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Physiology: Cardiovascular

Physiology: Cardiovascular

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@EffusiveClearQuartz
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Questions and Answers

What happens to resistance when blood vessel radius decreases by a factor of 2?

It increases by a factor of 16

What is the effect on total resistance when an artery is added in parallel?

It decreases

What is the equation for the total resistance of parallel arteries?

Rtot = 1 / (1/Ra + 1/Rb + 1/Rn)

What is the relationship between resistance and vessel radius?

<p>Resistance is inversely proportional to the fourth power of vessel radius</p> Signup and view all the answers

What is the effect on blood flow when resistance increases by a factor of 16?

<p>It decreases by a factor of 16</p> Signup and view all the answers

What type of resistance is illustrated by the systemic circulation?

<p>Parallel resistance</p> Signup and view all the answers

Which part of the series arrangement contributes the largest proportion of resistance?

<p>Arterioles</p> Signup and view all the answers

What is the main reason for the lower velocity of blood in the capillaries?

<p>To optimize conditions for exchange of substances across the capillary wall</p> Signup and view all the answers

What is the unit of measurement for cardiac output (Q) in the equation Q=AP/R?

<p>mL/min</p> Signup and view all the answers

What is the analogy for blood flow in the equation Q=AP/R?

<p>Ohm's law for electrical circuits</p> Signup and view all the answers

What is the direction of blood flow according to the equation Q=AP/R?

<p>From high pressure to low pressure</p> Signup and view all the answers

What is the relationship between blood flow and resistance in the equation Q=AP/R?

<p>Blood flow is inversely proportional to resistance</p> Signup and view all the answers

What is the factor that affects resistance according to the Poiseuille equation?

<p>Viscosity, length, and radius of blood vessel</p> Signup and view all the answers

What is the effect of increasing hematocrit on blood flow?

<p>It decreases blood flow</p> Signup and view all the answers

What is the relationship between resistance and length of the blood vessel according to the Poiseuille equation?

<p>Resistance is directly proportional to length</p> Signup and view all the answers

What is the relationship between blood flow through the largest artery and total blood flow through all capillaries?

<p>Blood flow through the largest artery is the same as total blood flow through all capillaries</p> Signup and view all the answers

What type of flow is characterized by a streamlined, straight-line flow?

<p>Laminar flow</p> Signup and view all the answers

What is the purpose of the Reynolds number?

<p>To predict whether blood flow will be laminar or turbulent</p> Signup and view all the answers

What is the effect of increasing blood viscosity on the Reynolds number?

<p>It decreases the Reynolds number</p> Signup and view all the answers

What is the main cause of the Korotkoff sounds used in the auscultatory measurement of blood pressure?

<p>Turbulent flow</p> Signup and view all the answers

What is the relationship between shear and blood velocity in a blood vessel?

<p>Shear is highest at the wall of the vessel</p> Signup and view all the answers

What is the relationship between capacitance and elastance in blood vessels?

<p>Capacitance is inversely related to elastance</p> Signup and view all the answers

What is the effect of increasing blood velocity on the Reynolds number?

<p>It increases the Reynolds number</p> Signup and view all the answers

What is the primary determinant of pulse pressure?

<p>Stroke volume</p> Signup and view all the answers

What happens to pulse pressure when arterial capacitance decreases?

<p>It increases</p> Signup and view all the answers

What is the highest arterial pressure during a cardiac cycle?

<p>Systolic pressure</p> Signup and view all the answers

What is the lowest arterial pressure during a cardiac cycle?

<p>Diastolic pressure</p> Signup and view all the answers

During which phase of the cardiac cycle is diastolic pressure measured?

<p>Diastole</p> Signup and view all the answers

What is the effect on systolic pressure when blood is ejected into the arterial system?

<p>It increases</p> Signup and view all the answers

What is the relationship between pulse pressure and systolic pressure?

<p>Pulse pressure increases with increasing systolic pressure</p> Signup and view all the answers

What is the effect of the aging process on pulse pressure?

<p>It increases</p> Signup and view all the answers

What is the relationship between elastance and compliance in blood vessels?

<p>Elastance is inversely proportional to compliance</p> Signup and view all the answers

What happens to unstressed volume when venous capacitance decreases?

<p>It decreases</p> Signup and view all the answers

What is the effect of aging on the capacitance of arteries?

<p>It decreases</p> Signup and view all the answers

Where does the largest decrease in pressure occur in the systemic circulation?

<p>Arterioles</p> Signup and view all the answers

What is the mean pressure in the aorta?

<p>100 mm Hg</p> Signup and view all the answers

What is the characteristic of arterial pressure?

<p>It is pulsatile</p> Signup and view all the answers

What is the relationship between volume and pressure in blood vessels?

<p>Volume is inversely proportional to pressure</p> Signup and view all the answers

What is the main reason why mean arterial pressure is not the simple average of diastolic and systolic pressures?

<p>Because a greater fraction of the cardiac cycle is spent in diastole</p> Signup and view all the answers

What is the approximate formula to calculate mean arterial pressure?

<p>Diastolic pressure plus one-third of pulse pressure</p> Signup and view all the answers

What is the reason why venous pressure is very low?

<p>Because veins have a high capacitance</p> Signup and view all the answers

What does the P wave in an electrocardiogram (ECG) represent?

