Physiopatho - cardio Flashcards
Which of the following is true for both cardiac muscle and skeletal muscle?
a. The muscle forms a functional syncytium.
b. An action potential in the muscle cell membrane is required
to initiate contraction.
c. Pacemaker cells spontaneously depolarize to threshold and
initiate action potentials.
d. Frequent action potentials in motor neurons can cause a
sustained (tetanic) muscle contraction.
e. Extracellular Ca2+ enters the muscle cell during an action
potential and triggers the release of additional Ca2+ from the sarcoplasmic reticulum.
B
A, C and E are only cardiac
D is muscle
At the moment when an action potential begins propagating slowly through the AV node in a normal resting dog, the ventricular muscle cells are:
a. At their resting membrane potential.
b. Depolarizing slowly toward threshold for formation of an action potential.
c. Undergoing rapid depolarization at the beginning of an action potential.
d. At the plateau of an action potential.
e. Just ending their action potential (i.e., repolarizing back
toward resting membrane potential).
A
During which phase of a normal ventricular action potential is it most likely that fast Na+ channels are in an inactivated state, slow Ca2+ channels are open, and most K+ channels are closed?
a. Phase 0 (rapid depolarization)
b. Phase 1 (partial repolarization)
c. Phase 2 (plateau)
d. Phase 3 (repolarization)
e. Phase 4 (rest)
c - plateau itself caused by slow Ca entrance
An increase in heart rate could result from:
a. An increase in sympathetic nerve activity to the heart.
b. A decrease in parasympathetic nerve activity to the heart.
c. An abnormally rapid decrease in permeability of SA node
cells to K+ during diastole.
d. An abnormally rapid increase in permeability of SA node
cells to Na+ during diastole. e. All the above are correct.
E - all
In which of the following arrhythmias will there be more atrial beats per minute than ventricular beats?
a. Complete (third-degree) AV block
b. Frequent premature ventricular contractions
c. Sick sinus syndrome (sinus bradycardia)
d. First-degree AV block
e. Ventricular tachycardia
a - complete 3d AV block has less ventricular contraxctions but normal atrial contractions - complete block of propagation along AV node
Which of the following types of drugs would be the best choice to treat a patient with both supraventricular tachycardia and inadequate cardiac contractility?
a. Local anesthetic (fast Na+ channel blocker)
b. Muscarinic cholinergic antagonist
c. Beta-adrenergic agonist + +
d. Cardiac glycoside (inhibits Na , K pump)
e. Calcium channel blocker
D - cardiac glycoside (digitalis) - by inhibiting Na K pump, slows down propagation (anti arrhythmic) and allow more Ca to accumulate in the cell and cause stronger contraction
Calcium and beta blockers are anti arrhythmic that instead decrease contractility.
Local anaesthetic are only antiarrhtythmic with no effect on contractility
What would the lead I ECG look like if an ectopic pacemaker in the free wall of the left atrium subsumed the role of the SA node (i.e., “took over” the initiation of atrial action potentials)?
a. The ECG would appear normal.
b. The order of waves would be reversed (i.e. T-QRS-P, instead of P-QRS-T).
c. The P waves and T waves would appear normal, but there would be no R waves.
d. The P wave would be negative and the R wave would be positive.
e. The P wave would be negative and the R wave would be negative.
D - negative P (because ectopic pacemaker on left atrium causes depolarizazion away from point A (left forelimb), therefore curve is negative!
Positive R because ventricular depolarization is not affected (AV node blocks extra beats and do not conduct abnormal act potantial to ventricles)
The T wave in a normal lead I ECG is:
a. Always negative.
b. Always positive if the R wave is positive.
c. Also known as the pacemaker potential.
d. Caused by the delay between atrial and ventricular
depolarization.
e. Caused by ventricular repolarization.
E - T can be positive or negative, depending on animal.
In many normal dogs, ventricular repolarization proceeds in the same direction as the depolarization (from inside the ventricles to outside). This pattern of repolarization creates a negative voltage in the left forelimb compared with the right forelimb; that is, the T wave is negative. Whether positive or negative, T waves are caused by repolarization of the ventricles.
During a normal cardiac cycle, which of the following events happens soonest after the first heart sound is heard?
a. Atrial contraction begins.
b. The mitral valve opens.
c. Atrial depolarization begins.
d. Ventricular ejection begins.
e. The aortic valve closes.
D - the first sound is caused by closure of mitral and tricuspid valves with ventricular contraction in preparation for ejection
In the normal cardiac cycle:
a. The P wave in the electrocardiogram coincides with the
beginning of ventricular ejection.
b. The second heart sound coincides with the beginning of
isovolumetric relaxation.
c. Left ventricular pressure reaches its highest level just as the
aortic valve closes.
d. Aortic pressure reaches its highest level at the beginning of
ventricular systole.
e. The mitral valve is open throughout ventricular diastole.
