Systems Phys Homework (for Final)

If the Purkinje fibers, situated distal to the A-V junction, become the pacemaker of the heart, what is the expected heart rate? A) 30/min B) 50/min C) 60/min D) 70/min E) 80/min

A) If the Purkinje fibers are the pacemaker of the heart, the heart rate ranges between 15 and 40 beats/ min. In contrast, the rate of firing of the A-V nodal fibers are 40 to 60 times a minute, and the sinus node fires at 70 to 80 times per minute. If the sinus node is blocked for some reason, the A-V node will take over as the pacemaker, and if the A-V node is blocked, the Purkinje fibers will take over as the pacemaker of the heart.

If the S-A node discharges at 0.00 seconds, when will the action potential normally arrive at the A-V node? A) 0.03 second B) 0.09 second C) 0.12 second D) 0.16 second E) 0.80 second

A) It takes 0.03 second for the action potential to travel from the S-A node to the A-V node.

A decrease in which of the following tends to increase lymph flow? A) Capillary hydrostatic pressure B) Interstitial hydrostatic pressure C) Plasma colloid osmotic pressure D) Lymphatic pump activity E) Arteriolar diameter

C) The rate of lymph flow increases in proportion to the interstitial hydrostatic pressure and the lymphatic pump activity. A decrease in plasma colloid osmotic pressure would increase filtration rate, interstitial volume, interstitial hydrostatic pressure, and lymph flow. A decrease in arteriolar diameter would decrease capillary hydrostatic pressure, capillary filtration, and lymph flow.

What is the normal QT interval? A) 0.03 second B) 0.13 second C) 0.16 second D) 0.20 second E) 0.35 second

E) The contraction of the ventricles lasts almost from the beginning of the Q wave and continues to the end of the T wave. This interval is called the Q-T interval and ordinarily lasts about 0.35 second.

A 60-year-old woman has experienced dizziness for the past 6 months when getting out of bed in the morning and when standing up. Her mean arterial pressure is 130/90 mm Hg while lying down and 95/60 while sitting. Which set of physiological changes would be expected in response to moving from a supine to an upright position? Parasympathetic Nerve Activity, Plasma Renin Activity, Sympathetic Activity A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

G) Moving from a supine to a standing position causes an acute fall in arterial pressure that is sensed by arterial baroreceptors located in the carotid sinuses and aortic arch. Activation of the baroreceptors results in a decrease in parasympathetic activity (or vagal tone) and an increase in sympathetic activity, which leads to an increase in plasma renin activity (or renin release).

A 60-year-old woman has experienced dizziness for the past 6 months when getting out of bed in the morning and when standing up. Her mean arterial pressure is 130/90 mm Hg while lying down and 95/60 while sitting. Which set of physiological changes would be expected in response to moving from a supine to an upright position? Parasympathetic Nerve Activity, Plasma Renin Activity, Sympathetic Activity A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

G) Moving from a supine to a standing position causes an acute fall in arterial pressure that is sensed by arterial baroreceptors located in the carotid sinuses and aortic arch. Activation of the baroreceptors results in a decrease in parasympathetic activity (or vagal tone) and an increase in sympathetic activity, which leads to an increase in plasma renin activity (or renin release).

A 25-year-old man enters the hospital emergency department after severing a major artery during a farm accident. It is estimated that the patient has lost approximately 800 milliliters of blood. His mean blood pressure is 65 mm Hg, and his heart rate is elevated as a result of activation of the chemoreceptor reflex. Which set of changes in plasma concentration would be expected to cause the greatest activation of the chemoreceptor reflex? Oxygen, Carbon Dioxide, Hydrogen A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

G) When blood pressure falls below 80 mm Hg, carotid and aortic chemoreceptors are activated to elicit a neural reflex to minimize the fall in blood pressure. The chemoreceptors are chemosensitive cells that are sensitive to oxygen lack, carbon dioxide excess, or hydrogen ion excess (or fall in pH). The signals transmitted from the chemoreceptors into the vasomotor center excite the vasomotor center to increase arterial pressure.

. When does the first heart sound occur in the ventricular pressure-volume relationship? A) At point B B) Between point A and point B C) Between point B and point C D) Between point C and point D E) Between point D and point A

A) During the diastolic filling phase, the mitral and tricuspid valves open and blood flows into the ventricles. At point B the isovolumic contraction phase begins, which closes the A-V valves. The closing of these valves causes the first heart sound.

. What happens at the end of ventricular isovolumic relaxation? A) The A-V valves close B) The aortic valve opens C) The aortic valve closes D) The mitral valve opens E) The pulmonary valve closes

D) At the end of isovolumic relaxation, the mitral and tricuspid valves open, which is followed by the period of diastolic filling.

If a person has been exercising for 1 hour, which organ will have the smallest decrease in blood flow? A) Brain B) Intestines C) Kidneys D) Nonexercising skeletal muscle E) Pancreas

A) During increases in sympathetic output, the main two organs that maintain their blood flow are the brain and the heart. During exercise for 1 hour, the intestinal flow decreases significantly, as does the renal and pancreatic blood flows. The skeletal muscle blood flow to non-exercising muscles also decreases at this time. Therefore, the cerebral blood flow remains close to its control value.

If the S-A node discharges at 0.00 seconds, when will the action potential normally arrive at the epicardial surface at the base of the left ventricle? A) 0.22 second B) 0.18 second C) 0.16 second D) 0.12 second E) 0.09 second

. A) After the S-A node discharges, the action potential travels through the atria, through the A-V bundle system, and finally to the ventricular septum and throughout the ventricle. The last place that the impulse arrives is at the epicardial surface at the base of the left ventricle, which requires a transit time of 0.22 second.

Which vasoactive agent is usually the most important controller of coronary blood flow? A) Adenosine B) Bradykinin C) Prostaglandins D) Carbon dioxide E) Potassium ions

. A) Although bradykinin, prostaglandins, carbon dioxide, and potassium ions serve as vasodilators for the coronary artery system, the major controller of coronary blood flow is adenosine. Adenosine is formed as adenosine triphosphate degrades to adenosine monophosphate. Small portions of the adenosine monophosphate are then further degraded to release adenosine into the tissue fluids of the heart muscle, and this adenosine vasodilates the coronary arteries.

Which statement best explains how sympathetic stimulation affects the heart? A) The permeability of the S-A node to sodium decreases B) The permeability of the A-V node to sodium decreases C) The permeability of the S-A node to potassium increases D) There is an increased rate of upward drift of the resting membrane potential of the S-A node E) The permeability of the cardiac muscle to calcium decreases

. D) During sympathetic stimulation, the permeabilities of the S-A node and the A-V node increase. In addition, the permeability of cardiac muscle to calcium increases, resulting in an increased contractile strength. Furthermore, an upward drift of the resting membrane potential of the S-A node occurs. Increased permeability of the S-A node to potassium does not occur during sympathetic stimulation.

