The cerebellum is located behind the upper part of the brainstem (where the spinal cord joins the brain) and is formed by two hemispheres or halves.
The cerebellum receives information from sensory systems, the spinal cord and other parts of the brain and then regulates motor movements. The cerebellum coordinates voluntary movements such as posture, balance, coordination and speech, resulting in a smooth and balanced muscular activity. It is also important for motor behaviors.
- 1 Anatomy of the cerebellum
- 2 The white substance
- 3 Gray substance
- 4 Cerebellar references
- 5 Cerebellum Eferences
The cerebellum is relatively small, weighs 90% less than the brain, but contains approximately half of the neurons than the brain, specialized cells that transmit information through electrical signals.
On the surface of cerebellum two hemispheres can be observed, and a central region called vermis.
The surface of the cerebellum contains numerous folds that are called folia (plates). In addition, on the surface of the cerebellum we can distinguish a series of grooves that divide the cerebellum into three lobes.
The cerebellum is divided into three lobes:
Most of the cerebellum is composed of gray matter, which is found on the surface (cerebellar cortex) and this in turn surrounds the white substance. The white substance branches to the gray forming what is calledtree of Life.
The white substance is mainly composed of axon extensions with myelin and has the function of transporting nerve information. It is found in the inner part of the cerebellum and is composed of: afferent fibers to the cortex and deep nuclei, efferent fibers of the deep nuclei and axons of Purkinje cells
Gray matter is responsible for developing the appropriate responses to the different stimuli (part of the modulator). It is formed by neuronal bodies and extensions without myelin (dendrites, unmyelinated axons and teledendrons) and is divided into the cerebellar cortex and the deep cerebellar nuclei.
It is an area of the cerebellum full of folds, so from the outside you can only observe 15% of its total area. This feature allows its surface to be much more extensive without having to increase the total volume of the cerebellum.
In turn, the cerebellum's cortex is organized in three layers:
- Molecular layer: It is the outermost layer and is formed by interneurons. It is a layer formed mainly by multiple dendrites of Purkinje cells and axons of granular cells (parallel fibers).
- The Purkinje cell layer: It lies between the molecular layer and the granular layer and is formed by a single row of soma from Purkinje cells that are the only projection cells of the cerebellar cortex.
- Granular layer: It is the innermost layer and consists of two types of interneurons, granular cells and Golgi cells. The axons of the granular cells rise to the outermost layer, the molecular layer, where they are divided into two branches parallel to the folia. For this reason they are called parallel fibers.
Deep cerebellar nuclei
Inside the cerebellum in the white substance, four pairs of nuclei can be located, which reach information on Purkinje cell inhibitors.
The deep nuclei of the cerebellum are as follows:
- Nucleus of the annoyance
- Globose core
- Emboliform nucleus
- Serrated nucleus
The cerebellum receives a large number of afferences that originate in the spinal cord, brainstem and vestibular organ.
The spinal cord sends to the cerebellum information from the skin and muscles, as well as information on the motor orders that reach the motor neurons.
The brain stem also sends sensory and motor information in the cerebellum.
These cerebellar references can do the following actions:
- Go directly to the cerebellar cortex, or
- go through the deep nuclei before.
All cerebellar activity is conducted through the axons of Purkinje cells, which are the only projection cells of the cerebellar cortex. Later axons of Purkinje cells are directed towards the deep nuclei of the cerebellum.
Eferences from the deep nuclei are directed to the thalamus and the brainstem.
The efferent fibers of the cerebellum, mossy and climbers, influence the cells of the deep nuclei and the cortex of the cerebellum.
Diamond, M.C .; Scheibel, A.B. and Elson, L.M. (nineteen ninety six). The human brain Work book. Barcelona: Ariel.
Guyton, A.C. (1994) Anatomy and physiology of the nervous system. Basic Neuroscience Madrid: Pan American Medical Editorial.
Kandel, E.R .; Shwartz, J.H. and Jessell, T.M. (eds) (1997) Neuroscience and Behavior. Madrid: Prentice Hall.
Martin, J.H. (1998) Neuroanatomy. Madrid: Prentice Hall.
Nolte, J. (1994) The human brain: introduction to functional anatomy. Madrid: Mosby-Doyma.