B - the second heart sound consist with the closure of aortic and pulmonic valve following ejection
An abnormality that causes a sustained decrease in left ventricular compliance is most likely to result in an increased:
a. Left ventricular stroke volume
b. Left atrial volume and pressure
c. Left ventricular afterload
d. Pulmonary blood flow
e. Left ventricular end-diastolic volume
B - with less ventricular compliance (less distension) causes left atrium to increase in pressure and volume
Which of the following cause-and-effect statements is true for a normal heart?
a. Sympathetic activation causes end-systolic ventricular
volume to increase.
b. An increase in ventricular preload causes end-diastolic ven-
tricular volume to decrease.
c. Pacing the heart at a high rate causes stroke volume to
decrease.
d. An increase in ventricular contractility causes systolic dura-
tion to increase.
e. An increase in ventricular contractility causes the external
work of the heart to decrease.
C - the faster the heart, the less time to fill with blood and to pump it out
You examine a 7-year-old poodle and find evidence of a systolic murmur (no diastolic murmur), pulmonary edema (indicated by rapid, noisy respiration and cough), left ventricular hyper- trophy (no right ventricular hypertrophy), and exercise intoler- ance. The most likely explanation for the symptoms is:
a. Mitral regurgitation
b. Mitral stenosis
c. Aortic regurgitation
d. Pulmonic stenosis
e. Patent ductus arteriosus
A
The magnitude of pulsations in blood pressure (caused by the pulsatile ejection of blood from the heart) is greatest in the:
a. Arteries
b. Arterioles
c. Capillaries d. Veins
e. Venae cavae
A - Arterioles are the site not only of the highest resistance in the circulation but also of adjustable resistance. Variation in arteriolar resistance is the main factor that determines how much blood flows through each organ in the body; an increase in arteriolar resistance in an organ decreases the blood flow through that organ and vice versa. Arterioles change their resistance, moment to moment, by changing their radius.
Which of the following is a correct comparison between segments of the systemic circulation?
a. The aorta and large arteries have a higher resistance to blood
flow than the capillaries.
b. The arterioles have a higher resistance to blood flow than
the capillaries.
c. The veins have a higher resistance to blood flow than the
capillaries.
d. The aorta and large arteries have a higher compliance than
the veins.
e. The aorta and large arteries contain a greater volume of
blood than the veins and venae cavae.
B - arterioles have the highest resistance of all vessels
Which of the following would cause mean aortic pressure to increase?
a. Stroke volume increases from 30 to 40 mL, and heart rate decreases from 100 to 60 beats/min.
b. Arterial compliance decreases.
c. Cardiac output decreases.
d. Arterioles throughout the body dilate.
e. TPR increases.
E - this is because the mean aortic pressure is determined by CARDIAC OUTPUT x SVR
If aortic compliance decreases while heart rate, cardiac output, and total peripheral resistance (TPR) remain unchanged:
a. Pulse pressure will be unchanged.
b. Pulse pressure will increase.
c. Pulse pressure will decrease.
d. One cannot know the effect on pulse pressure because
stroke volume may have changed.
e. One cannot know the effect on pulse pressure because mean
aortic pressure may have changed.
B - pulse pressure increases when:
- stroke volume increases
- heart rate decreases
or - arterial compliance decreases
The following measurements are made on a dog exhibiting distress following surgery: heart rate, 80 beats/min; stroke volume, 30 mL; mean aortic pressure, 96 mm Hg; mean pulmonary artery pressure, 26 mm Hg; left atrial pressure, 5 mm Hg; and right atrial pressure, 12 mm Hg. Which of the following is the best estimate for the TPR of this dog?
a. 8.75 mm Hg/L/min
b. 10.83 mm Hg/L/min c. 29.17 mm Hg/L/min d. 35.00 mm Hg/L/min e. 40.00 mm Hg/L/min
D
Formula is:
(mean aortic pressure - mean caval pressure) / cardiac output
(96 - 12) / (80 x 30)
35 mmHg / L / min
The blood flow through the brain of a resting dog would be decreased most by a 20% decrease in the:
a. Mean arterial pressure
b. Heart rate
c. Systemic perfusion pressure
d. Radius of arteries in the brain
e. Radius of arterioles in the brain
E - arterioles radius always influence blood flow the most
The rate of diffusion of glucose molecules from capillary blood to interstitial fluid is most directly affected by the:
a. Capillary plasma oncotic pressure.
b. Interstitial fluid hydrostatic pressure.
c. Size and number of capillary pores.
d. Amount of oxygen in the blood.
e. Hematocrit.
