Cardiovascular Physiology AQ Answers

Cardiovascular Physiology AQ Answers : Question 1  1a: The heart has two separate pumps: the left pump and the right pump. Where does the left side of the heart pump blood to, and where does the right side of the heart pump blood to?  Answer: The left side of the heart pumps blood to the systemically (i.e., the body), while the right side of the heart pumps blood to the lungs.  1b: What is oxygenated and deoxygenated blood?  Answer: Oxygenated blood is filled with oxygen from the lungs. In contrast, deoxygenated blood has had most of its oxygen removed and is returning to the lungs to become oxygenated.  1c: What vessels carry oxygenated and deoxygenated blood in the pulmonary circuit?  Answer: In the pulmonary circuit, the arteries carry deoxygenated blood and the veins carry oxygenated blood.  1d: What vessels carry oxygenated and deoxygenated blood in the systemic circuit?  Answer: In the systemic circuit, the arteries carry oxygenated blood and the veins carry deoxygenated blood. Question 2  2a: What are the four chambers of the heart?  Answer: The right and left atria, and the right and left ventricles.  2b: What vessel does the right ventricle pump blood into?  Answer: The right ventricle pumps blood into the pulmonary trunk, which leads to the pulmonary arteries.  2c: What vessel does the left ventricle pump blood into?  Answer: The left ventricle pumps blood into the aorta, which leads to the systemic arteries.  2d: What are the three vessels that deliver blood to the right atrium?  Answer: The inferior vena cava, the superior vena cava, and the coronary sinus.  2e: What are the vessels that deliver blood to the left atrium?  Answer: The pulmonary veins.  2f: What are the five vessels that emanate from the aorta?  Answer: The vessels that emanate from the aorta are the right and left coronary arteries, the left subclavian artery, the left common carotid artery, and the left brachiocephalic artery. Question 3  3a: What is the name for the valve between the right atrium and the right ventricle?  Answer: The tricuspid valve (i.e., the right AV valve).  3b: What is the name for the valve between the left atrium and the left ventricle?  Answer: The bicuspid valve (i.e., the left AV valve or the mitral valve).

 3c: What is the name of the valve between the right ventricle and the pulmonary trunk?  Answer: The pulmonary semilunar valve (i.e., the pulmonary valve or the right semilunar valve).  3d: What is the name of the valve between the left ventricle and the aorta?  Answer: The aortic semilunar valve (i.e., the aortic valve or the left semilunar valve).  3e: What is the name of the wall between the ventricles?  Answer: The interventricular septum.  3f: What is the name of the wall between the atria?  Answer: The interatrial septum. Question 4  You are microscopic, sitting atop a red blood cell and floating around inside the right atrium of a heart that is not beating. Once the heart begins beating, can you describe how you would travel through the heart and the entire cardiovascular system and arrive back in the right atrium?  Answer: You start in the right atrium, travel through the right AV valve and are now in the right ventricle. From here, you are pushed through the pulmonary semilunar valve into the pulmonary trunk, where then you will travel through the pulmonary arteries to the lungs. At the lungs, the arteries will branch into smaller arterioles, and these will feed into the capillary beds of the lungs. From the capillary beds, the blood will travel into venules and then into larger veins. These veins will bring the blood into the pulmonary veins, which deposit the blood into the left atrium. From here, the blood will travel through the left AV valve into the left ventricle. When the left ventricle contracts, the blood will be pushed through the aortic semilunar valve into the aorta. The aorta will branch into arteries, then arterioles, and finally into the capillaries in the organs. Once gas exchange has occurred in the capillaries, the blood will flow into the venules, then veins. The blood will flow through the vena cava to be dumped back into the right atrium, where this process will begin again. Question 5  5a: What do the left coronary artery and right coronary artery supply blood to?  Answer: The left coronary artery supplies blood to the left side of the heart, and the right coronary artery supplies blood to the right side of the heart.  5b: What very important vessel is located in the interventricular sulcus? What is the purpose of this vessel?  Answer: The left anterior descending (LAD) coronary artery is located in the interventricular sulcus. It supplies blood to the front of the left side of the heart.  5c: Why is the LAD called the “widow maker”?  Answer: Since the LAD carries fresh blood to the heart, if it is blocked, the heart can die very fast.