<p>Atrial depolarization</p> Signup and view all the answers

What is the PR interval in an electrocardiogram (ECG)?

<p>The interval from the beginning of the P wave to the beginning of the Q wave</p> Signup and view all the answers

What is the effect on the PR interval if AV nodal conduction decreases?

<p>The PR interval increases</p> Signup and view all the answers

What is the purpose of measuring pulmonary wedge pressure?

<p>To estimate left atrial pressure</p> Signup and view all the answers

What is the typical location where the largest decrease in pressure occurs in the systemic circulation?

<p>In the arterioles</p> Signup and view all the answers

What is the period during which a conducted action potential cannot be elicited?

<p>Effective refractory period</p> Signup and view all the answers

What is the effect of a negative chronotropic effect on heart rate?

<p>It decreases heart rate</p> Signup and view all the answers

What is the effect of a positive dromotropic effect on conduction velocity?

<p>It increases conduction velocity</p> Signup and view all the answers

What is the period during which an action potential can be elicited, but more than the usual inward current is required?

<p>Relative refractory period</p> Signup and view all the answers

What is the effect of a positive chronotropic effect on heart rate?

<p>It increases heart rate</p> Signup and view all the answers

What is the effect of a negative dromotropic effect on conduction velocity?

<p>It decreases conduction velocity</p> Signup and view all the answers

What is the primary cause of the slow conduction velocity in the AV node?

<p>Small inward Ca+ current</p> Signup and view all the answers

What is the period during which no action potential can be initiated, regardless of how much inward current is supplied?

<p>Absolute refractory period</p> Signup and view all the answers

What is the function of the absolute refractory period?

<p>Preventing re-excitation of the cardiac cell</p> Signup and view all the answers

What is the relationship between autonomic effects on heart rate and conduction velocity?

<p>Autonomic effects affect both heart rate and conduction velocity</p> Signup and view all the answers

What determines the conduction velocity in cardiac tissue?

<p>Size of the inward Ca+ current</p> Signup and view all the answers

What is the consequence of increased conduction velocity in the AV node?

<p>Compromised ventricular filling</p> Signup and view all the answers

What is the characteristic of cardiac cells during the absolute refractory period?

<p>Low excitability</p> Signup and view all the answers

What is the purpose of the relative refractory period?

<p>Gradually increasing cardiac excitability</p> Signup and view all the answers

Which part of the heart has parasympathetic vagal innervation?

<p>SA node, atria, and AV node</p> Signup and view all the answers

What is the relationship between the size of the inward current and conduction velocity?

<p>Larger inward current, faster conduction velocity</p> Signup and view all the answers

What is the effect of acetylcholine on the heart rate?

<p>Decreases heart rate</p> Signup and view all the answers

What is the mechanism of the negative chronotropic effect?

<p>Decreased inward Na+ current</p> Signup and view all the answers

Where is conduction velocity fastest in the heart?

<p>Purkinje system</p> Signup and view all the answers

What is the effect of parasympathetic stimulation on conduction velocity through the AV node?

<p>Decreases conduction velocity</p> Signup and view all the answers

What is the neurotransmitter responsible for sympathetic effects on the heart?

<p>Norepinephrine</p> Signup and view all the answers

What is the receptor type involved in sympathetic effects on the heart?

<p>β-Adrenergic receptors</p> Signup and view all the answers

What is the effect of parasympathetic stimulation on the PR interval?

<p>Increases the PR interval</p> Signup and view all the answers

What is the mechanism of the negative dromotropic effect?

<p>Decreased inward Ca2+ current and increased outward K+ current</p> Signup and view all the answers

What is the primary mechanism by which the positive chronotropic effect increases heart rate?

<p>Increased inward Na+ current</p> Signup and view all the answers

What is the functional unit of the myocardial cell?

<p>Sarcomere</p> Signup and view all the answers

What is the primary function of intercalated disks in cardiac muscle cells?

<p>To facilitate rapid electrical spread of action potentials</p> Signup and view all the answers

What is the sliding filament model of muscle contraction?

<p>The model where actin and myosin filaments slide past each other during contraction</p> Signup and view all the answers

What is the result of the positive dromotropic effect on the cardiac conduction system?

<p>Decreased PR interval</p> Signup and view all the answers

What is the primary component of the thick filaments in cardiac muscle cells?

<p>Myosin</p> Signup and view all the answers

What is the purpose of gap junctions in intercalated disks?

<p>To facilitate rapid electrical spread of action potentials</p> Signup and view all the answers

What is the functional significance of the positive chronotropic effect?

<p>Increased cardiac output</p> Signup and view all the answers

What is the primary function of the sarcoplasmic reticulum in muscle physiology?

<p>To store and release calcium ions</p> Signup and view all the answers

What is the structural characteristic of sarcoplasmic reticulum in relation to the contractile elements?

<p>Small-diameter tubules in close proximity to the contractile elements</p> Signup and view all the answers

What is the ion primarily involved in the contraction of muscle fibers, stored and released by the sarcoplasmic reticulum?

<p>Calcium ions</p> Signup and view all the answers

What is the significance of the sarcoplasmic reticulum in regulating muscle contraction?

<p>It facilitates the release of calcium ions to trigger muscle contraction</p> Signup and view all the answers

What is the functional relevance of the sarcoplasmic reticulum in muscle physiology?

