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99 terms

Cardiac

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Which of the following choices gives the correct sequence of events following the depolarization of transverse tubules in excitation-contraction coupling in cardiac muscle?
Calcium ion influx through sarcolemma, calcium release into sarcoplasm, actin and myosin attach, thin myofilaments slide toward the middle of sarcomeres
The conclusion of cardiac muscle contraction is marked by which of the following
Both concentration of calcium ions in the cytosol is greatly reduced by active transport; Ca2+-ATPase pumps and concentration of calcium ions in the cytosol is greatly reduced by active transport; Ca2+/Na+ cotransporters in sarcoplasmic reticulum and sarcolemma are correct
In cardiac muscle contractile cells the release of calcium through L-type calcium channels depolarizes the sarcoplasmic reticulum and inhibits the release of any additional calcium necessary for excitation-contraction coupling.
False
What is mainly responsible for the delay between the atrial and ventricular contractions
the action potential conduction velocity of the AV node cells
If the permeability of the SA node to sodium increases, which of the following do you expect to occur?
the heart rate will increase
Closure of the atrioventricular valve occurs when ________.
pressure inside the ventricle is greater than pressure inside the atrium
________ provide the pathway for the movement of electrical current between the cells of the conduction pathway and the ventricular myocytes.
Gap junctions
What causes the rapid depolarization phase of a contractile cell action potential
sodium movement into the cell
Which of the following is NOT a part of the excitation-contraction coupling in cardiac muscle?
calcium binds to calmodulin in the cytosol.
Which of the following vessels has the greatest total cross-sectional area in the circulatory system
capillaries
The contractile activity of smooth muscle cells within ________ is primarily involved in the control of the organ blood flow and mean arterial pressure.
Arterioles
Which of the following would decrease mean arterial pressure?
increase in arterial diameter
Under normal conditions, which Starling forces favor filtration?
capillary hydrostatic pressure and interstitial fluid osmotic pressure
The hydrostatic and osmotic pressures across a muscle capillary are as follows: capillary hydrostatic pressure, 25 mmHg; plasma osmotic pressure, 25 mmHg; interstitial hydrostatic pressure, 0 mmHg; and interstitial osmotic pressure, 10 mmHg. What is the net pressure for fluid movement outward through the capillary pores?
10 mmHg
Which of the following is the correct conduction pathway through the heart?
SA node; AV node; bundle of His; bundle branches; Purkinje fibers
A patient's heart rate is 90 BPM, what would the R-R interval be on this patient's ECG?
0.67 seconds
If conduction through the AV node slowed down due to damage, what would be observed on an ECG?
a longer PR interval
Under normal conditions, which Starling forces oppose filtration?
interstitial fluid hydrostatic pressure and plasma osmotic pressure
Which of the following equations correctly relates flow, pressure, and resistance?
Pressure = Flow × Resistance
The enzyme carbonic anhydrase catalyzes the following reaction: CO2 + H2O ↔ H2CO3, then H2CO3 dissociates reversibly to form H+ + HCO3-. When tissue becomes more active, carbon dioxide increases due to its production in ________, causing hydrogen ion concentration to ________.
mitochondria : increase
The driving force for blood flow through the systemic circuit is ________.
mean arterial pressure
Which equation correctly describes the relationship between cardiac output (CO), mean arterial pressure (MAP) and total peripheral resistance (TPR)?
TPR = MAP/CO
The semilunar valve on the left side of the heart opens when the pressure in the ________ exceeds the pressure in the ________.
left ventricle : aorta
Which of the following chambers has the thickest musculature?
left ventricle
A person goes to the doctor and is told his blood pressure is 90/60 and his pulse is 80. Which of the following is FALSE?
Pulse pressure is 80 mm Hg.
The effects of epinephrine on vascular resistance are dependent upon the ________.
relative distribution of alpha and beta adrenergic receptors
In comparison to the systemic circuit, the pulmonary circuit ________.
In comparison to the systemic circuit, the pulmonary circuit ________.
The R-R interval on a patient's ECG is 1 second, what is her heart rate?
60 BPM
During exercise, which organs receive an increase in the proportion of cardiac output delivered to it?
skeletal muscle, heart, and skin
skeletal muscle, heart, and skin
CO = SV x HR
The atrioventricular valve on the left side of the heart opens when the pressure in the ________ exceeds the pressure in the ________.
left atrium : left ventricle
If the permeability of the SA node to potassium increases, which of the following do you expect to occur?
