Hello guys. Today I'm going through UW block which I finished long back. Taking lot of time because have to read the whole q and then think about the q and then read the explanation. Its like doing it again. Then after that thinking of doing heme-onc from FA.
@zeeviq waiting for your explanation :-)
Direct as the name indicates is shorter , straighter pathway .Indirect is longer.
Direct drives movements.Indirect inhibits movements .Balance of both is essential for normal movements.
Both pathways begin at the cerebral cortex , end at the cerebral cortex , Both use striatum , both use Globus pallidus internus.Striatum is major input and GPi is the major output .Both input and output release GABA.
Dopamine from substantial nigra creates a small side circuit. It is a promoter of direct pathway .Through D1it supports the direct pathway , through D2 it inhibits the indirect pathway>> both ways it creates movement.Lost in Parkinsons disease.
Both pathways start simultaneously and help carry out one fluid movement.
Thalamus is under inhibition of GP Internus and subthalamus is under inhibition of GP Externus.Both globus pallidus nuclei are GABA secretors.
Thalamus is a movement maker .Purpose of Direct pathway is to free thalamus from GPi inhibition so that movement can occur.
It starts at the cerebral cortex which stimulates the striatum AS WELL AS substantia niagra ( kaplan misses this) . Substantia niagra and the cerebral cortex both excite the striatum ( GABA releaser ) it inhibits the next player in the step which is Globus pallidus internus .If GPI is inhibited ( inhibit the inhibitor) then thalamus is free to make movements .
Clinical correlation : loss of dopamine in substantia niagra will adversely affect the initiation of movement >>bradykinesia
The purpose of Indirect pathway is to release subthalamus that can stop thalamus through Gpi.
Its a longer pathway.
When cortex stimulates striatum ,the GABA releaser, it inhibits GPe This leaves subthalamus free of inhibition to stimulate Gpi .Gpi takes thalamus under its inhibition.>>stoppage of movement.
Loss of GABA in this pathway or subthalamic nuclei causes over excitation of muscles >> Huntingtons chorea , hemiballism
What does substantia niagra do here ?Substantia niagra through D2 receptors inhibits the striatum in the indirect pathway.In this way unwanted movement is stopped but not to the extent of rigidity >>something we fail to integrate while studying this pathway .
If substantial niagra degenerates then there is no check on the indirect pathway causing classic rigidity seen in Parkinsons.
Hi cvd and bugguy .
I put up my explanation .Unfortunately there is no diagram .Sorry for the delay .I got caught up in You tube videos and Dr najeebs lectures on this ( 3 hrs long ) and had to pull myself back because really it does not have to be that complicated. I do know the exact reasons behind bradykinesia , leadpipe rigidity and pill rolling tremors , reverberating circuits , acetylcholine and dopamine balance , why only GABA in one pathway is affected not the other .At the end of the day whatever First aid says is quite sufficient .Whatever else is best left alone for a PhD.
Thank-you zeeviq so so much , I will print your explanation and posted on my Fa
I know this is very complicated topic. Thank-you again for your effort
This is week 2 of me without my anxiety and depression medicine, its very tough for me to overcome all this and continue to study , this post help me a lot to motivate my self and to feel connected , Thank-you guys all
Just started my study for today its 2:20 pm Sunday . I want to finish some uw qs then I want to finish ethics + some hy note revision
Hi guys!!
Really nice @zeeviq- thank you!
2 weeks without medicines, it sounds that you are winning, congratulations, @bugguy!
Keep posting… this has helped me so much in recovering my study fuel. Really thank you guys!
For today, I keep my pace at HY neuroanatomy and some revision. Let's see how today will come out … so many things still need to master… seems never ending!
Here we go!
That's a long explanation. Thank you so much @zeeviq. Read it once. Should go over it again.
Yeah rush its very hard to set and study for me , each min is so painful, I diagnosed with depression and general anxiety 2 years ago , this is why I am on and of my study but I am recovering now and my doctor taper my dose so I will be medications free by end of this year , but still very difficult for my to concentrate and sit in my chair for long hours but I will not quite
doing my best every day
GL everyone
@cvd...hahaha you are right its long .
Just remember direct pathway directly inhibits GPinternus to create movement and indirect pathway stimulates GPi to stop movement.
Substantia nigra modulates both .>>stimulates direct pathway and inhibits indirect pathway and in both ways it creates movement .
Bugguy said he forgets the neurotransmitters so thats why I put in all the detail.Pretty much everything secretes GABA except substantia nigra which secretes dopamine ( and thats v easy to remember by now) and subthalamus which secretes glutamate .
It is the disinhibition phenomenon that creates all the "think in reverse " complication.I agree .
With this check the images of neuro to identify the locations of basal ganglia and its parts in CT etc .Know the mechanism behind the the 3 main diseases: parkinsons , huntingtons and hemibellismus and solve a couple of questions and you( we ) are good to go .
@bugguy SKIP the meds today .
My advice : when in doubt ; workout!!
Stay positive and keep improving one small step at a time .
Smiles