Cerebellum A/P

Question 1

Generally describe the structure and location of the cerebellum

Answer 1

The cerebellum is a “leafy” structure that is found behind (dorsal to) the pons and medulla. It’s found in between the cerebral cortex and the spinal cord.

Question 2

Describe the function of the cerebellum.

Answer 2

Coordination of movement, planning and execution of movement, maintenance of posture and coordination of head and eye movement. Basically integrates sensory information from the spinal cord, motor information from the cerebral cortex and balance information from the vestibular system.

Question 3

What are the two motor control centers of the CNS?

Answer 3

Cerebellum and the Basal Ganglia.

Question 4

What is the midline of the cerebellum called?

Answer 4

It’s called the “Vermis,” which has the superior and inferior vermis component. Superior vermis in anterior lobe, inferior vermis in posterior

Question 5

Describe the 3 sections of the cerebellum.

Answer 5

The vermis (superior and inferior) is the center of the cerebellum, adjacent to that in either side is called the paravermal or intermediate hemisphere, and lateral to that is the lateral hemisphere (which dominates most of the size of the cerebellum).

Question 6

What is the “fluconodular lobe?”

Answer 6

It is the thin middle horizontal slice of the cerebellum that runs all the way through the lateral hemisphere, the intermediate hemisphere and the vermis.

Question 7

What are the 3 lobes of the cerebellum?

Answer 7

Anterior, posterior and floculonodular lobes.

Question 8

Where are both the cerebellum and pons derived from?

Answer 8

Derived from the “Metencephalon.”

Question 9

What separates the cerebellum and the dorsal aspect of the pons?

Answer 9

The 4th ventricle.

Question 10

What can be found inside the cerebellar cortex?

Answer 10

It has multiple parallel folds that has “maps” of the skeletal muscles of the body.

Question 11

What is the function of the vermis?

Answer 11

Controls the axial (trunk) and proximal musculature of the limbs.

Question 12

What is the function of the paravermal or intermediate hemisphere? (of cerebellum)

Answer 12

Control of the distal musculture.

Question 13

What is the function of the lateral hemispheres of the cerebellum?

Answer 13

It is involved in motor planning, which mainly involves the distal musculature.

Question 14

What is the function of the flocculonodular lobe?

Answer 14

It’s function is to control balance, smooth execution of movements, and eye movement.

Question 15

Generally, what can we say that the vermis and the intermediate hemispheres of the cerebellum doing?

Answer 15

It is control ALL motor executions of the entire body regardless of being axial or limb located.

Question 16

Major input TO the cerebellum comes from where?

Answer 16

It comes from the spinal cord inputs (from golgi tendons and muscle spindle) and then up to the middle and inferior cerebellar peduncle, which relays information into the cerebellum.

Question 17

Major input FROM the cerebellum goes where?

Answer 17

It goes out through the superior cerebellar peduncle.

Question 18

Where is the lateral hemisphere of the cerebellum getting its input from? What’s it involved with?

Answer 18

Since it is involved with motor planning and coordination, much of its input comes from the cerebral motor cortex (indirectly via the cortical spinal tract), and also the inferior olivary nucleus.

Question 19

What is the inferior olivary nucleus’ role?

Answer 19

Acts as an “error detector,” meaning that it projects axons into the cerebellum and influences the cerebellar neurons to change how a movement is performed in the future (in a way to correct a previously “wrong” movement?)

Question 20

Where is the input of the flocculonodular lobe coming from?

Answer 20

Since it is involved in balance and eye movements it makes sense that the input comes from the vestibular nuclei (CN 8).

Question 21

Where are the inferior cerebellar peduncles coming from and what does it do?

Answer 21

It arises from the medulla and carries information from the spinal cord and olive into the cerebellum.

Question 22

Where are the middle cerebellar peduncles coming from and what does it do?

Answer 22

Coming from the motor cortex into the cerebellum (thus, they are affarent pathways) and it simply relays the information from the motor cortex to the cerebellum.

Question 23

What is the purpose of the superior cerebellar peduncle?

Answer 23

Takes information from the cerebellum out, this is the only way information from the cerebellum leaves, wheres the MCP and ICP delivers information TO the cerebellum.

Question 24

What are the 3 layers of the cerebellar cortex?

Answer 24

Molecular layer, purkinje layer, and granule cell layer.

Question 25

What is the outer most layer of the cerebellar cortex called and what does it do?

Answer 25

Outer most layer is called the “Molecular layer,” largely acellular with a lot of parallel fibers (axons of the granule cells). It also has baskets and stellate cells, and the dendric tree of the purkinje cells extend into this layer.

