Cerebellum Flashcards
1
Q
The cerebellum is packed full of _________ cells.
A
Granular
NOTE:
The cerebellum constitutes only 10% of the brain’s volume, yet it contains over 50% of all neurons
2
Q
Does the cerebellum come from the alar or basal plate?
A
It develops from the dorsolateral portion of the alar plate
3
Q
The embryology of the cerebellum suggests it’s a __________ structure
A
sensory
4
Q
The cerebellum develops from the ___________portions of the alar plate.
A
dorso-lateral
5
Q
Its major output is to ___________ of the thalamus which projects to areas __________of the cortex
A
Ventrolateral nucleus; 4 & 6
6
Q
Does sensory information transmitted tot he cerebellum reach cosciusness?
A
NO sensory information, transmitted to the cerebellum reaches consciousness
*the cerebellum receives sensory input from essentially all sensory receptors.
7
Q
Will alesion to the cerebellum produce sensory problems?
A
No. Lesion will produce motor problems but not sensory problems
8
Q
Feed forward
A
Everything has been programmed and there is no way to adjust once the object of concern reaches the point of no return
9
Q
What must be “known” in feedforward actions?
A
- starting position
- (anticipated) target position
- properly timed sequence of muscle contractions of appropriate velocities/strengths
10
Q
It is currently thought that the cerebellum acts a comparator that compensates for errors in movements by comparing ___________ with performance
A
intentions
11
Q
What is corollary discharge?
A
Internal feedback or efferent copy for the intended movement
12
Q
What is reafference?
A
External (sensory) feedback for the actual movement response
13
Q
When you look at the input the cerebellum receives, in terms of intentions, if the cortex says “I want to execute this movement” the cerebellum gets a copy of it; this is called _____________.
A
corollary discharge
*A signal is going down to the spinal cord to the area of the upper limb, cervical spinal cord, and that is what the motor cortex is telling it to do.
14
Q
The sensory info the cerebellum receives does not reach consciousness. What is it used for?
A
The sensory information that the cerebellum receives is used for the automatic regulation and control of motor function (including posture).
15
Q
Through comparisons of external & internal feedback signals, the cerebellum is able to:
A
- Correct ongoing movements when they deviate from the intended course (efferent copy)
- Modify motor programs in the CNS so that future movements attain their goals, ie. motor learning
16
Q
External feedback to the cerebellum come from:
A
- Vestibular nuclei
- Spinal cord
17
Q
The cerebellum receives a massive amount of input from the vestibular system; it receives direct afferents, first order neurons, from bipolar neurons of vestibular system and some of these neurons go directly to the _____________ of the cerebellum
A
flocculonodular lobe
18
Q
From the spinal cord, the cerebellum receives information from the ___________and around the joint.
A
golgi tendon
19
Q
The dorsal and ventral spinocerebellar tracts send information from the ________ half of the body
A
lower
20
Q
The cuneocerebellar and rostrocerebellar give positional information about the positions of the ___________ limb
A
upper
21
Q
What information does the trigeminocerebellar tract provide to the cerebellum?
A
Informationa bout the postion of the head
22
Q
Main source of internal feedback is from the _________.
A
cortex
NOTE: The info from the cortex first passes through the pons and is then sent to the cerebellum via pontocerebellar fibers which are contralateral
23
Q
What type of projections are the vestibulocerebellar fibers?
A
Bilateral
24
Q
The output of the cerebellum goes to __________ systems of the brain
A
motor
25
The cerebellum forms a roof over the \_\_\_\_\_\_\_\_\_.
4th ventricle
26
Which part of the cerebellum communicates with the vestibular nuclei?
flocculonodular node
27
When are the cerebellar tonsils clinically important?
When there is an increase in **intracranial pressure**
**NOTE:** If this happens they can herniate through the foramen magnum, compress the medulla, and cause death
28
Herniation of the cerebellar tonsils causes compression of the \_\_\_\_\_\_\_\_\_\_\_
Medulla
29
The cerebellar tonsils- they can herniate through the foramen, compress the medulla and compress the cardiovascular and respiratory centers in the medulla and cause cessation of breathing and death. This is an \_\_\_\_\_\_\_\_\_malformation.