The GFR of a 26-year-old man with glomerulonephritis decreases by 50% and remains at that level. For which substance would you expect to find the greatest increase in plasma concentration? A) Creatinine B) K+ C) Glucose D) Na+ E) Phosphate F) H+

A) A 50% reduction of GFR would approximately double the plasma creatinine concentration because creatinine is not reabsorbed or secreted and its excretion depends largely on glomerular filtration. Therefore, when GFR decreases, the plasma concentration of creatinine increases until the renal excretion of creatinine returns to normal. Plasma concentrations of glucose, potassium, sodium, and hydrogen ions are closely regulated by multiple mechanisms that keep them relatively constant even when GFR falls to very low levels. Plasma phosphate concentration is also maintained near normal until GFR falls to below 20% to 30% of normal.

The diameter of a precapillary arteriole is decreased in a muscle vascular bed. Which change in the microcirculation would be expected? A) Decreased capillary filtration rate B) Increased interstitial volume C) Increased lymph flow D) Increased capillary hydrostatic pressure E) Decreased arteriolar resistance

A) A decrease in the diameter of a precapillary arteriole increases arteriolar resistance while decreasing vascular conductance and capillary blood flow, hydrostatic pressure, filtration rate, interstitial volume, and interstitial hydrostatic pressure.

A healthy 28-year-old woman stands up from a supine position. Moving from a supine to a standing position results in a transient decrease in arterial pressure that is detected by arterial baroreceptors located in the aortic arch and carotid sinuses. Which set of cardiovascular changes is most likely to occur in response to activation of the baroreceptors? Mean Circulatory Filling Pressure, Strength of Cardiac Contraction, Sympathetic Nerve Activity A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

A) Activation of the baroreceptors leads to an increase in sympathetic activity, which in turn increases heart rate, strength of cardiac contraction, and constriction of arterioles and veins. The increase in venous constriction results in an increase in mean circulatory filling pressure, venous return, and cardiac output.

An increase in which of the following tends to increase capillary filtration rate? A) Capillary wall hydraulic conductivity B) Arteriolar resistance C) Plasma colloid osmotic pressure D) Interstitial hydrostatic pressure E) Plasma sodium concentration

A) An increase in capillary wall permeability to water would increase capillary filtration rate, whereas increases in arteriolar resistance, plasma colloid osmotic pressure, and interstitial hydrostatic pressure would all decrease filtration rate. Plasma sodium concentration would have no effect on filtration.

At the onset of exercise, the mass sympathetic nervous system strongly discharges. What would you expect to occur? A) Increased sympathetic impulses to the heart B) Decreased coronary blood flow C) Decreased cerebral blood flow D) Reverse stress relaxation E) Venous dilation

A) At the beginning of exercise, increases in sympathetic stimulation of the heart strengthens the heart and increases the heart rate. Coronary and cerebral blood flow are spared from any decrease. Reverse stress relaxation does not occur. Venous constriction occurs, not dilation.

When recording lead I on an ECG, the right arm is the negative electrode and the positive electrode is the A) Left arm B) Left leg C) Right leg D) Left arm + left leg E) Right arm + left leg

A) By convention, the left arm is the negative electrode for lead I of an ECG.

When recording lead II on an ECG, the negative electrode is the A) Right arm B) Left leg C) Right leg D) Left arm + left leg E) Right arm + left leg

A) By convention, the right arm is the negative electrode for lead II of an ECG.

While participating in a cardiovascular physiology laboratory, a medical student isolates an animal's carotid artery proximal to the carotid bifurcation and partially constricts the artery with a tie around the vessel. Which set of changes would be expected to occur in response to constriction of the carotid artery? Heart Rate, Sympathetic Nerve Activity, Total Peripheral Resistance A) ↑ ↑ ↑ B) ↑ ↑ ↓ C) ↑ ↓ ↓ D) ↑ ↓ ↑ E) ↓ ↓ ↓ F) ↓ ↓ ↑ G) ↓ ↑ ↑ H) ↓ ↑ ↓

A) Constriction of the carotid artery decreases blood pressure at the level of the carotid sinus. A decrease in carotid sinus pressure leads to a decrease in carotid sinus nerve impulses to the vasomotor center, which in turn leads to enhanced sympathetic nervous activity and decreased parasympathetic nerve activity. The increase in sympathetic nerve activity results in peripheral vasoconstriction and an increase in total peripheral resistance and heart rate.

Increases in both renal blood flow and GFR are caused by which mechanism? A) Dilation of the afferent arterioles B) Increased glomerular capillary filtration coefficient C) Increased plasma colloid osmotic pressure D) Dilation of the efferent arterioles

A) Dilation of the afferent arterioles leads to an increase in the glomerular hydrostatic pressure and therefore an increase in GFR, as well as an increase in renal blood flow. Increased glomerular capillary filtration coefficient would also raise the GFR but would not be expected to alter renal blood flow. Increased plasma colloid osmotic pressure or dilation of the efferent arterioles would both tend to reduce the GFR. Increased blood viscosity would tend to reduce renal blood flow and GFR.

A 30-year-old man is resting, and his sympathetic output increases to maximal values. Which set of changes would be expected in response to this increased sympathetic output? Resistance to Venous Return // Mean Systemic Filling Pressure // Venous Return A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

A) During increases in sympathetic output to maximal values, several changes occur. First, the mean systemic filling pressure increases markedly, but at the same time the resistance to venous return increases. Venous return is determined by the following formula: mean systemic filling pressure − right atrial pressure/ resistance to venous return. During maximal sympathetic output, the increase in systemic filling pressure is greater than the increase in resistance to venous return. Therefore, in this formula the numerator has a much greater increase than the denominator, which results in an increase in the venous return.

A nitric oxide donor is infused into the brachial artery of a 22-year-old man. Which set of microcirculatory changes would be expected in the infused arm? Capillary Hydrostatic Pressure, Interstitial Hydrostatic Pressure, Lymph Flow A) ↑ ↑ ↑ B) ↑ ↑ ↓ C) ↑ ↓ ↓ D) ↑ ↓ ↑ E) ↓ ↓ ↓ F) ↓ ↓ ↑ G) ↓ ↑ ↑ H) ↓ ↑ ↓

A) Nitric oxide is a vasodilator that is believed to play a role in regulating blood flow. Infusion of a nitric oxide donor into the brachial artery would increase arteriolar diameter and decrease arteriolar resistance. The decrease in arteriolar resistance would also result in an increase in capillary hydrostatic pressure and filtration rate. The increase in filtration rate leads to an increase in interstitial hydrostatic pressure and lymph flow.

A 55-year-old man with a history of normal health visits his physician for a checkup. The physical examination reveals that his blood pressure is 170/98 mm Hg. Further tests indicate that he has renovascular hypertension as a result of stenosis in the left kidney. Which set of findings would be expected in this man with renovascular hypertension? Total Peripheral Resistance, Plasma Renin Activity, Plasma Aldosterone Concentration A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

A) Stenosis of one kidney results in the release of renin and the formation of angiotensin II from the affected kidney. Angiotensin II stimulates aldosterone production and increases total peripheral resistance by constricting most of the blood vessels in the body.

