Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

18. The Heart

Electrical Conduction System of the Heart

Anatomy & Physiology

18. The Heart

Electrical Conduction System of the Heart

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4:07 minutes

Problem 15

Textbook Question

The activity of the heart depends on intrinsic properties of cardiac muscle and on neural factors. Thus:
a. Vagus nerve stimulation of the heart reduces heart rate
b. Sympathetic nerve stimulation of the heart decreases time available for ventricular filling
c. Sympathetic stimulation of the heart increases its force of contraction
d. All of the above

Verified step by step guidance

Step 1: Understand the intrinsic properties of cardiac muscle and neural factors. Cardiac muscle has automaticity, meaning it can generate its own electrical impulses, but neural factors modulate its activity.

Step 2: Analyze the role of the vagus nerve in heart rate regulation. The vagus nerve is part of the parasympathetic nervous system and releases acetylcholine, which slows down the heart rate by decreasing the firing rate of the sinoatrial (SA) node.

Step 3: Examine the effects of sympathetic nerve stimulation on ventricular filling. Sympathetic stimulation increases heart rate, which reduces the time available for ventricular filling during diastole.

Step 4: Investigate how sympathetic stimulation affects the force of contraction. Sympathetic nerves release norepinephrine, which binds to beta-adrenergic receptors on cardiac muscle cells, increasing calcium influx and enhancing the force of contraction.

Step 5: Evaluate the options provided in the problem. Consider whether each statement (a, b, c) is correct based on the physiological mechanisms discussed, and determine if 'all of the above' is the correct answer.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Intrinsic Properties of Cardiac Muscle

The intrinsic properties of cardiac muscle refer to the unique characteristics of cardiac myocytes, including their ability to generate action potentials and contract independently of external stimuli. This property is crucial for maintaining the heart's rhythmic contractions and is primarily governed by the pacemaker cells in the sinoatrial node.

Neural Regulation of Heart Function

Neural regulation involves the autonomic nervous system's control over heart rate and contractility. The vagus nerve, part of the parasympathetic system, decreases heart rate, while sympathetic nerve stimulation increases heart rate and contractility, affecting the heart's overall performance during different physiological states.

Cardiac Cycle Dynamics

The cardiac cycle encompasses all events that occur during one heartbeat, including diastole (ventricular filling) and systole (ventricular contraction). Understanding how sympathetic stimulation affects the duration of diastole is essential, as it influences the heart's ability to fill with blood and subsequently impacts cardiac output.