Arnold Chiari Type II
30
As an epidural hematoma gets larger, the uncus of the temporal lobe will herniate through the tentorium cerebelli and compress the \_\_\_\_\_\_\_\_\_
**Oculomotor nerve**
**\***patient has fixed and dilated pupils
31
The \_\_\_\_\_\_\_\_\_\_\_\_\_\_separates flucculonodular & posterior lobes.
posterolateral fissure
32
Label
33
The cerebellum is divided into 3 subdivisions. What are they and what is the function of each?
**Vestibulocerebellum**
* regulates balance and eye movements
**Spinocerebellum**
* receives somatosensory input from the spinal cord
* it uses this information to **modify descending motor commands** to facilitate movement, maintain balance, and control posture.
**Cerebrocerebellum**
* communicates with the cerebral cortex and is thought to be involved with planning and initiating movement.
34
The vestibular cerebellum corresponds directly to which part of the cerebellum?
flocculonodular lobe
35
What are the two parts of the spinocerebellum?
* The vermis
* The paravermal lobe (intermediate)
36
What are the components of the cerebrocerebellum?
The 2 lateral hemispheres
37
The flocculonodular lobe receives a lot of input from \_\_\_\_\_\_\_\_\_\_\_\_.
Vestibular nuclei **bilaterally** and the vestibular nerve
38
The vermis receives input from \_\_\_\_\_\_\_\_\_\_\_.
* Receives input from the **trigeminal system** and **body trunk**, afferents; golgi tendon organs and muscle spindles
* Receives input from **visual and auditory systems** because they are centrally located sensory receptors
39
The intermediate lobe receives input from receptors found in the \_\_\_\_\_\_\_\_\_.
limbs
40
Medial descending system- axons are going to rexed lamina\_\_\_\_\_\_\_\_\_
9
41
What two tracts are apart of the lateral descending system?
Lateral corticospinal tract
Rubrospinal tract
42
What tracts are apart of the medial descending system?
1. anterior corticospinal
2. vestibulospinal
3. reticulospinal
43
How is the cerebellum connected to the rest of the brain?
It gets afferents and efferents through peduncles
44
Peduncles connect the cerebellum to the \_\_\_\_\_\_\_\_\_\_\_.
brainstem
45
\_\_\_\_\_\_\_\_\_\_\_\_\_connects to cerebellum to the midbrain
superior cerebellar peduncle
46
\_\_\_\_\_\_\_\_\_\_\_\_\_\_ connects cerebellum to the pons.
middle cerebellar peduncle
47
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ connects the cerebellum to the medulla.
inferior cerebellar peduncle
48
Primarily, the cerebellum sends it's efferents through \_\_\_\_\_\_\_\_\_\_\_\_\_.
Superior cerebellar peducle
## Footnote
**NOTE:** The superior cerebellar peducle receives a small amount of afferents
49
Of the cerebellar peduncles, which _only_ recieves **afferents?**
MIDDLE CEREBELLAR PEDUNCLE
50
In general, the cerebellum receives it afferents from which structures?
In general, the cerebellum receives its afferents through the:
* **inferior cerebellar peduncle** (spinal cord & medulla)
* Has a tiny bit of efferents
* **middle cerebellar peduncle** (pons - cortical input)
* ONLY afferents
\*The superior cerebellar peduncle also has a bit of peducles
51
The inferior peducle receives afferents from which fibers?
1. Vestibulocerebellar
2. Spinocerebellar
3. Inferior olivocerebellar
52
There is output through the inferior peduncle and they form the ___________ and \_\_\_\_\_\_\_\_\_\_\_tracts.
cerebellovestibular; cerebelloreticular
53
The middle cerebellar peduncle receives afferents from which fibers?
Pontocerebellar
\*Cortical input goes to basilar pons, synapses with pontine neurons and these neurons cross and send projections to the **contralateral** side
54
There is input through the superior peduncle and it forms the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_, coming from the lower part of the spinal cord from the lower limbs
ventrospinocerebellar tract
**REMEMBER:** The superior cerebellar peduncle is the MAJOR **output** from the cerebellum
55
What are the efferents coming from the superior cerebellar peduncle?
