Final answer:
Norepinephrine (NE) has either an excitatory or inhibitory effect on the effector depending on the type of adrenergic receptor to which it binds. It can increase blood pressure through vasoconstriction or cause dilation of the bronchi, highlighting its varied influences as part of the body’s fight-or-flight response.
Step-by-step explanation:
The correct answer for the question regarding the effects of norepinephrine (NE) on the effector is (b) has either an excitatory or inhibitory effect on the effector. NE, as a neurotransmitter, can produce different outcomes depending on the type of adrenergic receptor it binds to. Specifically, NE acts through alpha receptors which can have different effects on various target cells.
For example, NE can cause vasoconstriction when binding to the alpha-1 adrenergic receptors on blood vessels, leading to an increase in blood pressure, which is an excitatory effect. Conversely, when it binds to alpha-2 receptors in other areas, it can produce inhibitory effects such as dilation of the bronchi.
Additionally, the role of NE as part of the fight-or-flight response involves multiple functions such as increasing heart rate and diverting blood to essential organs, illustrating its versatile effects on the body. Therefore, NE does not always have a consistent excitatory or inhibitory outcome. Its effect is context-dependent, largely influenced by the specific receptor subtype that is activated.