Menace response involves which cranial nerves?

Menace response involves which cranial nerves?

• A. II and VII
• B. II and III
• C. II only
• D. VII only

Answer: (A)

The menace response tests a learned visual threat reflex that requires both intact vision and the motor blink pathway. The afferent limb is the optic nerve, carrying the visual signal from the retina to the brain. The efferent limb is the facial nerve, which activates the orbicularis oculi to close the eyelid. If either the optic nerve or the facial nerve is impaired, the horse may not show a menace response. Therefore, both the optic nerve (II) and the facial nerve (VII) must be functioning for a normal menace response. Choosing a combination that includes only one nerve or adds a different nerve doesn’t fit because the reflex isn’t mediated by the oculomotor nerve (III) or by vision alone without a motor eyelid response. So the correct pairing is II and VII.

The menace response tests a learned visual threat reflex that requires both intact vision and the motor blink pathway. The afferent limb is the optic nerve, carrying the visual signal from the retina to the brain. The efferent limb is the facial nerve, which activates the orbicularis oculi to close the eyelid. If either the optic nerve or the facial nerve is impaired, the horse may not show a menace response. Therefore, both the optic nerve (II) and the facial nerve (VII) must be functioning for a normal menace response.

Choosing a combination that includes only one nerve or adds a different nerve doesn’t fit because the reflex isn’t mediated by the oculomotor nerve (III) or by vision alone without a motor eyelid response. So the correct pairing is II and VII.