Final answer:
The optic chiasm and the optic tracts, located above the midbrain, are essential components of the visual processing system, transmitting visual information from the eyes to the brain and potentially indicative of health issues when dysfunctional.
Step-by-step explanation:
The question refers to the optic chiasm and the optic tracts as the "two orbs that sit on top of the midbrain". These structures play a crucial role in the visual processing system. The optic nerves from each eye merge at the optic chiasm, which is located just below the cerebral cortex at the front of the brain. Here, the information from the right visual field is sent to the left side of the brain, and information from the left visual field is sent to the right side of the brain. The optic tracts extend from the optic chiasm to the thalamus, specifically the lateral geniculate nucleus, and then project to the visual cortex in the occipital lobe. Another target of the optic tract is the superior colliculus in the midbrain, which is involved in orienting movements of the eyes and head.
Dysfunction in this pathway can lead to deficits in visual field perception. For example, loss of peripheral vision may indicate a pituitary tumor pressing on the optic chiasm, illustrating the delicate relationship between the optic pathways and surrounding structures like the pituitary gland.