Studying for neuroanatomy

Since my own personal notes are pretty shitty, I'll put up all my notes here so hopefully my imaginary reader can learn something and I'll have to put up non-bullshit information.

So far, I'm studying the spinal cord. It is segmented into 4 regions from rostral to caudal: cervical, thoracic, lumbar, and sacral. There's actually a coccygeal section too, but we don't really need to know much about it.

I guess I'll start with the sacral area. No I'll start off with the big 3-D image. BTW, all of the special terms arise from areas before the foramen magnumThere are some tracts that run down the entire cord through to the brain stem:
-Ascending pathways
--posterior columns [positioning feedback]
---fasciculus gracilis (dorsal medial)
---fasciculus cuneatus (dorsal lateral-ish)
---------these two pathways actual begin in joint capsule receptors where the neurons receive sensory input and thus travel up a primary neuron, becoming respectively the cuneatus and gracilis. then these pathways reach the respective nuclei. then we have some differentiation; both nuclei synapse with secondary neurons, traveling up internal arcuate fibers and ascend into the medial lemniscus (somewhere medial to ventral in cross section positioning). The medial lemniscus synapses with the ventral posterior lateral nucleus of the thalamus (ventral and posterior almost sounds oxymoronic) and ascends into a tertiary neron becoming the internal capsule at the corona radiata. This makes up the postcentral gyrus of the cerebral cortex, which ultimately means that sensory input is travelling up the two main fasciculi in the posterior columns to the medial lemniscus into the corona radiata to give feedback to the conscious brain. The corona radiata, by the way, is the area where all the body sensations are processed.
Some other key terms to note here would be epicritic and kinesthesis, which are really just fancy ways of saying epicritic = localized touch and kinesthesis = sense of position and movement.
The posterior columns make it possible for you to put a key in a door lock without light or visualize positions of your body without looking. Lesions would stymie tactile sensation and movement/position sense.
--lateral spinothalamic tract [pain]
---Lissauer's fasciculus
---reticular formation
----periaqueductal gray
---ventral posterior lateral nucleus of the thalamus
----These are the key players in the lateral spinothalamic tract. Here we have pain and temperature receptors carrying the signals through the primary neuron/Lissauer's fasciculus, which then diverges into a multisynaptic cleft with the medial and peripheral fibers. The fibers ascent the tract, while branching out onto the reticular formation (which eventually becomes the periaqueductal gray of the midbrain). This reticular formation is thought to be slow ascension and responsible for dull and poorly localized pain. The spinothalamic fibers are responsible for the quick sharp pains and the two fibers ultimately synapse with the VPL (ventral posterior lateral nucleus) and the intralaminar nucleus of the thalamus. The intralaminar nucleus receives slow pain input from the reticular formation (which also goes posterior [PO]) while the VPL continues to reach the corona radiata and postcentral gyrus in addition to projecting to the secondary sensory cortex of the lateral fissure. Also note that the anterior spinothalamic tract really has no anatomical difference. It's just slightly ventral.
--spinocerebellar tract [impulse movement]
---posterior spinocerebellar tract
---posterior cuneocerebellar tract
---anterior spinocerebellar tract [don't worry about this guy]
---rostral spinocerebellar tract [don't worry about him either]
----Clarke's column
----inferior cerebellar peduncle
-----In the spinocerebellar pathway, input comes from movement sensations below the C8 region of the cervical segment of the spinal cord. Enter via primary neuron into posterior column and into Clarke's column. When it enters Clarke's column, it goes from gracilis to cuneatus and ascends a secondary neuron and eventually into the inferior cerebellar peduncle which goes to the cerebellum. The inferior peduncle [restiform body] is where the fibers of this tract terminate ipsilateral-medially on the cerebellar cortex for lower limb muscle input and position sense.