muscle cells are multinucleated. Cardiac cells are involuntarily controlled, while skeletal muscle cells are voluntarily controlled. Cardiac cells are interconnected by gap junctions. In cardiac cells, DHPR is also a channel; it is the L-type calcium channel.  9b: What are intercalated discs?  Answer: Intercalated discs are regions in cardiac tissue where there is a high density of gap junctions.  9c: What does it mean that the heart is a functional syncytium?  Answer: The heart is referred to as a functional syncytium because the cells are interconnected by gap junctions. The cells contract in unison. Question 10  10a: What is the sinoatrial (SA) node, and what is its purpose?  Answer: The SA node is a small body of specialized muscle tissue that acts as a pacemaker by producing a contractile signal at regular intervals to generate heart rhythm.  10b: Where is it located?  Answer: In the upper wall of the right atrium of the heart.  10c: What are internodal fibers, and what are their purpose?  Answer: Internodal fibers are the cardiac conductile cells that emanate from the SA node, innervate the atrial myocardium and terminate at the AV node. Their function is to conduct the signal from the SA node to the myocardial cells of the atria.  10d: Where are they located?  Answer: They are located in the atria.  10e: What is the atrioventricular (AV) node, and what is its purpose?  Answer: The AV node electrically connects the right atrium and right ventricle . The AV node both generates and conducts action potentials.  10f: Where is it located?  Answer: The AV node lies at the floor of the right atrium.  10g: What does it mean that pacemaker cells of the SA and AV nodes are self- excitable?  Answer: The pacemaker cells are self -excitable or autorhythmic. They can spontaneously generate action potentials without innervation.  10h: What sends the signal to contract to the ventricular myocardium?  Answer: Purkinje fibers.  10i: What is the function of the moderator band, and what would happen if it were severed?  Answer: The moderator band is a muscular band of heart tissue found in the right ventricle of the heart. It helps prevent the right ventricle from being overstretched when the left ventricle contracts. It also carries part of the right bundle branch to the papillary muscle . If the moderator band was damaged, the AV valves would prolapse into the atria. Question 11  Beginning with the SA node, can you describe how the signal for the heart to contract travels through the cardiac conduction system?

 Answer: The signal begins at the SA node, and is sent through the internodal fibers to the AV node. The bundle of His transfers the signal to the right and left bundle branches. The signal is directed through the moderator band, which stimulates the papillary muscle in the ventricles, and then propagates up the Purkinje fibers. Question 12  12a: What is the normal rate of prepotentials generated by SA nodal cells?  Answer: The normal rate of prepotentials generated by SA nodal cells is approximately 70 beats per minute.  12b: What is the normal rate of prepotentials generated by AV nodal cells?  Answer: The normal rate of pre potentials generated by AV nodal cells is approximately 50 beats per minute.  12c: What is the normal rate of prepotentials generated by Purkinje fibers?  Answer: The normal rate of pre potentials generated by Purkinje fibers is approximately 30 beats per minute.  12d: If the SA node is nonfunctional (i.e., “derailed”), what is this condition referred to? What autorhythmic cardiomyocyte takes over to replace the SA node?  Answer: This is referred to as sick sinus syndrome. The AV node has control.  12e: If the AV node is nonfunctional (i.e., “derailed”), what is this condition referred to? What autorhythmic cardiomyocyte takes over to replace the AV node?  Answer: This is referred to as complete heart block. The Purkinje fibers have control, since the SA node is derailed as well, being that it is attached to the AV node via internodal fibers.  12f: If the Purkinje fibers are firing signals rapidly, what is this condition referred to?  Answer: This is referred to as ventricular tachycardia. Question 13  13a: What is the resting membrane potential (RMP) and threshold potential (TP) of a slow cell?  Answer: The RMP is -60 mV and the TP is -40 mV.  13b: What is occurring at phase 4?  Answer: At phase 4, the prepotential occurs via funny channels, which allows sodium to enter the cell. This causes threshold to be reached.  13c: What is occurring at phase 0?  Answer: At phase 0, calcium is entering the cell via L-type calcium channels.  13d: What is occurring at phase 3?  Answer: At phase 3, potassium is leaving the cell via voltage-gated potassium channels. Question 14

