TopicRevCVW11

TopicRevCVW11 - January 22, 2011 NPB101 – W11...

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Unformatted text preview: January 22, 2011 NPB101 – W11 Topical Review of Cardiovascular Physiology Page 1 of 6 It is important that you understand the anatomy of the heart and the flow of blood through the right and left hearts and the corresponding vascular system. If you do not understand these anatomical relationships, activation of the heart, the cardiac cycle and the relationship of the peripheral vascular system to the right and left hearts will be very confusing for you. Understand the answers to questions posed on the slides and the additional questions I pose to the class. Hemodynamics Know what determines pressure in the vascular system  ­ role of volume and capacitance. What is the interaction between these two parameters in determining pressure on the arterial side of the vascular system, within the capillaries, and on the venous sides of the vascular system? Why is the pressure on the arterial segment high while that on the venous side is low? What is the role of vascular resistance in determining arterial ­venous differences in volume and arterial ­venous differences in pressures in the vascular system? How do changes in arteriolar resistance affect arterial to venous distribution of blood volume and therefore, changes in arterial and venous pressure? Why does a change in volume of blood (stroke volume flowing from the arterial into the venous side of the vascular system) from the arterial side to the venous side of the vascular system produce a large change in arterial pressure and little change in venous? Understand the concept of Mean Circulatory Pressure, and how it is determined. Understand the interaction of volume and capacitance in determining the mean circulatory pressure. Understand the difference between Mean Circulatory Pressure and Mean Arterial or Mean Blood Pressure. Understand Poisseulle’s Law and the relationship between the pressure gradient and resistance in determining blood flow. Know the factors (viscosity, length and radius) that govern resistance and the functional importance of each in determining resistance and blood flow through the vascular system. Know the affects of changing resistances in series and in parallel on total vascular resistance. Cardiac Electrophysiology Recognize that there different cell types within the heart and that these cell types have different action potential configurations. Recognize that these differences in action potentials are a consequence of differences in the membrane channels and properties of thesemembrane channels. Understand the concepts related to current flow and generation of the cardiac action potential. Understand how diastolic depolarization of SA nodal pacemaker cells and the rate of rise and amplitude of the action potentials from the specialized tissues of the heart relate to their respective electrophysiological function. For example, what defines a pacemaker cells? What parameters of AV nodal action potentials contribute to slow conduction through the AV node? What are the TopicRevCVW11.docx January 22, 2011 NPB101 – W11 Topical Review of Cardiovascular Physiology Page 2 of 6 parameters of the Purkinje fiber action potential that generate fast conduction through the His Bundle and Bundle Branch system? Ionic basis of the cardiac action potential. How does it differ from a nerve action potential. Understand the role of Na, Ca and K channels and their respective currents in generating the upstroke of the cardiac action potential. Understand the interaction between Ca and K channels and current in generating the plateau and the long duration of the cardiac action potential relative to those in nerve and skeletal muscle. Understand why the plateau of a Purkinje fiber action potential has a downward slope and the electrophysiological event that terminates the plateau and initiates the terminal repolarization. Be able to determine how the absence or change in Na, Ca or K channel activation (opening) and inactivation (closing) would affect the rate of rise, amplitude and shape, and duration of an action potential from a Purkinje fiber. Understand the Parameters that Determine Conduction through Cardiac Tissue. Concepts of absolute, effective and relative refractory periods. Understand the concept of absolute and relative refractory periods of a cell. Understand the concept of effective and relative refractory periods in cardiac tissue. Understand the application of the effective and relative refractory periods on activation of the heart. Understand the relationship of the absolute and relative refractory periods of cells and the effective and relative refractory periods of tissue and conduction through the heart. Can a tissue be effectively refractory with cells in their relative refractory periods? Can a tissue be effectively refractory with cells in their absolute refractory period? Can you conclude; if a tissue segment is effectively refractory, all the cells in the segment are absolute refractory? What is the temporal relationship between the cardiac action potential and cardiac contraction, and what is the temporal relationship between the duration of the effective refractory period and cardiac activation and contraction? Can cardiac muscle be tetanized? Would the ability to produce frequency summation of activation and subsequent contraction of the heart enhance the pumping function of the heart? Sequence of activation of and conduction through the heart. Relationship of