LEC 24 - Cerebellum

Question 1

Describe the role of the cerebellum in motor function.

Answer 1

Coordinates rapid, sequential motor output (e.g., speech).
Integrates sensory-motor input, modulating motor function.
Regulates supraspinal reflexes via extrapyramidal system.

Question 2

How does the cerebellum evaluate and correct motor movements?

Answer 2

Compares intended vs. actual movement.
Adjusts motor cortex and brainstem activity.
Modulates muscle tone and reflexes via rubro- and reticulospinal tracts.

Question 3

What is the function of the tentorium cerebelli

Answer 3

supports the occipital lobe and protects the cerebellum from its weight.

Question 4

What are the main lobes of the cerebellum in anterior and posterior views?

Answer 4

The cerebellum contains three lobes: anterior, posterior, and flocculonodular.

Question 5

What are the cerebellar peduncles and their connections to the brainstem?

Answer 5

Superior cerebellar peduncle (SCP): Contains axons to/from the midbrain.

Middle cerebellar peduncle (MCP): Contains axons from the pons; the largest of the three.

Inferior cerebellar peduncle (ICP): Contains axons to/from the medulla.

All axons entering or exiting the cerebellum must pass through these peduncles.

Question 6

What are the four pairs of nuclei found within the white matter of the cerebellum?

Answer 6

Dentate nuclei: Located laterally.

Interposed nuclei: Comprising the emboliform and globose nuclei (two globose nuclei on each side).

Fastigial nuclei: Located medially.

Question 7

Describe the structure of the cerebellar cortex.

Answer 7

The cerebellar cortex consists of three uniform neuronal layers: the Molecular layer, the Purkinje layer, and the Granular cell layer.

Question 8

How does the cerebellum differ in terms of interconnectivity between its lobes?

Answer 8

The cerebellum lacks association fibers, meaning its lobes are not interconnected and cannot share or coordinate information.

Question 9

Define the communication capabilities of the cerebellar hemispheres.

Answer 9

The cerebellum lacks commissural fibers, which means the two cerebellar hemispheres do not communicate with each other.

Question 10

Describe the structure and function of the Molecular Layer in the cerebellar cortex.

Answer 10

The Molecular Layer is comprised of parallel axons and dendrites.
Its afferent input comes from the parallel fibers of granule cell axons, while its efferent output targets the dendrites of Purkinje cells.

Question 11

Define the role of Purkinje cells in the cerebellar cortex.

Answer 11

Thin row of large cells. They receive afferent input from parallel fibers of granule cells and climbing fibers from the inferior olivary nucleus, and their efferent output goes to the deep cortical nuclei.

Question 12

Granular Cell Layer of the cerebellar cortex, and what are their main functions?

Answer 12

Closely packed granule cells. These cells receive afferent input from mossy fibers and provide efferent output to the dendrites of Purkinje cells.

Question 13

What are the key features of afferent and efferent connections in the cerebellum?

Answer 13

1. All afferent fibers go to the cerebellum end in the cerebellar cortex.
2. Collateral copies of afferent fibers go to the cerebellar nuclei.
3. Efferent fibers from the cerebellar cortex are inhibitory, targeting cerebellar nuclei neurons.
4. Most efferent fibers from the cerebellum are excitatory and originate from the cerebellar nuclei.

Question 14

How does the cerebellum utilize feedback mechanisms for motor function?

Answer 14

Proprioceptive (sensory) feedback is received via spinocerebellar pathways and cranial nerves (e.g., trigeminal, glossopharyngeal).

Motor action (command) is communicated through pyramidal and extrapyramidal pathways.

Question 15

What are the key functions of the cerebellum in error detection and correction?

Answer 15

Cerebellum compares motor actions with sensory feedback for error correction.
Essential for movement coordination; lesions cause ataxia (uncoordinated movement).

Question 16

What are the three major proprioceptive sensory receptors

Answer 16

muscle spindles

golgi tendon organ

ruffini corupuscles

Question 17

Describe the role of muscle spindles in proprioception.

Answer 17

Muscle spindles provide information about changes in muscle length, specifically indicating muscle stretch.

Question 18

Define the function of Golgi tendon organs in the musculoskeletal system.

Answer 18

Golgi tendon organs provide information about changes in muscle tension, indicating muscle contraction.

Question 19

How do Ruffini corpuscles contribute to proprioception?

Answer 19

Ruffini corpuscles are located in joint capsules and provide information related to joint position.

Question 20

Describe the function of the posterior spinocerebellar tract.

Answer 20

Posterior spinocerebellar tract relays lower limb and torso signals to the cerebellum, including sensory feedback from muscle spindles and Golgi tendon organs.

Question 21

How does the glossopharyngeal nerve contribute to sensory perception?

Answer 21

The glossopharyngeal nerve (CN IX) provides sensory functions for taste and touch from the posterior one-third of the tongue.

Question 22

Define the role of the vagus nerve in sensory feedback.