A 22-year-old man enters the hospital emergency department after severing a major artery in a motorcycle accident. It is estimated that he has lost approximately 700 milliliters of blood. His blood pressure is 90/55 mm Hg. Which set of changes would be expected in response to hemorrhage in this man? Heart Rate, Sympathetic Nerve Activity, Total Peripheral Resistance A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

A) The arterial baroreceptors are activated in response to a fall in arterial pressure. During hemorrhage, the fall in arterial pressure at the level of the baroreceptors results in enhanced sympathetic outflow from the vasomotor center and a decrease in parasympathetic nerve activity. The increase in sympathetic nerve activity leads to constriction of peripheral blood vessels, increased total peripheral resistance, and a return of blood pressure toward normal. The decrease in parasympathetic nerve activity and sympathetic outflow would result in an increase in heart rate.

(pic of ECG on pg 30 of G&H) 34. What is her heart rate in beats per minute? A) 70 B) 78 C) 84 D) 94 E) 104

A) The heart rate can be calculated by 60 divided by the R-R interval, which is 0.86 second. This results in a heart rate of 70 beats/min.

What is the membrane potential (threshold level) at which the S-A node discharges? A) −40 millivolt B) −55 millivolt C) −65 millivolt D) −85 millivolt E) −105 millivolt

A) The normal resting membrane potential of the S-A node is −55 millivolts. As the sodium leaks into the membrane, an upward drift of the membrane potential occurs until it reaches −40 millivolts. This is the threshold level that initiates the action potential at the S-A node.

Which of the following segments of the circulatory system has the highest velocity of blood flow? A) Aorta B) Arteries C) Capillaries D) Venules E) Veins

A) The velocity of blood flow within each segment of the circulatory system is inversely proportional to the total cross-sectional area of the segment. Because the aorta has the smallest total cross-sectional area of all circulatory segments, it has the highest velocity of blood flow.

An increase in which of the following tends to decrease capillary filtration rate? A) Capillary hydrostatic pressure B) Plasma colloid osmotic pressure C) Interstitial colloid osmotic pressure D) Venous hydrostatic pressure E) Arteriolar diameter

B) An increase in plasma colloid osmotic pressure would reduce net filtration pressure and capillary filtration rate. Increases in capillary hydrostatic pressure and interstitial colloid osmotic pressure would also favor capillary filtration. An increase in venous hydrostatic pressure and arteriolar diameter would tend to increase capillary hydrostatic pressure and capillary filtration rate.

Which of the following would have the slowest rate of net movement across the capillary wall? A) Sodium B) Albumin C) Glucose D) Oxygen

B) Because oxygen is lipid soluble and can cross the capillary wall with ease, it has the fastest rate of movement across the capillary wall. The ability of lipid-insoluble substances such as sodium, albumin, and glucose to move across a capillary wall depends on the permeability of the capillary to lipid-insoluble substances. Because the capillary wall is relatively impermeable to albumin, it has the slowest rate of net movement across the capillary wall.

When recording lead II on an ECG, the right arm is the negative electrode and the positive electrode is the A) Left arm B) Left leg C) Right leg D) Left arm + left leg E) Right arm + left leg

B) By convention, the left leg is the positive electrode for lead II of an ECG.

Cognitive stimuli such as reading, problem solving, and talking all result in significant increases in cerebral blood flow. Which set of changes in cerebral tissue concentrations is the most likely explanation for the increase in cerebral blood flow? Carbon Dioxide, pH, Adenosine A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

B) Cognitive stimuli increase cerebral blood flow by decreasing cerebral vascular resistance. The diameter of cerebral vessels is decreased by various metabolic factors in response to cognitive stimuli. Metabolic factors that enhance cerebral blood flow include increases in carbon dioxide, hydrogen ion (decreased pH), and adenosine.

While participating in a cardiovascular physiology laboratory, a medical student isolates the carotid artery of an animal and partially constricts the artery with a tie around the vessel. Which set of changes would be expected to occur in response to constriction of the carotid artery? Sympathetic Nerve Activity, Renal Blood Flow, Total Peripheral Resistance A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

B) Constriction of the carotid artery reduces blood pressure at the carotid bifurcation where the arterial baroreceptors are located. The decrease in arterial pressure activates baroreceptors, which in turn leads to an increase in sympathetic activity and a decrease in parasympathetic activity (or vagal tone). The enhanced sympathetic activity results in constriction of peripheral blood vessels, including the kidneys. The enhanced sympathetic activity leads to an increase in total peripheral resistance and a decrease in renal blood flow. The combination of enhanced sympathetic activity and decreased vagal tone also leads to an increase in heart rate.

At the onset of exercise, what normally occurs?

B) During exercise there is very little change in cerebral blood flow, and coronary blood flow increases. Because of the increased sympathetic output, mean systemic filling pressure increases and the veins constrict. During exercise there is also a decrease in parasympathetic impulses to the heart.

Using the following data, calculate the filtration coefficient for the capillary bed. Plasma colloid osmotic pressure = 30 mm Hg Capillary hydrostatic pressure = 40 mm Hg Interstitial hydrostatic pressure = 5 mm Hg Interstitial colloid osmotic pressure = 5 mm Hg Filtration rate = 150 ml/min Venous hydrostatic pressure = 10 mm Hg A) 10 ml/min/mm Hg B) 15 ml/min/mm Hg C) 20 ml/min/mm Hg D) 25 ml/min/mm Hg E) 30 ml/min/mm Hg

B) Filtration coefficient (Kf) = filtration rate ÷ net filtration pressure. Net filtration pressure = capillary hydrostatic pressure − plasma colloid osmotic pressure + interstitial colloid osmotic pressure − interstitial hydrostatic pressure. The net filtration pressure in this example is 10 mm Hg. Thus, Kf = 150 ml/min ÷ 10 mm Hg, or 15 ml/min/mm Hg.

Listed below are the hydrostatic and oncotic pressures within a microcirculatory bed. Plasma colloid osmotic pressure = 25 mm Hg Capillary hydrostatic pressure = 25 mm Hg Venous hydrostatic pressure = 5 mm Hg Arterial pressure = 80 mm Hg Interstitial hydrostatic pressure = −5 mm Hg Interstitial colloid osmotic pressure = 5 mm Hg Filtration coefficient = 15 ml/min/mm Hg What is the filtration rate (ml/min) of the capillary wall? A) 100 B) 150 C) 200 D) 250 E) 300

B) Filtration rate is the product of the filtration coefficient (Kf ) and the net pressure across the capillary wall. The net pressure for fluid movement across a capillary wall = capillary hydrostatic pressure − plasma colloid osmotic pressure − interstitial colloid osmotic pressure − interstitial hydrostatic pressure. The net pressure in this question calculates to be 10 mm Hg, and the Kf is 15. Thus, the filtration rate is 15 × 10, or 150 ml/min.

Which condition will result in a dilated, flaccid heart? A) Excess calcium ions in the blood B) Excess potassium ions in the blood C) Excess sodium ions in the blood D) Increased sympathetic stimulation E) Increased norepinephrine concentration in the blood

B) Having excess potassium ions in the blood and ex- tracellular fluid causes the heart to become dilated and flaccid and also slows the heart. This effect is important because of a decrease in the resting membrane poten- tial in the cardiac muscle fibers. As the membrane po- tential decreases, the intensity of the action potential decreases, which makes the contraction of the heart progressively weaker. Excess calcium ions in the blood and sympathetic stimulation and increased norepi- nephrine concentration of the blood all cause the heart to contract vigorously.

