Final answer:
The brain stem, comprising the midbrain, medulla oblongata, and pons, functions similarly in sheep and humans as a relay center and controller of basic functions. However, the human brain stem works within a more complex brain with a significantly higher number of neurons, reflecting greater cognitive capabilities.
Step-by-step explanation:
The brain stem is a crucial part of both sheep and human brains, serving as a key relay point between the rest of the brain and the spinal cord. It comprises the midbrain, medulla oblongata, and the pons. While the fundamental structure is quite similar, with motor and sensory neurons facilitating communication, and ascending neural pathways allowing for cross-hemispheric control, there are differences in scale and complexity. The human brain stem is part of a larger and more complex brain, which includes an extensively folded neocortex supporting advanced mental abilities. Meanwhile, the sheep's brain stem supports basic functions and is adequate for the sheep's more limited cognitive demands. The neural density is also greater in humans, with about 86 billion neurons in the human brain as opposed to the lesser number in the sheep's brain, reflecting the broader array of complex behaviors and cognitive capabilities exhibited by humans.