so in the next several slides we'll talk about the circuitry that makes the basal nuclei work
and how it works with the rest of your motor systems so it's complicated I cannot even go
into how complicated it is and for the level of neural anatomy that I want you to know for
this particular MOOC I'm not going to ask you to memorize lots and lots of complicated you know
inhibitory inputs and excitatory inputs because it's really really complicated and we're still
learning quite a bit about this system so we're gonna just kind of talk in broad broad
strokes so in general our motor cortex is up here motor cortex sends information not just
through the internal capsule to your muscles but to the striatum and just for simplicity's sake
I just have the arrow drawn to the putamen other components are the Globus pallidus the subthalamic
nucleus in the substantia nigra in general the substantia nigra is sending information back up
to the striatum there's another part of the brain that's deep in the brain called the thalamus and
the thalamus is really important for both motor and sensory systems it's a sensory relay that we
talked about as that third neuron in the in the three neuron paths with sensory sensations that
made sense sensory sensations and it then sends information back up to motor cortex so there
are two pathways that I want you to be aware of there's a direct pathway and an indirect pathway
the direct pathway facilitates appropriate motor programs so the the direct pathway some of the
differences between direct and indirect are going to revolve around the Globus pallidus
the subthalamic nucleus and their connections back and forth to the nigra and the thalamus
what I want you to know and all I want you to know for this course is that the direct
pathway facilitates appropriate motor program so if there's something wrong with your direct
pathway you may be unable to initiate a normal habitual motor behavior like you may be unable to
initiate walking the indirect pathway is involved in inhibiting unwanted motor behaviors so again
the basic circuitry exists it from nigra back to to striatum from thalamus to motor cortex and
motor cortex down to striatum and again there are going to be differences in how the Globus
pallidus and the subthalamic nucleus play into this but the bottom line and what I want you to
understand and know for this at this level is that the indirect pathway inhibits so if you had damage
to one of the components of your indirect motor pathway here within the basal nuclei you may have
unwanted motions like a tremor perhaps or some sort of unwanted writhing motion those are all
going to be associated with the indirect pathway so in summary what I want you to know are what
are the components of the basal nuclei and what larger parts of the brain are they associated
where are they in the brain if I gave you a big picture of a coronal section I'd want you to be
able to point out the caudate and the putamen and the Globus pallidus and the nigra what's
the basic circuitry so those three big arrows that I had drawn on that on the diagram of the
brain and then really what's the difference between the direct and the indirect pathways
with regard to motor function if you know all that then you're ready for the assessment