Spinal Tracts Flashcards
Name the three Spinal Tracts
Anterolateral, Corticospinal and the Dorsal Column-Medial Lemniscus Pathway
Describe the route of the DCML pathway
Sensory nerve to the dorsal column and runs up in either the gracile (T7 and below) or the Cuneate (T6 and above) white matter tract. Will then run to the caudal medulla to either the gracile/cuneate nucleuswhere it will synapse with the second neuron. Will then decussate and travel as articulate fibres in the medial lemniscus tract to the thalamus, more specificall the lateral ventral posterior nucleus. Will then synapse at the LVP and the third neuron will move along the internal capsule in the anterior limb to the post central gyrus (Primary sensory cortex)
Describe the route of the Anterolateral pathway
The sensory nerves will enter the dorsal horn after the dorsal root ganglia into the dorsal horn. Before it synapses it will give off the Tract of Lissauer and asscend 1 or 2 levels, which is critical for reflex roles. The second order neuron will then synapse and decussate to the contralateral side through the anterior commissure and it will run up the anterolateral segment of spinal cord. This can also occur off the Tract of Lissauer. Will run to the LVP nuclei of the thalamus where it will synapse with the third order neurons. The third order neurons then project to the sensory cortex by passing through the internal capsule in the anterior limb.
Desribe the different divisions of the Corticospinal tract
There is the lateral branch which is important for mine motor control of limbs (80% of branches) and there is the ventral corticospinal tract which is involved in postural functions
Describe the route of the lateral corticospinal tract
Begins at the Pre-central gyrus (primar motor cortex) and runs to the anterior grey matter where it will synapse with lower motor neurons (alpha motor neurons). On the way down the tract will run through the internal capsule through the posterior limb. It will then pass through the peduncles of the midbrain (Crus cerebri) and then to the pyramids of the medulla before decussating to form the lateral corticospinal tract in the spinal cord. The LMN will then innervate muscles via the neuromuscular junction
Describe Upper Motor Lesion Signs
Spastic paresis, heightened reflexes, clonus, babinski reflexes, weakness of muscles, Upper limb flexion and lower limb extension during period of unconscienceness
Describe Lower Motor Lesion Signs
Flaccid Paresis, absent reflexes, muscle weakness, muscle atrophy, fasiculations and fibrillations,
Describe the types of sensory nerve fibres for touch, propreoception and vibrations
Ia (propreoception), Ib (Golgi sensor), Adelta and Abeta
Describe the types of sensory axons in pain and temperature
C fibres(Delayed) and Adelta (Quick) fibres
Describe the types of motor axons
Alpha (extrafusal) and gamma (intrafusal) fibres
The divisions of the Anterolateral pathway
Spinothalamic, spinoreticular (alertness arousal to pain stimuli), the spinotectal or spinomesencephalic (conscience orientation to pain and activation of Periaquaductal gray region)
Describe the Periaqueductal Gray (PAG) pathway
Located around the cerebral aquaduct pathway within the tegmentum of the midnrain and plays a role in the modulation of pain by activating the raphe nuclei in the brainstem which will project to Laminae II region of the dorsal column and will secrete either enkephalin or dynorphin to activate mu receptors and modulate pain
What is the function of the Reticulospinal tract
Consists of the pontine reticular formation pathway (inervates the spindles/intrafusal muscles via gamma pathways) and the medulla reticular formation pathways (inhibitory signals to the exstensor muscles of lower limb)
What is the function of the Rubospinal tract
Will innervate the flexors of the upper limbs
What is the corticobulbar tract
Will be the UMNs that supply motor commands to the CN nuclei (except the occulomotor nerves) all bilateral except lower CNVII and CNXII