Question 17  17a: What is an electrocardiogram (ECG) a measure of?  Answer: An ECG is a measurement of the heart’s electrical activity.  17b: What is occurring during the P wave?  Answer: During the P wave, there is a depolarization of the atria.  17c: What is occurring during the QRS complex?  Answer: During the QRS complex, there is a depolarization of the ventricles and a repolarization of the atria.  17d: What is occurring during the T wave?  Answer: The T wave represents a repolarization of the ventricles.  17e: What is occurring during the PR segment?  Answer: During the PR segment, the atria contract.  17f: What is occurring during the ST segment?  Answer: During the ST segment, the ventricles contract.  17g: What is occurring during the TP interval?  Answer: During the TP interval, the ventricles passively fill with blood.  17h: What does the RR interval represent?  Answer: The RR interval is equivalent to the heart rate. Question 18  18a: How is tachycardia clinically defined?  Answer: Tachycardia is a heart rate of more than 100 beats per minute.  18b: How is bradycardia clinically defined?  Answer: Bradycardia is a heart rate of less than 60 beats per minute.  18c: Can someone be clinically bradycardic and still considered to have a normal heart rate? If so, explain.  Answer: Yes, you can be clinically bradycardic and be considered to have a normal heart rate. A slow heart rate does not cause any problems. Bradycardia can be a sign of being very fit. Healthy young adults and athletes often have heart rates of less than 60 beats per minute.  18d: How would you describe an ECG tracing of tachycardia and bradycardia?  Answer: During tachycardia, the RR interval decreases in length. During bradycardia, the RR interval increases in length.  18e: How would you describe an ECG tracing of PVC and PAC?  Answer: During a PVC, the ventricles contract before the ST segment, making the QRS complex abnormal. During a PAC, the TP segment is shorter because the P wave is occurring prematurely.  18f: How would you describe an ECG tracing of ventricular fibrillation and atrial fibrillation?  Answer: During ventricular fibrillation, the QRS complex decreases in size and the signal is noisy. During atrial fibrillation, the P waves in the ECG are absent and the signal is noisy.  18g: How would you describe an ECG tracing for complete heart block?  Answer: In complete heart block, QRS complexes may be missing and the signal is conducting slowly due to a blockage.

 18h: How does an ST segment elevation clinically differ from an ST segment depression?  Answer: An ST segment elevation is transmural, or full thickness, ischemia and indicative of a myocardial infarction. An ST segment depression results from subendothelial partial thickness ischemia, indicative or coronary artery disease. Question 19  19a: What do atrial and ventricular systole mean?  Answer: Atrial and ventricular systole are the contraction phases of the heart.  19b: What are atrial and ventricular diastole?  Answer: Atrial and ventricular diastole are the relaxation phases of the heart.  19c: Does the heart spend more time during systole or diastole?  Answer: The heart spends more time in diastole (specifically, the heart spends 2/3 of the cardiac cycle in diastole).  19d: Can you describe the six events of a cardiac cycle? Be sure to describe how the changes in chamber size affects pressure.  Answer: The cardiac cycle begins with atrial systole, where the atria contract and fill the ventricles. Then, the heart moves into atrial diastole, where the atria relax. Next, early ventricular systole occurs, where the ventricles contract isovolumetrically. This means that, although the ventricle contracts, pressure within the ventricle is not great enough to open the semilunar valve. Then, late ventricular systole occurs, which is the rapid ejection phase. Following this, early ventricular diastole occurs. Here, the ventricles relax isovolumetrically. The atria is filling with blood, but the pressure is not great enough to open the AV valve so that blood can passively fill into the ventricles. Finally, late ventricular diastole allows for passive ventricular filling.  19e: What happens during isovolumetric ventricular contraction?  Answer: During isovolumetric ventricular contraction, although the ventricle contracts, pressure within the ventricle is not great enough to open the semilunar valve.  19f: What happens during isovolumetric ventricular relaxation?  Answer: During isovolumetric ventricular relaxation, the atria is filling with blood, but the pressure is not great enough to open the AV valve so that blood can passively fill into the ventricles.  19g: What happens during rapid ejection?  Answer: During rapid ejection, blood is ejected from the ventricles into the pulmonary trunk or aorta.  19h: What happens during passive ventricular filling?  Answer: During passive ventricular filling, blood passively fills the ventricles from the atria. Question 20