The heart rate will decrease
If funny channels in the SA node are inhibited by a toxin, which of the following do you expect to occur?
The heart rate will decrease
Which of the following statements about the plateau phase of a contractile cell action potential is FALSE?
The membrane potential remains the same as the peak of the action potential for about 200 milliseconds
Which of the following is NOT a part of the excitation-contraction coupling in cardiac muscle?
Calcium triggers contraction by inducing the phosphorylation of myosin light chain
The SA node is innervated by ________.
the sympathetic and parasympathetic nervous systems
Which of the following would increase the rate of blood flow through a blood vessel?
increased pressure of the blood entering the vessel
Which of the following describes the effect of end-diastolic volume on stroke volume?
An increase in end-diastolic volume stretches ventricular muscle cells to lengths closer to optimum, increasing the strength of contraction and thereby increasing stroke volume.
In response to a decrease in tissue metabolic activity, tissue oxygen concentrations ________, which causes a(n) ________
increase : constriction of the arterioles
During exercise, which of the following tissues receive less blood flow compared to resting conditions?
gastrointestinal tract only
As mean arterial pressure increases, the ________, informing the medulla oblongata that blood pressure has indeed increased.
frequency of action potentials from the baroreceptors increases
Which of the following equations correctly relates flow, pressure, and resistance?
Resistance = Pressure / Flow
A person's blood pressure is 90/60 and his pulse is 80. Which of the following is FALSE?
Pulse pressure is 80 mm Hg
Blood flow velocity is greatest in the _____ and slowest in the _____.
arteries : capillaries
Which of the following components of an ECG represents ventricular repolarization?
T wave
The end-diastolic volume minus the end-systolic volume is the ________.
stroke volume
Compared to veins, arteries have ________ compliance
low
Intrinsic control of organ blood flow refers to the fact that ________.
arterioles respond to local factors that regulate the resistance to blood flow through an organ
The opening and closing of the atrioventricular and semilunar valves is driven by ________.
differences in pressure across the valve
What is occurring during ventricular ejection
the AV valves are closed and the semilunar valves are open as blood is leaving the ventricles
The small increase in ventricular pressure observed late in diastole is caused by ________.
ventricular relaxation
On an episode of the TV series Blue Bloods, a few high school students die at a party because they snorted a drug laced with potassium chloride, which is the same compound sometimes used for lethal injections. Which of the following best explains the lethal effect of potassium chloride?
The resulting high extracellular K+ causes the cardiac myocytes to become depolarized. Thus, the inactivation gate of the voltage-gated Na+ channels remains closed and the channels can no longer open, which prevents subsequent action potentials.
Which of the following is an effect of parasympathetic activity to the heart?
The SA node becomes hyperpolarized causing the rate of action potential firing in SA node to decrease
What is the role of ryanodine receptors in cardiac muscle?
They release calcium from the sarcoplasmic reticulum
Which of the following is responsible for the repolarization phase within the SA node?
An increase in PK
What causes the plateau phase of a cardiac myocyte action potential?
calcium movement into the cell
Which of the following equations is correct?
cardiac output = stroke volume × heart rate
Resistance to blood flow is regulated primarily by what blood vessels
arterioles
Which of the following would most increase the rate of blood flow through a blood vessel?
increased pressure difference and decreased vessel resistance
Chemicals released by metabolically active cells will cause which of the following?
relaxation of arteriolar smooth muscle to increase blood flow
Which of the following would help restore homeostasis in the first few moments after a person's mean arterial pressure became elevated?
A decrease in action potential frequency along sympathetic neurons to arterioles
In cardiac and skeletal muscle vasculature, the distribution of alpha and beta receptors is such that epinephrine will ________.
induce a dilation that increases blood flow to these tissues
With a systolic pressure of 135 mm Hg and a diastolic pressure of 75 mm Hg, mean arterial pressure would be _____.
95 mm Hg
With a systolic pressure of 135 mm Hg and a diastolic pressure of 75 mm Hg, pulse pressure would be ________.
60 mm Hg
In an ECG recording, the RR interval is 0.5 seconds. What is the heart rate?
120 beats/min
Which of the following components of an ECG represents ventricular depolarization
QRS complex
Conduction through which of the following is slow to allow the atria to contract before the ventricles
AV node
Which of the following would most decrease the rate of blood flow through a blood vessel?
decreased pressure difference and increased vessel resistance
Which of the below set of changes will occur in response to a decrease in sympathetic stimulation?
