When a client is taking an adrenergic agonist drug the nurse expects to observe which effect?
A.
Bronchial constriction
B.
Increased heart rate
C.
Increased Gl peristalsis
D.
Constricted pupils
The Correct Answer and Explanation is :
The correct answer is:
B. Increased heart rate
Explanation:
Adrenergic agonists, also known as sympathomimetics, are drugs that stimulate the sympathetic nervous system (SNS) by mimicking the effects of endogenous catecholamines such as norepinephrine, epinephrine, and dopamine. These drugs activate adrenergic receptors, which are classified into two major types: alpha (α) and beta (β) receptors. The specific effects of adrenergic agonists depend on which type of receptor they activate.
- Increased Heart Rate (Tachycardia): Adrenergic agonists commonly stimulate beta-1 (β1) adrenergic receptors, primarily located in the heart. Activation of β1 receptors leads to increased heart rate (chronotropy) and enhanced force of cardiac contraction (inotropy). This response is part of the “fight or flight” mechanism initiated by the sympathetic nervous system, preparing the body to respond to stress or danger. Thus, when a client takes an adrenergic agonist drug, an increased heart rate is a common and expected effect. This effect helps improve blood flow and oxygen delivery to vital organs.
- Other Choices:
- A. Bronchial constriction: Adrenergic agonists, particularly those that stimulate beta-2 (β2) receptors, cause bronchial dilation rather than constriction. β2 receptors are located in the smooth muscle of the bronchi, and their activation leads to relaxation and widening of the airways, making it easier to breathe. Therefore, adrenergic agonists are used to treat conditions like asthma and chronic obstructive pulmonary disease (COPD).
- C. Increased GI peristalsis: Activation of the sympathetic nervous system inhibits gastrointestinal (GI) activity, including peristalsis, as part of the body’s energy conservation during stress. Adrenergic agonists reduce GI motility, not increase it. Therefore, GI peristalsis is decreased, not increased, when taking these drugs.
- D. Constricted pupils: Adrenergic agonists generally cause pupil dilation (mydriasis), not constriction. This occurs due to stimulation of alpha-1 (α1) adrenergic receptors in the iris, which leads to the contraction of the dilator muscle and an increase in pupil size, improving vision in low-light conditions.
In conclusion, adrenergic agonists predominantly increase heart rate and dilate the bronchi and pupils while reducing GI motility. These effects are essential for the body’s preparation to respond to stressful situations effectively.