Textbook Question
Which chamber generates the highest pressure during systole?
a. Right atrium
b. Right ventricle
c. Left atrium
d. Left ventricle
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18. The Heart
Cardiac Cycle
Problem 18
Textbook Question
Which of the following statements is false?
a. The sympathetic nervous system releases epinephrine and norepinephrine, which are positive chronotropic and inotropic agents.
b. The endocrine system regulates cardiac output through chronotropic and inotropic hormones and through hormones that regulate water balance.
c. The parasympathetic nervous system releases acetylcholine and epinephrine, which are strongly negative inotropic agents.
d. Factors such as electrolyte concentrations, body temperature, and age all affect cardiac output.
Verified step by step guidance1
Step 1: Begin by understanding the key terms in the question. Chronotropic agents affect heart rate, while inotropic agents affect the strength of heart contractions. Positive chronotropic agents increase heart rate, and positive inotropic agents increase contraction strength. Negative agents have the opposite effects.
Step 2: Analyze statement (a). The sympathetic nervous system releases epinephrine and norepinephrine, which are known to be positive chronotropic and inotropic agents. This statement is true based on physiological principles.
Step 3: Evaluate statement (b). The endocrine system regulates cardiac output through hormones that influence heart rate (chronotropic effects), contraction strength (inotropic effects), and water balance (e.g., antidiuretic hormone). This statement is also true.
Step 4: Examine statement (c). The parasympathetic nervous system primarily releases acetylcholine, which has a negative chronotropic effect (slows heart rate). However, it does not release epinephrine, nor is acetylcholine a strongly negative inotropic agent. This statement is false.
Step 5: Review statement (d). Factors such as electrolyte concentrations (e.g., potassium and calcium), body temperature, and age are known to influence cardiac output. This statement is true. Therefore, the false statement is (c).
Verified video answer for a similar problem:This video solution was recommended by our tutors as helpful for the problem above
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Sympathetic Nervous System
The sympathetic nervous system is part of the autonomic nervous system that prepares the body for 'fight or flight' responses. It releases neurotransmitters like epinephrine and norepinephrine, which increase heart rate (positive chronotropic effect) and the force of heart contractions (positive inotropic effect), thereby enhancing cardiac output during stress or physical activity.
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Sympathetic Nervous System Example 3
Parasympathetic Nervous System
The parasympathetic nervous system is the counterpart to the sympathetic system, promoting 'rest and digest' functions. It primarily uses acetylcholine as a neurotransmitter, which generally decreases heart rate (negative chronotropic effect) and can reduce the force of heart contractions (negative inotropic effect), counteracting the effects of the sympathetic nervous system.
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Cardiac Output Regulation
Cardiac output is the volume of blood the heart pumps per minute, influenced by heart rate and stroke volume. Various factors, including hormonal regulation from the endocrine system, electrolyte balance, body temperature, and age, can affect cardiac output. Understanding these factors is crucial for assessing cardiovascular health and function.
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