2. Cerebellum
• The cerebellum (Latin for little brain) is a region of the brain that
plays an important role in motor control.
• It is also involved in some cognitive functions such as attention and
language, and probably in some emotional functions such as
regulating fear and pleasure responses.
• does not initiate movement but it contributes to coordination,
precision, and accurate timing.
• receives input from sensory systems and from other parts of the
brain and spinal cord, and integrates these inputs to fine tune
motor activity.
• receives input from sensory systems and from other parts of the
brain and spinal cord, and integrates these inputs to fine tune
motor activity.
3. Structure
• At the level of large scale anatomy, the cerebellum
consists of a tightly folded and crumpled layer of
cortex, with white matter underneath, several deep
nuclei embedded in the white matter, and a fluid-filled
ventricle at the base.
• At the microscopic level, each part of the cortex
consists of the same small set of neuronal elements,
laid out with a highly stereotyped geometry
• At an intermediate level, the cerebellum and its
auxiliary structures can be decomposed into several
hundred or thousand independently functioning
modules called "microzones" or "microcompartments".
4.
5.
6. Function
• The cerebellum is comprised of small lobes
and receives information from the balance
system of the inner ear, sensory nerves, and
the auditory and visual systems. It is involved
in the coordination of motor movements as
well as basic facets of memory and learning.
7. Subdivisions
flocculonodular lobe
• The smallest region is often called the
vestibulocerebellum. It is the oldest part in
evolutionary terms
• participates mainly in balance and spatial
orientation
• its primary connections are with the vestibular
nuclei, although it also receives visual and other
sensory input.
• Damage to it causes disturbances of balance and
gait.
8. spinocerebellum
• also known as paleocerebellum.
• functions mainly to fine-tune body and limb
movements.
• It receives proprioception input from the dorsal
columns of the spinal cord as well as from visual
and auditory systems.
• It sends fibres to deep cerebellar nuclei that, in
turn, project to both the cerebral cortex and the
brain stem, thus providing modulation of
descending motor systems.
9. cerebrocerebellum
• also known as neocerebellum.
• It receives input exclusively from the cerebral
cortex (especially the parietal lobe) via the
pontine nuclei and sends output mainly to the
ventrolateral thalamus and to the red nucleus.
10. Cell Components
• Two types of neuron play dominant roles in the cerebellar
circuit:
• Purkinje cells
• granule cells.
• Three types of axons also play dominant roles:
• mossy fibers
• climbing fibers (which enter the cerebellum from outside)
• parallel fibers (which are the axons of granule cells).
• There are two main pathways through the cerebellar
circuit, originating from mossy fibers and climbing fiber
limbing fibers, both eventually terminating in the deep
cerebellar nuclei.
11. Purkinje cells
• Purkinje cells are among the most distinctive
neurons in the brain, and also among the earliest
types to be recognized.
• Purkinje cells are a class of GABAergic neurons
located in the cerebellar cortex.
• named after their discoverer, Czech anatomist Jan
Evangelista Purkyně
• -with an intricately elaborate dendritic arbor,
characterized by a large number of dendritic
spines.
12. Granule Cells
• Granule cells refer to tiny neurons that are around 10
micrometres in diameter.
• found within the granular layer of the cerebellum
• In humans, estimates of their total number average
around 50 billion, which means that about 3/4 of the
brain's neurons are cerebellar granule cells.
• A granule cell emits only four to five dendrites, each of
which ends in an enlargement called a dendritic claw.
These enlargements are sites of excitatory input from
mossy fibers and inhibitory input from Golgi cells.
13. Mossy fibers
• In the human cerebellum, the total number of
mossy fibers has been estimated at about 200
million.
• form excitatory synapses with the granule cells
and the cells of the deep cerebellar nuclei.
• generates a series of enlargements called
rosettes
14. Climbing fibers
• Climbing fibers are the name given to a series of
neuronal projections from the inferior olivary
nucleus located in the medulla oblongata.
• Climbing fiber activation is thought to serve as a
motor error signal sent to the cerebellum, and is
an important signal for motor timing.
• carry information from various sources such as
the spinal cord, vestibular system, red nucleus,
superior colliculus, reticular formation and
sensory and motor cortices.
15. Deep nuclei
• These nuclei receive inhibitory (GABAergic)
inputs from Purkinje cells in the cerebellar
cortex and excitatory (glutamatergic) inputs
from mossy fiber and climbing fiber pathways
• Most output fibers of the cerebellum originate
from these nuclei