Which set of physiological changes would be expected to occur in a person who stands up from a supine position? Venous Hydrostatic Pressure in Legs, Heart Rate, Renal Blood Flow A) ↑ ↑ ↑ B) ↑ ↑ ↓ C) ↑ ↓ ↓ D) ↓ ↓ ↓ E) ↓ ↓ ↑ F) ↓ ↑ ↑

B) Moving from a supine to a standing position results in pooling of blood in the lower extremities and a fall in blood pressure. The pooling of blood in the legs increases venous hydrostatic pressure. The fall in arterial pressure activates the arterial baroreceptors, which in turn increases sympathetic nerve activity and decreases parasympathetic nerve activity. The increase in sympathetic activity constricts renal vessels and reduces renal blood flow. The heart rate also increases.

Which statement about cardiac muscle is most accurate? A) The T-tubules of cardiac muscle can store much less calcium than the T-tubules in skeletal muscle B) The strength and contraction of cardiac muscle depends on the amount of calcium surrounding cardiac myocytes C) In cardiac muscle, the initiation of the action potential causes an immediate opening of slow calcium channels D) Cardiac muscle repolarization is caused by opening of sodium channels E) Mucopolysaccharides inside the T-tubules bind chloride ions

B) The cardiac muscle stores much more calcium in its tubular system than does skeletal muscle and is much more dependent on extracellular calcium than is the skeletal muscle. An abundance of calcium is bound by the mucopolysaccharides inside the T-tubule. This calcium is necessary for contraction of cardiac muscle, and its strength of contraction depends on the calcium concentration surrounding the cardiac myocytes. At the initiation of the action potential, the fast sodium channels open first, which is followed later by opening of the slow calcium channels.

Which of the following tends to increase the net movement of glucose across a capillary wall? A) Increase in plasma sodium concentration B) Increase in the concentration difference of glucose across the wall C) Decrease in wall permeability to glucose D) Decrease in wall surface area without an increase in the number of pores E) Decrease in plasma potassium concentration

B) The factors that determine the net movement of glucose across a capillary wall include the wall permeability to glucose, the glucose concentration gradient across the wall, and the capillary wall surface area. Thus, an increase in the concentration difference of glucose across the wall would enhance the net movement of glucose.

Which of the following is associated with the first heart sound? A) Inrushing of blood into the ventricles as a result of atrial contraction B) Closing of the A-V valves C) Closing of the pulmonary valve D) Opening of the A-V valves E) Inrushing of blood into the ventricles in the early to middle part of diastole

B) The first heart sound by definition is always associated with the closing of the A-V valves. The heart sounds are usually not associated with opening of any of the valves but with the closing of the valves and the associated vibration of the blood and the walls of the heart. One exception is an opening snap in some mitral valves.

(pic at bottom of pg 30 in G&H) 42) What is the heart rate using lead I for the calculation? A) 70 B) 88 C) 100 D) 112 E) 148

B) The heart rate can be calculated by 60 divided by the R-R interval, which is 0.68 second. This calculation results in a heart rate of 88 beats/min.

What is the delay between the S-A node discharge and arrival of the action potential at the ventricular septum? A) 0.80 second B) 0.16 second C) 0.12 second D) 0.09 second E) 0.03 second

B) The impulse coming from the S-A node to the A-V node arrives at 0.03 second. Then there is a total delay of 0.13 second in the A-V node and bundle system, allowing the impulse to arrive at the ventricular septum at 0.16 second.

A healthy 27-year-old female medical student runs a 5K race. Which set of physiological changes is most likely to occur in this woman's skeletal muscles during the race? Arteriole Diameter, Vascular Conductance, Tissue Oxygen Concentration A) ↑ ↑ ↑ B) ↑ ↑ ↓ C) ↑ ↓ ↓ D) ↑ ↓ ↑ E) ↓ ↓ ↓ F) ↓ ↓ ↑ G) ↓ ↑ ↑ H) ↓ ↑ ↓

B) The increase in local metabolism during exercise increases oxygen utilization and decreases tissue oxygen concentration. The decrease in tissue oxygen concentration increases arteriolar diameter and increases vascular conductance and blood flow to skeletal muscles.

A 50-year-old woman has a renal blood flow of 1200 ml/min and hematocrit of 50. Her arterial pressure is 125 mm Hg, and her renal venous pressure is 5 mm Hg. She also has a plasma colloid osmotic pressure of 25 mm Hg and a glomerular capillary hydrostatic pressure of 50 mm Hg. What is the total renal vascular resistance (in mm Hg/ml/min) in this woman? A) 0.05 B) 0.10 C) 0.50 D) 1.00 E) 1.50

B) Vascular resistance is equal to arterial pressure minus venous pressure divided by blood flow. In this example, arterial pressure is 125 mm Hg, venous pressure is 5 mm Hg, and blood flow is 1200 ml/min. Thus, vascular resistance is equal to 120/1200, or 0.10 mm Hg/ml/min.

What would tend to decrease GFR by more than 10% in a normal kidney? A) Decrease in renal arterial pressure from 100 to 85 mm Hg B) 50% decrease in afferent arteriolar resistance C) 50% decrease in efferent arteriolar resistance D) 50% increase in the glomerular capillary filtration coefficient E) Decrease in plasma colloid osmotic pressure from 28 to 20 mm Hg

C) A 50% reduction in efferent arteriolar resistance would cause a large decrease in GFR—greater than 10%. A decrease in renal artery pressure from 100 to 85 mm Hg would cause only a slight decrease in GFR in a normal, autoregulating kidney. A decrease in afferent arteriole resistance, a decrease in plasma colloid osmotic pressure, or an increase in the glomerular capillary filtration coefficient would all tend to increase GFR.

Autoregulation of tissue blood flow in response to an increase in arterial pressure occurs as a result of which of the following? A) Decrease in vascular resistance B) Initial decrease in vascular wall tension C) Excess delivery of nutrients such as oxygen to the tissues D) Decrease in tissue metabolism

C) An increase in perfusion pressure to a tissue results in excessive delivery of nutrients such as oxygen to a tissue. The increase in tissue oxygen concentration constricts arterioles and returns blood flow and nutrient delivery toward normal levels.

Which event normally occurs during exercise? A) Arteriolar dilation in non-exercising muscle B) Decreased sympathetic output C) Venoconstriction D) Decreased release of epinephrine by the adrenals E) Decreased release of norepinephrine by the adrenals

C) During exercise the sympathetic output increases markedly, which causes arteriolar constriction in many places of the body, including non-exercising muscle. The increased sympathetic output also causes venoconstriction throughout the body. During exercise there also is an increased release of norepinephrine and epinephrine by the adrenal glands.