<p>It facilitates the contraction of muscle fibers</p> Signup and view all the answers

What is the primary function of the sarcoplasmic reticulum (SR) in muscle physiology?

<p>Storage and release of calcium ions</p> Signup and view all the answers

What is the structural characteristic of sarcoplasmic reticulum (SR) in relation to muscle fibers?

<p>Small-diameter tubules in close proximity to the contractile elements</p> Signup and view all the answers

What is the significance of the sarcoplasmic reticulum (SR) in muscle contraction?

<p>It stores and releases calcium ions necessary for muscle contraction</p> Signup and view all the answers

What is the relationship between the sarcoplasmic reticulum (SR) and the contractile elements of the muscle fiber?

<p>The SR is in close proximity to the contractile elements, surrounding them</p> Signup and view all the answers

What is the functional significance of the sarcoplasmic reticulum (SR) in muscle physiology?

<p>It stores and releases calcium ions necessary for muscle contraction</p> Signup and view all the answers

What is the primary function of the sarcoplasmic reticulum in muscle physiology?

<p>Storage and release of calcium ions</p> Signup and view all the answers

What is the close proximity of the sarcoplasmic reticulum to the contractile elements important for?

<p>Facilitating rapid calcium release</p> Signup and view all the answers

What is the significance of the small-diameter tubules of the sarcoplasmic reticulum?

<p>Reducing the distance for calcium ion release</p> Signup and view all the answers

What would be the consequence of a sarcoplasmic reticulum dysfunction in muscle physiology?

<p>Reduced calcium release and impaired muscle contraction</p> Signup and view all the answers

What is the primary role of calcium ions in muscle physiology, as related to the sarcoplasmic reticulum?

<p>Triggers muscle contraction through binding to troponin and tropomyosin</p> Signup and view all the answers

What is the effect of a decrease in total peripheral resistance on cardiac output?

<p>Increased cardiac output</p> Signup and view all the answers

What is the equation for ejection fraction?

<p>Ejection fraction = Stroke volume / End-diastolic volume</p> Signup and view all the answers

What is the result of a simultaneous decrease in total peripheral resistance and increase in venous return?

<p>Increased cardiac output and venous return</p> Signup and view all the answers

What is the equation for cardiac output?

<p>Cardiac output = Stroke volume x Heart rate</p> Signup and view all the answers

What is the effect of a decrease in aortic pressure on cardiac output?

<p>Increased cardiac output</p> Signup and view all the answers

What is the effect of an increase in venous return on right atrial pressure?

<p>Unchanged right atrial pressure</p> Signup and view all the answers

What is the equation for stroke volume?

<p>Stroke volume = End-diastolic volume - End-systolic volume</p> Signup and view all the answers

What is the result of a simultaneous decrease in total peripheral resistance and decrease in venous return?

<p>Decreased cardiac output and venous return</p> Signup and view all the answers

What is the main cause of the first heart sound?

<p>Closure of the mitral valve</p> Signup and view all the answers

What is the name of the phase where ventricular pressure increases isovolumetrically?

<p>Isovolumetric ventricular contraction</p> Signup and view all the answers

What is the term for the phase where ventricular volume is constant?

<p>Isovolumetric contraction</p> Signup and view all the answers

What is the ECG wave that represents electrical activation of the atria?

<p>P wave</p> Signup and view all the answers

What is the term for the increase in atrial pressure caused by atrial systole?

<p>A wave</p> Signup and view all the answers

When does the first heart sound occur?

<p>When ventricular pressure becomes greater than atrial pressure</p> Signup and view all the answers

What is the phase that immediately follows atrial systole?

<p>Isovolumetric ventricular contraction</p> Signup and view all the answers

What is the name of the fourth heart sound?

<p>Fourth heart sound</p> Signup and view all the answers

What is the primary energy source for stroke work in the heart?

<p>Fatty acids</p> Signup and view all the answers

What is the equation that expresses stroke work?

<p>Stroke work = Aortic pressure x Stroke volume</p> Signup and view all the answers

What is the factor that increases cardiac oxygen consumption?

<p>Increased aortic pressure</p> Signup and view all the answers

What is the formula for calculating cardiac output using the Fick principle?

<p>Cardiac output = 02 consumption / (Arterial O2 content - Venous O2 content)</p> Signup and view all the answers

What is the unit of measurement for cardiac output?

<p>L/min</p> Signup and view all the answers

What is the calculation for stroke volume?

<p>Stroke volume = Cardiac output / Heart rate</p> Signup and view all the answers

What is the effect of increased heart rate on cardiac oxygen consumption?

<p>It increases cardiac oxygen consumption</p> Signup and view all the answers

What is the relationship between cardiac oxygen consumption and ventricular tension?

<p>They are directly related</p> Signup and view all the answers

What occurs during the rapid ejection phase of the cardiac cycle?

<p>Ventricular volume decreases dramatically</p> Signup and view all the answers

What marks the end of ventricular contraction and rapid ventricular ejection?

<p>The onset of the T wave</p> Signup and view all the answers

What is the reason for the C wave on the venous pulse curve?

<p>The bulging of the tricuspid valve into the right atrium</p> Signup and view all the answers

What happens to ventricular pressure during the reduced ejection phase?

<p>It decreases as the ventricle begins to relax</p> Signup and view all the answers

What is the relationship between aortic pressure and ventricular pressure during the rapid ejection phase?

