Decreased cardiac contractility

Oct 13, 2025 by wbrum.org 22 views

Lab 2 Chap 12: Understanding the Effects of Metropolol, Norepinephrine, and Atropine on the Sympathetic and Parasympathetic Systems

A. How Metropolol will affect the organs in the Sympathetic System

Metropolol, a beta-blocker medication, is commonly used to treat high blood pressure, angina, and certain heart-related conditions. In this section, we will explore how metropolol affects the organs in the sympathetic system.

The sympathetic nervous system (SNS) is responsible for the body's "fight or flight" response, which prepares the body to respond to stress or danger. The SNS stimulates various organs to increase heart rate, blood pressure, and energy levels. Metropolol, as a beta-blocker, works by blocking the effects of epinephrine (adrenaline) and norepinephrine on the heart and other organs.

When metropolol is administered, it binds to beta-1 receptors in the heart, reducing the heart rate and contractility. This leads to a decrease in cardiac output, which in turn reduces blood pressure. Metropolol also blocks beta-2 receptors in the lungs, bronchi, and other smooth muscle tissues, causing bronchodilation and vasodilation.

The effects of metropolol on the sympathetic system can be summarized as follows:

Reduced heart rate: Metropolol decreases the heart rate by blocking beta-1 receptors, leading to a decrease in cardiac output and blood pressure.
Decreased cardiac contractility: Metropolol reduces the contractility of the heart, leading to a decrease in cardiac output and blood pressure.
Bronchodilation: Metropolol causes bronchodilation by blocking beta-2 receptors in the lungs and bronchi.
Vasodilation: Metropolol causes vasodilation by blocking beta-2 receptors in the blood vessels.

B. How Norepinephrine will affect the organs in the Sympathetic System

Norepinephrine, also known as noradrenaline, is a neurotransmitter that plays a crucial role in the sympathetic nervous system. In this section, we will explore how norepinephrine affects the organs in the sympathetic system.

Norepinephrine is released from the adrenal glands and binds to alpha-1 and beta-1 receptors in the heart, blood vessels, and other organs. The effects of norepinephrine on the sympathetic system can be summarized as follows:

Increased heart rate: Norepinephrine increases the heart rate by stimulating beta-1 receptors, leading to an increase in cardiac output and blood pressure.
Increased cardiac contractility: Norepinephrine increases the contractility of the heart, leading to an increase in cardiac output and blood pressure.
Vasoconstriction: Norepinephrine causes vasoconstriction by stimulating alpha-1 receptors in the blood vessels, leading to an increase in blood pressure.
Increased energy levels: Norepinephrine increases energy levels by stimulating beta-2 receptors in the muscles and other tissues.

C. How Atropine will affect the organs in the Parasympathetic System

Atropine is an anticholinergic medication that is commonly used to treat bradycardia, heart block, and other conditions related to the parasympathetic nervous system. In this section, we will explore how atropine affects the organs in the parasympathetic system.

The parasympathetic nervous system (PNS) is responsible for the body's "rest and digest" response, which promotes relaxation and reduces energy expenditure. The PNS stimulates various organs to decrease heart rate, blood pressure, and energy levels. Atropine, as an anticholinergic, works by blocking the effects of acetylcholine on the heart and other organs.

When atropine is administered, it binds to muscarinic receptors in the heart, lungs, and other organs, causing a decrease in parasympathetic activity. The effects of atropine on the parasympathetic system can be summarized as follows:

Increased heart rate: Atropine increases the heart rate by blocking muscarinic receptors, leading to an increase in cardiac output and blood pressure.
Decreased cardiac contractility: Atropine reduces the contractility of the heart, leading to a decrease in cardiac output and blood pressure.
Bronchodilation: Atropine causes bronchodilation by blocking muscarinic receptors in the lungs and bronchi.
Vasodilation: Atropine causes vasodilation by blocking muscarinic receptors in the blood vessels.

Conclusion

In conclusion, metropolol, norepinephrine, and atropine have distinct effects on the sympathetic and parasympathetic systems. Metropolol reduces heart rate and cardiac contractility, while norepinephrine increases heart rate and cardiac contractility. Atropine, on the other hand, increases heart rate and cardiac contractility by blocking parasympathetic activity. Understanding the effects of these medications on the sympathetic and parasympathetic systems is crucial for their safe and effective use in clinical practice.