Answer 22

Vagus nerve (CN X) provides general sensory feedback from the laryngopharynx, larynx, and visceral sensory feedback: thoracic/abdominal viscera.

Question 23

What is the significance of the trigeminal nerve in sensory processing?

Answer 23

Trigeminal nerve (CN V) transmits pain, temperature, and touch from the face and mucous membranes, plus proprioception from mastication and facial muscles.

Question 24

Describe the role of mossy fibers in the cerebellum.

Answer 24

Mossy fibers carry afferent info to the cerebellum from sources like pontine nuclei, spinal cord, vestibular nerve, and reticular formation, ending in the granule cell layer.

Question 25

How do climbing fibers differ from mossy fibers in their function?

Answer 25

Climbing fibers from the inferior olivary nucleus target the Purkinje cell layer, carrying info from the spinal cord, reticular system, red nucleus, cerebral cortex, and cerebellum.

Question 26

Do climbing fibers provide input or output to the cerebellum?

Answer 26

Climbing fibers provide input to the cerebellum, specifically targeting the Purkinje cell layer.

Question 27

How are Purkinje cells structurally adapted to their function?

Answer 27

Purkinje cells have dense dendrites to accommodate the axons of the granule cells.

Question 28

What is the vestibulocerebellum and its composition?

Answer 28

Unconscious functional loop, doesn’t require cerebral cortex.
Composed of the flocculonodular lobe

Question 29

How does the vestibulocerebellum receive input and send feedback?

Answer 29

receives input from vestibular nuclei and nerve.
Sends feedback to vestibular nuclei via fastigial nuclei, influencing vestibulospinal tracts.

Question 30

What is the function of the vestibulospinal reflex in the vestibulocerebellum?

Answer 30

The vestibulospinal reflex maintains body equilibrium by keeping the body centered and maintaining muscle tone, primarily through the lateral vestibulospinal tracts.

Question 31

What roles do the vestibulocervical reflex play?

Answer 31

The vestibulocervical reflex stabilizes the position of the head through the medial vestibulospinal tracts.

Question 32

What roles does the vestibulo-ocular reflex play?

Answer 32

The vestibulo-ocular reflex stabilizes gaze during head movement, involving the medial vestibular nucleus.

Question 33

What are the components and functions of the spinocerebellum?

Answer 33

Regulates muscle tone, posture, and balance via medial motor pathways (e.g., reticulospinal tract).
Involved in involuntary activities like swallowing.

Question 34

How does the spinocerebellum receive and send information?

Answer 34

Spinocerebellum receives input from extrapyramidal tracts (unconscious motor plans) and brainstem (e.g., swallowing).

Sends information back via fastigial and interposed nuclei to extrapyramidal tracts and brainstem.

Question 35

What are the components and main functions of the cerebrocerebellum?

Answer 35

The cerebrocerebellum is composed of the lateral hemispheres and receives afferent projections primarily from the contralateral neocortex (e.g., motor cortex).

Function: coordinating fast and alternating movements, such as writing and speech production, by planning movements regarding direction, timing, and force (muscle strength).

Question 36

What is the role of the middle cerebellar peduncle in the cerebrocerebellar loop?

Answer 36

Transmits afferent input from pontine nuclei to cerebellum.

Contains afferent axons from the pons (pontocerebellar tract).

Question 37

What are the key features of the superior cerebellar peduncle in the cerebrocerebellar loop?

Answer 37

Superior cerebellar peduncle: Contains efferent axons directed to the midbrain.

Includes dentatothalamic tract (projects to motor cortex via thalamus).

Includes dentatorubral tract (targets parvocellular red nucleus).

Question 38

What are the effects of alcohol consumption on cerebellar function?

Answer 38

Alcohol can impair cerebellar function, causing:
Ataxic gait (loss of balance)
Nystagmus (involuntary eye movements)
Slurry speech
Dyspraxia (loss of skilled movement)

Question 39

What is cerebellar ataxia and its causes?

Answer 39

Cerebellar ataxia: Caused by faulty proprioception integration.

Spinocerebellar/vestibulocerebellar lesions: Lead to truncal ataxia.

Cerebrocerebellar lesions: Cause limb ataxia and dysarthria.

Question 40

What is dysarthria and how does it relate to cerebellar damage?

Answer 40

Dysarthria: Impaired speech modification, causing slow, slurred, and disjointed speech.
Common in bilateral cerebellar lesions due to compromised motor control.

Question 41

What is ataxic dysarthria and its characteristics?

Answer 41

Ataxic dysarthria: Caused by damage to the cerebellar control circuit.
Affects respiration, phonation, resonance, and articulation.
Results in issues with articulation and prosody, with a harsh vocal quality and excessive syllable stress.

Question 42

How do cerebellar loops modulate motor pathways?

Answer 42

Cerebellum influences spinal motor neurons via descending motor pathways, without direct input.

Three loops:
Cerebrocerebellar: Plans and regulates fast movements.
Vestibulocerebellar: Regulates balance and eye movement.
Spinocerebellar: Coordinates head, neck, trunk, and limb movements.