 Answer: CO = SV x HR.  23c: How would you define heart rate?  Answer: Heart rate is how many times the heart beats per minute. The heart beats about approximately 75 beats per minute.  23d: How would you define stroke volume?  Answer: Stroke volume is the volume of blood pumped during each beat. This is approximately 70 mL.  23e: How is stroke volume calculated, in relation to EDV and ESV?  Answer: SV = EDV – ESV.  23f: How would you define end-diastolic volume (EDV)?  Answer: EDV is the volume of blood in the ventricles at the end of passive ventricular filling. This is approximately 120 mL.  23g: How would you define end-systolic volume (ESV)?  Answer: ESV is the volume of blood in the ventricles at the end rapid ejection. This is approximately 50 mL. Question 24  24a: How does the ANS affect heart rate?  Answer: The ANS modulates the heart rate by the sympathetic and parasympathetic branches. Stimulation of the sympathetic branch increases heart rate, and stimulation of the parasympathetic branch decreases heart rate.  24b: What is a funny channel?  Answer: The funny channels are activated by repolarization and cAMP. Sympathetic innervation increases cAMP, which binds to funny channels and increases the probability that they are open. Parasympathetic innervation decreases cAMP, which is now unbound to funny channels and therefore decreases the probability that they are open.  24c: There is a “vagal brake” on the heart. What does this mean and how does the brake work?  Answer: The SA node is innervated by the vagus nerve. It drips acetylcholine onto the pacemaker, slowing heart rate. When vagal tone to the heart’s pacemaker is high, a baseline or resting heart rate is produced. In other words, the vagus nerve acts as a restraint, or brake, limiting heart rate. Question 25  25a: Stroke volume is regulated in two ways: via changes in contractility and the Frank-Starling effect. What is contractility, and how does it affect stroke volume?  Answer: Contractility in how hard and fast myocardial cells are contracting. Increases in contractility increase stroke volume.  25b: What is the Frank-Starling effect, and how does it affect stroke volume?  Answer: The Frank –Starling law of the heart states that the stroke volume increases in response to an increase in the volume of blood filling the heart. Increases in preload will increase stroke volume.

Question 26  26a: How would you define ejection fraction (EF)?  Answer: EF is the fraction of blood ejected from a ventricle of the heart with each heartbeat. A normal ejection fraction value is approximately 55%. Below that indicates heart failure.  26b: How is ejection fraction calculated?  Answer: EF = SV / EDV.  26c: What is HFrEF?  Answer: Heart failure with a reduced ejection fraction occurs when the ejection fraction is below 40%. The heart is too weak to pump properly.  26d: What is HFpEF?  Answer: Heart failure with a preserved ejection fraction occurs when the heart is too stiff to pump properly. The ejection fraction, in this case, is normal. Question 27  27a: What is preload and what is afterload?  Answer: Preload is the blood return venously to the heart. Afterload is the blood within the arteries that blood being pumped from the heart has to push against.  27b: How do changes in preload and afterload affect EDV, ESV, and SV?  Answer: An increase in preload will increase EDV, decrease ESV, and increase SV. An increase in afterload will decrease SV and increase ESV.  27c: How do changes in contractility affect ESV and SV?  Answer: An increase in contractility will decrease end systolic volume and increase stroke volume. Question 28  Can you, in general, compare and contrast the anatomy of arteries and veins?  Answer: Arteries have 3 layers, prominent smooth muscle, no valves and are deeper in the subcutaneous tissue. Veins have 3 layers, valves and are more superficial in the subcutaneous tissue. Question 29  29a: What is microcirculation?  Answer: It is the part of the vascular system and consists of the small vessels called arterioles, capillaries, and venules.  29b: What is the function of arterioles?  Answer: The arteriole is involved in resistance.  29c: What is the function of venules?  Answer: The venule is involved in capacitance.  29d: What is the function of capillaries?  Answer: Capillaries are involved in exchange.

