Spinocerebellar tract
Encyclopedia
The spinocerebellar tract is a set of axonal
fibers originating in the spinal cord
and terminating in the ipsilateral cerebellum
. This tract conveys information to the cerebellum about limb and joint position (proprioception
).
and muscle spindles
.
All of these neurons are "first order" or "primary", are sensory (and thus have their cell bodies in the dorsal root ganglion
) and pass through Rexed laminae
layers I-VI of the dorsal horn, to form synapses with "second order" or "secondary" neurons in the layer just beneath the dorsal horn (layer VII)
This is a column of relay neuron cell bodies within the medial gray matter within the spinal cord
in layer VII (just beneath the dorsal horn), specifically between T1-L3. These neurons then send axons up the spinal cord
, and project ipsilaterally to medial zones of the cerebellum through the inferior cerebellar peduncle.
Below L3, relevant neurons pass into the fasciculus gracilis
(usually associated with the dorsal column-medial lemniscal system) until L3 where they synapse with Clarke's nucleus (leading to considerable caudal enlargement).
From above T1, neurons enter the fasciculus cuneatus
directly and again synapse with neurons in the accessory cuneate nucleus. This pathway is known as the spinocuneocerebellar tract.
The neurons in the accessory cuneate nucleus have axons leading to the ipsilateral cerebellum via the inferior cerebellar peduncle.
and proceed up the spinal cord to synapse with neurons in the superior cerebellar peduncle. The fibers then often cross over again within the cerebellum to end on the ipsilateral side. For this reason the tract is sometimes termed the "double-crosser."
The Rostral Tract synapses at the dorsal horn lamina of the spinal cord and ascends ipsilaterally to the cerebellum through the inferior cerebellar peduncle.
Axon
An axon is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma....
fibers originating in 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...
and terminating in the ipsilateral cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
. This tract conveys information to the cerebellum about limb and joint position (proprioception
Proprioception
Proprioception , from Latin proprius, meaning "one's own" and perception, is the sense of the relative position of neighbouring parts of the body and strength of effort being employed in movement...
).
Origins of proprioceptive information
Proprioceptive information is obtained by Golgi tendon organsGolgi organ
The Golgi organ , is a proprioceptive sensory receptor organ that is located at the insertion of skeletal muscle fibers into the tendons of skeletal muscle...
and muscle spindles
Muscle spindle
Muscle spindles are sensory receptors within the belly of a muscle, which primarily detect changes in the length of this muscle. They convey length information to the central nervous system via sensory neurons. This information can be processed by the brain to determine the position of body parts...
.
- Golgi tendon organsGolgi organThe Golgi organ , is a proprioceptive sensory receptor organ that is located at the insertion of skeletal muscle fibers into the tendons of skeletal muscle...
consist of a fibrous capsule enclosing tendon fasciculi and bare nerve endings that respond to tension in the tendon by causing action potentialAction potentialIn physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
s in Ib afferent neurons (relatively large, myelinated, quickly conducting).
- Muscle spindleMuscle spindleMuscle spindles are sensory receptors within the belly of a muscle, which primarily detect changes in the length of this muscle. They convey length information to the central nervous system via sensory neurons. This information can be processed by the brain to determine the position of body parts...
s fibers are complicated systems of length monitoring within muscles which result in information being carried via Ia neurons (larger and faster than Ib) (from both nuclear bag fibers and nuclear chain fibers) and II neurons (solely from nuclear chain fibers).
All of these neurons are "first order" or "primary", are sensory (and thus have their cell bodies in the 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:...
) and pass through Rexed laminae
Rexed laminae
The Rexed laminae comprise a system of ten layers of grey matter , identified in the early 1950s by Bror Rexed to label portions of the spinal cord...
