this is not conclusive. This may reduce the sensitivity of

touch The somatosensory system, or somatic sensory system is a subset of the sensory nervous system. The main functions of the somatosensory system are the perception of external stimuli, the perception of internal stimuli, and the regulation of bo ...

and

proprioception Proprioception ( ) is the sense of self-movement, force, and body position. Proprioception is mediated by proprioceptors, a type of sensory receptor, located within muscles, tendons, and joints. Most animals possess multiple subtypes of propri ...

Other animals

In some other animals, a third nucleus is present, known as the median accessory nucleus. This may carry information from the

tail The tail is the elongated section at the rear end of a bilaterian animal's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolution, evolved to los ...

Additional images

File:Gray713.png, Scheme showing the course of the fibers of the lemniscus; medial lemniscus in blue, lateral in red. File:Gray759.png, The sensory tract. File:Slide2PITER.JPG, Fourth ventricle. Posterior view. Deep dissection.

References

{{DEFAULTSORT:Dorsal Column Nuclei Brainstem