A 50-year-old man has a 3-year history of hypertension. He reports fatigue and occasional muscle cramps. There is no family history of hypertension. The patient has not had any other significant medical problems in the past. Examination reveals a blood pressure of 168/104 mm Hg. Additional laboratory tests indicate that the patient has primary hyperaldosteronism. Which set of findings would be expected in this man with primary hyperaldosteronism hypertension? Extracellular Fluid Volume, Plasma Renin Activity, Plasma Potassium Concentration A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

C) Excess secretion of aldosterone results in enhanced tubular reabsorption of sodium and secretion of potassium. The increased reabsorption of sodium and water leads to an increase in extracellular fluid volume, which in turn suppresses renin release by the kidney. The increase in potassium secretion leads to a decrease in plasma potassium concentration, or hypokalemia.

What would decrease venous hydrostatic pressure in the legs? A) Increase in right atrial pressure B) Pregnancy C) Movement of leg muscles D) Presence of ascitic fluid in the abdomen

C) Movement of the leg muscles causes blood to flow toward the vena cava, which reduces venous hydrostatic pressure. An increase in right atrial pressure would decrease venous return and increase venous hydrostatic pressure. Pregnancy and the presence of ascitic fluid in the abdomen would tend to compress the vena cava and increase venous hydrostatic pressure in the legs.

Which of the following structures will have the slowest rate of conduction of the cardiac action potential?

C) The atrial and ventricular muscles have a relatively rapid rate of conduction of the cardiac action potential, and the anterior internodal pathway also has fairly rapid conduction of the impulse. However, the A-V bundle myofibrils have a slow rate of conduction because their sizes are considerably smaller than the sizes of the normal atrial and ventricular muscle. In addition, their slow conduction is partly caused by diminished numbers of gap junctions between successive muscle cells in the conducting pathway, causing a great resistance to conduction of the excitatory ions from one cell to the next.

Which of the following vessels has the greatest total cross-sectional area in the circulatory system? A) Aorta B) Small arteries C) Capillaries D) Venules E) Vena cava

C) The capillaries have the largest total cross-sectional area of all vessels of the circulatory system. The venules also have a relatively large total cross-sectional area, but not as great as the capillaries, which explains the large storage of blood in the venous system compared with that in the arterial system.

A decrease in which of the following tends to increase pulse pressure? A) Systolic pressure B) Stroke volume C) Arterial compliance D) Venous return E) Plasma volume

C) The difference between systolic pressure and diastolic pressure is called the pulse pressure. The two main factors that affect pulse pressure are stroke volume and arterial compliance. Pulse pressure is directly proportional to the stroke volume and inversely proportional to the arterial compliance. Thus, a decrease in arterial compliance would tend to increase pulse pressure.

Which component of the circulatory system contains the largest percentage of the total blood volume? A) Arteries B) Capillaries C) Veins D) Pulmonary circulation E) Heart

C) The percentage of total blood volume in the veins is approximately 64%.

A decrease in which of the following tends to increase lymph flow? A) Capillary hydrostatic pressure B) Interstitial hydrostatic pressure C) Plasma colloid osmotic pressure D) Lymphatic pump activity E) Arteriolar diameter

C) The rate of lymph flow increases in proportion to the interstitial hydrostatic pressure and the lymphatic pump activity. A decrease in plasma colloid osmotic pressure would increase filtration rate, interstitial volume, interstitial hydrostatic pressure, and lymph flow. A decrease in arteriolar diameter would decrease capillary hydrostatic pressure, capillary filtration, and lymph flow

Which of the following capillaries has the lowest capillary permeability to plasma molecules? A) Glomerular B) Liver C) Muscle D) Intestinal E) Brain

E) The brain has tight junctions between capillary endothelial cells that allow only extremely small molecules such as water, oxygen, and carbon dioxide to pass in or out of the brain tissues.

A twofold increase in which of the following would result in the greatest increase in the transport of oxygen across the capillary wall? A) Capillary hydrostatic pressure B) Intercellular clefts in the capillary wall C) Oxygen concentration gradient D) Plasma colloid osmotic pressure E) Capillary wall hydraulic permeability

C) The transport of oxygen across a capillary wall is proportional to the capillary surface area, capillary wall permeability to oxygen, and oxygen gradient across the capillary wall. Thus, a twofold increase in the oxygen concentration gradient would result in the greatest increase in the transport of oxygen across the capillary wall. A twofold increase in intercellular clefts in the capillary wall would not have a significant impact on oxygen transport because oxygen can permeate the endothelial cell wall.

Which part of the circulation has the highest compliance? A) Capillaries B) Large arteries C) Veins D) Aorta E) Small arteries

C) The vascular compliance is proportional to the vascular distensibility and the vascular volume of any given segment of the circulation. The compliance of a systemic vein is 24 times that of its corresponding artery because it is about 8 times as distensible and has a volume about 3 times as great.

A 72-year-old man had surgery to remove an abdominal tumor. Pathohistological studies revealed that the tumor mass contained a large number of vessels. The most likely stimulus for the growth of vessels in a solid tumor is an increase in which of the following? A) Growth hormone B) Plasma glucose concentration C) Angiostatin growth factor D) Vascular endothelial growth factor E) Tissue oxygen concentration

D) A decrease in tissue oxygen tension is thought to be an important stimulus for vascular endothelial growth factor and the growth of blood vessels in solid tumors.

Under normal physiological conditions, blood flow to the skeletal muscles is determined mainly by which of the following? A) Sympathetic nerves B) Angiotensin II C) Vasopressin D) Metabolic needs E) Capillary osmotic pressure

D) Although sympathetic nerves, angiotensin II, and vasopressin are powerful vasoconstrictors, blood flow to skeletal muscles under normal physiological conditions is mainly determined by local metabolic needs.

A 65-year-old man with a 10-year history of essential hypertension is being treated with an angiotensinconverting enzyme (ACE) inhibitor. Which set of changes would be expected to occur in response to the ACE inhibitor drug therapy? Plasma Renin Concentration, Total Peripheral Resistance, Renal Sodium Excretory Function A) ↑ ↑ ↑ B) ↑ ↑ ↓ C) ↑ ↓ ↓ D) ↑ ↓ ↑ E) ↓ ↓ ↓ F) ↓ ↓ ↑ G) ↓ ↑ ↑ H) ↓ ↑ ↓

D) Angiotensin I is formed by an enzyme (renin) acting on a substrate called angiotensinogen. Angiotensin I is converted to angiotensin II by a converting enzyme. Angiotensin II also has a negative feedback effect on juxtaglomerular cells to inhibit renin secretion. Angiotensin II is a powerful vasoconstrictor and sodiumretaining hormone that increases arterial pressure. Administration of an ACE inhibitor would increase plasma renin concentration, decrease angiotensin II formation, enhance renal sodium excretory function, and decrease total peripheral resistance and arterial pressure.

Under control conditions, flow through a blood vessel is 100 ml/min with a pressure gradient of 50 mm Hg. What would be the approximate flow through the vessel after increasing the vessel diameter by 50%, assuming that the pressure gradient is maintained at 100 mm Hg? A) 100 ml/min B) 150 ml/min C) 300 ml/min D) 500 ml/min E) 700 ml/min

D) Blood flow in a vessel is directly proportional to the fourth power of the vessel radius. Increasing vessel diameter by 50% (1.5 × control) would increase blood flow 1.5 to the fourth power × normal blood flow (100 ml/min). Thus, blood flow would increase to 100 ml/min × 5.06, or approximately 500 ml/min.