**•Cerebellothalamic** goes to VL of the thalamus
**•Cerebellorubal** is another target (aka the red nucleus)
56
The gray matter of the cerebellum forms a\_\_\_\_\_\_\_\_\_\_\_\_\_ and \_\_\_\_\_\_\_\_\_\_\_\_.
cortex; deep cerebellar nuclei
57
The cortex of the cerebellum is organized into 3 distinct layers. What are they?
1. **molecular layer**
* largest and thickest
2. **Purkinje cell layer**
* single layer of large cells
3. **granular layer**
* packed full of probably half the neurons in the brain
58
Which component of the cerebellum is the input component? Which is the output component?
**Cortex-** Input
**Deep cerebellar nuclei-** Output
59
What are the deep cerebellar nuclei?
* Dentate nuclei
* Interposed nuclei (emboliform and globose)
* Fastigal
60
Label the layers of the cerebellum cortex
61
There are 5 cells with the in the cerebellar cortex. List them and state whether they are excitatory or inhibitory.
1. **granular cells\*** excitatory
2. **Purkinje cells\*** inhibitory
3. **stellate cells** inhibitory
4. **basket cells** inhibitory
5. **Golgi cells** inhibitory
62
Which cell type (of the cerebellar cortex) is being described below?
## Footnote
* very small cell bodies, probably the smallest in the nervous system
* They have long axons that go to the molecular layer and then it splits and runs **parallel** to the folia, forming parallel fibers of the cerebellum.
* Small but **excitatory**
Granular cells
63
Which cell type (of the cerebellar cortex) is being described below?
* cells- largest in the nervous system
* Large cell bodies and dendritic arborization which can synapse with millions of axons
**Purkinje Fibers**
**NOTE:** Even though you have zillions of granular cells the output of the entire cortex is coming from Purkinje cells
64
The axon of ___________ cells is the sole output of the cerebellar cortex.
Purkinje
\*Projects to the **deep cerebellar nuclei** (& vestibular nuclei)
65
Dendrites of Pukinje neurons fan out ___________ to the folia; however, they appear as narrow sprouts in sections parallel to the folia.
perpendicular
66
Purkinje cells project to the _____________ and are the sole (inhibitory) output of the cortex.
**deep cerebellar nuclei**
**EXCEPTION:** Purkinje cells of the *flucculonodular lobe* project to the 4 vestibular nuclei which can be thought of as deep cerebellar nuclei
67
The deep cerebellar nuclei goes to the \_\_\_\_\_\_\_\_\_\_, \_\_\_\_\_\_\_\_\_,\_\_\_\_\_\_\_\_\_\_\_, and \_\_\_\_\_\_\_\_\_.
thalamus, red nucleus, brainstem, and reticular formations
68
Three different categories of afferent fibers conduct nerve impulses to the cerebellum:
1. Aminergic fibers (modulatory)
2. Mossy fibers (exicitatory)
3. Climbing fibers (excitatory)
69
What are the two sources of aminergic fibers that modulate activitity cerebellum neurons?
1. Dorsal raphe nuclei: seratonin
2. locus ceoruleus: norepinephrine
70
The locus coeruleus of the midbrain sends \_\_\_\_\_\_\_\_\_\_\_fibers to cerebellum and most of the CNS.
noradrenergic
\*It is thought to modulate the activity of the cerebellum and most the CNS
71
Climbing Fibers originate from the \_\_\_\_\_\_\_\_\_\_\_\_.
inferior olivary nucleus (complex)
\*These axons pass through the pons and enter the cerebellum via the **inferior cerebellar peduncle** where they form synapses with the deep cerebellar nuclei and Purkinje cells.
72
Climbing fibers wrap around the soma and climb the dendrites of ___________ cells making numerous excitatory contacts
**Purkinje**
\*Early in development, Purkinje cells are innervated by multiple climbing fibers, but as the cerebellum matures, these inputs gradually become eliminated resulting in a single climbing fiber input per Purkinje cell.