<p>Aortic pressure is less than ventricular pressure</p> Signup and view all the answers

What is the characteristic of the ventricular contraction phase?

<p>It is a rapid and forceful contraction</p> Signup and view all the answers

What occurs during the isovolumetric ventricular contraction phase?

<p>The ventricle contracts without a change in volume</p> Signup and view all the answers

What is the significance of the PR interval in an electrocardiogram?

<p>It represents the time between the onset of the P wave and the onset of the QRS complex</p> Signup and view all the answers

What does the V wave on the venous pulse curve represent?

<p>Blood flow into the right atrium and from right atrium into right ventricle</p> Signup and view all the answers

What happens during the isovolumetric ventricular relaxation phase?

<p>Ventricular pressure decreases rapidly</p> Signup and view all the answers

What is the characteristic of the third heart sound?

<p>It is associated with disease in adults</p> Signup and view all the answers

What is the longest phase of the cardiac cycle?

<p>Reduced ventricular filling (diastasis)</p> Signup and view all the answers

What is the reason for the splitting of the second heart sound?

<p>Inspiration delays closure of the pulmonic valve</p> Signup and view all the answers

What is the name of the 'blip' in the aortic pressure tracing?

<p>Dicrotic notch</p> Signup and view all the answers

What happens when ventricular pressure becomes less than atrial pressure?

<p>The mitral valve opens</p> Signup and view all the answers

What is the relationship between aortic pressure and ventricular volume during the isovolumetric ventricular relaxation phase?

<p>Aortic pressure decreases and ventricular volume is constant</p> Signup and view all the answers

What is the primary response of the vasomotor center to a decrease in mean arterial blood pressure?

<p>Increased sympathetic outflow to the heart and blood vessels</p> Signup and view all the answers

What is the effect of increased sympathetic tone on the heart?

<p>Increased heart rate and contractility</p> Signup and view all the answers

What is the effect of increased sympathetic outflow on arterioles?

<p>Vasoconstriction and increased total peripheral resistance</p> Signup and view all the answers

What is the net effect of the baroreceptor reflex on mean arterial pressure?

<p>Increased mean arterial pressure</p> Signup and view all the answers

What is the role of the parasympathetic nervous system in the baroreceptor reflex?

<p>Decreased parasympathetic outflow to the heart and blood vessels</p> Signup and view all the answers

What is the effect of increased sympathetic tone on venous return?

<p>Increased venous return</p> Signup and view all the answers

What is the relationship between heart rate and contractility in the baroreceptor reflex?

<p>Heart rate and contractility both increase</p> Signup and view all the answers

What is the primary mechanism by which the baroreceptor reflex increases arterial pressure?

<p>Increased heart rate and contractility</p> Signup and view all the answers

Which of the following is a result of vasoconstriction of veins?

<p>A decrease in unstressed volume and an increase in venous return to the heart</p> Signup and view all the answers

What happens to cardiac output and arterial pressure during the Valsalva maneuver?

<p>Cardiac output decreases, and arterial pressure decreases</p> Signup and view all the answers

What is the role of the baroreceptor reflex in the Valsalva maneuver?

<p>It senses the decrease in arterial pressure and increases sympathetic outflow</p> Signup and view all the answers

What is the function of angiotensinase in the renin-angiotensin-aldosterone system?

<p>It degrades angiotensin II</p> Signup and view all the answers

What is the effect of the rebound increase in venous return after the Valsalva maneuver?

<p>An increase in heart rate and blood pressure</p> Signup and view all the answers

What is the main function of the renin-angiotensin-aldosterone system?

<p>It regulates blood volume in the long-term</p> Signup and view all the answers

What is the effect of increased sympathetic outflow on cardiac output?

<p>It increases cardiac output by the Frank-Starling mechanism</p> Signup and view all the answers

What is the response to acute blood loss?

<p>An increase in sympathetic outflow and cardiac output</p> Signup and view all the answers

What is the primary function of angiotensin-converting enzyme in the renin-angiotensin-aldosterone system?

<p>To convert angiotensin I to angiotensin II</p> Signup and view all the answers

Which of the following effects of angiotensin II leads to contraction alkalosis?

<p>Increase in Na+-H+ exchange in the proximal convoluted tubule</p> Signup and view all the answers

What is the site of angiotensin II conversion from angiotensin I?

<p>Lungs</p> Signup and view all the answers

Which of the following is a slow effect of angiotensin II?

<p>Stimulation of aldosterone synthesis and secretion</p> Signup and view all the answers

What is the target of angiotensin receptor antagonists, such as losartan?

<p>Angiotensin receptor</p> Signup and view all the answers

What is the effect of angiotensin II on blood volume?

<p>Increase in blood volume</p> Signup and view all the answers

What is the primary role of juxtaglomerular cells in the renin-angiotensin-aldosterone system?

<p>To secrete renin</p> Signup and view all the answers

What is the effect of angiotensin II on aldosterone synthesis and secretion?

<p>Stimulation of aldosterone synthesis and secretion</p> Signup and view all the answers

What is the response of the brain to cerebral ischemia?

<p>Increased sympathetic outflow to the heart and blood vessels</p> Signup and view all the answers

What is the effect of constriction of arterioles on blood flow?

<p>Significant reduction in blood flow to other organs</p> Signup and view all the answers

What is the role of the renin-angiotensin-aldosterone system in response to acute blood loss?

