Physiopatho - cardio Flashcards
(42 cards)
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