layers I-VI of the dorsal horn, to form synapses with "second order" or "secondary" neurons in the layer just beneath the dorsal horn (layer VII)
Subdivisions of the tract
The tract is divided into:| Division | Information | Limbs >- | dorsal (posterior) spinocerebellar tract Dorsal spinocerebellar tract The dorsal spinocerebellar tract conveys inconscient proprioceptive information from the body to the cerebellum.... |
from muscle spindle Muscle spindle Muscle spindles are sensory receptors within the belly of a muscle, which primarily detect changes in the length of this muscle. They convey length information to the central nervous system via sensory neurons. This information can be processed by the brain to determine the position of body parts... s |
lower limb Lower limb The lower limb is a limb of the body.According to Terminologia Anatomica, it includes the pelvic girdle, buttocks, hip, and thigh, as well as the components distal to the knee.-References:... >- | ventral (anterior) spinocerebellar tract Ventral spinocerebellar tract The ventral spinocerebellar tract conveys proprioceptive information from the body to the cerebellum. It is part of the somatosensory system and runs in parallel with the dorsal spinocerebellar tract... |
from golgi tendon organs Golgi organ The Golgi organ , is a proprioceptive sensory receptor organ that is located at the insertion of skeletal muscle fibers into the tendons of skeletal muscle... |
lower limb Lower limb The lower limb is a limb of the body.According to Terminologia Anatomica, it includes the pelvic girdle, buttocks, hip, and thigh, as well as the components distal to the knee.-References:... >- | spinocuneocerebellar tract |
from muscle spindle Muscle spindle Muscle spindles are sensory receptors within the belly of a muscle, which primarily detect changes in the length of this muscle. They convey length information to the central nervous system via sensory neurons. This information can be processed by the brain to determine the position of body parts... s |
upper limb Upper limb The upper limb or upper extremity is the region in an animal extending from the deltoid region to the hand, including the arm, axilla and shoulder.-Definition:... >- | rostral spinocerebellar tract Rostral spinocerebellar tract The rostral spinocerebellar tract is a tract which transmits information from the golgi tendon organs of the cranial half of the body to the cerebellum.... |
from golgi tendon organs Golgi organ The Golgi organ , is a proprioceptive sensory receptor organ that is located at the insertion of skeletal muscle fibers into the tendons of skeletal muscle... |
upper limb Upper limb The upper limb or upper extremity is the region in an animal extending from the deltoid region to the hand, including the arm, axilla and shoulder.-Definition:... |
Pathway for dorsal and posterior spinocuneocerebellar tracts
In the dorsal tract, the sensory neurons synapse in an area known as Clarke's nucleus or "Clarke's column".This is a column of relay neuron cell bodies within the medial gray matter 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...
in layer VII (just beneath the dorsal horn), specifically between T1-L3. These neurons then send axons up 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...
, and project ipsilaterally to medial zones of the cerebellum through the inferior cerebellar peduncle.
Below L3, relevant neurons pass into the fasciculus gracilis
Fasciculus gracilis
The fasciculus gracilis is a bundle of axon fibres in the posterior column of the spinal cord and carries information from the middle thoracic and lower limbs of the body...
(usually associated with the dorsal column-medial lemniscal system) until L3 where they synapse with Clarke's nucleus (leading to considerable caudal enlargement).
From above T1, neurons enter the fasciculus cuneatus
Fasciculus cuneatus
The fasciculus cuneatus is a tract of nerves in the spinal cord which primarily transmits information from the arms...
directly and again synapse with neurons in the accessory cuneate nucleus. This pathway is known as the spinocuneocerebellar tract.
The neurons in the accessory cuneate nucleus have axons leading to the ipsilateral cerebellum via the inferior cerebellar peduncle.
Pathway for ventral and rostral spinocerebellar tracts
Some neurons of the ventral spinocerebellar tract instead form synapses with neurons in layer VII of L4-S3. Most of these fibers cross over to the contralateral lateral funiculus via the anterior white commissureAnterior white commissure
The anterior white commissure, also known as the alba anterior medullae spinalis, is a bundle of nerve fibers which cross the midline of the spinal cord just anterior to the gray commissure...
and proceed up the spinal cord to synapse with neurons in the superior cerebellar peduncle. The fibers then often cross over again within the cerebellum to end on the ipsilateral side. For this reason the tract is sometimes termed the "double-crosser."
The Rostral Tract synapses at the dorsal horn lamina of the spinal cord and ascends ipsilaterally to the cerebellum through the inferior cerebellar peduncle.
External links
- http://www.anatomyatlases.org/MicroscopicAnatomy/Section17/Plate17327.shtml