C
For continuous capillaries, such as those found in skeletal muscle, the capillary surface area available for diffusion is greatest for which of the following?
a. Glucose
b. Dissolved oxygen
c. Ions, such as Na+, K+, and Cl−
d. Amino acids
e. Plasma proteins
B
An increase in the venous resistance (e.g., too tight a bandage on an extremity) causes edema because:
a. Lymph flow increases.
b. Pinocytosis cannot remove excess interstitial fluid fast
enough.
c. Capillary hydrostatic pressure increases.
d. The interstitial proteins block up lymph channels. e. The interstitial fluid pressure decreases.
C - capillary hydrostatic pressure increases if venous return is reduced - with higher capillary hydrostatic pressure fluid goes into interstitium
Which of the following will NOT cause pulmonary edema?
a. An increase in pulmonary capillary permeability to protein b. A blockage of pulmonary lymph vessels
c. An increase in left atrial pressure
d. A constriction of pulmonary arterioles
e. Left-sided heart failure
D - constriction of arterioles cause capillary hydrostatic pressure too decrease - therefore less fluid is pushed out into interstitium
A patient with a form of protein-losing kidney disease has a plasma colloid osmotic pressure of 10 mm Hg. The patient has edema but is not getting any worse. Blood pressure and heart rate are normal. Which of the following is probably preventing further edema?
a. Increased capillary hydrostatic pressure
b. Decreased lymph flow
c. Decreased concentration of plasma proteins in the plasma d. Increased interstitial fluid oncotic pressure
e. Increased interstitial fluid hydrostatic pressure
E - is pushing fluid from interstitium to the vessels
The following parameters exist in the microcirculation of a skeletal muscle during a period of vigorous exercise:
Pc (capillary hydrostatic pressure) = 34 mm Hg
Pi (interstitial fluid hydrostatic pressure) = 10 mm Hg
πc (capillary plasma oncotic pressure) = 24 mm Hg πi (interstitial fluid oncotic pressure) = 3 mm Hg Which of the following is true?
a. These conditions favor filtration.
b. These conditions favor reabsorption.
c. These conditions favor neither filtration nor reabsorption.
d. It is not clear what these conditions favor because the con-
centration of plasma protein is not specified.
e. It is not clear what these conditions favor because the rate
of lymph flow is not specified.
A
34+3 (forces that drive fluid out - filtration) = 37
24+10 (forces driving fluid in - reabsorption) = 34
Filtration is favoured by 3mmHg, therefore fluid out
Histamine and bradykinin cause edema by increasing BOTH:
a. Capillary permeability to plasma protein AND interstitial
hydrostatic pressure.
b. Interstitial colloid osmotic pressure AND lymph flow.
c. Capillary hydrostatic pressure AND capillary permeability
to plasma protein.
d. Capillary hydrostatic pressure AND plasma colloid osmotic
pressure.
e. Lymph flow AND interstitial hydrostatic pressure.
C - An injury or antigen challenge stimulates the release of the chemical histamine from mast cells in the affected tissue and also stimulates the production of the peptide bradykinin in the blood and interstitial fluid. Both histamine and bradykinin have a pair of effects that cause edema in the reacting tissue.
First, these chemicals increase the permeability of capillaries to plasma proteins. As proteins leave the bloodstream and accumulate in the interstitial space, they increase the interstitial fluid oncotic pressure, which promotes filtration of fluid. Second, histamine and bradykinin relax arteriolar smooth muscle. The arterioles dilate, and the resulting decrease in arteriolar resistance allows more of the arterial blood pressure to impinge on the capil- laries. This leads to an increase in the capillary hydrostatic pressure, which promotes filtration.
Intrinsic control of blood flow is most likely to predominate over extrinsic control of blood flow in:
a. The splanchnic circulation
b. The kidneys
c. Resting skeletal muscle
d. Exercising skeletal muscle
e. Skin
D
The increase in coronary blood flow during exercise is:
a. Called Starling’s law of the heart.
b. Called reactive hyperemia.
c. Caused by activation of parasympathetic nerves to the
heart.
d. Caused by compression of the coronary blood vessels during
systole.
e. Closely matched to the increased metabolic requirements
of the heart muscle.
E
The metabolic control mechanism serves to match blood flow in a tissue to the tissue’s metabolic activity. Which of the fol- lowing variables is actually being regulated (i.e., held constant) by the metabolic control mechanism?
a. Perfusion pressure applied to the tissue.
b. Blood flow to the tissue.
c. Arteriolar resistance in the tissue.
d. Oxygen concentration in the tissue interstitial fluid.
e. The number of open capillaries (i.e., the number of capil-
laries carrying blood flow at any one time).
