Human Physiology: An Integrated Approach (8th Edition)
8th Edition
ISBN: 9780134605197
Author: Dee Unglaub Silverthorn
Publisher: PEARSON
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Textbook Question
Chapter 14.3, Problem 15CC
Lidocaine is a molecule that blocks the action of voltage-gated cardiac Na+ channels. What happens to the action potential of a myocardial contractile cell if lidocaine is applied to the cell?
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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?
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The pressure in the aorta changes throughout the cardiac cycle. During systole, as the heart contracts, the outflux
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whereas during diastole the pressure decreases as the
heart relaxes. A simple model for the aortic pressure
waveform is given by the Windkessel effect described by
the image below. In this model, the heart is considered a
pressure generating pump which is directly connected to
an elastic compartment (the aorta), which in turn is
connected to a rigid set of peripheral vessels (the hose of
the firefighter).
5
Pump
Heart
Air
Windkessel
Elastic arteries
In order to find the aortic pressure waveform from the Windkessel model, a mass balance formulation around the aorta
must be formulated. Coming into the aorta from the heart we have the flowrate Q(t). According to conservation of mass,
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Chapter 14 Solutions
Human Physiology: An Integrated Approach (8th Edition)
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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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biology and related others by exploring similar questions and additional content below.Similar questions
- Knowing that a patient with chronic heart failure is using digoxin (digitalis) for more than 1 year, what effect has this treatment on the distribution of ions across the membrane of cardiac muscle cells? What is effect will be of digitalis on cardiac contractility? What is an inotropic effect? How does digitalis help to treat patients with heart failure?arrow_forwardIn a sheet of ventricular cardiac muscle tissue, we should be able to observe electricity spreading between adjacent muscle cells (TRUE or FALSE) and from Purkinje fibers to muscle cells (TRUE or FALSE) via electrical synapses that form between the cell membranes.arrow_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_forward
- Why is the rate of cardiac muscle relaxation faster when a positive inotropic agent is present?arrow_forwardWhy is the cardiac action potential propagated more slowly in an AV node cell then in an atrial or ventricular myocyte? How can be AV conduction affected by hypokalemia? Briefly explain the mechanism by which the most popular beta-blocker metoprolol would affect cardiac muscle contractility and blood flow. How it affects heart rate and conduction?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
- a) A consequence of the Frank-Starling law of the heart is that the outputs of the right and left ventricles match. Explain why this is important and how this match is made.b) The excitation-contraction matching mechanism within the heart muscle is different from that of the skeletal muscle. How might these differences be related to the difference between action potentials in cardiac muscle and skeletal muscle?arrow_forwardWhy is it necessary for cells of the cardiac atria and ventricles to contract in a coordinated manner? How is this accomplished?arrow_forwardWhat are the uses of cardiac troponins?arrow_forward
- In the calculation of the heart rate using the number 300 method in the ECG, where did the number 300 come from? Why exactly was this method adopted?arrow_forwardHow does the L-type voltage-gated channels on the contractile myocardial fibers rapidly closing affect the heart? the on the contractile myocardial cells will have a lower resting potential long action potentials on the contractile myocardial cells faster depolarization in the contractile myocardial cells Shorter action potentials on the contractile myocardial cells larger magnitude of depolarization in the contractile myocardial cellsarrow_forwardUnlike skeletal muscle, cardiac muscle doesn’t undergo tetany. Explain how this is achieved and why is this necessary?arrow_forward
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