Part 4: Brainstem & Cerebellum

What are the three regions of the brainstem?

Midbrain, pons, and medulla oblongata.

How is the brainstem similar to the spinal cord?

It contains white matter fiber tracts and gray matter nuclei embedded within it.

What are the main functions of the brainstem?

It controls automatic behaviors necessary for survival and serves as a pathway between higher and lower brain centers.

How many pairs of cranial nerves are associated with the brainstem?

Ten out of the twelve pairs of cranial nerves.

Where is the midbrain located?

Between the diencephalon (thalamus) and the pons.

What are the cerebral peduncles?

Two bulging structures in the midbrain that contain descending pyramidal motor tracts.

What is the cerebral aqueduct?

A hollow tube that connects the third and fourth ventricles.

What are the corpora quadrigemina?

Four dome-like protrusions on the dorsal surface of the midbrain.

What are the superior colliculi responsible for?

Visual reflex centers that coordinate head and eye movements.

What are the inferior colliculi responsible for?

Auditory reflex centers that help respond to sounds.

What is the substantia nigra?

A darkly pigmented midbrain nucleus that functions with the basal nuclei; degeneration here causes Parkinson’s disease.

What is the red nucleus?

A large nucleus in the midbrain involved in motor coordination and part of the reticular formation.

Where is the pons located?

Between the midbrain and the medulla oblongata.

What is the main function of the pons?

It connects higher brain centers and the spinal cord, and relays impulses between the motor cortex and the cerebellum.

What important structure is found in the pons?

The reticular formation, which helps regulate alertness and arousal.

Where is the medulla oblongata located?

It is the most inferior part of the brainstem, connecting to the spinal cord.

What are the pyramids of the medulla?

Two longitudinal ridges formed by corticospinal tracts descending from the motor cortex.

What is decussation of the pyramids?

The crossover of motor fibers in the medulla, causing each side of the brain to control the opposite side of the body.

What are the main nuclei found in the medulla oblongata?

Cardiovascular control center and respiratory control centers.

What does the cardiovascular control center regulate?

The rate and force of heart contractions and blood vessel diameter.

What do the respiratory centers of the medulla control?

The rate and depth of breathing.

Why are lesions to the brainstem often fatal?

Because it houses vital reflex centers for respiration, heart rate, and other basic survival functions.

What is meant by “reptilian brain”?

It refers to the brainstem as the most primitive part of the brain, controlling instinctive survival functions.

Where is the cerebellum located?

Dorsal to the pons and medulla, under the occipital lobes of the cerebrum.

What percentage of the brain’s mass does the cerebellum make up?

About 11% of total brain mass.

What is the main function of the cerebellum?

It provides precise timing and coordination of skeletal muscle movements and helps maintain balance.

How does the cerebellum process movement?

It receives input on intended movement, compares it with body position, and sends a coordinated movement plan to the motor cortex.

Are cerebellar pathways contralateral or ipsilateral?

Ipsilateral (same side of the body).

What is cerebellar cognitive function?

The cerebellum also aids in sequential planning, problem-solving, language, and predicting movement sequences.

How does alcohol affect the cerebellum?

Alcohol impairs cerebellar function first, causing loss of coordination (ataxia) before affecting judgment.

Why is the cerebellum compared to a “file cabinet of muscle movements”?

Because it stores learned movement patterns like walking, playing sports, or typing.

What happens when the cerebellum is damaged?

It leads to ataxia — loss of coordination, balance, and smooth muscle movement.