Cerebellum Flashcards
The cerebellum is responsible for what 3 things?
coordination of movements
posture & balance
tone of muscles
Where is the cerebellum located?
posterior end of brainstem
The cerebellum is a derivative of what?
Rhombencephalon (part of hindbrain)
What are the 3 lobes of the cerebellum? Give their alternative names as well.
anterior/paleocerebellum
posterior/neocerebellum
flocculus/archicerebellum
What is the paleocerebellum responsible for?
muscle tone
What is the neocerebellum responsible for?
movement coordination
What is the archicerebellum responsible for?
balance
Is cerebellar control of the motor system ipsilateral or contralateral?
ipsilateral
Describe topographic representation along the vermis.
Vermis receives motor information from the neck, shoulders, trunk, hips, eyes. Paravermal region receives sensory (particularly regarding motor function) info from the periphery (hands, feet) of the body.
How many homunculi are there in the cerebellum?
2
Damage to the primary motor cortex produces contralateral or ipsilateral motor deficit?
contralateral
What happens in the prefrontal lobe?
have idea to do something, but motor system is not activated
What happens in the premotor area?
receive idea to do something from prefrontal lobe; receives motor program from basal ganglia (after it passes through thalamus)
What happens in the basal ganglia?
receives info about movement; get motor program
What happens in the primary motor, secondary motor, and somatosensory areas?
receive motor program
What do corticospinal fibers do, broadly speaking?
travel, fire, and cause muscle contraction (movement)
How does CNS know initial position of body (necessary to get to final position)?
proprioception
What test can you do to check for working proprioception, which is necessary for movement coordination?
have patient touch index fingers in front of chest when eyes are closed
The cerebellum is a massive collector of what?
information (constantly updated)
The cerebellum is a massive collector of what?
information (constantly updated)
Is the cerebellum responsible for conscious or unconscious movement?
unconscious
What 2 structures in the brain are responsible for movement?
basal ganglia & cerebellum
What type of information does the cerebellum receive regarding movement?
info for intended movement
What structure gives the cerebellum the movement plan?
cerebral cortex
After the cerebellum receives the movement plan what happens?
movement begins: muscle contracts, spindles (sensory) fire
Once firing begins in the body and ligaments, tendons, joints, golgi, etc. fire, what happens?
copy of the movement plan is sent to cerebellum telling it how the movement is being carried out
What happens in the absence of cerebellar function?
no rapid start of movement or termination of movement; lack image & awareness
Are fibers the enter the cerebellum excitatory or inhibitory?
excitatory
What types of fibers enter the cerebellum?
mossy & climbing
Where do mossy fibers come from?
everywhere but the inferior olive
Where do climbing fibers come from?
inferior olive
Does the lateral part of the cerebellum contain a homunculus?
no
What neurotransmitter is associated with climbing fibers?
aspartate
What neurotransmitter is associated with mossy fibers?
glutamate
What neurotransmitter is associated with purkinje fibers?
GABA
What are the layers of the cerebellum, beginning with the outermost?
molecular - purkinje - granular
What type of fibers activate the deep nuclei of the cerebellum? Name their associated neurotransmitters.
mossy fibers (glutamate) & climbing fibers (aspartate)
What inhibits the deep nuclei of the cerebellum, and how?
purkinje cells via GABA
How are deep nuclei of the cerebellum activated?
directly via climbing or mossy fibers
How are deep nuclei or the cerebellum indirectly inhibited by climbing fibers?
One climbing fiber will ascend to the molecular level near the cerebellar cortex, where it will stimulate stimulate the dendrites of one purkinje cell. Activated purkinje cells release GABA onto deep nuclei, inhibiting them.
How are deep nuclei of the cerebellum indirectly inhibited by climbing fibers?
One climbing fiber will ascend to the molecular level near the cerebellar cortex, where it will stimulate stimulate the dendrites of one purkinje cell. Activated purkinje cells release GABA onto deep nuclei, inhibiting them.
How many purkinje cells do climbing cells stimulate?
one each
How many purkinje cells do mossy cells stimulate?
one mossy cell can stimulate many purkinje cells
Which fibers directly stimulate purkinje cells?
climbing fibers
Which fibers indirectly & diffusely stimulate purkinje cells?
mossy fibers
How are deep nuclei of the cerebellum indirectly inhibited by mossy fibers at the granular level?
Mossy fibers stimulate granular cells, which then sends axons to the molecular level, after which they travel to the cerebellar cortex, where they bifurcate and travel long distances all along the cortex, connecting w/ millions of purkinje cells along the way.
Which fibers terminate at the granular level?
mossy fibers
Are golgi cells excitatory or inhibitory? What do they act upon?
inhibitory; granular cells
Describe the 2 ways in which golgi cells may operate.
Mossy cell can directly stimulate the golgi cell in the granular layer to inhibit the granular cell via the release of GABA OR it can stimulate the granular cell, whose fibers at the molecular level stimulate the axon of the golgi cell, which is also in the molecular level, which then sends signals to the golgi cell body residing in the granular level to release GABA.
Where are basket and stellate cells located?
molecular level
Where are basket and stellate cells located?
molecular level
Are basket and stellate cells excitatory or inhibitory?
inhibitory
What is the purpose of stellate and excitatory cells?
to sharpen stimulation of a particular purkinje cell by dampening the the purkinje cells surrounding it, thus enhancing the stimulated cell’s neuronal signal
Where do mossy fibers terminate?
flocculus/archicerebellum
Via what nerve/fibers does the vestibular apparatus send information to the brainstem?
vestibular nerve (via CN VIII)
Describe what happens to vestibular fibers after they leave the vestibular apparatus.
they either go directly to the cerebellum or indirectly to the vestibular nuclei and then the cerebellum via the inferior cerebellar peduncle
What happens to vestibular fibers after they reach the cerebellum?
Fibers in the cerebellum go to the cortex, then stimulate the deep nuclei of the cerebellum, which send fibers to the vestibular complex. From here they then either descend as the vestibulospinal tract or ascend as the MLF.
What happens to vestibular fibers after they reach the cerebellum?
Fibers in the cerebellum go to the cortex, then stimulate the deep nuclei of the cerebellum, which send fibers to the vestibular complex. From here they then either descend as the vestibulospinal tract or ascend as the MLF.
Describe the purpose of the vestibulospinal tract.
keeps balance by activating extensor muscle (anti-gravity muscles) tone
Describe the purpose of the MLF.
internal connections of brainstem nuclei (CN III, IV, VI) created by this tract are responsible for eye movements that compensate for head movement to maintain gaze
What important structures are found in the spinocerellum?
vermis & paravermal area
What does the spinocerebellum do?
brings info from trunk & limbs to cerebellum
Which spinocerebellar tract is responsible for the lower limbs?
dorsal spinocerebellar