the word cerebellum translates to little brain not because it's the brain of a tiny animal or baby but rather because the fact that the cerebellum looks like a smaller version of the human cerebrum very simply the cerebellum assists with coordinating and adjusting voluntary movement it plays a major role in posture balance maintenance of muscle tone and coordinating skilled voluntary motor activities things like riding a bicycle or for the more adventurous walking a tightrope in order for the cerebellum to undertake these functions it has to be in constant communication with the cerebral cortex it also sends and receives signals to many other structures in Central and peripheral nervous systems processing information about current movement and positional States in order to help refine correct and improve the motion now the cerebellum sits in the posterior part of the cranium called the posterior cranial fossa and it's covered by the tentorium cerebelli which separates the cerebellum from the occipital and temporal lobes of the brain anterior to the cerebellum lies the fourth ventricle pons a medulla oblongata just like the cerebrum the cerebellum consists of two hemispheres these two hemispheres are connected by a narrow Ridge in the middle called the vermis from an inferior view parallel to the vermis there are two distinguishable lobules called the cerebella tonsils the cerebellum can be divided into three lobes the anterior lobe the posterior lobe and the flocculonodular lobe from a superior view we can identify the anterior lobe functionally referred to as a spinal cerebellum which is responsible for the regulation of muscle tone and adjusting ongoing movements posterior to the anterior lobe is the v-shaped primary fissure from a superior View and posterior to this primary fissure is the posterior lobe functionally referred to as a cerebro cerebellum or pontocerebellum which contains a horizontal fissure separating the superior and inferior surface of the cerebellum the cerebral cerebellum is the largest part of the cerebellum Anders responsible for assisting in planning and programming of skilled or fine motor movements looking at the cerebellum from an anterior view the posterior lobe is bounded by the posterolateral fissure this fissure separates the posterior lobe from the third lobe of the cerebellum called the flocculonodular lobe or functionally referred to as the vestibulose cerebellum the foculonodular lobe is responsible for the maintenance of posture and balance the floccular nodular lobe is named such because it contains essential part of the vermis called the nodule as well as two lateral flocculi if we continue to view the cerebellum from the anterior aspect we can see bundles of dense white matter that attach the cerebellum to the brain stem these white matter stalks are called cerebellar peduncles and consists of superior middle and inferior divisions they contain efferent and afferent axons that signal back and forth between the cerebellum and the central nervous system the superior cerebellar peduncle connects the cerebellum with the midbrain the middle cerebellar peduncle connects with the pons and the inferior cerebellar peduncle attaches to the Medela oblongata afferent fibers to the cerebellum can be found within all three cerebellar peduncles but the majority of afferent signals easy inferior and middle peduncles for Passage efferent signals from the cerebellum however travel mainly through the superior bed uncle On A sagittal section the cerebellum looks similar to the cerebrum in that the cortex is folded creating ridges with small sulci in between the difference however is that in the cerebellum the cortical rigids are thinner smaller and organized into more parallel layers which are called Folia these Folia not only increase the surface area but enable the large area of Cortex to fit into a smaller space just like the cerebrum the folio contain an external gray matter layer called the cerebellar cortex and a subcortical white matter region deep to the external gray matter as we see the shape of this white matter within the Folia creates a tree-like Arrangement or branching pattern referred to as Arbor Vitae or Tree of Life on a transverse section of the cerebellum we can see four clusters of deep gray matter nuclei buried deep within subcortical white matter these deep cerebellar nuclei or interest cerebral nuclei contain multi-polar neurons that receive signals from the cerebellar cortex and other parts of the nervous system and their axons contribute to the formation of the three cerebellar peduncles from lateral to medial these deep cerebellar nuclei consists of the dentate Ebola form globose and fastidious nuclei to remember these remind yourself that in order to have a healthy cerebellum you don't eat greasy Foods in addition to having anatomical divisions the cerebellar cortex can also be divided into three functional regions that are positioned longitudinally the most lateral and largest functional region is a lateral Zone the lateral Zone sends signals to the dentate nucleus the largest of the deep cerebellar nuclei and together they assist in planning and programming movements medial to the lateral zone is the intermediate Zone also known as a paramedian or paravermal Zone the intermediate Zone sends signals to the Ebola form and globos nuclei collectively these two nuclei are known as the interposed nuclei and are usually referred to together as they both work in the intermediate Zone