↓ ↓ ↓
The hydrostatic and osmotic pressures across a muscle capillary are as follows: capillary hydrostatic pressure, 25 mmHg; plasma osmotic pressure, 25 mmHg; interstitial hydrostatic pressure, (-5) mmHg; and interstitial osmotic pressure, 10 mmHg. What is the net pressure for fluid movement outward through the capillary pores
15 mmHg
The opening and closure of the atrioventricular and semilunar valves is driven by ________.
differences in pressure across the valve
Consider the equation F = ΔP/R. It describes the flow (F) of fluid in a tube in which there is a pressure difference (ΔP) between the two ends and a resistance (R) to flow. The equation indicates that
The flow of fluid from point A to point B in a tube depends upon the difference in pressure between A and B
Which of the following changes would most increase the resistance to blood flow in a blood vessel?
Halving the diameter of the vessel
Cardiac and smooth muscle share some characteristics, including
Gap junctions and pacemaker capability in some cells
The pacemaker of the heart is normally the
Sinoatrial node
Which of the following criteria must be met for the heart to function efficiently?
Both excitation and the consequent contraction of the cardiac muscle fibers of each heart chamber should be coordinated to assure efficient pumping and the atria should be excited and contract before the onset of ventricular contraction to assure that ventricular filling is complete are correct
Which of the following statements concerning the differences between action potentials in skeletal muscle cells and in ventricular cardiac muscle cells is true?
After sodium influx through fast channels occurs in ventricular cells, an influx of calcium occurs. No such calcium influx occurs after sodium influx in the skeletal muscle cells
Which of the following statements is true concerning the depolarization of a cell in the SA node?
The pacemaker potential is slower in achieving threshold when acetylcholine (neurotransmitter for parasympathetic nervous system) is applied to the SA cells
The plateau of the action potential in cardiac ventricular cells results from the opening of voltage-gated slow ___________ channels in the plasma membrane of the cell.
Calcium
Which of the following statements about membrane potentials in different types of cardiac cells is correct?
Both myocardial cells have a resting membrane potential of about -90 mV; pacemaker cells do not have a true resting membrane potential and voltage-gated calcium channels are opened at some time during the action potential in both myocardial and pacemaker cells are correct
In an electrocardiogram, the QRS complex represents the
Depolarization of the ventricles
An ECG would be useful for determining a patient's
Blockage of conduction of electrical signals between the atria and the ventricles
Which of the following statements about the absolute refractory period of cardiac muscle cells is true
Both it lasts almost as long as the resultant period of contraction of the cells and it is much longer than the refractory period of skeletal muscle cells are true
Which of the following statements about the refractory period of nerve or muscle membranes is correct?
In ventricular cells, the absolute refractory period coincides with the period of increased Na+ and Ca2+ permeability
Which of the following statements about the cardiac cycle is true?
Closure of the atrioventricular valves occurs at the onset of systole
Which of the following statements regarding the cardiac cycle is correct?
The AV valves are open during mid-to-late diastole
During the cardiac cycle,
The duration of diastole is greater than that of systole
The aortic valve
Prevents the backflow of blood into the left ventricle during ventricular diastole
During isovolumetric ventricular contraction
No blood enters or leaves the ventricles
No blood enters or leaves the ventricles
A pressure difference on the two sides of the valve
Cardiac output is the
Both volume of blood flowing through the systemic circulation each minute and product of the number of heartbeats per minute and the volume pumped per beat are correct
Sinoatrial node cells
Both are normally the pacemakers of the heart and exhibit spontaneous depolarization that is speeded by activation of their beta-adrenergic receptors are correct
With regard to the regulation of heart rate,
All of the choices are true
The discharge rate of the SA node is
Increased by epinephrine
The Frank-Starling mechanism of the heart describes
The Frank-Starling mechanism of the heart describes
According to the Frank-Starling mechanism of the heart
Stroke volume increases with increased venous return
Which of the following is not an effect of sympathetic stimulation of the heart?
It decreases the slope of the pacemaker potential
Which of the following statements about blood vessel structure and function is false?
Arterioles, capillaries, and veins all have valves that allow only one-way flow of blood
Which of the following statements concerning regulation of blood flow is true?
Which of the following statements concerning regulation of blood flow is true?