<p>To preserve blood flow to the brain</p> Signup and view all the answers

What is the effect of the Cushing reaction on mean arterial pressure?

<p>Increased mean arterial pressure</p> Signup and view all the answers

What is the response of chemoreceptors in the vasomotor center to cerebral ischemia?

<p>Increased sympathetic outflow to the heart and blood vessels</p> Signup and view all the answers

What is the effect of increased TPR on blood flow to other organs?

<p>Decreased blood flow to other organs</p> Signup and view all the answers

What is the role of aldosterone in the renin-angiotensin-aldosterone system?

<p>To stimulate Na+-H+ exchange</p> Signup and view all the answers

What is the response of the renin-angiotensin-aldosterone system to hemorrhage?

<p>To increase blood pressure</p> Signup and view all the answers

What is the effect of increased intracranial pressure on cerebral blood vessels?

<p>Constriction</p> Signup and view all the answers

What is the response of chemoreceptors in the carotid and aortic bodies to decreased partial pressure of oxygen?

<p>Increased vasoconstriction</p> Signup and view all the answers

What is the primary function of vasopressin in response to hemorrhage?

<p>Vasoconstriction and water reabsorption</p> Signup and view all the answers

What is the effect of atrial natriuretic peptide on blood pressure?

<p>Decreases blood pressure</p> Signup and view all the answers

What is the effect of increased sympathetic outflow on arterial pressure?

<p>Increased arterial pressure</p> Signup and view all the answers

What is the response of the vasomotor center to increased intracranial pressure?

<p>Increased sympathetic outflow</p> Signup and view all the answers

What is the effect of vasopressin on arterioles?

<p>Vasoconstriction</p> Signup and view all the answers

What is the effect of decreased blood volume on vasopressin release?

<p>Increased vasopressin release</p> Signup and view all the answers

What is the primary mechanism by which coronary circulation is controlled?

<p>Local metabolic factors play a major role</p> Signup and view all the answers

What is the main cause of vasodilation of the cerebral arterioles?

<p>Increased PCO2</p> Signup and view all the answers

What is the effect of mechanical compression of the coronary vessels during systole?

<p>Blood flow decreases</p> Signup and view all the answers

What is the role of sympathetic nerves in regulating cerebral circulation?

<p>Minor role</p> Signup and view all the answers

What is the effect of increased myocardial contractility on coronary vessels?

<p>Vasodilation</p> Signup and view all the answers

What is the effect of reactive hyperemia on blood flow?

<p>Blood flow increases</p> Signup and view all the answers

What is the primary factor that regulates skeletal muscle circulation?

<p>Local metabolic factors</p> Signup and view all the answers

What is the effect of increased PCO2 on cerebral blood flow?

<p>Increased blood flow</p> Signup and view all the answers

What is the primary regulator of blood flow to skeletal muscle at rest?

<p>Sympathetic innervation</p> Signup and view all the answers

What is the effect of stimulating a1 receptors on blood vessels in skeletal muscle?

<p>Vasoconstriction</p> Signup and view all the answers

What is the main function of the cutaneous sympathetic nerves?

<p>Temperature regulation</p> Signup and view all the answers

What is the response observed in skin due to trauma?

<p>The triple response</p> Signup and view all the answers

During exercise, what is the primary mechanism regulating blood flow to skeletal muscle?

<p>Local metabolic control</p> Signup and view all the answers

What is the effect of mechanical compression during exercise on blood flow to skeletal muscle?

<p>Decreased blood flow</p> Signup and view all the answers

What is the primary determinant of total peripheral resistance (TPR)?

<p>State of constriction of arterioles in skeletal muscle</p> Signup and view all the answers

What is the effect of increased ambient temperature on cutaneous blood vessels?

<p>Vasodilation</p> Signup and view all the answers

What is the primary mechanism underlying reactive hyperemia?

<p>Increased production of vasodilator metabolites</p> Signup and view all the answers

What is the result of increased arteriolar smooth muscle contraction in response to increased perfusion pressure?

<p>Maintained constant blood flow to the organ</p> Signup and view all the answers

What happens to parasympathetic outflow to the heart in response to a coordinated response from the vasomotor center?

<p>It decreases</p> Signup and view all the answers

What is the primary match made by the metabolic hypothesis?

<p>Tissue supply of O2 to tissue demand for O2</p> Signup and view all the answers

What occurs in individuals with impaired baroreceptor reflex mechanism?

<p>Orthostatic hypotension</p> Signup and view all the answers

What is the origin of the central command in exercise?

<p>Motor cortex</p> Signup and view all the answers

What is the effect of increased metabolic activity on blood flow to an organ?

<p>Increased blood flow due to increased vasodilator metabolites</p> Signup and view all the answers

What is the effect of a decrease in venous return on cardiac output?

<p>It decreases</p> Signup and view all the answers

What is the effect of increased blood flow to an organ on O2 delivery?

<p>Increased O2 delivery due to increased blood flow</p> Signup and view all the answers

What is the primary cause of reactive hyperemia?

<p>Occlusion of blood flow to an organ</p> Signup and view all the answers

What is the effect of increased sympathetic outflow to the heart on heart rate?

<p>It increases</p> Signup and view all the answers

What is the relationship between the length of occlusion and the increase in blood flow?

