Lecture 8- The Cerebellum Flashcards
What is the reticular formation?
Composed of clusters of gray matter scattered throughout midbrain, pons and medulla
Neurons project up via the thalamus
What is the reticular formation’s functions?
- Governing the arousal of the brain
- involved in habituation (a process in which the brain learns to ignore repetitive, inconsequential stimuli while remaining sensitive to others)
What is the reticular formation depressed by?
- depressed by alcohol, sleep-inducing drugs & tranquilisers
- inhibited by sleep centres located in the hypothalamus & other brain regions
What happens if the reticular formation is damaged?
-brainstem injury: permanent unconsciousness (irreversible coma)
Where is the cerebrum located in terms of the cranial fossas?
Posterior cranial fossa
What meningeal fold sits above the cerebellum?
The tentorium cerebelli separating the cerebrum from the cerebellum
What does the cerebellum consist of?
Consists of cortex, white matter and deep nuclei
What is the cerebellum’s primary function?
-synchronised, precisely timed movement across multiple joints = synergistic multijoint limb movement
Eg. throwing a ball, finger-to-nose test
• control of muscle tone (posture)
• maintenance of balance
Does the cerebellum receive more sensory or motor output?
receives vast amount of sensory
information, but does not give rise
to conscious sensory perceptions
• 40x more afferents than efferents
How much of the neurons of the brain does the cerebellum contain? What allows this?
- containing 50% of the neurons in the entire brain in order to synchronize movements
- It’s very ordered structure allows this
How is synergistic multijoint movement achieved?
-Frontal motor association areas (eg. premotor cortex)
via the corticopontine-cerebellar tract, inform cerebellum
of intent to start voluntary muscle contractions.
-At the same time, the cerebellum receives information
from proprioceptors throughout the body, as well as visual
and vestibular (balance) input.
-The proprioceptive information includes tension in
muscles and tendons and the position of joints.
-This information allows the cerebellum to evaluate body
position and momentum = where the body is and where it
intends to go.
-The cerebellar cortex and the deep cerebellar nuclei then
calculate the best way to coordinate the force of each
muscle contraction to prevent overshoot, maintain posture
& ensure smooth coordinated movement.
-Then, the cerebellum dispatches to the motor cerebral
cortex its “blueprint” for coordinating movement. The
primary motor cortex then influences motor neurons in
the spinal cord to produce movement.
What is the cerebellar lesion patient usually capable and not capable of?
A patient with a cerebellar lesion is usually capable of
carrying out general outlines of movement, but each
movement is executed with suboptimal coordination and
precision.
In order to be able to carry out it’s function what anatomy does the cerebellum need?
Cerebellum needs to be connected to the motor input
from cerebral cortex, the various sensory inputs and needs
to send its output or blueprint back to the cerebral cortex
Needs the cerebellar peduncles
Where are the different cerebellar peduncles located in the brain stem
- Superior cerebellar peduncle= midbrain
- Middle cerebellar peduncle= pons
- Inferior cerebellar peduncle= medulla
Label the peduncles on anterior and superior views of the cerebellum…
One note
