Final answer:
Epinephrine and norepinephrine serve as hormones released by the adrenal medulla and neurotransmitters released by nerve cells, affecting the fight-or-flight response and central nervous functions respectively, with hormonal actions being slower and more prolonged than their rapid and transient neurotransmitter actions.
Step-by-step explanation:
Epinephrine and norepinephrine are catecholamines that have dual roles as hormones and neurotransmitters (nt). As hormones released by the adrenal medulla, they are central to the fight-or-flight response, increasing heart rate and force of contraction, and redirecting blood flow to critical areas like muscles and heart. They act more slowly than nt but have longer-lasting effects. Conversely, when they function as nt, they are rapidly released by nerve cells and have immediate but short-lived effects on target cells. For instance, nt norepinephrine binds to alpha and beta receptors affecting blood vessel constriction, heart rate, and more nuanced central nervous functions like mood and vigilance.
In the context of the renal system, these catecholamines constrict afferent arterioles, impacting kidney function and initiating the renin-angiotensin-aldosterone system. It is important to note that while there are similarities in the effects of epinephrine and norepinephrine as hormones and nt, their modality of action and duration differ significantly due to the difference in signaling mechanisms.