Human Anatomy & Physiology
1st Edition
ISBN: 9780805382952
Author: Erin C. Amerman
Publisher: PEARSON
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Chapter 17, Problem 4AYKB
Summary Introduction
To review:
The outcome of a toxin that results in creating the same length of the refractory period in cardiac muscles as present in the skeletal muscles.
Introduction:
The heart muscles generate an action potential due to the depolarization of the sinoatrial node (SA node) of the heart, which acts as a natural pacemaker. The action potential leads to muscular contraction, which helps the heart to supply blood to the whole body. The other cells that have the capability to generate an action potential as a result of the depolarization are the skeletal muscle cells and the neuron cells. After one action potential is generated, the cell becomes resistant to generating another action potential for a few seconds. This period is termed as the refractory period.
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Students have asked these similar questions
Briefly describe why pacemaker cells are able to depolarize in the absence of a stimulus.
Which statement about activation of heart muscle cells is TRUE?
A
when a person is resting only a few small motor units in each ventricle are activated in each heartbeat
B
all of the muscle cells in the ventricles depolarize and contract together because they are connected by gap junctions
C
motor neurons must synapse with all of the muscle cells in the ventricles at the same time or fibrillation will occur
D
all of the heart muscle cells have unstable resting membrane potenitals and slowly depolarize to threshold at the same rate
How is long refractory period beneficial for cardiac muscles?
Chapter 17 Solutions
Human Anatomy & Physiology
Ch. 17.1 - Where is the heart located, and how large is it?Ch. 17.1 - What are the hearts upper and lower chambers...Ch. 17.1 - 3. From what sources does blood flow into the...Ch. 17.1 - 4. Which side of the heart is considered the...Ch. 17.1 - Which side of the heart is considered the systemic...Ch. 17.2 - Prob. 1QCCh. 17.2 - Prob. 2QCCh. 17.2 - 3. What are the three layers of the heart wall,...Ch. 17.2 - 4. What are the four main great vessels? From...Ch. 17.2 - How do the right and left ventricles differ in...
Ch. 17.2 - 6. Why do you think it is important to ensure via...Ch. 17.2 - 7. What is the overall pathway of blood flow...Ch. 17.2 - Prob. 4QCCh. 17.2 - Prob. 5QCCh. 17.2 - Prob. 6QCCh. 17.3 - How do pacemaker and contractile cells differ?...Ch. 17.3 - 2. What are intercalated discs? What is their...Ch. 17.3 - Prob. 5QCCh. 17.3 - Prob. 6QCCh. 17.3 - What is the sequence of events of a contractile...Ch. 17.3 - How does the refractory period of cardiac muscle...Ch. 17.3 - 7. What does an ECG record?
Ch. 17.3 - What are the five waves in an ECG, and what do...Ch. 17.4 - What causes the heart sounds S1 and S2?Ch. 17.4 - Prob. 2QCCh. 17.4 - Prob. 3QCCh. 17.4 - Is the end-diastolic or the end-systolic volume of...Ch. 17.4 - 5. Walk through the mechanical events of the...Ch. 17.4 - How do the ECG waves correlate with each part of...Ch. 17.4 - 7. How does the left ventricular pressure...Ch. 17.5 - Prob. 1QCCh. 17.5 - What is cardiac output? How does it relate to...Ch. 17.5 - Prob. 3QCCh. 17.5 - What is the Frank-Starling law, and how does it...Ch. 17.5 - What is a chronotropic agent?Ch. 17.5 - Prob. 6QCCh. 17.5 - 7. What effects does the parasympathetic nervous...Ch. 17.5 - How would a hormone that decreases the amount of...Ch. 17.5 - How is heart failure defined?Ch. 17 - 1. Mark the following statements as true or false....Ch. 17 - 2. The pericardial cavity is located between:
a....Ch. 17 - 3. Which of the following statements is true?
a....Ch. 17 - Match the following terms with the correct...Ch. 17 - Fill in the blanks: The coronary arteries are the...Ch. 17 - 6. How do pacemaker cardiac muscle cells differ...Ch. 17 - 7. Cardiac muscle cells are joined by structures...Ch. 17 - Prob. 8CYRCh. 17 - Prob. 9CYRCh. 17 - 10. The _________is the primary pacemaker of the...Ch. 17 - The AV node delay: a. allows the atria and...Ch. 17 - Explain what each of the following terms...Ch. 17 - 13. Mark the following statements as true or...Ch. 17 - Prob. 14CYRCh. 17 - 15. Fill in the blanks: The first heart sound is...Ch. 17 - Cardiac output is equal to: a. end-diastolic...Ch. 17 - Prob. 17CYRCh. 17 - 18. Which of the following statements is false?
a....Ch. 17 - 1. A birth defect called transposition of great...Ch. 17 - 2. Predict which would be more damaging to...Ch. 17 - 3. When the SA node doesn’t function properly, the...Ch. 17 - Prob. 4CYUCh. 17 - Prob. 1AYKACh. 17 - You are a nursing student in a hospital, and a...Ch. 17 - Prob. 3AYKACh. 17 - Prob. 4AYKB
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- Caffeine lowers the heart rate by increasing rates of depolarization at the SA node True False Nicotine raises the heart rate because it stimulates the activity of the sympathetic neurons in medulla oblongata True False The Frank-Starling Law of the Heart states that the force of heart contraction is directly proportional to the initial length of the muscle fiber, within optimal limits of length True False If the sarcomeres stretched beyond the optimal length, the force of contraction would go down, but that can potentially happen only during open heart surgery when the heart is not constrained by the pericardium, lungs, ribs and diaphragm. True False It is the Na+ channel-driven spontaneous depolarization that is affected by sympathetic and parasympathetic inputs to speed up or slow down the firing rate of the SA node and other conductive cells. True Falsearrow_forwardActivation of β2-adrenergic receptors in vascular smooth muscle stimulates vasodilation / vasoconstriction. Give an example of organs where this occurs.arrow_forwardWhy is pulse rate faster in small and young animals compared to that inlarge and older animals?arrow_forward
- Read this article (http://openstaxcollege.org/l/ strokespell) to learn about a teenager who experiences a series of spells that suggest a stroke. He undergoes endless tests and seeks input from multiple doctors. In the end, one expert, one question, and a simple blood pressure cuff answers the question. Why would the heart have to beat faster when the teenager changes his body position from lying down to sitting, and then to standing?arrow_forwardIn your study of neuron physiology, you learned that depolarization is dependent on the sodium entry (influx), and repolarization contingent on the potassium exit (efflux.) Compare the action potential in the heart’s intrinsic conduction and contractile cells, then explain why the electrocardiogram has different parts (P, QRS complex, and T wave.)?arrow_forwardCardiac muscle is described as being under involuntary control. Why is it that some individuals can seemingly “control” theirheart rate through meditation?arrow_forward
- You are supervising a student who is carrying out several experiments on an animal species that has cardiac muscle almost identical to that of humans. She has recorded the electrical and contractile response of the muscle after stimulation and asks you to take a look at the graph.arrow_forwardUnlike skeletal muscle, cardiac muscle doesn’t undergo tetany. Explain how this is achieved and why is this necessary?arrow_forwardExplain in detail why the neurotransmitter acetylcholine has different effects in skeletal vs. cardiac muscle cells.arrow_forward
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