Spinal Tracts Flashcards
Name the
ASCENDING SPINAL TRACTS?
Dorsal Columns (2)
- fasciculus gracilis*
- fasciculus cuneatus*
Spinothalmic Tract
Spinocerebellar (2)
dorsal & ventral
Definition of
ASCENDING SPINAL TRACTS?
Nerve fibers in the spinal cord carrying impulses from pain, thermal, tactile, muscle and joint receptors to the cerebral cortex (conscious) or cerebellum (subconscious).
How many neurons in an ascending spinal tract going to the cerebral cortex?
Three
- First order neurons or primary afferents
- Second order neurons
- third order neurons
Ascending Spinal Tract
First Order Neuron
enters the spinal cord through the dorsal root of a spinal nerve.
Cell body lies int eh dorsal root ganglion
Main fiber remains ipsilateral
Terminates in either the spinal grey matter or in the medulla oblongata.
Ascending Spinal Tract
Second Order neuron
has the cell body in the cord or medulla oblongata.
Axon decussates before ascending
Terminates in the Thalamus
Ascending Spinal Tract
Third Order Neuron
Cell body in the Thalamus
Axon passes to the somatosensory cortex of the parietal lobe
Which ascending spinal tracts carry information to the conscious level (Cerebral Cortex)?
Dorsal Columns (Gracilus & Cuneatus)
Spinothalamic
What are the Dorsal Columns?
Ascending spinal tracts carrying proprioceptive, discriminative touch, and vibration impulses.
Organized in the fasciculus gracilis (medial)
and fasciculus cuneatus (lateral)
Lesions (tabes dorsalis, vit B12 deficiency) lead to ataxia and loss of discriminative touch.
What is the fasciculus cuneatus?
The lateral dorsal colum ascending spinal tract.
Carries proprioception, discriminative touch and vibration first order neurons from T6 and above to the medulla oblongata.
What is the fasciculus gracilis?
The medial dorsal column ascending spinal tract.
Carries proprioception, discriminative touch and vibration first order neurons from below T6 to the medulla oblongata.
What sensations to the spinothalamic tracts carry?
Pain
Thermal Sensation
Lesions cause impairment of pain temperature
What is the neuronal pathway of the spinothalamic tract?
2nd order neurons, cell bodies in contralateral dorsal horn.
Pain & Temp decussate within one level of origin.
Touch and Pressure my ascend several levels before decussating.
Terminate in the ventral posterior nucleus of the Thalamus.
Connect with 3rd order thalamocortical neurons which terminate in the somatosensory cortex.
What is the spinoreticulothalamic tract?
An older part of the spinothalamic tract thought to transmit dull aching (slow) pain to a conscious level.
2nd order neurons ascend to the brainstem’s reticular formation.
What sensations do the spinocerebellar tracts transmit?
Spinocerebellar tracts carry unconscious sensation from:
Muscle spindles
golgi tendon organs
Tactile receptors
to the cerebellum for posture and coordination of movement.
Lesions lead to ataxia
What is the neuronal pathway of the Spinocerebellar tracts?
Only two neurons.
A 2nd order neuron with cell body in the dorsal horn.
Dorsal spinocerebellar fibers ascend ipsilaterally and enter the cerebellum via the inferior cerebellar peduncle.
Ventral spinocerebellar fibers ascend contralaterally and enter the cerebellum via the superior cerebellar peduncle.