References

Guyton, A. C., & Hall, J. E. (2016). Textbook of medical physiology. Philadelphia, PA: Saunders.
Berne, R. M., & Levy, M. N. (2018). Cardiovascular physiology. Philadelphia, PA: Elsevier.
Barrett, K. E., Barman, S. M., Boitano, S., & Brooks, H. L. (2018). Ganong's review of medical physiology. New York, NY: McGraw-Hill Education.
Lab 2 Chap 12: Understanding the Effects of Metropolol, Norepinephrine, and Atropine on the Sympathetic and Parasympathetic Systems - Q&A

Q: What is the primary function of the sympathetic nervous system?

A: The primary function of the sympathetic nervous system (SNS) is to prepare the body for "fight or flight" responses, which involves increasing heart rate, blood pressure, and energy levels.

Q: How does metropolol affect the heart rate?

A: Metropolol decreases the heart rate by blocking beta-1 receptors, leading to a decrease in cardiac output and blood pressure.

Q: What is the effect of norepinephrine on cardiac contractility?

A: Norepinephrine increases the contractility of the heart, leading to an increase in cardiac output and blood pressure.

Q: How does atropine affect the parasympathetic nervous system?

A: Atropine blocks the effects of acetylcholine on the heart and other organs, leading to an increase in heart rate and cardiac contractility.

Q: What is the primary effect of atropine on the heart?

A: The primary effect of atropine on the heart is to increase heart rate by blocking muscarinic receptors.

Q: How does metropolol affect blood pressure?

A: Metropolol decreases blood pressure by reducing cardiac output and vasodilation.

Q: What is the effect of norepinephrine on blood vessels?

A: Norepinephrine causes vasoconstriction by stimulating alpha-1 receptors in the blood vessels, leading to an increase in blood pressure.

Q: How does atropine affect the lungs?

A: Atropine causes bronchodilation by blocking muscarinic receptors in the lungs and bronchi.

Q: What is the primary function of the parasympathetic nervous system?

A: The primary function of the parasympathetic nervous system (PNS) is to promote relaxation and reduce energy expenditure, which involves decreasing heart rate, blood pressure, and energy levels.

Q: How does metropolol affect the sympathetic nervous system?

A: Metropolol blocks the effects of epinephrine and norepinephrine on the heart and other organs, leading to a decrease in sympathetic activity.

Q: What is the effect of norepinephrine on the sympathetic nervous system?

A: Norepinephrine stimulates alpha-1 and beta-1 receptors in the heart, blood vessels, and other organs, leading to an increase in sympathetic activity.

Q: How does atropine affect the parasympathetic nervous system?

A: Atropine blocks the effects of acetylcholine on the heart and other organs, leading to a decrease in parasympathetic activity.

Q: What are the common uses of metropolol?

A: Metropolol is commonly used to treat high blood pressure, angina, and certain heart-related conditions.

Q: What are the common uses of norepinephrine?

A: Norepinephrine is commonly used to treat hypotension, septic shock, and other conditions related to the sympathetic nervous system.

Q: What are the common uses of atropine?

A: Atropine is commonly used to treat bradycardia, heart block, and other conditions related to the parasympathetic nervous system.

Conclusion

In conclusion, understanding the effects of metropolol, norepinephrine, and atropine on the sympathetic and parasympathetic systems is crucial for their safe and effective use in clinical practice. These medications have distinct effects on the heart, blood vessels, and other organs, and their use requires a thorough understanding of their mechanisms of action.

References

Guyton, A. C., & Hall, J. E. (2016). Textbook of medical physiology. Philadelphia, PA: Saunders.
Berne, R. M., & Levy, M. N. (2018). Cardiovascular physiology. Philadelphia, PA: Elsevier.
Barrett, K. E., Barman, S. M., Boitano, S., & Brooks, H. L. (2018). Ganong's review of medical physiology. New York, NY: McGraw-Hill Education.