In which phase of the ventricular muscle action potential is the potassium permeability the highest? A)0 B) 1 C)2 D)3 E) 4

D) During phase 3 of the ventricular muscle action potential, the potassium permeability of ventricular muscle greatly increases, which causes a more negative membrane potential.

Which mechanism would tend to decrease capillary filtration rate? A) Increased capillary hydrostatic pressure B) Decreased plasma colloid osmotic pressure C) Increased interstitial colloid osmotic pressure D) Decreased capillary water permeability E) Decreased arteriolar resistance

D) Filtration rate is the product of the filtration coefficient (Kf ) and the net pressure across the capillary wall. The net pressure for fluid movement across a capillary wall is promoted by increases in capillary hydrostatic pressure and positive interstitial colloid osmotic pressure, whereas negative plasma colloid osmotic pressure and a positive interstitial hydrostatic pressure oppose filtration. Thus, increased capillary hydrostatic pressure, decreased plasma colloid osmotic pressure, and increased interstitial colloid osmotic pressure would all promote filtration. Decreased arteriolar resistance would also promote filtration by increasing capillary hydrostatic pressure. The filtration coefficient is the product of capillary surface area and the capillary water permeability. A decrease in capillary water permeability would decrease the filtration coefficient and reduce the filtration rate.

. Sympathetic stimulation of the heart does which of the following? A) Releases acetylcholine at the sympathetic endings B) Decreases sinus nodal discharge rate C) Decreases excitability of the heart D) Releases norepinephrine at the sympathetic endings E) Decreases cardiac contractility

D) Increased sympathetic stimulation of the heart increases heart rate, atrial contractility, and ventricular contractility and also increases norepinephrine release at the ventricular sympathetic nerve endings. It does not release acetylcholine. It does cause an increased sodium permeability of the A-V node, which increases the rate of upward drift of the membrane potential to the threshold level for self-excitation, thus increasing the heart rate.

Which condition at the S-A node will cause heart rate to decrease? A) Increased norepinephrine level B) Increased sodium permeability C) Increased calcium permeability D) Increased potassium permeability E) Decreased acetylcholine level

D) Increases in sodium and calcium permeability at the S-A node result in an increase in heart rate. An increased potassium permeability causes a hyperpolarization of the S-A node, which causes the heart rate to decrease.

A healthy 60-year-old woman with a 10-year history of hypertension stands up from a supine position. Which set of cardiovascular changes is most likely to occur in response to standing up from a supine position? Sympathetic Nerve Activity, Parasympathetic Nerve Activity, Heart Rate A) ↑ ↑ ↑ B) ↑ ↑ ↓ C) ↑ ↓ ↓ D) ↑ ↓ ↑ E) ↓ ↓ ↓ F) ↓ ↓ ↑ G) ↓ ↑ ↑ H) ↓ ↑ ↓

D) Moving from a supine to a standing position causes an acute fall in arterial pressure that is sensed by arterial baroreceptors located in the carotid bifurcation and aortic arch. Activation of the arterial baroreceptors leads to an increase in sympathetic outflow to the heart and peripheral vasculature and a decrease in parasympathetic outflow to the heart. The increase in sympathetic activity to peripheral vessels results in an increase in total peripheral resistance. The increase in sympathetic activity and decrease in parasympathetic outflow to the heart result in an increase in heart rate.

A decrease in the production of which of the following would most likely result in chronic hypertension? A) Aldosterone B) Thromboxane C) Angiotensin II D) Nitric oxide

D) Nitric oxide is a potent vasodilator and natriuretic substance. Thus, a reduction in nitric oxide production would result in an increase in arterial pressure. In contrast, angiotensin II, thromboxane, and aldosterone are vasoconstrictor and/or antinatriuretic factors. A decrease in the production of these factors would tend to decrease arterial pressure.

(pic at bottom of pg 31 in G&H) 46. What is her heart rate? Use lead I for the calculation. A) 56 B) 66 C) 76 D) 103 E) 152

D) Note in the figure below that the QRS complex has a large negative deflection in lead I and a positive deflection in lead III, which indicates that there is a rightward axis deviation. Heart rate is calculated by 60/R-R interval and is 103 beats per minute.

Blood flow to a tissue remains relatively constant despite a reduction in arterial pressure (autoregulation). Which of the following would be expected to occur in response to the reduction in arterial pressure? A) Decreased conductance B) Decreased tissue carbon dioxide concentration C) Increased tissue oxygen concentration D) Decreased vascular resistance E) Decreased arteriolar diameter

D) Reduction in perfusion pressure to a tissue leads to a decrease in tissue oxygen concentration and an increase in tissue carbon dioxide concentration. Both events lead to an increase in arteriolar diameter, decreased vascular resistance, and increased vascular conductance.

Which condition normally causes arteriolar vasodilation during exercise? A) Decreased plasma potassium ion concentration B) Increased histamine release C) Decreased plasma nitric oxide concentration D) Increased plasma adenosine concentration E) Decreased plasma osmolality

D) Several factors cause arteriolar vasodilation during exercise, including increases in potassium ion concentration, plasma nitric oxide concentration, plasma adenosine concentration, and plasma osmolality. Although histamine causes arteriolar vasodilation, histamine release does not normally occur during exercise.

Which of the following would be expected to occur during a Cushing reaction caused by brain ischemia? A) Increase in parasympathetic activity B) Decrease in arterial pressure C) Decrease in heart rate D) Increase in sympathetic activity

D) The Cushing reaction is a special type of CNS ischemic response that results from increased pressure of the cerebrospinal fluid around the brain in the cranial vault. When the cerebrospinal fluid pressure rises, it decreases the blood supply to the brain and elicits a CNS ischemic response. The CNS ischemic response includes enhanced sympathetic activity, decreased parasympathetic activity, and increased heart rate, arterial pressure, and total peripheral resistance.

If the S-A node discharges at 0.00 seconds, when will the action potential normally arrive at the A-V bundle (bundle of His)? A) 0.22 second B) 0.18 second C) 0.16 second D) 0.12 second E) 0.09 second

D) The action potential arrives at the A-V bundle at 0.12 second. It arrives at the A-V node at 0.03 second and is delayed 0.09 second in the A-V node, which results in an arrival time at the bundle of His of 0.12 second.

. What is her ventricular ejection fraction? A) 33% B) 50% C) 60% D) 67% E) 80%

D) The ejection fraction is the stroke volume/enddiastolic volume. Stroke volume is 100 milliliters, and the end-systolic volume at point D is 150 milliliters. Thus, the ejection fraction is 0.667, or in terms of percentage, 66.7%.

What is the normal total delay of the cardiac impulse in the A-V node + bundle? A) 0.22 second B) 0.18 second C) 0.16 second D) 0.13 second E) 0.09 second

D) The impulse from the S-A node travels rapidly through the internodal pathways and arrives at the A-V node at 0.03 second, at the A-V bundle at 0.12 second, and at the ventricular septum at 0.16 second. The total delay is thus 0.13 second.

