Psychobiology part 2 unit 5

Question 1

Question: What does the word “cerebellum” mean, and how does its neuron count compare to the cerebral cortex?

Answer 1

Answer: The cerebellum means “little brain,” but it contains 50 billion neurons—more than twice the 22 billion neurons in the cerebral cortex.

Question 2

Question: What key functions does the cerebellum manage?

Answer 2

Answer: The cerebellum manages balance, posture, muscle tone, and the coordination of movement, all unconsciously.

Question 3

How does the cerebellum help with muscle tone?

Answer 3

Answer: Muscle tone refers to the tension in a muscle at rest, and the cerebellum adjusts it to maintain posture.

Question 4

What sensory and motor inputs does the cerebellum integrate to produce movement?

Answer 4

Answer: The cerebellum combines visual, auditory, vestibular, somatosensory, and motor commands from the brain to create smooth, coordinated actions.

Question 5

Question: What symptoms can occur if the cerebellum is damaged?

Answer 5

Answer: Damage can cause jerky, uncoordinated movements, difficulty with rhythmic actions (like clapping), trouble speaking or writing, and struggles with fine motor skills.

Question 6

Why is the cerebellum important in sobriety tests like the finger-to-nose test?

Answer 6

Answer: Alcohol impairs cerebellar function, making it difficult to perform tasks requiring precise coordination, like touching the nose with a finger.

Question 7

Question: How is the cerebellum connected to the brainstem?

Answer 7

Answer: The cerebellum is attached to the brainstem by three cerebellar peduncles:

Superior peduncle connects to the midbrain.
Middle peduncle connects to the pons.
Inferior peduncle connects to the medulla.

Question 8

Question: What are the main structural divisions of the cerebellum?

Answer 8

Answer: The cerebellum has two hemispheres joined by a central region called the vermis. The surface is folded into structures called folia, which maximize surface area.

Question 9

Question: How is the cerebellum divided into lobes?

Answer 9

Picture a pizza with three slices. The cerebellum has three “lobes” divided by grooves called fissures:

Anterior lobe: The small slice at the front, responsible for basic motor tasks.
Posterior lobe: The larger slice at the back, involved in coordination of fine movements.
Flocculonodular lobe: A tiny slice underneath, critical for balance and eye movements.

Question 10

Question: What are the main layers of the cerebellum, and what are their functions?

Answer 10

Answer:

Outer grey matter (cerebellar cortex): Processes incoming information.
Inner white matter: Contains axons forming a branching pattern called the arbor vitae (“tree of life”).
Deep cerebellar nuclei: Output center sending signals to other brain regions.

Question 11

Question: What are the three layers of the cerebellar cortex, and what do they contain?

Answer 11

Molecular layer (outer): Contains the branches (dendrites) of specialized neurons called Purkinje cells and axons called parallel fibers, where many connections happen.
Purkinje layer (middle): A single row of Purkinje cells, which act like master regulators. They collect all the input and send processed information to the deep nuclei.
Granular layer (inner): The entry point for signals coming into the cerebellum, where cells process input and pass it upward.

Question 12

Question: What is the role of Purkinje cells in the cerebellum?

Answer 12

Answer:

Purkinje cells are the only neurons that send output from the cerebellar cortex.
They project to the deep cerebellar nuclei and control cerebellar output using inhibitory signals via GABA.

Question 13

Question: What are the two main types of afferent fibers in the cerebellum?

Answer 13

Answer:

Mossy fibers: Terminate in the granular layer and communicate with granule cells.
Climbing fibers: Directly synapse with Purkinje cells and sometimes project to deep nuclei.

Question 14

Question: What is the “arbor vitae,” and what does it contain?

Answer 14

Answer: The “arbor vitae” is the branching pattern of white matter in the cerebellum. It contains:

Axons of Purkinje cells projecting to the deep nuclei.
Afferent axons like mossy and climbing fibers.

Question 15

Question: What are the deep cerebellar nuclei, and what is their function?

Answer 15

Answer:

The nuclei include the dentate, emboliform, globose, and fastigial nuclei.
They are the primary output center, sending signals to influence movement.

Question 16

Question: What are afferent and efferent pathways in the cerebellum?

Answer 16

Afferent pathways bring sensory, somatosensory, and motor information into the cerebellum.
Efferent pathways send signals from the cerebellum to influence motor commands.

Question 17

Question: What symptoms occur with damage to the flocculonodular lobe or vermis?

Answer 17

Disturbances in posture and balance.
Inability to stand or sit without falling over, even if limb coordination is preserved when lying down.

Analogy: Imagine a chair missing its central support. It collapses when you try to sit on it.

Question 18

Question: What deficits can occur due to damage to the anterior lobe of the cerebellum?

Answer 18

This can cause rigidity in your limbs, making them feel stiff and hard to move.
Analogy: Think of a rusty hinge—it still moves but with difficulty and resistance.

Question 19

Why does cerebellar damage affect the same side of the body (ipsilateral)?

Answer 19

The cerebellum communicates directly with the spinal cord on the same side of the body.
In some cases, it sends signals to the opposite side of the brain, but those signals cross back to the original side.

Analogy: Imagine sending a package through two couriers who meet and hand it off. Even if the couriers switch sides, the package still arrives back on its original route.

Question 20

What symptoms occur with bilateral damage to the neocerebellum?

Answer 20

If one side of the neocerebellum is damaged, the same-side arm and leg can’t coordinate well.
Movements become jerky, and walking might feel unsteady, like limping or staggering.
Analogy: Imagine a car with one flat tire—it wobbles and doesn’t move smoothly.

Question 21

How does cerebellar damage affect rapid movements?

Answer 21

Speech becomes slow and broken, like separating syllables (“hel-lo”).
Both arms might move awkwardly, and walking becomes a staggering, wide-based motion (cerebellar ataxia).

Analogy: Think of someone trying to walk across ice—they spread their feet wide to avoid falling but still wobble unsteadily.

Question 22

How does cerebellar damage affect eye movements?

Answer 22

Damage can cause nystagmus, where the eyes involuntarily flick back and forth, especially when looking to one side.

Analogy: Imagine a camera with a shaky tripod—it struggles to stay steady, especially when panning to one side.