D - decrease availability of O2 cause increasing metabolic products causing vasodilation like CO2, lactic acid, NO… all causing vasodilation and increased blood flow (carrying O2) to that tissue.
Which of the following characteristically acts as a paracrine to cause vasoconstriction in systemic arterioles?
a. Carbon dioxide
b. Nitric oxide
c. Endothelin-1 (ET1)
d. Prostacyclin (PGI2)
e. Bradykinin
C - all the others are vasodilators
The normal reflex responses to a sudden increase in arterial blood pressure include an increase in:
a. Heart rate.
b. Renin release from the kidney.
c. Parasympathetic activity directed to the heart.
d. Sympathetic activity directed to blood vessels in kidneys,
resting skeletal muscles, and splanchnic organs.
e. Sympathetic activity directed to blood vessels in brain,
coronary circulation, and exercising skeletal muscles.
C
Vasovagal syncope:
a. Involves decreased blood pressure and heart rate.
b. Involves increased sympathetic activity.
c. Involves decreased cardiac parasympathetic activity. d. Involves constriction of splanchnic arterioles.
e. Prepares an animal for “fight or flight.”
A - vaso (vasodilation - drop in BP) vagal (vagal nerve stim - decreased HR) - increased parasympathetic activity and decreased sympathy
What goes in the blank in the following sequence of cause and effect?
Myocardial failure → Decreased cardiac contractility → _______________ → Decreased stroke volume.
a. Increased end-diastolic volume
b. Decreased end-diastolic volume
c. Increased end-systolic volume
d. Decreased heart rate
e. Increased mean aortic pressure
C - more blood remains in ventricle post systole if decreased contractility
Which of the following is most likely to be the cause of dependent edema (swelling in regions of the body below the level of the heart) in a dog with chronic heart failure secondary to hypertrophic cardiomyopathy?
a. Increased lymph flow
b. Increased capillary hydrostatic pressure
c. Increased interstitial fluid hydrostatic pressure
d. Increased plasma colloid osmotic (oncotic) pressure
e. Increased interstitial fluid colloid osmotic (oncotic)
pressure
B
What goes in the blank in the following sequence of cause and effect?
Hemorrhage → Decreased central venous pressure → Decreased ventricular preload → _____________________ → Decreased stroke volume.
a. Decreased ventricular contractility
b. Decreased systolic duration
c. Decreased arterial baroreceptor activity d. Decreased diastolic filling time
e. Decreased end-diastolic volume
E - decreased preload means decreased end-diastolic volume as ventricle does nit expand as much
Which of the following is most likely to be below normal in a dog that is beginning to compensate for a significant hemorrhage?
a. Activity of the arterial baroreceptors
b. Release of ADH from the pituitary gland
c. Sensation of thirst
d. Sympathetic nerve activity to the systemic arterioles e. Sympathetic nerve activity to the heart
A
A dog suffers a sudden, severe hemorrhage. One hour later, the dog is resting quietly, but his arterial pulse pressure, mean pressure, and hematocrit are all below normal. His mucous membranes are pale, and capillary refill time is longer than normal. Which of the following is most likely?
a. The diminished pulse pressure results from an abnormally low heart rate.
b. The diminished mean pressure results from an abnormally low total peripheral resistance.
c. The diminished hematocrit results from reabsorption of interstitial fluid into the bloodstream.
d. The pale mucous membranes result from abnormally low plasma protein concentration
e. The prolonged capillary refill time results from decreased sympathetic nerve activity to the blood vessels.
C
What goes in the blank in the following sequence of cause and effect?
Initiation of skeletal muscle exercise → Increased metabolic rate in exercising muscles → _________________ → Increased blood flow in exercising muscles.
a. Decreased cardiac output
b. Decreased arterial pressure
c. Vasodilation in exercising muscle
d. Increased total peripheral resistance
e. Increased delivery of oxygen to exercising muscle
C
During the transition from rest to exercise in a normal dog, which of the following will decrease?
a. The external work (pumping work) of the heart
b. The heart muscle’s total work (total energy consumption) c. Blood flow through the lungs
d. Systolic duration
e. Velocity with which action potentials are conducted
through the AV node
D
When a horse is running, the deep breathing and rhythmic contraction/relaxation of skeletal muscles help to maintain an elevated cardiac output by increasing:
a. Venous return and central venous pressure
b. Venous distending pressure in the legs c. Cardiac contractility
d. Total peripheral resistance
e. Intrathoracic (intrapleural) pressure
A - resp and skeletal PUMP
The responses to myocardial failure, hemorrhage, and exercise have in common that ________________ will be elevated above its normal, resting level.
a. Total peripheral resistance
b. Heart rate
c. Cardiac contractility
d. Stroke volume
e. Central venous pressure
B - increased HR
