Midbrain

Question 1

What marks the boundary between the midbrain and the diencephalon?

Answer 1

The posterior Commissure

Question 2

Describe the progressing symptoms of a pinealoma.

Answer 2

First diagnostic symptom is paralysis of upward eye movements. As tumor grows it will also put pressure on the pretectal area, blocking the pupillary light reflex, resulting in fixed, somewhat dilated pupils. As it expands it will damage other portions of the tectum and nearby structures, and obstruct the cerebral aqueduct, causing hydrocephalus.

Question 3

What nucleus makes up the vertical gaze center, where do fibers coordinating upward gaze travel?

Answer 3

The interstitial nucleus or Nucleus of Cajal. The upward gaze fibers pass through the posterior commissure.

Question 4

What is the periaqueductal gray involved in?

Answer 4

involved in stereotyped emotional behaviors, it also plays a role in controlling the perception of pain through a descending pain-suppression system and receives a projection from the ALS

Question 5

Describe the types of neurons in the substantia nigra, where they project, and what they are involved with. What disease is associated with loss of there function?

Answer 5

Dopaminergic neurons project to the striatum and are involved in motor control. Loss of these neurons is characteristic of parkinsons disease. (Black because it produces melanin granules)

Question 6

Describe the role of cholinergic neurons in the pons-midbrain jn?

Answer 6

Cholinergic neurons at this junction send descending projections to the pontine and reticular formation and ascending projections to the thalamus. These are important for regulating arousal and sleep-wake cycles. When this region is damaged the result is a coma.

Question 7

What midbrain cholinergic nucleus projects directly to the cortex and is lost early in alzheimers disease?

Answer 7

Basal Nucleus of Meynert

Question 8

How do you test for the trochlear nerve?

Answer 8

Have the patient look medially and ask them to look down.