<p>The longer the occlusion, the greater the increase in blood flow</p> Signup and view all the answers

What is the effect of increased total peripheral resistance (TPR) on blood pressure?

<p>It increases</p> Signup and view all the answers

What is the compensatory response to standing in terms of arterial blood pressure?

<p>It increases</p> Signup and view all the answers

What is the primary mechanism underlying active hyperemia?

<p>Increased production of vasodilator metabolites</p> Signup and view all the answers

What is the effect of increased central venous pressure on cardiac output?

<p>It increases</p> Signup and view all the answers

What is the effect of histamine on blood vessels?

<p>Arteriolar dilation and venous constriction</p> Signup and view all the answers

What is the mechanism of action of nitric oxide (NO) in vascular smooth muscle?

<p>Activation of guanylate cyclase and production of cyclic guanosine monophosphate (cGMP)</p> Signup and view all the answers

What is the effect of autoregulation on blood flow to an organ?

<p>Blood flow to the organ remains constant over a wide range of perfusion pressures</p> Signup and view all the answers

What is the effect of standing on blood flow to the dependent limbs?

<p>Edema in the dependent limbs</p> Signup and view all the answers

What is the effect of severe liver disease on plasma protein concentration?

<p>Decreased plasma protein concentration</p> Signup and view all the answers

What is the effect of burn injury on blood vessels?

<p>Vasodilation and increased blood flow</p> Signup and view all the answers

What is the effect of protein malnutrition on plasma protein concentration?

<p>Decreased plasma protein concentration</p> Signup and view all the answers

What is the effect of heart failure on venous pressure?

<p>Increased venous pressure</p> Signup and view all the answers

What is the primary response to standing up, in terms of cardiovascular physiology?

<p>Increased venous return and cardiac output</p> Signup and view all the answers

What is the effect of exercise on total peripheral resistance?

<p>It decreases due to vasodilation of skeletal muscle beds</p> Signup and view all the answers

What is the effect of sympathetic outflow on the heart during exercise?

<p>It increases heart rate and contractility</p> Signup and view all the answers

What is the primary mechanism by which exercise increases cardiac output?

<p>Increased stroke volume</p> Signup and view all the answers

What is the effect of parasympathetic outflow on the heart during exercise?

<p>It decreases heart rate and contractility</p> Signup and view all the answers

What is the effect of vasodilation of skeletal muscle beds on blood flow during exercise?

<p>It increases blood flow to the muscles</p> Signup and view all the answers

What is the effect of exercise on venous return?

<p>It increases venous return due to increased contraction of skeletal muscles</p> Signup and view all the answers

What is the effect of exercise on baroreceptor reflex?

<p>It increases baroreceptor reflex due to increased blood pressure</p> Signup and view all the answers

What is the primary reason for the increase in cardiac output during exercise?

<p>Increased heart rate and stroke volume</p> Signup and view all the answers

What is the effect of increased metabolic activity of skeletal muscle during exercise?

<p>Increased blood flow to the muscle due to vasodilation</p> Signup and view all the answers

What is the effect of increased venous return on cardiac output?

<p>Increased cardiac output</p> Signup and view all the answers

What is the effect of exercise on blood flow to inactive muscles and organs such as the skin, splanchnic regions, and kidneys?

<p>Decreased blood flow</p> Signup and view all the answers

What is the effect of hemorrhage on cardiac output?

<p>Decreased cardiac output</p> Signup and view all the answers

What is the effect of sympathetic nervous system activation on total peripheral resistance (TPR)?

<p>Increased TPR</p> Signup and view all the answers

What is the effect of exercise on total peripheral resistance (TPR)?

<p>Decreased TPR</p> Signup and view all the answers

What is the reason for the increase in oxygen delivery to the exercising muscle?

<p>Increased blood flow to the muscle</p> Signup and view all the answers

What is the result of arteriolar vasoconstriction on capillary absorption?

<p>It is favored</p> Signup and view all the answers

What is the role of the adrenal medulla in the response to hypoxia?

<p>It releases hormones that supplement the sympathetic nervous system</p> Signup and view all the answers

What is the effect of angiotensin II on total peripheral resistance?

<p>It increases it</p> Signup and view all the answers

What is the response of the renin-angiotensin-aldosterone system to a decrease in renal perfusion pressure?

<p>It is activated</p> Signup and view all the answers

What is the effect of ADH on blood pressure?

<p>It increases it</p> Signup and view all the answers

What is the stimulus for the release of ADH?

<p>A decrease in blood volume</p> Signup and view all the answers

What is the response of chemoreceptors in the carotid and aortic bodies to hypoxia?

<p>They are activated</p> Signup and view all the answers

What is the effect of cerebral ischemia on sympathetic outflow?

<p>It increases it</p> Signup and view all the answers

What is the role of aldosterone in the response to hypoxia?

<p>It increases NaCl reabsorption in the kidney</p> Signup and view all the answers

What is the primary mechanism by which the body responds to hypoxia?

<p>Increasing sympathetic outflow</p> Signup and view all the answers

What is the primary response of the carotid sinus baroreceptors to a decrease in arterial pressure?

<p>Increased sympathetic outflow to the heart and blood vessels</p> Signup and view all the answers

What is the effect of hemorrhage on venous return?

<p>Increased venous return due to venoconstriction</p> Signup and view all the answers

What is the primary role of the renin-angiotensin-aldosterone system in response to hemorrhage?

