Answer:D
Explanation: The pulmonary air sacs of birds only permit a unidirectional flow of air through the lungs. Unidirectional flow means that air is inhale and exhale through one trachea alternatively. This means the bird lungs only receive largely fresh air which has a high oxygen content during inhalation and do not receive fresh during exhalation. While air flow bidirectional in mammals.
Answer:
Stomach
Explanation:
Its an organ, not a gland
Answer:
In the mentioned scenario, norepinephrine and acetylcholine are the neurotransmitters, which would have been present at the higher concentrations in Sean's brain. Norepinephrine signifies to a neurotransmitter that plays an important part in dreaming, emotions, sleeping, attentiveness, and learning.
It also gets released in the bloodstream as a hormone, where it augments the rate of heart and causes the blood vessels to contract. Another neurotransmitter called acetylcholine signifies the chemical that is released by the motor neurons to instigate the muscles.