Question 26

What is the middle layer of the cerebellar cortex called and what does it do?

Answer 26

Middle (and most important!) layer is called the “Purkinje layer,” and it has purkinje cells. Only axons of the purkinje cells leave the cerebellum cortex, and all inputs into the cerebellum is trying to modulate the firing of the purkinje cells.

Question 27

What is the inner most layer of the cerebellar cortex called and what is its function?

Answer 27

Innermost is called “Granule cell layer,” and it contains intrinsic granule cells, golgi cells and glomeruli. Granule cells are the only cells in the cerebellar cortex that is excitatory, whereas all other cells are inhibitory.

Question 28

What are “glomerulus” in the cerebral cortex?

Answer 28

A glomerulus contains a granule cell, axons from golgi cells, and is surrounded by glial capsule.

Question 29

What are the largest cells of the CNS?

Answer 29

The purkinje cells.

Question 30

What is the role of granule cells?

Answer 30

2 roles, 1. is to synapse into purkinje cells and 2. it is the only excitatory cell of cerebellar cortex.

Question 31

What are “golgi cells?”

Answer 31

Inhibitory interneurons that synapses into the dendrites of granule cells.

Question 32

How do all the inputs to the cerebellum contrast with all the neurons (except one type) within the cortex?

Answer 32

All neurons within the cerebellar cortex are inhibitory except the granule cells, whereas all the inputs to the cerebellum are excitatory.

Question 33

What are the 2 types of afferent fibers entering the cerebellum?

Answer 33

Excitatory mossy fibers and excitatory climbing fibers.

Question 34

Where do climbing fibers come from? What is the tract called? How do they enter the cerebellum?

Answer 34

Inferior olivary nucleus, the dominant feature of the upper medulla sections grossly. The tract is called the “Olivocerebellar tract,” enters through the inferior cerebellar peduncle. where it decussates.

Question 35

Where do climbing fibers go?

Answer 35

From the olivary nucleus to the cerebellum through the inferior cerebellar peduncle, where it will terminate on excitatory terminals of the purkinje cells.

Question 36

Where are mossy fibers coming from?

Answer 36

All inputs into the cerebellum not coming from the olivary nucleus uses the mossy fibers. This includes from the motor cortex (cortico or pontocerebellar tract), the spinocerebellar tract (from the spinal cord) and the vestibulocerebellar tract (from the vestibular nucleus).

Question 37

What is the excitatory neuron used by the CNS?

Answer 37

Glutamate.

Question 38

What do mossy fibers do?

Answer 38

Since they are affarent fibers into the cerebellum they are excitatory and thus their target is the excitatory terminals of the granule cells.

Question 39

Where do purkinje cells of the cerebellum synapse?

Answer 39

It synapses onto the deep cerebellar nuclei.

Question 40

How do climbing fibers differ in their excitation of Purkinje cells from Mossy fibers?

Answer 40

Climbing fibers provide both direct and indirect (through stimulation of the deep cerebellar nuclei) stimulus to the purkinje cells. Mossy fibers can only do so indirectly.

Question 41

How do mossy fibers stimulate the purkinje cells?

Answer 41

Regardless from where they come from, they all stimulate the granule cells, which sends its axons up to the molecular layer, bifurcates and through parallel fibers stimulate the purkinje fibers.

Question 42

How do the input and output from the cerebellum differ?

Answer 42

All input into cerebellum is excitatory, all output from cerebellum is inhibitory and mediated exclusively from the axons of the purkinje fibers, which happens to be the only axons leaving the cerebellum.

Question 43

Where do axons of the purkinje cells, stellate cells, golgi cells, basket cells and granule cells terminate? Which of these cells are excitatory and inhibitory?

Answer 43

Golgi cell axons terminate in granule cells, purkinje cell axons terminates in the deep cerebellar nuclei, and all others terminate in the purkinje cells. Everything but the granule cells area inhibitory, and granule cells are excitatory.

Question 44

What are the neurotransmitters used for excitatory and inhibitory fibers in the cerebellum?

Answer 44

Excitatory uses glutamate, inhibitory uses gamma amino buteryc acid (GABA).

Question 45

What are the 3 types of deep cerebellar nucleus?

Answer 45

Fastigal nucleus, the Interposed nucleus (composed of Emboliform and Globose nucleus) and the dentate nucleus.

Question 46

What are the deep cerebellar nucleus known as “interposed nucleus” composed of?

Answer 46

2 nucleus, the emboliform nucleus and the globose nucleus.