<p>To promote fluid absorption and increase blood volume</p> Signup and view all the answers

What is the purpose of the compensatory responses to hemorrhage?

<p>To restore normal arterial blood pressure</p> Signup and view all the answers

Which vascular beds do not constrict in response to hemorrhage?

<p>Coronary and cerebral vascular beds</p> Signup and view all the answers

What is the effect of increased sympathetic outflow on heart rate?

<p>Increased heart rate</p> Signup and view all the answers

What is the effect of hemorrhage on the release of circulating epinephrine and norepinephrine?

<p>Increased release of circulating epinephrine and norepinephrine</p> Signup and view all the answers

What is the effect of increased total peripheral resistance on blood pressure?

<p>Increased blood pressure</p> Signup and view all the answers

Study Notes

Resistance in Blood Vessels

  • Resistance is inversely proportional to the fourth power of the vessel radius
  • If blood vessel radius decreases by a factor of 2, resistance increases by a factor of 16 and blood flow decreases by a factor of 16

Parallel and Series Resistance

  • Parallel resistance is illustrated by the systemic circulation
  • Each organ is supplied by an artery that branches off the aorta
  • Total resistance is less than the resistance of any individual arteries
  • In each parallel artery, the pressure is the same

Series Resistance

  • Series resistance is illustrated by the arrangement of blood vessels within a given organ
  • Each organ is supplied by a large artery, smaller arteries, arterioles, capillaries, and veins arranged in series
  • The largest proportion of resistance is contributed by the arterioles
  • Blood velocity is higher in the aorta than in the capillaries

Blood Flow

  • Blood flow can be expressed by the equation: Q = AP/R
  • Where Q is flow or cardiac output, AP is pressure gradient, and R is resistance or total peripheral resistance
  • The equation is analogous to Ohm's law for electrical circuits
  • Pressure gradient drives blood flow, which is from high pressure to low pressure
  • Blood flow is inversely proportional to the resistance of the blood vessels

Poiseuille's Equation

  • Resistance is directly proportional to the viscosity of blood and the length of the vessel
  • Resistance is inversely proportional to the radius of the vessel to the fourth power
  • Increasing hematocrit or blood viscosity increases resistance and decreases blood flow

Laminar and Turbulent Flow

  • Laminar flow is streamlined, while turbulent flow is not
  • Reynolds number predicts whether blood flow will be laminar or turbulent
  • Factors that increase Reynolds number, such as increased blood viscosity or velocity, cause turbulence

Shear and Capacitance

  • Shear is a consequence of adjacent layers of blood traveling at different velocities
  • Shear is highest at the wall of the vessel and lowest at the center
  • Capacitance, or compliance, is the distensibility of blood vessels
  • Capacitance is inversely related to elastance, or stiffness
  • Capacitance is not constant during a cardiac cycle

Arterial Pressure

  • Systolic pressure is the highest arterial pressure during a cardiac cycle
  • Diastolic pressure is the lowest arterial pressure during a cardiac cycle
  • Pulse pressure is the difference between systolic and diastolic pressures
  • Mean arterial pressure is the average arterial pressure with respect to time
  • Mean arterial pressure is not the simple average of diastolic and systolic pressures

Venous Pressure

  • Venous pressure is very low
  • Veins have a high capacitance and can hold large volumes of blood at low pressure
  • Atrial pressure is slightly lower than venous pressure

Cardiac Electrophysiology

  • The electrocardiogram (ECG) represents the electrical activity of the heart
  • The P wave represents atrial depolarization
  • The PR interval is the interval from the beginning of the P wave to the beginning of the Q wave
  • The PR interval depends on conduction velocity through the atrioventricular (AV) node

Autonomic Effects

  • The autonomic nervous system affects heart rate and conduction velocity
  • Parasympathetic effects:
    • Decrease heart rate (negative chronotropic effect)
    • Decrease conduction velocity through the AV node (negative dromotropic effect)
  • Sympathetic effects:
    • Increase heart rate (positive chronotropic effect)
    • Increase conduction velocity through the AV node (positive dromotropic effect)

Cardiac Muscle and Cardiac Output

  • Cardiac muscle structure:
    • Sarcomere is the contractile unit of the myocardial cell
    • Intercaled disks occur at the ends of the cells
    • Gap junctions allow for rapid electrical spread of action potentials
  • Cardiac output is the product of stroke volume and heart rate
  • Stroke volume is the volume ejected from the ventricle on each beat
  • Ejection fraction is the fraction of the end-diastolic volume ejected in each stroke volume
  • Stroke work is the work the heart performs on each beat### Cardiac Cycle
  • The cardiac cycle consists of two phases: ventricular diastole and ventricular systole
  • Ventricular diastole:
    • Atrial filling begins
    • Ventricular volume is constant (isovolumetric)
    • Aortic valve is closed
    • AV valves are open
  • Ventricular systole:
    • Consists of four phases: isovolumetric ventricular contraction, rapid ventricular ejection, reduced ventricular ejection, and isovolumetric ventricular relaxation
    • The aortic valve opens, and the AV valves are closed
    • Ventricular volume decreases dramatically during rapid ventricular ejection