. Which condition at the A-V node will cause a decrease in heart rate? A) Increased sodium permeability B) Decreased acetylcholine levels C) Increased norepinephrine levels D) Increased potassium permeability E) Increased calcium permeability

D) The increase in potassium permeability causes a hyperpolarization of the A-V node, which will decrease the heart rate. Increases in sodium permeability will actually partially depolarize the A-V node, and an increase in norepinephrine levels increases the heart rate.

Movement of solutes such as Na+ across the capillary walls occurs primarily by which process? A) Filtration B) Active transport C) Vesicular transport D) Diffusion

D) The primary mechanism whereby solutes move across a capillary wall is simple diffusion.

An increase in which of the following would be expected to decrease blood flow in a vessel? A) Pressure gradient across the vessel B) Radius of the vessel C) Plasma colloid osmotic pressure D) Viscosity of the blood E) Plasma sodium concentration

D) The rate of blood flow is directly proportional to the fourth power of the vessel radius and to the pressure gradient across the vessel. In contrast, the rate of blood flow is inversely proportional to the viscosity of the blood. Thus, an increase in blood viscosity would decrease blood flow in a vessel.

Listed below are the hydrostatic and oncotic pressures within a microcirculatory bed. Plasma colloid osmotic pressure = 25 mm Hg Capillary hydrostatic pressure = 25 mm Hg Venous hydrostatic pressure = 5 mm Hg Arterial pressure = 80 mm Hg Interstitial fluid hydrostatic pressure = −5 mm Hg Interstitial colloid osmotic pressure = 10 mm Hg Capillary filtration coefficient = 10 ml/min/mm Hg What is the rate of net fluid movement across the capillary wall? A) 25 ml/min B) 50 ml/min C) 100 ml/min D) 150 ml/min E) 200 ml/min

D) The rate of net fluid movement across a capillary wall is calculated as capillary filtration coefficient × net filtration pressure. Net filtration pressure = capillary hydrostatic pressure − plasma colloid osmotic pressure + interstitial colloid osmotic pressure − interstitial hydrostatic pressure. Thus, the rate of net fluid movement across the capillary wall is 150 ml/min. Filtration rate = Capillary filtration coefficient (Kf) × Net filtration pressure Filtration rate = Kf × [Pc − Πc + Πi − PI ] Filtration rate = 10 ml/min/mm Hg × [25 − 25 + 10 − (−5)] Filtration rate = 10 × 15 = 150 ml/min

The tendency for turbulent flow is greatest in which of the following? A) Arterioles B) Capillaries C) Small arterioles D) Aorta

D) The tendency for turbulent flow occurs at vascular sites where the velocity of blood flow is high. The aorta has the highest velocity of blood flow.

Which of the following would cause the greatest decrease in GFR in a person with otherwise normal kidneys? A) Decrease in renal arterial pressure from 100 to 80 mm Hg in a normal kidney B) 50% increase in glomerular capillary filtration coefficient C) 50% increase in proximal tubular sodium reabsorption D) 50% decrease in afferent arteriolar resistance E) 50% decrease in efferent arteriolar resistance F) 5 mm Hg decrease in Bowman's capsule pressure

E) A 50% decrease in efferent arteriolar resistance would cause a substantial decrease in GFR. A decrease in renal arterial pressure from 100 to 80 mm Hg in a normal kidney would cause only a slight reduction in GFR in a normal kidney because of autoregulation. All of the other changes would tend to increase GFR.

In control conditions, flow through a blood vessel is 100 ml/min under a pressure gradient of 50 mm Hg. What would be the approximate flow through the vessel after increasing the vessel diameter to four times normal, assuming that the pressure gradient was maintained at 50 mm Hg? A) 300 ml/min B) 1600 ml/min C) 1000 ml/min D) 16,000 ml/min E) 25,600 ml/min

E) According to Poiseuille's law, flow through a vessel increases in proportion to the fourth power of the radius. A fourfold increase in vessel diameter (or radius) would increase 4 to the fourth power, or 256 times normal. Thus, flow through the vessel after increasing the vessel 4 times normal would increase from 100 to 25,600 ml/min.

In an experimental study, administration of a drug decreases the diameter of arterioles in the muscle bed of an animal subject. Which set of physiological changes would be expected to occur in response to the decrease in diameter? Vascular Conductance, Capillary Filtration, Blood Flow A) ↑ ↑ ↑ B) ↑ ↓ ↑ C) ↑ ↓ ↓ D) ↑ ↑ ↓ E) ↓ ↓ ↓ F) ↓ ↑ ↓ G) ↓ ↑ ↑ H) ↓ ↓ ↑

E) Administration of a drug that decreases the diameter of arterioles in a muscle bed increases the vascular resistance. The increased vascular resistance decreases vascular conductance and blood flow. The reduction in arteriolar diameter also leads to a decrease in capillary hydrostatic pressure and capillary filtration rate.

A 65-year-old man has congestive heart failure. He has a cardiac output of 4 L/min, arterial pressure of 115/85 mm Hg, and a heart rate of 90 beats/min. Further tests by a cardiologist reveal that the patient has a right atrial pressure of 10 mm Hg. An increase in which of the following would be expected in this patient? A) Plasma colloid osmotic pressure B) Interstitial colloid osmotic pressure C) Arterial pressure D) Cardiac output E) Vena cava hydrostatic pressure

E) An increase in atrial pressure of 10 mm Hg would tend to decrease venous return to the heart and increase vena cava hydrostatic pressure. Plasma colloid osmotic pressure, interstitial colloid osmotic pressure, arterial pressure, and cardiac output would generally be low to normal in this patient.

The diameter of a precapillary arteriole is increased in a muscle vascular bed. A decrease in which of the following would be expected? A) Capillary filtration rate B) Vascular conductance C) Capillary blood flow D) Capillary hydrostatic pressure E) Arteriolar resistance

E) An increase in the diameter of a precapillary arteriole would decrease arteriolar resistance. The decrease in arteriolar resistance would lead to an increase in vascular conductance and capillary blood flow, hydrostatic pressure, and filtration rate.

Which event is associated with the first heart sound? A) Closing of the aortic valve B) Inrushing of blood into the ventricles during diastole C) Beginning of diastole D) Opening of the A-V valves E) Closing of the A-V valves

E) As seen in Chapter 9, the first heart sound by definition occurs just after the ventricular pressure exceeds the atrial pressure, which causes the A-V valves to mechanically close. The second heart sound occurs when the aortic and pulmonary valves close.

A healthy 22-year-old female medical student has an exercise stress test at a local health club. An increase in which of the following is most likely to occur in this woman's skeletal muscles during exercise? A) Vascular conductance B) Blood flow C) Carbon dioxide concentration D) Arteriolar diameter E) All the above

E) During exercise, tissue levels of carbon dioxide and lactic acid increase. These metabolites dilate blood vessels, decrease arteriolar resistance, and enhance vascular conductance and blood flow.

