Basal ganglia Direct and indirect pathways - #Usmle Neuroanatomy Animations

[Music] welcome to another video on Anatomy in this video we'll be discussing about the direct and indirect pathways of the basal ganglia on a daily basis we perform thousands of movements from walking to writing to grabbing a cup of coffee and so many other skill based works did it ever cross your mind that what in the brain is actually responsible for organizing in smoothening all these tasks the answer to that question lies within the structure called basal ganglia two major pathways emerged from the basal ganglia which project onto various structures of the brain communicating with them they are called the direct or the excitatory and the indirect or the inhibitory pathways the basal ganglia are a part of the extra pyramidal system and participate in the movement modulation input signals from the cerebral cortex are received processed within the basal ganglia after that it will create a focused output signal that ends up within the motor neurons of the frontal lobe in the brainstem these signals serve for planning and proper execution of a movement unlike the cerebellum basal ganglia do not receive input signals from the spinal cord but they are directly connected to the cerebral cortex from the stratum the two main pathways from the basal ganglia arise which are called the direct and indirect pathways the direct pathway begins in the cortex and follows the following pathway please pay close attention to it begins from the cortex travels to the striatum to the Globus pallidus internus and substantia pars reticulata s' to the thalamus and eventually closing it back to the cortex this loop or this pathway is excitatory which means it promotes movement now let's see individual components of this pathway the direct pathway starts from the cortex to the striatum now remember that stratum is comprised of caudate nucleus and putamen this pathway from the cortex to the striatum is excitatory the neurons office radom are activated by the input signals from the cortex by the neurotransmitter called glutamate these neurons which are activated in the striatum are inhibitory neurons which use the gamma amino butyric acid as their main inhibitory neurotransmitter the axons from the stratum reached the Globus pallidus internus and substantia pars reticulata s' so the pathway from the striatum all the way to the Globus pallidus internus is inhibitory the neurons from the Globus pallidus internus and substantia pars reticulata s' send their axons to the thalamus and remember that even these neurons are inhibitory type these fibers going from the Globus pallidus to the thalamus form two fascicles of white matter called the anti lenticularis and the lenticular fasciculus that before entering the thalamus fused into one pathway called the thalamic fasciculus now hence the pathway from the Globus pallidus internus to the thalamus is again inhibitory pathway from the thalamus excitatory pathways go to the cortex which is the prefrontal and the promoter and the supplementary areas of the cortex these excitatory pathways affect the planning of the movement by synapsing with the neurons of the corticospinal in the cortical bulb our tracks thus the tract from the thalamus to the motor cortex is excitatory note that functionally the first and the last one are excitatory whereas the second and the third are inhibitory this is very important to understand the function of the basal ganglia this entire system works on a positive feedback mechanism the question arises is how well because two of the inhibitory synapses are connected one after another the first inhibitory neuron which is striatum suppresses the activity of the second inhibitory neuron which is the Globus pallidus due to this there will be a reduction of inhibitory influence of the Globus pallidus or the thalamus so there will be a disinhibition of the thalamus which is equivalent to the excitation of the motor cortex that is a negative of negative resulting in a positive so the general function of the direct pathway of the basal ganglia is to excite the motor cortex or to increase the motor activity now let's take a look at the indirect pathway the indirect pathway also begins in the cortex and proceeds as follows the indirect pathway starts from the cortex travels to the striatum travels to the Globus pallidus external further on to involve the subthalamic nucleus and then comes back to the Globus pallidus internus and the substantia pars reticulata eventually terminating into the lamina and back to the cortex now this loop or circuit is inhibitory which means it inhibits the movement unlike the direct pathway which is excitatory wherein it promotes movement now let's get into the details of indirect pathway step by step the indirect pathway starts from the cortex to the striatum this pathway from the cortex to the striatum is excitatory it activates the inhibitory neurons within the striatum the inhibitory neurons from the striatum synapses with the external segment of the globus pallidus the neurons of the external segment of the globus pallidus sends inhibitory fibers to the subthalamic additionally the subthalamic sends excitatory projections back to the Globus pallidus internus and the substantia pars reticulata so functionally the striatum inhibits the Globus pallidus external and that causes a disinhibition of the subthalamic for this reason the neurons of the subthalamic become more active and they excite the internal segment or the Globus pallidus so finally this loop inhibits the thalamic nuclei the end result of this pathway is a decreased activity of the cortical motor neurons and the consequential suppression of the extemporaneous movement now it is thought that the direct pathway promotes voluntary movement in targeted muscles whereas the indirect pathway simultaneously inhibits the movement in other muscles that do not contribute to the overall wanted movement the result is a coordinated smooth movement in which those muscles necessary for the desired movement are recruited while the other muscles that might affect the flow off of the decide movement are inhibited

Channel: Dr.G Bhanu Prakash Animated Medical Videos

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Keywords: Basal ganglia Direct and indirect pathways, basal ganglia physiology, basal ganglia pathway, basal ganglia, basal ganglia direct and indirect pathways animation, basal ganglia direct and indirect pathways usmle, basal ganglia direct vs indirect pathway, basal ganglia direct pathway, basal ganglia indirect pathway, basal ganglia animation, basal ganglia neuroanatomy, basal ganglia direct and indirect pathway youtube, basal ganglia youtube, basal ganglia anatomy, neet pg, usmle, mrcp

Id: UtacLPnoa28

Length: 8min 56sec (536 seconds)

Published: Sun Jul 05 2020