 32c: What is a typical value for the mean arterial pressure?  Answer: 70 to 110 mmHg. Question 33  33a: How do changes in cardiac output affect mean arterial pressure?  Answer: They have a direct relationship, so an increase in cardiac output will increase mean arterial pressure.  33b: How do changes in total peripheral resistance affect mean arterial pressure?  Answer: They have a direct relationship, so an increase in total peripheral resistance will increase mean arterial pressure.  33c: How are cardiac output and total peripheral resistance pharmacologically modulated to lower mean arterial pressure?  Answer: Cardiac output is modulated by ß 1 blockers to reduce the cardiac output by weakening the pump. Total peripheral resistance is modulated by α 1 blockers to reduce total peripheral resistance by vasodilating blood vessels. Question 34  34a: What is the arterial baroreflex?  Answer: The arterial baroreflex is the most important mechanism for moment-to-moment control of arterial blood pressure.  34b: Where are its components located?  Answer: The components are located in the carotid sinuses and aortic arch.  34c: How would this reflex respond to an acute bout of hypotension or hypertension?  Answer: In a response to acute h ypotension, there would be an increase sympathetic activity to the heart and vasculature, and a reduction in parasympathetic activity to the heart. In a response to acute hypertension, there would be a decrease in sympathetic activity to the heart and vasculature, and an increase in parasympathetic activity to the heart. Question 35  35a: What is the arterial chemoreflex?  Answer: The arterial chemoreflex senses changes in blood gases.  35b: Where are its components located?  Answer: Its components are located in the carotid and aortic bodies.  35c: How would this reflex respond to an acute increase in plasma carbon dioxide or oxygen levels?  Answer: A response to an acute elevation of carbon dioxide would include an increase sympathetic activity to the heart and vasculature, and a reduction in parasympathetic activity to the heart. A response to an acute increase in oxygen would include a decrease in sympathetic activity to the heart and vasculature, and an increase parasympathetic activity to the

heart. Question 36  What are the three different types of capillaries and where are their representative locations in the human body?  Answer: The three types of capillaries are the continuous, fenestrated, and sinusoidal capillaries. Continuous capillaries are found in muscle, neural, and connective tissue. Fenestrated capillaries are found in the kidneys and intestines. Sinusoidal capillaries are found in bone marrow, the liver, and the spleen. Question 37  37a: Describe capillary hydrostatic pressure.  Answer: This force pushes fluid out of the capillary due to the high pressure within the capillary. Pressure drops because of the change in resistance along the length of the capillary from 37 to 17 millimeters of mercury.  37b: Describe interstitial fluid hydrostatic pressure.  Answer: This force pushes fluid into the capillary, but this force is very small, due to the fact that there is more pressure within the capillary than within the interstitial fluid.  37c: Describe capillary oncotic pressure.  Answer: This force pushes fluid into the capillary, due to high amount of solutes within the capillary.  37d: Describe interstitial fluid oncotic pressure.  Answer: This force pushes fluid out of the capillary, but this force is very small, since there are more solutes in the capillary than there are in the interstitial fluid.  37e: What is the only force that changes over the length of a capillary?  Answer: Capillary hydrostatic pressure. Question 38  38a: If your lymphatic vessels were clogged, how much fluid volume would accumulate in your interstitial compartment each day?  Answer: 3 L.  38b: How are lymphatic capillaries and veins anatomically similar?  Answer: They both have one-way valves.  38c: What are the two pathways for the delivery of lymph into the venous system?  Answer: The right lymphatic duct and thoracic duct. Question 39  39a: What is an edema?  Answer: An edema is an accumulation of fluid in the tissues.