Which statement about the results of sympathetic stimulation is most accurate? A) Epicardial flow increases B) Venous resistance decreases C) Arteriolar resistance decreases D) Heart rate decreases E) Venous reservoirs constrict

E) During sympathetic stimulation, venous reservoirs constrict, venous vascular resistance also increases, arterioles constrict (which increases their resistance), and the heart rate increases. The epicardial coronary vessels have a large number of alpha receptors, but the subendocardial vessels have more beta receptors. Therefore, sympathetic stimulation causes at least a slight constriction of the epicardial vessels. This results in a slight decrease in epicardial flow

Which phase of the cardiac cycle follows immediately after the beginning of the QRS wave? A) Isovolumic relaxation B) Ventricular ejection C) Atrial systole D) Diastasis E) Isovolumic contraction

E) Immediately after the QRS wave, the ventricles be- gin to contract, and the first phase that occurs is iso- volumic contraction. Isovolumic contraction occurs before the ejection phase and increases the ventricular pressure enough to mechanically open the aortic and pulmonary valves.

Sympathetic stimulation of the heart normally causes which condition? A) Acetylcholine release at the sympathetic endings B) Decreased heart rate C) Decreased rate of conduction of the cardiac impulse D) Decreased force of contraction of the atria E) Increased force of contraction of the ventricles

E) Sympathetic stimulation of the heart normally causes an increased heart rate, increased rate of conduction of the cardiac impulse, and increased force of contraction in the atria and ventricles. However, it does not cause acetylcholine release at the sympathetic endings because they contain norepinephrine. Parasympathetic stimulation causes acetylcholine release. The sympathetic nervous system firing increases in the permeability of the cardiac muscle fibers, the S-A node, and the A-V node to sodium and calcium.

(pic at bottom of pg 33 in G&H) 64. What is his ventricular heart rate in beats/min? A) 37.5 B) 60 C) 75 D) 100 E) 150

E) The average ventricular rate is 150 beats/min in this ECG, which is typical of atrial flutter. Once again notice that the heart rate is irregular because of the inability of the impulses to quickly pass through the A-V node because of its refractory period.

An ACE inhibitor is administered to a 65-year-old man with a 20-year history of hypertension. The drug lowered his arterial pressure and increased his plasma levels of renin and bradykinin. Which mechanism would best explain the decrease in arterial pressure? A) Inhibition of angiotensin I B) Decreased conversion of angiotensinogen to angiotensin I C) Increased plasma levels of bradykinin D) Increased plasma levels of renin E) Decreased formation of angiotensin II

E) The conversion of angiotensin I to angiotensin II is catalyzed by a converting enzyme that is present in the endothelium of the lung vessels and in the kidneys. The converting enzyme also serves as a kininase that degrades bradykinin. Thus, a converting enzyme inhibitor not only decreases the formation of angiotensin II but also inhibits kininases and the breakdown of bradykinin. Angiotensin II is a vasoconstrictor and a powerful sodium-retaining hormone. The major cause for the decrease in arterial pressure in response to an ACE inhibitor is the decrease in formation of angiotensin II.

Which of the following is most likely to cause the heart to go into spastic contraction? A) Increased body temperature B) Increased sympathetic activity C) Decreased extracellular fluid potassium ions D) Excess extracellular fluid potassium ions E) Excess extracellular fluid calcium ions

E) The heart goes into spastic contraction after a large increase in the calcium ion concentration surrounding the cardiac myofibrils, which occurs if the extracellular fluid calcium ion concentration increases too much. An excess potassium concentration in the extracellular fluids causes the heart to become dilated because of the decrease in resting membrane potential of the cardiac muscle fibers.

(pic above question on pg 34 of G&H) 72. What is his heart rate? A) 40 beats/min B) 50 beats/min C) 75 beats/min D) 100 beats/min E) 150 beats/min

E) The heart rate can be determined by 60 divided by the R-R interval, which gives a value of 150 beats/min. This patient has tachycardia, which is defined as a heart rate greater than 100 beats/min.

A 25-year-old well-conditioned athlete weighs 80 kilograms (176 pounds). During maximal sympathetic stimulation, what is the plateau level of his cardiac output function curve? A) 3 liters per minute B) 5 liters per minute C) 10 liters per minute D) 13 liters per minute E) 25 liters per minute

E) The normal plateau level of the cardiac output function curve is 13 L/min. This level decreases in any kind of cardiac failure and increases markedly during sympathetic stimulation.

Which mechanism is associated with the third heart sound? A) Inrushing of blood into the ventricles as a result of atrial contraction B) Closing of the A-V valves C) Closing of the pulmonary valve D) Opening of the A-V valves E) Inrushing of blood into the ventricles in the early to middle part of diastole

E) The third heart sound is associated with inrushing of blood into the ventricles in the early to middle part of diastole. The next heart sound, the fourth heart sound, is caused by inrushing of blood in the ventricles caused by atrial contraction. The first heart sound is caused by the closing of the A-V valves, and the second heart sound is caused by the closing of the pulmonary and aortic valves.

An increase in which of the following would tend to increase lymph flow? A) Hydraulic conductivity of the capillary wall B) Plasma colloid osmotic pressure C) Capillary hydrostatic pressure D) Arteriolar resistance E) A and C

E) The two main factors that increase lymph flow are an increase in capillary filtration rate and an increase in lymphatic pump activity. An increase in plasma colloid osmotic pressure decreases capillary filtration rate, interstitial volume and hydrostatic pressure, and lymph flow. In contrast, an increase in hydraulic conductivity of the capillary wall and capillary hydrostatic pressure increase capillary filtration rate, interstitial volume and pressure, and lymph flow. An increase in arteriole resistance would decrease capillary hydrostatic pressure, capillary filtration rate, interstitial volume and pressure, and lymph flow

A 60-year-old woman has a resting heart rate of 70 beats per minute, arterial pressure of 130/85 mm Hg, and normal body temperature. Use the pressure-volume diagram of her left ventricle below to answer Questions 1-4. (pic of normal pressure-volume diagram- in notes) What is her cardiac output in milliliters per minute? A) 2000 B) 3000 C) 4000 D) 6000 E) 7000

E) This patient has a heart rate of 70 beats per minute. The cardiac output can be determined by using the following formula: cardiac output = heart rate × stroke volume. The stroke volume can be determined from the figure, which is the volume change during the C-D segment, or 100 milliliters. By using this formula, you can determine that the cardiac output is 7000 milliliters per minute

A 60-year-old man has a mean arterial blood pressure of 130 mm Hg, a heart rate of 78 beats/min, a right atrial pressure of 0 mm Hg, and a cardiac output of 3.5 L/min. He also has a pulse pressure of 35 mm Hg and a hematocrit of 40. What is the approximate total peripheral vascular resistance in this man? A) 17 mm Hg/L/min B) 1.3 mm Hg/L/min C) 13 mm Hg/L/min D) 27 mm Hg/L/min E) 37 mm Hg/L/min

E) Total peripheral vascular resistance = arterial pressure − right atrial pressure ÷ cardiac output. In this example, total peripheral vascular resistance = 130 mm Hg ÷ 3.5 L/min, or approximately 37 mm Hg/L/min.