Physiology: Cardiovascular
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Questions and Answers

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

  • It decreases by a factor of 2
  • It increases by a factor of 2
  • It increases by a factor of 16 (correct)
  • It increases by a factor of 4

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

  • It increases
  • It becomes zero
  • It decreases (correct)
  • It remains the same

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

  • Rtot = Ra × Rb × Rn
  • Rtot = 1 / (1/Ra + 1/Rb + 1/Rn) (correct)
  • Rtot = Ra - Rb - Rn
  • Rtot = Ra + Rb + 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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    Description

    This quiz covers the principles of blood flow and circulation, including velocity, cross-sectional area, and the equation for cardiac output. It also explores the concept of total peripheral resistance.

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