Cerebellum Flashcards
What’s the structure of the cerebellum?
It has an outer cortex consisting of gray matter and a deep nuclei consisting of white matter.
What are the three components/distinct events that occur when you make a voluntary action?
Which brain regions mediate these events to occur?
You plan/program it.
You Initiate it.
You Execute it.
[1] Planning/Programming:
- Pre-Motor Areas (PMA) of Frontal Cortex (includes Broca’s area) -Contain stored motor programs, acquired through practice & rehearsal (i.e., Procedural Memory)
- These are Required to generate complex movement sequences (e.g. speech)
[2] Initiation:
- The Primary Motor Cortex (M1) mediates this.
- It Activates the Intended motor program
[3] Execution:
• Posterior Parietal Cortex (PPC) & the Cerebellum Supervise & Coordinate movements in progress
What are the sensory aspects of motor control?
(i.e. what sensory informtion do you take in for volunatry/motor control?)
The Motor Plan/Program:
- takes account of sensory information about
- current head, eye, body & limb positions
- which are rarely ever the same!
Execution of the Movement itself:
- generates sensory feedback, in different systems, for example:
- changes in head position (vestibular system)
- muscle contraction & joint positions (proprioceptive system)
- body parts moving in the field of view (visual system)
The Cerebellum receives all this information:
•And calculates the best way to coordinate the timing, force & amplitude of the desired muscle contractions
[The arrow with the update plan written above it represents the motor plan/program being changed/tweaked by the cerebellum (which nearly always happens) before the act is executed]
What do cerebellar cortex dysfunctions cause?
Because its normal sensory-motor coordination functions involve regulating:
- Proper force & sequences of muscle contraction (timing)
- Accurate movement sizes & amplitudes (space)
Cerebellar lesions (damage) cause ‘Ataxia’ - A disorder characterized by clumsy & misdirected movements- which are as follows:
•Intention Tremor & ‘Decomposition’ (this is basically mis-timing of muscle forces & contraction sequences)
•Dysmetria (this is basically inaccurate movement amplitudes (over- or under-shooting))
What is the gross anatomy of the cerebellum?
How many regions is the outer cortex made up of and what are they?
What do the regions of the outer cortex do?
Where do neurones in the deep nuclei recieve information from?
How many pairs of nuclei are there in the deep nuclei and what are they called?
The outer cortex and deep nuclei.
The outer cortex is made up of three regions. The midline region which is called the Vermis (means worm in greek) and the two lateral regions which are the two hemispheres of the cerebellum.
The three regions recieve and integrate sensory and motor inputs.
The neurones in the deep nuclei receive information from the outer cortex and they send out motor outputs involved in coordinating responses.
3 Pairs - they are called Fastigal, Interposed and dentate.
Two or false- the three outer cortex regions of the cerebellum have grey matter on the outside and white matter inside & are deeply folded.
True
[This is similar to the structure of the cerebral cortex)
True or false - Just like the cerebral cortex, the hemispheres of the cerebellum are concerned with events happening on the opposite side.
False - Unlike the cerebral cortex, they are concerned with events on
the same side of the body.
Describe the structure of the cerebellar cortex.
The cerebellar cortex is made up of three regions (the vermis and two lateral hemispheres) which are made up of a further 3 sub lobes.
One of those sub lobes is the vermis itself and small medial extensions (called the Flocculo-Nodular Lobes).
The other two main sub lobes are the:
- Anterior Lobe (this consists of the superior surface, only)
- Posterior Lobe (this consists of the superior surface + entire inferior surface) = largest, most lateral part of the cerebellar cortex
True or false - Anterior & Posterior Lobes contain proprioceptive MAPS
of the body & are separated by the ‘Primary Fissure’.
True
What are the two types of input the cerebellar cortex receives?
All three sub-lobes recieve input about the motor plan/program - they get sensory information AND feedback (remember the plan will literally be getting altered as you do it - think back to the flashcard with that disgram he drew using shapes).
However Sensory Information & Feedback occurs specifically to each specific sub-lobes
- Vermis & FN lobe recieves input from vestibular system for head position & head movements
- Anterior lobe recieves proprioceptive information about muscle tensions & joint positions in all regions of the body, directly from the spinal cord & brainstem
- Posterior lobe receives similar proprioceptive information, but from the Somatosensory Cortex & also visual information from the Visual Cortex
Where does each part of the cerebellar cortex send outputs to?
The cerebellar cortex sends outputs to the deep nuclei.
Specifically:
- From Midline Vermis + FN Lobe to Fastigial Nucleus (medial, smallest)
- From Anterior Lobe to Interposed Nucleus (in-between)
- From Posterior Lobe to Dentate Nucleus (lateral, largest)
What is the difference between cerebellar and cerebral?
Cerebellar - refers to something relating to the cerebellum
Cerebral - refers to something relating to the cerebral cortex
Summarise cerebellar connections in the cerebellum (so all the pathways in the cerebellum only)
What are the three main cerebellar outputs?
The regulation of balance, posture and gait ( this refers to how you walk).
What does the red nucleus do?
Coordinates fine (hand, vocal) movements