finally most medial and occupying the cortex of the vermis is a third functional Zone the median or verbal Zone the median Zone will send signals to the fastidious nucleus which is the most medial of the deep cerebellar nuclei located within the vermis and next to the roof of the fourth ventricle the intermediate and median zones along with their deep cerebellar nuclei are involved in modulating motor execution of lateral and medial descending motor pathways respectively let's take a quick break and see if you can identify the lobes of the cerebellum as well as the functional zones and deep cerebellar nuclei now let's have a look at the afferent Pathways which bring information to the cerebellum to be processed and the efferent pathways which leave the cerebellum to help coordinate motor activity afferent Pathways generally originate from the spinal cord and brain stem the cerebral cortex and the vestibular system starting with the afferent Pathways from the spinal cord to the cerebellum let's look at the ventral or anterior spinal cerebellar pathway first it carries proprioceptive information from muscle spindles Golgi tendon organs and Joint receptors of the lower extremities then the afferent fibers enter the spinal cord where the synapse with spinal border cells located in lamina 7 of the spinal cord gray matter from here the majority of these axons crossed to the contralateral side of the spinal cord and form the ventral spinal cerebellar pathway which ascends in the white matter of the spinal cord to the brain stem here the axons cross back over and enter the cerebellum through the superior cerebellar peduncle to reach the cerebellar cortex the signals on the ventral spinal cerebellar pathway cross over the neural axis and then cross back so it's often referred to as a double Crosser next is the dorsal or posterior spinal cerebellar pathway this pathway contains fibers that receive proprioceptive information from muscle spindles Golgi tendon organs and Joint receptors mainly found in the trunk and lower extremities this information enters the spinal cord from peripheral nerves and the signal synapses on Clark's nucleus or Clark's column also known as nucleus dorsalis instead of crossing over after they synapse the axons Ascend in the ipsilateral white matter of the spinal cord to the brain stem where they then enter the cerebellum through the inferior cerebellar peduncle to reach the cerebellar cortex the final afferent pathway that carries proprioceptive information from the extremities is called the cuneocerebellar pathway the axons in this pathway receive proprioceptive information from muscle spindles Golgi tendon organs and Joint receptors within the Upper Limb and upper thorax signals within this pathway synapse in the external or accessory cuniate nucleus located in the medulla the axons travel ipsilaterally through the inferior cerebellar peduncle to reach the cerebellar cortex let's now move on to the afferent Pathways from the cerebral cortex to the cerebellum which include the cortico Ponto cerebellar cerebralovo cerebellar and cerebral reticulocerebellar pathway talk about your tongue twisters okay now these Pathways originating in the cerebral cortex signal through brain stem structures to reach the cerebellum and allow for these areas to communicate to further regulate and modify voluntary movements for example the initiation planning and timing of motor activities this information is important to the cerebellum to know so that it can take part in making the appropriate adjustments and modifications to that plan for Synergy and overall motor coordination the cortico Ponto cerebellar pathway is important in relaying motor commands of the cortex and begins with the afferent fibers arising from the cerebral cortex of the frontal temporal parietal and occipital lobe these fibers signal through the Corona radiata and internal capsule to synapse on pontine nuclei then the signals are sent along transverse fibers called pontocerebellar fibers the crossover and enter the middle cerebellar peduncle to terminate in the cortex of the contralateral cerebellar hemisphere the cerebral Olive ocerebellar pathway also begins in the cerebral cortex of the four lobes and sends its fibers through the Corona radiata and internal capsule where the fibrous synapse in the inferior olivary nuclei after synapsing these fibers cross the midline and travel through the inferior cerebellum peduncle to synapse with the contralateral cerebellar hemisphere the cerebral reticulo cerebellar pathway also arises from the cerebellar cortex however mainly from the sensory motor cortical regions associated with the parietal lobe the axons descend in the same way as the previous two Pathways and snaps at the nuclei of the reticular formation located in the ponds in medulla these fibers then travel through the middle and inferior cerebellar peduncles to terminate in the cerebellar hemisphere of the ipsilateral side finally the last major system to provide afferent information to the cerebellum is the vestibulose cerebellar pathway it plays a key role in the maintenance of balance posture body position and coordination of eye movements this pathway Begins by receiving sensory input regarding motion from the semicircular canals of the inner ear as well as body position relative to Gravity from the saccule and neutral via the vestibular nerve a portion of the vestibular cochlear cranial nerve during the course afferent fibers of the vestibular nerve either