Question 47

The purkinje cells from the cerebellum are all linked to different deep cerebellar nucleus based on their locations. To which nucleus are the purkinje cells from the vermis, the intermediate (or paravermal) hemispheres and the lateral hemispheres linked to?

Answer 47

Pkje cells from vermis synapse onto the fastigial nucleus, from the intermediate hemispheres to the interposed nuclei, and the lateral hemispheres to the dentate nucleus.

Question 48

Where do purkinje cells from the floculonodular lobe go to?

Answer 48

Into the lateral vestibular nucleus.

Question 49

What is the goal of cerebellar outflow (via the deep cerebellar nuclei)?

Answer 49

The firing of the upper motor neurons, and thereby also modulate the lower motor neurons indirectly.

Question 50

In an overarching view, what is the general function of the cerebellum?

Answer 50

Smoothes out the contractions and relaxation of all striated muscles by comparing the actual vs intended movement.

Question 51

What is the function of the anterior lobe of the cerebellum?

Answer 51

Anti-gravity muscles regulation to modulate posture.

Question 52

Function of the posterior love of the cerebellum?

Answer 52

It deals with fine motor coordination.

Question 53

What is “Anterior Vermis Syndrome?”

Answer 53

Most commonly caused by alcohol abuse, it leads to trunk, leg, and gait ataxia. Involves the anterior lobe of the cerebellum.

Question 54

What is “Posterior Vermis Syndrome?”

Answer 54

Is usually secondary to brain tumors in children (i.e. medulloblastomas and ependymomas), this involves the flocculonodular lobe and leads to truncal ataxia.

Question 55

Through what tract does the outflow of cerebellar information travel?

Answer 55

The “Dentatothalamic tract” through the superior cerebellar peduncle, which goes to the VL/VA nucleus of the thalamus. SCP also receives input from the ventral spinocerebellar tract affarents.

Question 56

Where does the MCP receive inputs from to send to the cerebellum?

Answer 56

From the pontocerebellar tract.

Question 57

Where does the ICP receive input to send to the cerebellum?

Answer 57

From olivocerebellar tract (from inferior olivary nucleus from contralateral medulla), the cuneocerebellar tract, and the dorsal spinocerebellar tract.

Question 58

Where do clinical manifestations of cerebral lesions present?

Answer 58

It presents in the ipsilateral side of cerebral lesions due to double decussations.

Question 59

What’s the “double decussation” in the cerebellar outflow fibers?

Answer 59

The deep cerebral nucleus fibers would leave the SCP and then cross over at the midbrain, and from there axons will travel down to:

1. The red nucleus, and the 2nd decussation occurs in the midbrain, axons descend down the rubrospinal tract ipsilateral to original side of the cerebellum that initiated the impulse.
2. VL/VA nucleus of the thalamus –> precentral gyrus –> axons descends down the corticospinal tract and second decussation in medulla (pyrimidal decussation) and then fibers descend down the CST again.

Question 60

What are the clinical symptoms of cerebellar damage?

Answer 60

Mnemonic is VANISHEDD: Vertigo, Ataxia, Nystagmus, Intention tremor, Slurred/Staccato speech, Hypotonic reflexes, Exaggurated broad-based gait, Dysdiadochokinesia (inability to do rapid alternating movements) and Dysmetria (inability to use voluntary movement to point to a place in 3D space, as presented by the finger-to-nose movements).

Question 61

Trace the axons coming out of the Dentate nucleus.

Answer 61

Crosses midline in the midbrain (1st decussation) and synapses in the motor nuclei of the thalamus (Ventral Lateral (VL) and Ventral Anterior (VA) nuclei of thalamus). These nuclei project to the motor cortex and influence the firing of Upper Motor Neurons (UMN) at their cellular locations and go down the CST.
** Note, the CST neurons would decussate a second time to influence the lower motor neurons.**

Question 62

What is the hallmark of cerebellar dysfunction?

Answer 62

Tremor with intended movement without weakness or paralysis.

Question 63

How do patients with a vermal lesion present and how does one differentiate between a lesion in the cerebellum vs a lesion in the dorsal column?

Answer 63

Presents with difficulty maintaining posture, gait or balance (an ataxic gait). In cerebellar lesion a pt will fall with their eyes open, meaning neg Romberg sign, but in a dorsal column lesion a patient will fall with their eyes closed + Romberg sign. (Motor vs sensory ataxia).

Question 64

How would a patient present with posterior vermal lesion?

Answer 64

This affects the truncal muscles so patient will have difficulty sitting up, thus truncal ataxia.