Venous Pulse Curve

  • The C wave on the venous pulse curve occurs due to the bulging of the tricuspid valve into the right atrium during right ventricular contraction
  • The V wave on the venous pulse curve represents blood flow into the right atrium (rising phase) and from the right atrium into the right ventricle (falling phase)

Baroreceptor Reflex

  • The baroreceptor reflex is a rapid response to changes in arterial pressure
  • It is mediated by the vasomotor center, which responds to changes in baroreceptor activity
  • The reflex helps to maintain a constant arterial pressure
  • Examples of the baroreceptor reflex:
    • Response to acute blood loss
    • Valsalva maneuver

Renin-Angiotensin-Aldosterone System

  • The renin-angiotensin-aldosterone system is a slow, hormonal mechanism that regulates blood pressure in the long term
  • It is activated in response to decreased renal perfusion pressure
  • The system increases blood pressure by:
    • Stimulating the synthesis and secretion of aldosterone
    • Increasing Na+ reabsorption
    • Constricting arterioles
    • Increasing thirst and water intake

Other Regulation of Arterial Blood Pressure

  • Cerebral ischemia:
    • Causes an increase in sympathetic outflow to the heart and blood vessels
    • Leads to intense peripheral vasoconstriction and increased TPR
    • Can cause a profound increase in arterial pressure
  • Chemoreceptors:
    • Respond to decreases in PaO2
    • Activate vasomotor centers, which produce vasoconstriction and increase TPR
  • Vasopressin (ADH):
    • Released in response to decreased blood volume or blood pressure
    • Causes vasoconstriction and increases water reabsorption
  • Atrial natriuretic peptide (ANP):
    • Released in response to increased blood volume and atrial pressure
    • Decreases blood pressure by increasing Na+ excretion

Regulation of Blood Flow

  • Autoregulation:
    • Blood flow remains constant over a wide range of perfusion pressures
    • Occurs in organs with high metabolic demand
  • Local metabolic control:
    • Blood flow is regulated by matching O2 supply to O2 demand
    • Vasodilator metabolites (CO2, K+, lactate, and adenosine) accumulate during increased metabolic activity
    • These metabolites cause arteriolar dilation and increase blood flow
  • Sympathetic innervation:
    • Plays a minor role in regulating blood flow to the brain and coronary circulation
    • Plays a major role in regulating blood flow to skeletal muscle

Special Circulations

  • Blood flow varies from one organ to another
  • Blood flow to an organ is regulated by altering arteriolar resistance
  • Examples of special circulations:
    • Pulmonary circulation
    • Renal circulation
    • Skeletal muscle circulation
    • Cerebral circulation
    • Cutaneous circulation

Exercise

  • The cardiovascular response to exercise is a combination of central command and local responses
  • Central command:
    • Initiates the cardiovascular response to exercise
    • Increases sympathetic outflow to the heart and blood vessels
    • Decreases parasympathetic outflow to the heart
  • Local responses:
    • Vasodilator metabolites accumulate in exercising muscle
    • Arteriolar dilation occurs in active skeletal muscle
    • Blood flow to active skeletal muscle is increased
  • Cardiovascular responses to exercise:
    • Increased heart rate and contractility
    • Increased cardiac output
    • Decreased TPR
    • Increased blood flow to skeletal muscle

Hemorrhage

  • The compensatory responses to acute blood loss are:

    • Decreased blood volume
    • Decreased venous return
    • Decreased cardiac output
    • Decreased arterial pressure

  • The body responds to hemorrhage by:

    • Increasing sympathetic outflow to the heart and blood vessels
    • Constricting arterioles
    • Increasing heart rate and contractility
    • Decreasing unstressed volume### Compensatory Responses to Hemorrhage

  • Chemoreceptors in the carotid and aortic bodies are sensitive to hypoxia, increasing sympathetic outflow to the heart and blood vessels.

  • Cerebral ischemia increases Pc, which activates chemoreceptors in the vasomotor center to increase sympathetic outflow.

  • Arteriolar vasoconstriction decreases P, favoring capillary absorption and helping to restore circulating blood volume.

Sympathetic Nervous System

  • The adrenal medulla releases epinephrine and norepinephrine, supplementing the sympathetic nervous system's actions on the heart and blood vessels.
  • The sympathetic nervous system increases heart rate, contractility, and TPR (total peripheral resistance).

Renin-Angiotensin-Aldosterone System

  • The decrease in renal perfusion pressure activates the renin-angiotensin-aldosterone system.
  • Angiotensin II is a potent vasoconstrictor, reinforcing the sympathetic nervous system's stimulatory effect on TPR.
  • Aldosterone increases NaCl reabsorption in the kidney, increasing circulating blood volume.

Antidiuretic Hormone (ADH)

  • ADH is released when atrial receptors detect the decrease in blood volume.
  • ADH causes both vasoconstriction and increased water reabsorption, increasing blood pressure.

Baroreceptor Reflex

  • The carotid sinus baroreceptors detect the decrease in arterial pressure.
  • The baroreceptor reflex increases sympathetic outflow to the heart and blood vessels, and decreases parasympathetic outflow to the heart.
  • This leads to increased heart rate, contractility, TPR, and venoconstriction, which increases venous return.

Cardiovascular Responses

  • Hemorrhage leads to constriction of arterioles in skeletal, splanchnic, and cutaneous vascular beds, but not in coronary or cerebral vascular beds.
  • These responses aim to restore normal arterial blood pressure.

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