signal straight through the inferior cerebellar peduncle to the ipsilateral cerebellar cortex or the synapse first in the vestibular nuclei of the brainstem before signaling to the cerebellum together these afferent fibers reach the cerebellar cortex of the floccular nodular lobe to be processed the vestibulo cerebellar pathway gathers visual input as well these afferent fibers originate from the superior colliculus and the primary visual cortex and the visual information is relayed through the superior cerebellar peduncle to reach the floccular nodular lobe okay now that was a lot to take in let's take a quick quiz and see if you can identify the afferent tongue twisters I mean Pathways from the brain to the cerebellum on this image so now that we've discussed the major afferent Pathways of the cerebellum what does the cerebellum do with all the information it's received well the cerebellum processes this information and the cerebellar cortex relays a movement modification message to the Deep cerebellar nuclei which then sends signals along different afferent fibers to places such as the vestibular nuclei Thalamus red nucleus reticular formation cerebral cortex and the spinal cord in doing so the cerebellum plays a continuous role in maintaining posture balance and modifying adjusting and coordinating movements of the body the first efferent pathway we're going to discuss is a vestigial vestibular pathway which is responsible for regulating extensor muscle tone fibers originate in the vestigial nucleus of the cerebellum and travel through the inferior cerebellar peduncle to synapse on the lateral vestibular nuclei from here some efferent fibers form the vestibulospinal tracts which signaled the motor neurons of the spinal cord that control anti-gravity musculature that helps maintain posture other efferent fibers will form the medial longitudinal fasciculus which transmits information to the motor nuclei of cranial nerves three four and six to modify and control movements of the eye another important efferent pathway of the cerebellum is a dentatothalamic pathway which is responsible for modifying ipsilateral motor activity this pathway begins in the dentate nucleus of the cerebellum where fibers cross the midline and travel through the superior cerebellar peduncle to the contralateral ventrilateral nucleus of the thalamus the fiber synapse in the thalamus and from there the signal continues through the internal capsule and Corona radiata to reach the primary motor cortex once here the information is relayed to motor pathways such as the corticospinal tract and this is how the cerebellum influences and modulates motor activity of descending motor pathways next there's a globose ebola form rubro pathway which also influences ipsilateral motor activity these efferent fibers begin in the globose and emboliform nuclei travel across the midline through the superior cerebellar peduncle and synapse with the contralateral red nucleus this pathway influences motor activity of the rubospinal tract which acts on proximal flexor musculature of the Upper Limb finally we have the vestigial reticular pathway where inferent signals originate in the fastidual nucleus travel through the inferior cerebellar praduncle and then synapse with neurons in the reticular formation these signals provide modulatory information to the medial and lateral reticular spinal tracts which collectively are involved in regulation of muscle tone and posture alright as a quick recap the cerebellum is located in the posterior cranial fossa below the occipital and temporal lobes and ventral to it is the fourth ventricle pons a medulla oblongata it has two hemispheres which are connected by the vermis and is divided into three lobes the primary fissure divides the anterior and posterior lobes while the posterolateral fissure separates the posterior lobe from the flocculonodular lobe from an anterior view the cerebellum is connected to the rest of the central nervous system via the superior middle and inferior cerebellar peduncles looking at a cross-section of the cerebellum it's composed of gray matter folds with white matter within that form Folia the four deep gray matter nuclei are the dentate and Bola form globose and fastidious nuclei the cerebellar cortex can be divided into three functional zones the median which helps to adjust medial descending motor pathways that include those that act on axial musculature the intermediate or paramedian Zone which assists in adjusting lateral descending motor pathways that include those that act on appendicular musculature and the lateral Zone that works on planning and evaluating movements major afferent Pathways from the spinal cord to the cerebellum include the ventral spinal cerebellar pathway the dorsal spinal cerebellar pathway and the cuneocellular pathway major afferent Pathways from the brain to the cerebellum include the corticopontocerebellar pathway the cerebral Olive ocerebellar pathway and the cerebral reticulocerebellar pathway the vestibular cerebellar pathway gathers information from the semicircular canals in her ear Superior colliculi and primary visual cortex to help maintain balance posture body position and coordinate eye movements and finally the efferent pathways from the cerebellum include the vestigial vestibular pathway the dentatothalamic pathway the globos and Bola form rubal pathway and the vestigial reticular pathway helping current and future clinicians Focus learn retain and Thrive learn more