-----The cuneocerebellar tract begins above C8, which accounts for impulses for all the muscle spindle, tendon organs, and skin in the upper half of the body. Again, sensory input comes through primary neuron, but it bypasses the gracilis and goes straight into the cuneatus and to an exterior nucleus, becoming the cuneocerebellar tract that reaches the same inferior cerebellar peduncle. Location-wise, this tract is very medial and posterior, but winds up kind of lateral. Blame the medial portion on the gracilis and cuneatus.
-Descending pathways
--Corticospinal tract [voluntary movement]
---pyramid
---crus cerebri
---lateral/anterior corticospinal tracts
----This is the tract where motor function is voluntary, originating in the motor strip of the cortex. At the primary motor area, covering the corona radiata, efferent information is sent back first through the internal capsule down to the midbrain and inferior colliculi/crus cerebri (this is a tricky part of the tract - it's mostly corticobulbar fiber separated by corticopontine fibers - thus making it cortex-medulla fibers), where the tract somewhat splits and reconvenes at the pyramids. At the pyramids some information decussates (85-90%) and descends down the lateral corticospinal tract, while the non-decussating information (10-15%) descends the anterior corticospinal tract. All tracts of this tract result in motor neuron innervation at the neuromuscular junction.
--Tectospinal and rubrospinal tracts
---superior colliculus
---tectospinal tract [visual following and eye-centering reflexes]
---dorsal tegmental decussation
---rubrospinal tract [flexor muscle group tone control]
---red nucleus
----The tectospinal tract begins at the superior colliculus, which is pretty dorsal within the midbrain and it immediately decussates just anterior of the MLF [medial longitudinal fasciculus]. From here it descends towards the optic neuromuscular junctions, traveling along a somewhat medial and ventral tract.
----The rubrospinal tract is thought to be an alternative route for efferent information from the cerebral cortex since it originates at the red nucleus and decussates to the tract and descends to the neuromuscular junctions. The tract responds to information relayed by the spinocerebellar tract based on posture and muscle movement.
-Mixed pathways
--Medial longitudinal fasciculus descending pathways: vestibulospinal tract
---vestibular nuclei
---vestibulospinal tract [inner ear, balance and coordination, antigravity extensor muscles for position/stance]
---medial longitudinal fasciculus [body movement-eye coordination, voluntary movement to reflexive activities]
---pontine reticular formation
---accessory oculomotor nuclei
----I was under the impression that I had already studied the MLF. I guess I was pretty mistaken. This is one of those extrapyramidal tracts that do not travel in the pyramid of the corticospinal system. Essentially a clump of axons near the midline of the brain stem ascend and descend with several areas of destination and origin. The descent originate usually from the medial vestibular nucleus of the upper medulla (very dorsal). Fibers from this nucleus send inhibitory signals to the anterior horn motor neurons of the cervical cord. You can also have descending fibers originating from the superior colliculus (for visual reflex), accessory oculomotor nuclei (visual tracking), pontine reticular formation (extensor muscle tone) and vestibular nuclei (balance and equilibrium). The MLF descends ipsilaterally throughout the entire anterior funiculus, synapsing on anterior horn motor neurons. Ascending fibers, originate, also in the vestibular nuclei in the upper medulla and terminate in the oculomotor (III), trochlear (IV), and abducens (VI) cranial nerve nuclei, which innervate the extraocular tracking muscles of the eyeball. This is a relatively complicated tract. Basically the vestibular nucleus is the center of things, where the tract begins either way (but tract can originate more rostrally if need be)
----The vestibulospinal pathway seems to be the 'ear' version of what I just explained. The nuclei for this tract receive afferent fibers from the vestibular nerve and afferents from the cerebellum. This controls balance and coordination. In the lateral vestibular nucleus, the tract descends ipsilaterally through the length of the entire spinal cord, at each segment terminating into laminae and into interneurons (which synapse with motor neurons at the NMJs). In case studies of injured patients, the vestibulospinal impulses are inhibited and results in decerebrate rigidity.