Final answer:
All vertebrates have chromaffin cells in the adrenal medulla that produce epinephrine and norepinephrine, hormones essential for the fight-or-flight response.
Step-by-step explanation:
It is true that all vertebrates have chromaffin cells located in the adrenal medulla. These cells are crucial components of the body's response to stress. Chromaffin cells, also known as pheochromocytes, are derived from the autonomic nervous system and are responsible for the production of the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline). These hormones are released into the bloodstream, where they exert powerful effects on distant cells, thus functioning as hormones.
The adrenal medulla comprises large, irregularly shaped neurosecretory cells that are innervated by preganglionic autonomic nerve fibers from the central nervous system. Originating from the neural crest along with the sympathetic ganglia, these cells develop pivotal hormones. Specifically, epinephrine is produced in a 4 to 1 ratio with norepinephrine and is responsible for mediating the body's fight-or-flight response during stressful situations, which includes increasing heart rate, blood-glucose levels, and redirecting blood flow towards skeletal muscles. The action of these hormones is integral to the body's ability to cope with stress.