Sensory and Motor Tracts of the Spinal Cord

Sensory Neurons

Neurons that deliver information to the CNS.

Motor Neurons

Neurons that cause the body to respond in various ways.

Ascending Tract

Sensory tract that delivers information to the brain.

Descending Tract

Motor tract that delivers information to the periphery.

Spinocerebellar Tract

Origin is spinal cord and destination is cerebellum.

Spinothalamic Tract

Origin is spinal cord and destination is the thalamus.

Corticospinal Tract

Origin is cerebral cortex and destination is spinal cord.

Vestibulospinal Tract

Origin is vestibular nuclei and destination is spinal cord.

Posterior Column

One of the three major sensory tracts that transmits information to the CNS.

Gracile Fasciculus

Transmits information to the cerebrum from areas inferior to T6.

Cuneate Fasciculus

Transmits information to the cerebrum from areas superior to T6.

Sensory Homunculus

A sensory map representing the body in the brain.

Lateral Spinothalamic Tract

Transmits pain and temperature sensations.

Anterior Spinothalamic Tract

Transmits crude touch and pressure sensations.

Posterior Spinocerebellar Tract

Involved in proprioception.

Anterior Spinocerebellar Tract

Involved in proprioception.

First-Order Neurons

Neurons that transmit sensory information from the periphery to the CNS.

Second-Order Neurons

Neurons that transmit sensory information from the spinal cord to the thalamus.

Third-Order Neurons

Neurons that transmit sensory information from the thalamus to the cerebral cortex.

Decussation

The crossing of nerve fibers from one side of the CNS to the other.

Ventral Posterolateral Nucleus

Final destination for the gracile fasciculus in the thalamus.

Axons of second-order neurons

Axons that join the medial lemniscus.

Dorsal root ganglia of lower body

Ganglia where axons enter the CNS in dorsal roots and ascend within the gracile fasciculus.

Gracile nucleus of medulla oblongata

Nucleus where axons decussate before entering the medial lemniscus.

Cuneate fasciculus

A structure that carries sensory information from the upper body.

Ventral posterolateral nucleus of thalamus

Nucleus in the thalamus that processes sensory information.

Primary somatosensory cortex

Cortex on the side opposite the stimulus that processes sensory input.

Proprioception, fine touch, pressure, and vibration

Sensory modalities from levels at or superior to T6.

Dorsal root ganglia

Ganglia of upper body; axons enter CNS in dorsal roots and ascend within cuneate fasciculus.

Cuneate nucleus

Located in the medulla oblongata; axons decussate before entering medial lemniscus.

Lateral spinothalamic tracts

Transmits pain and temperature sensations.

Ventral posterolateral nucleus

Final destination for lateral spinothalamic tracts.

Dorsal root ganglia (first-order neurons)

Location of neuron cell bodies for lateral spinothalamic tracts; axons enter CNS in dorsal roots and enter posterior horn.

Anterior spinothalamic tracts

Transmits crude touch and pressure sensations.

Primary somatosensory cortex

Final destination for sensations from both lateral and anterior spinothalamic tracts on side opposite stimulus.

Posterior spinocerebellar tracts

Transmits proprioception sensations; not present at site of decussation.

Cerebellar cortex

Final destination for posterior spinocerebellar tracts on side of stimulus.

Anterior spinocerebellar tracts

Transmits proprioception sensations; axons enter anterior spinocerebellar tract on same or opposite side.

Corticospinal tracts

Consist of three pairs of descending tracts that control skeletal muscles.

Corticobulbar tracts

Provide conscious control over eye, jaw, and face muscles.

Lateral corticospinal tracts

Provide conscious control over skeletal muscles; decussate in the pyramids of the medulla oblongata.

Anterior corticospinal tracts

Provide conscious control over skeletal muscles; decussate at the level of the lower motor neurons.

Motor Homunculus

A diagrammatic representation of control over the primary motor cortex.

Vestibulospinal tracts

Send information from the inner ear to monitor position of the head.

Tectospinal tracts

Send information to the head, neck, and upper limbs in response to bright lights and sudden movements.

Superior colliculi

Receive visual information.

Inferior colliculi

Receive auditory information.

Medial reticulospinal tracts

Send information to cause eye movements and activate respiratory muscles.

Rubrospinal tracts

Send information to the flexor and extensor muscles.

Corticobulbar tracts (upper motor neuron location)

Located in the primary motor cortex (cerebral hemisphere).

Lateral corticospinal tracts (upper motor neuron location)

Located in the primary motor cortex (cerebral hemisphere).

Anterior corticospinal tracts (upper motor neuron location)

Located in the primary motor cortex (cerebral hemisphere).

First-order neuron

The cell body of which sensory neuron may be located in either the spinal cord or the brainstem.

Second-order neuron

The cell body of which sensory neuron may be located in either the spinal cord or the brainstem.

Third-order neuron

The cell body of which sensory neuron may be located in either the spinal cord or the brainstem.