the sequence of activation to the electrocardiogram. Know the waves and intervals of the electrocardiogram and what each represents. Understand the information about the electrophysiology of the heart that is derived from the electrocardiogram. Be able to use the electrocardiogram to determine heart rate and conduction through the heart. Be able to recognize changes that would occur in the electrocardiogram if regions of the heart were effectively refractory. Be able to recognize changes that would occur in the electrocardiogram if a region of the heart were in its relative refractory period. If a component of the electrocardiogram is absent, be able to identify the region or regions that might be effectively refractory that would account for the loss of a component. TopicRevCVW11.docx January 22, 2011 NPB101 – W11 Topical Review of Cardiovascular Physiology Page 3 of 6 Autonomic effects on heart rate and conduction through the heart. Effect of sympathetic and parasympathetic activation on heart rate and conduction. Be able to understand how changes in the maximal diastolic potential and/or slope of the pacemaker potential would change heart rate. Be able to use the ECG to determine changes in sympathetic and parasympathetic affects on heart rate and conduction through the heart. Excitation  ­ Contraction Coupling Comparison to that in skeletal muscle. Sources of Ca++ in cardiac muscle and the relationship between sarcoplasmic Ca++ and the number of available actin ­myosin bonds used to generate pressure. Cardiac Muscle and Cardiac Mechanics. Understand the parameters of muscle fiber length (# of cross ­bridges mobilized) and contractility of the cross ­bridges in determing the pressure developed and the stroke volume ejected by the heart. Understand the roles of preload (muscle fiber length, use of available actin ­myosin bonds) and contractility (rate of cycling of the A ­M Cross ­ bridges) in generating pressure and ejecting the stroke volume. Know what determines preload or end diastolic volume (End Systolic Volume + filling of the heart from the venous side of the circulation) and how this can be changed. Understand the Frank  ­ Starling or Length  ­ Tension/Pressure/Stroke Volume Relationship for the heart and the relationship between end diastolic volume or muscle fiber length or preload in determining the number of A ­M Cross ­briges mobilized for the cycle and the stroke volume and pressure of the heart. Understand the functional consequence of the Frank ­ Starling Law of the Heart in maintaining flow through the cardiovascular system; specifically, the heart intrinsically matches its pressure and stroke volume to meet beat to beat changes in venous return. There is this relationship between preload (end diastolic volume) and tension or stroke volume because the heart operates at a muscle fiber length that is less than optimal of actin ­myosin overlap. What determines cardiac contractility and how can it be changed. Understand that the contractile energy mobilized by the heart for a contraction is the sum of the contractile energy generated by the number of cross ­bridges (muscle fiber length, preload) and the contractile energy generated by contractility. What is the effect of changes in cardiac contractility on the Length ­Tension/Pressure/Stroke Volume relationship for the heart? Understand the relationship between muscle fiber length (end diastolic volume) and contractility in determining stroke volume and cardiac output given in the graph of cardiac function. Understand the sequence of events and the interaction of pressure and valve opening and closing in the Pressure  ­ Volume loop for the heart. Think about what would happen to the loop (peak pressure, end diastolic volume and end systolic volume) if there was a change in venous return or if there was a change in contractility. Cardiac Cycle  ­ know this cycle and the sequence of events. See Fig. 9 ­16, pp. 321 – 323. Ideally, you should be able to draw the temporal relationships and explain TopicRevCVW11.docx January 22, 2011 NPB101 – W11 Topical Review of Cardiovascular Physiology Page 4 of 6 the sequence of events. The cardiac cycle differs from the pressure ­volume loop in that the cycle has time for the X axis and it also has atrial pressure, aortic or arterial pressure, and the electrocardiogram. Be able to use the cycle to explain and understand the interaction of the parameters that determine pressure developed by and stroke volume of the heart. The principles; electrical activation of a cardiac tissue must preceed its contraction, flow occurs down a pressure gradient, valves dictate the direction of flow and the ability of a pressure gradient to generate flow; apply to the cardiac cycle as they do to the pressure – volume loops. For some of you, understanding the cardiac cycle first might be easier than beginning with the pressure ­volume loop. Cardiac Output. Definition of cardiac output (CO = HRx SV). Over time the output from the left heart pumping blood into the systemic circulation must equal the output of the right heart pumping blood into the pulmonary circulation. (Two pumps in series in a closed system. Heart must get blood from its corresponding venous segment to pump it out.) Know factors that govern heart rate (interaction of sympathetic and parasympathetic components of the ANS) and the limit to heart rate mediated increases in cardiac output (limits to cardiac filling because of time limit to filling of the central veins and associated decreases in venous pressure). Understand that stroke