Unit 5 Flashcards
What does cerebellum mean and why is the name misleading?
„Little brain“
Has more neurones that rest of brain (50 billion vs 22 billion)
What does the cerebellum generally do?
Plays important role in motor functions that require coordination of muscle contractions, aim and timing
Forms connections with every major motor structure of cerebral cortex
Functions at unconscious level
-> influences balance, posture, muscle tone and coordination of movement
What is muscle tone?
Tension in a muscle at rest that helps maintain posture
How does the cerebellum control movement?
Receives visual, auditory, vestibular and somatosensory information + motor commands
-> integrates information to produce smooth, coordinated movements
What does damage to the cerebellum cause?
Jerky, erratic and uncoordinated movements
Difficulty tapping a rhythm, clapping hands, pointing to a moving object, speaking and writing
Finger-to-nose test
Used to quickly assess cerebellar functioning
Hold arm out straight, touch nose with index finger when instructed (as quickly as possible)
Why is this test used by the police?
Cerebellum one of first brain areas to be affected by alcohol
-> used to assess alcohol intoxication
What difficulties do people with damage to cerebellum have when doing the finger to nose test?
Disrupts ability to do the test
Miss nose/go to far/ unable to hold finger in front of nose
What are peduncles?
Bundles of axon fibres through which information enters and leaves cerebellum
Which peduncles are there?
Superior peduncle: connects to midbrain
Middle peduncle: from pons to cerebellum
Inferior peduncle: connects to medulla
What is the vermis?
Midline/central region of the two cerebellar hemispheres (separates them)
What is the folia?
The many folds the outer surface of the cerebellum consists of
What are the three lobes of the cerebellum?
Anterior, posterior and flocculonodular lobe
primary fissure
separates anterior from posterior lobe
posterolateral fissure
demarcates small region on the ventral side
-> flocculus
-> vermis
grey and white matter
white matter internal
grey matter external
What is the branching pattern the white matter in the cerebellum produces referred to?
arbor vitae (tree of life)
What are deep cerebellar nuclei?
grey matter
produce messages
sent from cerebellum to other areas
The layers of the cerebellum
molecular (outer)
Purkinje (middle)
granular (inner)
granular layer
cell bodies of granule cells
receive information from other parts of CNS and sent it to more external layers
parallel fibres
originate from granular cells
extend to molecular layer
-> branch out in parallel with each other
-> oriented in parallel with surface
What does the Purkinje layer consist of?
single layer of purkinje cells
-> have dendritic arborisations extending to outer layer
-> receive excitatory input from parallel fibres
What does the molecular layer consist of?
mostly of dendritic arborisations of purkinje cells
granule parallel fibres
Purkinje cells
only neurones in cerebellum projecting axons from cerebellar cortex to other parts of cerebellum-> carry information to deep cerebellar nuclei
which deep cerebellar nuclei are there?
consist of dentate, emboliform, globose and fastigial nuclei
-> primary source of output
-> organised into four bilateral pairs
Which neurotransmitter do deep cerebellar nuclei use?
GABA
mossy fibres
branch out and terminate in granular layer
climbing fibres
synapse with purkinje cells
some axons branch off and project directly to deep cerbellar nuclei
What do the signals the cerebellum receives consist of?
sensory, somatosensory and motor information
How does information arrive at the cerebellum?
through mossy and climbing fibres entering through peduncles
How does the cerebellum coordinate movement? (path)
information detected around body
-> sent to cerebellum
-> processes and integrates information
-> sends information back to body parts or brain to help it modify movement
what does damage to the flocculonodular lobe or vermis cause?
disturbances in posture and balance
damage to vermis can make it impossible to stand or sit without falling over
What does damage to the anterior lobe cause?
deficits in movement
e.g. limb rigidity
Does damage to the cerbellum cause contra- or ipsilateral deficits?
ipsilateral
-> cerebellum projects ipsilaterally to spinal cord
.> projects contralaterally to brain
What does damage to the neocerebellum cause?
disrupted timing of rapid movements
uncoordinated movement
-> unilateral damage only causes incoordination of ipsilateral arm and leg
-> damage to both sides (often through alcohol intoxication) causes slow speech and dysarthria
What is dysarthria?
breaking words into individual syllables
Nystagmus
involuntary to-and-fro motion of eyes
-> symptoms worse when gaze directed at same side as site of damage
-> damage to cerebellum causes impairments of coordination of eyes
