Explaining the Frank-Starling Law of The Heart
This document has hints and comments for some of the Short Answer questions. This should allow you to see the general types of things I am looking for. You can use this document to check your answers. If you are checking off the items in the question, you are off to a great start.
Organize your answer, write well, and present it in such a way that your information is easy to find. Your answers also need to be precise and concise. Some students add so much information (some of it relevant and some of it not) that it looks like they are throwing everything against the wall and hoping something sticks. This tells me you haven’t really thought about your response, and that is a no-no.
Remember whenever you see “homeostasis,” flow-down-gradients,” or “cell-to-cell signaling,” think about our core concept and the bulleted items. Then, apply that concept to the specific question. Finally, remember this is physiology so think about the function or “how” something occurs.
1 Explain the Frank-Starling law of the heart.
Make sure to give a short, explanation of the Frank-Starling law and the role of stretch on the cardiac contractile tissue has on the force of contraction. You should then explain how this property allows for the matching of venous return and stroke volume. Some important topics to consider as you answer this question are end-diastolic-volume (EDV), end-systolic-volume (ESV), venous return, preload, afterload, and Starling curves.
2 Compare excitation-contraction coupling and relaxation in cardiac and skeletal muscles.
Compare questions need to include similarities and differences. One way to do this is to start with how the ECC is similar in the two types of muscles (the roles of calcium and ATP -> ADP+P for example).End the paragraph with a sentence stating in general how they differ. Then spend a paragraph on discussing the specifics of how skeletal muscle is different and a paragraph outlining how the cardiac muscle is different. Some important topics to consider as you answer this question are action potential generation, sarcoplasmic reticulum, calcium, troponin, tropomyosin, myosin, actin, crossbridge formation, Calcium ATPase (CaATPase), Sodium-Calcium-Exchanger (NCX), t-tubules.
3 Compare the structure and function of skeletal, cardiac, and smooth muscles
Compare questions need to include similarities and differences. What do all three muscle types have in common. How are skeletal and cardiac muscle similar but different from smooth muscle? How are smooth muscle and cardiac muscle similar but different from skeletal muscle? Some topics to consider include summation, gradation, speed of contraction, fatigue, sarcomeres,
4 Compare the action potentials of contractile cardiac muscle, autorhythmic cardiac muscle and skeletal muscle.
Compare questions need to include similarities and differences. What do all of these types of action potentials have in common? How is an autorhythmic cardiac action potential different from skeletal and cardiac contractile action potentials? How do skeletal and cardiac contractile action potentials differ? Some important topics to consider as you answer this question are resting membrane potential, pacemaker potential, If channels, sodium voltage-gated channels, potassium voltage-gated channels, calcium voltage-gated channels, depolarization, repolarization, hyperpolarization, pacemaker.
5 Describe the conductions of electrical signals through the heart.
While you may learn this as a sequenced list, you must (as in you will lose points if you don’t) answer this question with a narrative of the structures involved in initiating and coordinating the contraction of the heart. You need to include the function of each structure. The topics you should consider as you answer this question include pacemaker cells, the sinoatrial node, atrioventricular node, internodal pathway, bundle of His, bundle branches, Purkinje fibers, first degree block, second degree block, and third degree block.
6 Describe the parts of the electrocardiogram (ECG) and explain how these electrical events are related to the mechanical events of the cardiac cycle.
The Wigger’s diagram is a good reference to use when preparing your answer to this question.
The most straight-forward approach to answering this question is to start at the P-wave and go through to the T-wave. Make sure to clearly state what each wave, interval, and segment represent. Make sure to clearly state the general rule concerning the timing of electrical and mechanical events as well as illustrate with specific examples. Some specific topics to consider when answering this question include P wave, QRS complex, T wave, PR interval, R-R interval, PR segment, ST segment, conduction system of the heart, autorhythmic cardiac cells, contractile cardiac cells, depolarization, repolarization, atria, ventricles, atrioventricular node.
7 Explain the role of the autonomic divisions in control of heart rate.
Figure 14.20 (pg 465) and the associated narrative in the text provide a good place to start.
8 Describe in detail how baroreceptor reflex demonstrates the core concept of homeostasis.
Figure 15.14 (pg 493) and the associated narrative in the text provide a good place to start.
9 Explain how the Starling forces regulate bulk flow in the capillaries using the core concept of flow-down-gradients.
Figure 15.18 (pg 498) and the associated narrative in the text provide a good place to start.
10 Explain the pressure changes which occur during the cardiac cycle and their relationship to the flow of blood through the heart and blood vessels.
The Wigger’s diagram (Figure 14.19 (page 463)) is a good reference when preparing your answer to this question.
11 Explain the principles underlying the measurement of blood pressure using a sphygmomanometer
Figure 15.7 (pg 483) and the associated narrative in the text provide a good place to start.
12 Explain Poiseuille’s law.
Make sure to state the equation. What are the three primary determinants of resistance in physiology? Which of these has the greatest impact?
Section 14.2 (pages 436-439),Figure 15.11b (pg 490), Table 15.1 (pg 481), and the associated narrative in the text provide a good place to start.
13 Discuss the factors which determine cardiac output.
Figure 14.23 (pg 471) and the associated narrative in the text provide a good place to start.
14 Discuss the factors which determine mean arterial pressure.
Figure 15.6 (pg 482), 15.8 (pg 485), and the associated narrative in the text provide a good place to start.