HUMAN PHYSIOLOGY: AN INTEG ACCESS C
8th Edition
ISBN: 9780134714837
Author: Silverthorn
Publisher: PEARSON
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Textbook Question
Chapter 14.4, Problem 23CC
Occasionally an ectopic pacemaker {θktopos, out of place} develops in part of the heart’s conducting system. What happens to heart rate if an ectopic atrial pacemaker depolarizes at a rate of 120 times per minute?
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The rapid depolarization phase of heart pacemaker cells is caused by which of the
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We analyzed the difference between the action potential of a cardiac contractile cell and an action potential in a neuron. Describe the physiological mechanisms behind the primary difference in the shape of these two action potentials. Why is this feature important to the normal workings of the heart?
Occasionally an ectopic pacemaker will develop in part of the conducting system of the heart. What happens to heart rate if an ectopic pacemaker depolarizes at a rate of 120 times per minute?
Chapter 14 Solutions
HUMAN PHYSIOLOGY: AN INTEG ACCESS C
Ch. 14.1 - A cardiovascular system has what three major...Ch. 14.1 - What is the difference between (a) the pulmonary...Ch. 14.2 - Which is more important for determining flow...Ch. 14.2 - The two identical tubes below have the pressures...Ch. 14.2 - All four tubes below have the same driving...Ch. 14.2 - Two canals in Amsterdam are identical in size, but...Ch. 14.3 - What prevents electrical signals from passing...Ch. 14.3 - Prob. 8CCCh. 14.3 - Prob. 9CCCh. 14.3 - Compare the receptors and channels involved in...
Ch. 14.3 - If a myocardial contractile cell is placed in...Ch. 14.3 - A drug that blocks all Ca2+ channels in the...Ch. 14.3 - Which ions moving in what directions cause the...Ch. 14.3 - At the molecular level, what is happening during...Ch. 14.3 - Lidocaine is a molecule that blocks the action of...Ch. 14.3 - What does increasing K+ permeability do to the...Ch. 14.3 - A new cardiac drug called ivabradine selectively...Ch. 14.3 - Do you think that the Ca2+ channels in...Ch. 14.3 - What happens to the action potential of a...Ch. 14.3 - In an experiment, the vagus nerve, which carries...Ch. 14.4 - Name two functions of the AV node. What is the...Ch. 14.4 - Prob. 22CCCh. 14.4 - Occasionally an ectopic pacemaker {ktopos, out of...Ch. 14.4 - Prob. 24CCCh. 14.4 - Which chamberatrium or ventriclehas higher...Ch. 14.4 - Prob. 26CCCh. 14.4 - Prob. 27CCCh. 14.4 - Prob. 28CCCh. 14.4 - Prob. 29CCCh. 14.4 - Why does ventricular pressure shoot up suddenly at...Ch. 14.4 - Prob. 31CCCh. 14.4 - Prob. 32CCCh. 14.4 - A persons aortic valve opening has become...Ch. 14 - What contributions to understanding the...Ch. 14 - List three functions of the cardiovascular system.Ch. 14 - Prob. 3RQCh. 14 - Prob. 4RQCh. 14 - Prob. 5RQCh. 14 - Prob. 6RQCh. 14 - Prob. 7RQCh. 14 - Distinguish between the two members of each of the...Ch. 14 - Prob. 9RQCh. 14 - Prob. 10RQCh. 14 - What is the proper term for each of the following?...Ch. 14 - List the events of the cardiac cycle in sequence,...Ch. 14 - Prob. 13RQCh. 14 - Compare and contrast the structure of a cardiac...Ch. 14 - Prob. 15RQCh. 14 - Correlate the waves of an ECG with mechanical...Ch. 14 - Prob. 17RQCh. 14 - List and briefly explain four types of information...Ch. 14 - Define inotropic effect. Name two drugs that have...Ch. 14 - Prob. 20RQCh. 14 - Police Captain Jeffers has suffered a myocardial...Ch. 14 - Prob. 22RQCh. 14 - Prob. 23RQCh. 14 - Police Captain Jeffers in question 21 has an...Ch. 14 - Prob. 25RQCh. 14 - Prob. 26RQCh. 14 - Prob. 27RQCh. 14 - A person has a total blood volume of 5 L. Of this...
