Cerebellum: Afferent and Efferent Pathways – Anatomy Review

00:01 So let's talk about the major cerebellar pathways.

00:04 the Cerebro-cerebellar, the spinocerebellar, and the vestibulocerebellar.

00:09 We're gonna walk through each of the pathways, and what we'll find is the cerebellum is connected to three things.

00:15 It's connected to the brain, to the spine, and to the ears.

00:19 And so we'll talk about three inputs: inputs from the brain, from the spine, and from the vestibular apparatus.

00:26 In order for things to get into the cerebellum, we'll find that everything has to relay in the brainstem.

00:32 So the first stop is in the brainstem.

00:35 From there, we'll find that the circuitry distributes to the major aspects of the cerebellum.

00:40 The brain is going to talk to the hemispheres, the spine will talk to the vermis, and the vestibular apparatus or ears will talk to the flocculonodular lobe.

00:49 In order for the cerebellum to get information out, all of that is relayed through the deep cerebellar nuclei.

00:55 And we'll walk through those nuclei that are involved.

00:58 And most of the cerebellar output will be through the superior cerebellar peduncle.

01:04 Inputs come in through the inferior and middle cerebellar peduncle, and most of the output is through the superior cerebellar peduncle.

01:12 Let's start with the Cerebro-cerebellar pathway.

01:15 This information starts in the cortex.

01:18 It descends down to the pontine nuclei, and that's the first major relay.

01:24 From there we see information travels to the cerebellar hemispheres.

01:28 Again, the brain typically talks with the cerebellar hemispheres.

01:32 That's how that the movement coordination and language is coordinated.

01:37 From there, the information relays into the deep nuclei, the deep gray matter nuclei, and then out through the superior cerebellar peduncle to the thalamus.

01:46 The thalamus is the relay ccenter for the brain.

01:48 And so information from there is distributed back to the cortex.

01:52 So we can see how the brain talks to the cerebellum.

01:55 And the cerebellum is able to modulate brain functions through this pathway.

02:00 The key as in our case, is the major output is the superior cerebellar peduncle.

02:07 The Cerebro-cerebellar pathways involved in coordinating and modulating movements, including the planning, and the timing, and rhythm of movements.

02:15 And so on exam, we look at those movements.

02:18 We look at rapid alternating movements, and finger-to-nose finger, and truncal tone.

02:23 But the cerebellum is also coordinating many other functions in the Cerebro-cerebellar pathway and circuitry is also involved in the intention, in language, and other cortical aspects of cerebellar function and cognition.

02:37 What about the spinocerebellar pathway? What are the inputs? Where does it relay? Where's the major relay center within the cerebellum and what are the outputs? This information starts in the spine.

02:51 And we see that information, a sends in the spine again to the pontine nuclei.

02:56 All the inputs start in the midbrain.

02:59 We see input travel to the vermis of the cerebellum, the spine talks to the vermis.

03:04 And that's what modulates and coordinates our movement and postural tone.

03:08 From the vermis, the output is to the deep cerebellar nuclei, those deep gray matter nuclei.

03:13 And then out to the red nucleus through the superior cerebellar peduncle.

03:17 Again, that superior peduncle is where all of the outputs are traveling.

03:21 From the red nucleus, we see information descend back down through the medullary reticulospinal tracts.

03:27 And those are tracks involved in posture.

03:29 They keep us upright, standing in a straight line and walking in a straight line.

03:34 Importantly, the cortex also sends information down to the red nucleus and to the spine itself to modulate some of that information as well.

03:44 So this is the spinocerebellar pathway.

03:47 What about the last pathway? The last circuit the vestibulocerebellar pathway.

03:53 Here we see afferets come in from the vestibular nerve.

03:57 And as opposed to other, our two other pathways we see that that input innervates directly on to the flocculonodular lobe.

04:05 It's really important that our head movement is coordinated rapidly with our posture and our eyes and that this is coordinated in a rapid fashion.

04:14 And so there's no relay or minimal relay in the deep brainstem nuclei this travels right to the flocculonodular lobe.

04:22 From there we see the output descends into the deep cerebellar nuclei.

04:26 And again, those are the major output nuclei of the cerebellum.

04:30 And then to the vestibular nuclei and the reticular formation, and those are going to be important for integrating the cerebellar coordination with other movements of the posture, and the eyes, and the head.

04:41 There are two major descending spinal tracks: The vestibulospinal tract and reticulospinal tract that are important in coordinating that our head, and eye, and posture, and arms, are all moving in the same direction.

04:53 And so those are the two major output tracks.

04:58 Now, let's talk about the Deep Cerebellar Nuclei.

05:01 Again, the way the cerebellum is structured, is it receives input from three places: the brain, spinal cord, or the ears, or vestibular apparatus.

05:09 That information relays and one of the major cerebellar lobes, the hemispheres, vermis, or flocculonodular lobe.

05:16 And before leaving the cerebellum, synapses in the deep cerebellar nuclei.

05:21 And that's that final place before information is outputted to the rest of the nervous system.

05:27 We're going to learn about these nuclei that dentate nuclei, the Ebola form and interposed nucleus, and the fastigial nucleus.