The Cerebellum
The Cerebellum analyzes and interprets motor signals and corrects at each step for execution of smooth movement. It utilizes a negative feedback control system (dampening) to do this. The cerebellum, or little brain has more than 50% of axons in the cerebral cortex, is separated into two hemispheres and connected by the vermis (worm). It is connected to the nervous system by three peduncles; the superior which outputs to the cortex via the thalamus; the middle which inputs and outputs via the pons; the inferior which inputs outputs with the brain stem and spinal cord.
A "blueprint" of coordinated movement is sent to the cerebral motor cortex via the cerebellum. The cerebellar peduncles integrate sensory information about skeletal muscle position and coordinate the extremities to maintain posture and also receives input of the intent to initiate voluntary muscle contraction. Proprioceptors and visual signs "inform" the cerebellum of the position of the body and momentum and the cerebellar cortex calculates the best way to perform a movement.
Connectivity is via pre-motor cortex, to motor cortex, to somatosensory cortex, to posterior parietal cortex to the pontine nuclei to the cerebellum to the ventral lateral thalamic nucleus. All inputs from mossy/climbing fibers to the cerebellum are excitatory. Deep nuclei 10^10 granule cells each connected to 500 Purkinje cells, each Purkinje cell has synapses from about 10^5 granule cells. The only output from the cerebellar cortex is from the inhibitory Purkinje cells. The main output from the cerebellum as a whole is mostly from the deep, excitatory cerebellar interneurons; basket, golgi and stellate cells.
Cerebellar blood supply; 3 branches of the vertebral/basilar artery; PICA, AICA, SCA
3 lobes, posterior, anterior, flocculonodular
3 peduncles, ICP, MCP, SCP
3 cortical layers; molecular, purkinje, granule cell
3 deep nuclei, dentate, emboliform/globose, fastigial
3 regions; neurocerebellum, paleocerebellum and archicerebellum
The three functional divisions of the cerebellar cortex are the vermis, intermediate and lateral zone.
Flocculonodular lobe.
A "blueprint" of coordinated movement is sent to the cerebral motor cortex via the cerebellum. The cerebellar peduncles integrate sensory information about skeletal muscle position and coordinate the extremities to maintain posture and also receives input of the intent to initiate voluntary muscle contraction. Proprioceptors and visual signs "inform" the cerebellum of the position of the body and momentum and the cerebellar cortex calculates the best way to perform a movement.
Connectivity is via pre-motor cortex, to motor cortex, to somatosensory cortex, to posterior parietal cortex to the pontine nuclei to the cerebellum to the ventral lateral thalamic nucleus. All inputs from mossy/climbing fibers to the cerebellum are excitatory. Deep nuclei 10^10 granule cells each connected to 500 Purkinje cells, each Purkinje cell has synapses from about 10^5 granule cells. The only output from the cerebellar cortex is from the inhibitory Purkinje cells. The main output from the cerebellum as a whole is mostly from the deep, excitatory cerebellar interneurons; basket, golgi and stellate cells.
Cerebellar blood supply; 3 branches of the vertebral/basilar artery; PICA, AICA, SCA
3 lobes, posterior, anterior, flocculonodular
3 peduncles, ICP, MCP, SCP
3 cortical layers; molecular, purkinje, granule cell
3 deep nuclei, dentate, emboliform/globose, fastigial
3 regions; neurocerebellum, paleocerebellum and archicerebellum
The three functional divisions of the cerebellar cortex are the vermis, intermediate and lateral zone.
Flocculonodular lobe.