73
Climbing fibers run ___________ to the folia
perpendicular
74
What type of response does the action potential evoked by climbing fibers produce?
A single action potential in a climbing fiber evokes a **complex spike** in the Purkinje cell
\*Climbing fibers provide excitatory and **low frequency** input (1 spike/s)
75
Along with the complex spike induced by the action potential of climbing fibers, what else is induced? What's the clinical significance of this?
A large Ca2+ influx
\*•It is believed that Ca is very important and involved for neuronal plasticity. So motor learning is thought to be related to these climbing fibers.
76
Mossy fibers originate from all cerebellum afferent. What is the exception?
**the inferior olivary nucleus**
\*Climbing fibers orginate from here
77
Aside from purkinje neurons, climbing fibers also send fibers to \_\_\_\_\_\_\_\_\_\_\_\_.
Deep cerebellar nuclei
78
Each mossy fibers stimulates Purkinje neurons _indirectly_ via ________ cells.
Granule cells
79
Differentiate climbing and mossy fibers.
**_Climbing_**
* Synapose _directly_ on Purkinje neurons
* Low frequency
* Complex spike activity
* Originate from **inferior olivary complex**
******_Mossy_**
* Synapse _indirectly_ Purkinje neurons (via granule cells)
* Orginate from **all** cerebellar afferents(execept one)
* Hight frequency, must be summated
80
Cerebellar \_\_\_\_\_\_\_\_\_\_\_\_cells project up through the Purkinje layer into the molecular layer where they branch out into parallel fibers that spread through Purkinje cell dendritic arbors. These parallel fibers form thousands of excitatory granule-cell–Purkinje-cell synapses onto the intermediate and distal dendrites of Purkinje cells using glutamate as a neurotransmitter.
granule
\*Granule cells have very little power overy a single Purkinje cels but have alot of power over many Purkinje cells.
81
You have a mossy fiber that synapses with a granule cell and it gives off fibers to the \_\_\_\_\_\_\_\_\_\_\_.
deep cerebellar nuclei
82
The spike below is evoked by which fiber type?
Climbing fibers
83
Which fiber type is the spike in the picture evoked by?
84
Label
85
All output from the cerebellar cortex comes from purkinje cells. Where is this output going?
To the deep cerebellar nuclei (Fastigal, Dentate, and interposed)
86
Label
87
The fibers from the vermis go to which deep cerebellar nuclei?
Fastigal
88
Fibers from the intermediate or paravermal region go to which deep nuclei?
Interposed nuclei
89
The cerebrocerebellum is going to connect to the ____________ (deep cerebellar nuclei)
Dentate
90
Of the major sections of the cerebellum, which section does not project to deep cerebellar nuclei?
**Vestibulocerebellum**
91
The _______ and ________ nuclei are involved in motor execution, via the medial and lateral descending pathways.
Fastigial and Interposed
92
The _______ nucleus is involved in motor planning via areas 4 and 6.
dentate
93
The cerebellum receives its MAJOR input from the cortex which is relayed through the \_\_\_\_\_\_\_\_.
pons
94
The corticopontine tract originates from which 4 areas?
1. premotor cortex (area 6)
2. motor cortex (area 4)
3. somatosensory cortex (areas 3, 1, 2)
4. higher order somatosensory cortex (area 5)
95
The corticospinal tract (pyramids) is about \_\_\_\_million fibers. The corticopontine tract is about\_\_\_\_\_\_\_\_ million.
1; 19
96
Corticopontine fibers pass through the \_\_\_\_\_\_\_\_\_\_\_on either side of the corticospinal tract
cerebral peduncle
97
Label
98
Corticopontine fibers terminate in nuclei found in the __________ pons.
basile
99
Pontocerebellar fibers cross in the pons & reach the cerebellum via the \_\_\_\_\_\_\_\_\_\_\_\_.
middle cerebellar peduncle
100
label
Caudal pons
101
Efferents from pontine nuclei form ___________ fibers terminating primarily in the **contralateral** cerebrocerebellum.
mossy
102
What is the pathway for denate nucleus?