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- In the figure below on the left, label the P, QRS and T waves. Describe what is happening in the heart in the P wave: Relate the P wave to the cardiac cycle:o Is the heart in systole or diastole?o Is the pressure high or low?o Where is blood flowing? Which valves are open? closed? o Which muscle fibers are contracting, if any?arrow_forwardIf leaky Na+ channels in the cells of the SA Node became more leaky (allowed Na+ through at a faster rate), what would happen to the heart rate? a-it wouldn't change b-it would decrease c-it would increasearrow_forwardDraw these five graphs on the same set of axes: atrial autorhythmic cell action potential atrial cardiac contractile cell action potential ventricular autorhythmic cell action potential ventricular cardiac contractile cell action potential ventricular myocardial muscle tensionarrow_forward
- If SA node (=natural pacemaker) firing rate is 100 potentials per minute, but resting heart rate of a person is 75bpm, what accounts for the difference? Iarrow_forwardWhy is ventricular fibrillation such a serious arrhythmia?arrow_forwardWhat is the consequence of the prolonged plateau of depolarization in ventricular myocytes? a-it causes ventricular myocytes to contract for a longer time, allowing the ventricles time to empty b-it gives additional time for the atria to contract, filling the ventricles more completely c-it causes repolarization to be delayed which slows heart rate d-it allows the ventricles a moment to rest before completing contractionarrow_forward
- Autorhythmic cells in the SA node intrinsically fire at a rate of - 90 action potentials per minute. During exercise, the heart ráte is increased primarily through modulation by: Increased sympathetic input and parasympathetic input Decreased sympathetic input and parasympathetic input The AV node O Decreased sympathetic input and increased parasympathetic input Increased sympathetic input and decreased parasympathetic input O O O OOarrow_forwardBelow are drawings of three different action potentials. Two of these occur in the heart, and one occurs in skeletal muscle. Which one comes from a contractile cardiac muscle cell? A skeletal muscle cell? A cardiac pacemaker cell? For each one, state which ion is responsible for the depolarization phase and which ion is responsible for the repolarization phase.arrow_forwardWhich of the following channels is responsible for generating the long plateau found in the action potentials of ventricular myocytes? a-slow Na+ channels b-slow Ca2+ channels c-leaky Ca2+ channels d-leaky Na+ channelsarrow_forward
- Cells of the sinoatrial node are the primary pacemakers of the heart. If we increase the potassium ions permeability of these cells, how many action potentials do these cells generate every minute?arrow_forwardAn elephant has an aorta that is approximately 8 cm in diameter and a restingheart beat of 35 beats/min. Over the cardiac cycle, do you think that velocityprofiles in the aorta will be: fairly flat, oscillating back and forth, or more parabolic, oscillating back and forth?Make and state necessary assumptions.arrow_forwardIn a cardiac contractile cell what is the mechanism involved in the change in membrane potential? Depolarization: P wave Repolarization: QRS Complex, Hyperpolarization: T wave Pacemaker: K+ and Na+ flow, Depolarization: Pca rises Repolarization: Pk rises Depolarization: Pna increases, Peak: Na channels close, Plateau: Calcium channels close & Potassium channels open, Repolarization Potassium flows out & Calcium flows in Pacemaker: K+ and Na+ flow, Depolarization: Pca rises Repolarization: Pk rises, 4. If channels close Depolarization: Pna increases, Peak: Na channels close, Plateau: Calcium channels open & Potassium channels close, Repolarization Potassium flows out & Calcium flows outarrow_forward
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