Which part of the mesencephalon coordinates reflex eye movements

Question 1

Which part of the mesencephalon coordinates reflex eye movements?

Question 2

A 20-year-old woman is brought to the emergency department 30 minutes after being found unconscious in her dormitory room. Part of the physical examination involves observing for conjugate eye movements after carefully opening the patient’s eyelids and turning the head to the right and then to the left. The presence of this reflex suggests that the neural pathway from which of the following receptors is intact?

A) Anterior semicircular canals

B) Horizontal semicircular canals

C) Posterior semicircular canals

D) Saccule

E) Utricle

Question 3

What part of the brain controls involuntary movement?

Answer to question 1

The part of the mesencephalon that coordinates reflex eye movements is the superior colliculi. The superior colliculi located at front, sides of the midbrain, and it has many different layers. These layers are often classified as superficial or deep layers. In addition to regulating eye movements, the mesencephalon also helps to control how easily a person can be distracted.

Answer to question 2

Step 1

Given information 

  • Patient is brought to the emergency after 30 minutes of unconsciousness.
  • Conjugate eye movements are observed by  opening the patient’s eyelids and turning the head to the right and then to the left.
  • The reflex is present. 

Step 2

Correct option

Option B

  • The given examination is a positive Supine roll test also called the Pagnini-McClure maneuver.
  • This test examines the reflex of horizontal canal benign paroxysmal positional vertigo BPPV.
  • The patient has an intact neural pathway of Horizontal semicircular canals.

Incorrect options

  • Anterior semicircular canals- In the side-lying test, this reflex is examined. In this test, the nose is turned away from the side being tested.
  • Posterior semicircular canals- Dix-Hallpike maneuver test is done in which the patient is sitting upright and the head is turned 45 degrees 
  • Saccule and Utricle- Vestibular-evoked myogenic potential is used to test their function.

Answer to question 3

The involuntary movement of the digestive, respiratory, and circulatory systems is controlled by the brain stem. The brain stem consists of the pons, the medulla, and the midbrain. The medulla controls heart rate, breathing, and swallowing, and the pons controls the sleep cycles and the rate and intensity of breathing.

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