volume is determined by end diastolic volume (muscle fiber length, # cross ­bridges mobilized) and contractility (assuming no changes in afterload or aortic diastolic pressure). Know the effects of changes in venous return, end diastolic volume (muscle fiber length; number of cross ­ bridges mobilized) and contractility in determining stroke volume. Understand the affect of venous pressure on cardiac filling and stroke volume. Understand the parameters that determine venous pressure. Understand parameters that determine venous volume (rate of venous filling and rate of venous emptying) and venous capacitance. Understand the effect of cardiac contractility (affect of cardiac contractility on systolic reserve volume or the end systolic volume) on stroke volume when there is no change in end diastolic volume and no change in fiber length. Recognize that the heart will always adjust its contractile energy to pump out the venous return in the face of changes in afterload or aortic diastolic pressure. Thus, stroke volume will match venous return. Peripheral Vascular System  ­ distributing network. Know the parameters that determine aortic/arterial diastolic pressure. [Aortic diastolic pressure determined by volume of blood in the arteries/aorta just before the ejection of the stroke volume.] Understand the effects of increases or decreases in both heart rate and arteriolar/peripheral vascular resistance on aortic/arterial diastolic pressure. Recognize that arterioles are the resistance elements in the peripheral vascular system. Understand the effects of the sympathetic neural input, endothelial derived factors and local metabolic factors on arteriolar radius and vascular resistance. Understand the effect of selectively changing resistances in a parallel vascular network on the distribution of blood flow – the cardiac output. TopicRevCVW11.docx January 22, 2011 NPB101 – W11 Topical Review of Cardiovascular Physiology Page 5 of 6 Capillaries  ­ exchange vessels. Understand what parameters determine pressure within the capillaries. Be able to manipulate changes in arterial and venous pressures and resistances and determine the changes in capillary volume and pressure. Understand how changes in arteriolar resistance and precapillary sphincter vasomotion influence inflow into the capillaries. Know the routes of exchange of ions, solutes, gases, and nutrients across capillaries. Understand fluid exchange (movement of water) across the capillaries including the Starling Filtration Hypothesis. Be able to manipulate the parameters, including Kf, in the Filtration Hypothesis and determine if there is n increase in filtration or a decrease in filtration (reabsorbtion). Venules and Small Veins  ­ capacitance vessels. While constriction of a blood vessel affects both the resistance to flow through the vessel and the capacitance of the vessel, understand why changes in caliber of arterioles change resistance in the vascular system and not vascular capacitance, and why changes in caliber of venules and small veins affect vascular capacitance and not resistance. Role of sympathetic nervous system in determining capacitance. Effect of changes in capacitance on venous pressure and venous return to the heart. Regulation of Blood Pressure. Recognize that arterial blood pressure determined by the steady state volume of blood in the arterial system. To increase arterial pressure, arterial volume must increase. To decrease arterial pressure, arterial volume must decrease. Know the location of pressure (baroreceptors) sensors. Understand how the baroreceptors sense pressure. Understand the affect of changes in arterial blood pressure on afferent nerve activity. Understand central (medullary) integration of afferent input – affect on sympathetic and parasympathetic neural outflow. What are the effects of changes in sympathetic and parasympathetic activity on the heart (heart rate, conduction, contractility) and affect of sympathetic output on the peripheral vascular system? How do changes sympathetic and parasympathetic activity to heart and sympathetic activity to the peripheral vascular system produce changes in blood pressure. Specific effects of ANS on heart (contractility, heart rate, stroke volume  ­ cardiac output and pressure developed by heart), arterioles, venules and small veins. What are the effects of changes in sympathetic activity on the arterioles and venules and how do these changes affect volume and pressure in each region and the effects of these changes on the heart, the pressure developed by the heart and the volume of blood ejected by the heart? Recognize that changes in arterial pressure occur through changes in the volume of blood present on the arterial side of the vascular system. Recognize the that arterial pressure changes through changes in arterial volume. Changes in arterial volume occur through changes in the rate of inflow to and outflow from the arterial vascular system. While I went over in class responses to a fall in blood pressure, be able to work through changes in sympathetic and parasympathetic TopicRevCVW11.docx January 22, 2011 NPB101 – W11 Topical Review of Cardiovascular Physiology Page 6 of 6 outflows on the heart and peripheral vascular system when there is an increase in pressure. TopicRevCVW11.docx ...
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This note was uploaded on 08/21/2011 for the course NPB 101 taught by Professor Fuller,charles/goldberg,jack during the Winter '08 term at UC Davis.

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