1. The axons will cross to the opposite side and they will terminate in thalamus, specifically the **VL.**
* The place that these axons decussate will form the **superior cerebellar peduncle**. So terminating **mostly** in VL, some will also go to the VA and then some to the VLP
2. From the thalamus, the thalamocortical neurons are going to be going to the motor cortex, most importantly area 4, 6.
\*Some axons from the dentate nucleus also project to the red nucleus.
103
A small portion of dentate efferents synapse in the __________ before being relayed to thalamus & cortex
red nucleus (**parvocellular part)**
104
Cerebellar signs are usually \_\_\_\_\_\_\_\_\_because the decussations of the corticopontine-cerebellar tract and the cerebellothalamic tract .
**Ipsilateral**
105
Decussation of the superior cerebellar peducle is a landmark of which part of the brainstem?
Mid brain
106
What is the pathway of the interpose nucleus?
1. Axons will cross at the decussation of the superior cerebellar peduncle
2. They will terminate mostly in VL and the axons of the thalamocortical neurons will terminate at motor areas of the cortex mostly areas 4 and 6.
**REMEMBER:** The interpose nucleus is involved is **execution of limb movements** (along with the fastigial nucleus)
107
Efferents from the interpose nucleus go to areas 4 and 6. Where else do they go?
**Red nucleus** (magnocellular part)
\*The decussate at the superior cerebellar peduncle and then synapse on the magnocellular part of the red nucleus, the older part of the nucleus. The axons from here cross the midline again and form the **rubrospinal tract**
108
Lesion of the cerebellar cortex delays the \_\_\_\_\_\_\_\_\_\_\_\_.
initiation of movement
109
The fastigial nucleus gets to its targets via the \_\_\_\_\_\_\_\_\_\_\_
**Inferior cerebellar peduncle**
110
What are the two main targets of the fastigial nucleus?
a. vestibular nuclei (vestibulospinal pathways)
b. reticular formation (reticulospinal pathways)
111
What are the effects of the inputs from the fastigial nucleus?
* Posture
* Automatic movements
112
What are possible symptoms of lesion to the cerebellum?
Dyssynergia
Dysmetria
Dysdiadochokinesia
Dysarthria
Ataxia
Wide Gait
Intentional tremor
Nystagmus
113
114
Explain intential tremor.
•If the patient is just standing, everything is fine. Ask them to touch their nose, as they get closer and closer to their nose you will start to see more and more tremors. This is because the **error signal**, the closer and closer you get to the target the greater the error signal so you start getting this tremor.
115
What conditions can cause the anterior lobe of the cerebellum to degenerate?
Alcoholism
Thiamine deficiency
116
117
What are the type of clinical signs that indicate a person has cerebellar lesion?
* The major changes is that it takes longer for that individual to execute the movement. That is very demonstratable.
**REMEMBER:** The cerebellum is responsible for initiating movement
118
If you had a _________ lesion, each joint would move independently and It would be a very jerky movement.
cerebellar
**NOTE:** Cerebellar lesions are **ipsilateral**
119
How can patients with vermal damage be distinguished from patients with damage to the dorsal columns?
With the **Romberg sign**
## Footnote
* Vermal lesion: patients loose balance with their eyes **open** falling towards the lesion.
* Dorsal column lesion – patients loose balance with their eyes **closed.**
120
121
What disorder is being described below?
## Footnote
An inherited autosomal recessive disease resulting in low levels of frataxin required for mitochondrial electron transport
Fredrick's Ataxia
122
What are the symptoms of Fredrick's ataxia?
A.Muscle weakness in extremities
B.Ataxia and loss of coordination and dysmetria
C.Dysarthria & Dysphagia
123
In Fredrick's ataxia, the CNS and PNS are both affected. Which parts of CNS are affected? What about the PNS?
**PNS:** Large myelinated axons & dorsal root ganglion
**CNS**: spinal cord
1) dorsal root ganglion
2) Clarke’s nucleus and **dorsal spinocerebellar tracts**
3) dorsal columns
4) corticospinal tracts (Betz cells)
**NOTE:** From Clarkes nucleus and the spinocerebellum tracts, the dorsal columns are affected.
