Heart Physiology Quiz

<p>The electrical coupling of cardiac muscle cells (B)</p> Signup and view all the answers

<p>Coronary arteries (D)</p> Signup and view all the answers

<p>-60 mV (B)</p> Signup and view all the answers

<p>They become inactive. (A)</p> Signup and view all the answers

<p>Voltage gated Ca2+ channels (D)</p> Signup and view all the answers

<p>They have a larger diameter. (D)</p> Signup and view all the answers

<p>0.06 seconds (B)</p> Signup and view all the answers

<p>Decreases the rate of rhythm of the sinus node (C)</p> Signup and view all the answers

<p>To enhance fast conduction of action potentials (A)</p> Signup and view all the answers

<p>It has primarily voltage gated Ca2+ channels that permit conduction. (C)</p> Signup and view all the answers

<p>It restores the negative resting membrane potential. (D)</p> Signup and view all the answers

<p>Epinephrine (D)</p> Signup and view all the answers

<p>Voltage produced by heart muscle fibers during each heartbeat. (C)</p> Signup and view all the answers

<p>Location and progress of ischemic damage. (A)</p> Signup and view all the answers

<p>A measurement of both force and direction. (D)</p> Signup and view all the answers

<p>Unipolar limb leads (D)</p> Signup and view all the answers

<p>Enlargement and damaged regions of the heart. (D)</p> Signup and view all the answers

<p>Closure of Ca2+ channels and removal of Ca2+ from cytosol. (C)</p> Signup and view all the answers

<p>To measure voltage differences between two electrodes on limbs. (D)</p> Signup and view all the answers

<p>Lead I (B)</p> Signup and view all the answers

<p>V1 and V2 (C)</p> Signup and view all the answers

<p>Biphasic (A)</p> Signup and view all the answers

<p>1 second (D)</p> Signup and view all the answers

<p>Each interval between dark lines represents 0.20 seconds. (A)</p> Signup and view all the answers

<p>V4 (D)</p> Signup and view all the answers

<p>Between the left leg and right arm (A)</p> Signup and view all the answers

<p>SV increases due to a greater force of contraction. (A)</p> Signup and view all the answers

<p>Degree of stretch of cardiac muscle cells. (B)</p> Signup and view all the answers

<p>It increases contractility by stimulating B1 receptors and raising intracellular calcium levels. (C)</p> Signup and view all the answers

<p>It is the pressure that must be overcome before the semilunar valve opens. (B)</p> Signup and view all the answers

<p>It increases EDV by enhancing venous return to the heart. (B)</p> Signup and view all the answers

<p>It decreases contractility by lowering intracellular calcium concentration. (B)</p> Signup and view all the answers

<p>Stroke volume decreases due to reduced ventricular filling time. (D)</p> Signup and view all the answers

<p>Increased preload increases the force of contraction. (D)</p> Signup and view all the answers

<p>Speeds up the rate of spontaneous depolarization (D)</p> Signup and view all the answers

<p>Lowers heart rate by hyperpolarizing the SA node (B)</p> Signup and view all the answers

<p>Leads to cardiac flaccidity and weak heartbeats (D)</p> Signup and view all the answers

<p>By increasing Ca2+ entry through voltage-gated slow Ca2+ channels (C)</p> Signup and view all the answers

<p>Decrease in heart rate to between 20 to 40 beats per minute (C)</p> Signup and view all the answers

<p>Potassium (K+) (C)</p> Signup and view all the answers

<p>Acetylcholine (Ach) (C)</p> Signup and view all the answers

<p>They enhance cardiac contractility and increase heart rate (B)</p> Signup and view all the answers

Specialized junctions that connect adjacent cardiac muscle cells, allowing for mechanical and electrical coupling.

Gap junctions within intercalated discs provide low-resistance pathways for electrical signals to pass between heart cells, ensuring synchronized contraction.

Desmosomes within intercalated discs provide strong mechanical connections, preventing cells from pulling apart during contraction.

A network of specialized pacemaker cells within the heart that generate and conduct electrical impulses, initiating and regulating heart contractions.

The heart acts as a single functional unit due to the electrical connections between its cells, allowing coordinated and synchronized contractions throughout the chambers.

The resting potential of a sinus nodal fiber is much less negative (-60 mV) compared to a ventricular muscle fiber (-90 mV).

Fast sodium channels inactivate at -55 mV, only slow sodium channels open, causing an action potential.

The AV node is specialized for slow conduction, relying on voltage-gated calcium channels for depolarization.

The bundle branches are specialized for fast conduction, passing impulses from the AV node to the ventricles.

The Purkinje fibers distribute the electrical signal from the apex of the heart to the ventricular myocardium, ensuring coordinated contraction.

Vagal nerve stimulation releases acetylcholine, which slows the heart rate and decreases excitability of the AV junctional fibers, ultimately reducing heart rate.

The opening of voltage-dependent potassium channels causes repolarization, returning intracellular potential to its negative resting level, ending the action potential.

The opening of voltage-gated calcium channels allows calcium influx, which triggers depolarization, leading to the action potential.

Electrical potential difference between the left arm and right arm.

Electrical potential difference between the right arm and the left leg.

Electrical potential difference between the left arm and the left leg.

Represents 1 mV on the ECG.

Represents 0.2 seconds on the ECG.

Represents 0.04 seconds on the ECG.

Electrodes placed on the chest surface to record electrical activity.

Electrodes are placed on the limbs, recording electrical activity from different sides of the heart.

The outflow of potassium ions (K+) from the cardiac muscle cell helps to restore the negative resting membrane potential (RMP) of -90 mV, contributing to the repolarization phase of the action potential.

Calcium channels in the sarcolemma and sarcoplasmic reticulum (SR) close, removing calcium ions (Ca2+) from the cytosol and contributing to repolarization. This is especially important after an action potential and for muscle relaxation.

The electrocardiogram (ECG) is a recording of the electrical activity of the heart over time, measured at the surface of the body.

The ECG uses electrodes to detect changes in electrical potential in the heart, which are then displayed on a graph, showing a series of waves representing different stages of electrical activity.

The ECG is a valuable tool for diagnosing various heart conditions, such as arrhythmias, heart attacks, and heart enlargement.

The ECG depicts a series of waves, each corresponding to a specific electrical event in the heart: P-wave, QRS complex, and T-wave.

The ECG is used to assess the heart's rate, rhythm, and electrical conduction pathways, providing valuable insights into the health of the heart.

The ECG helps determine the relative size of the heart chambers. A larger than expected size can indicate hypertrophy or other issues.

The relationship between muscle stretch (preload) and the force of contraction. A stretched muscle contracts more powerfully than an unstretched one.

The volume of blood in the ventricle at the end of diastole (relaxation). It is determined by venous return and ventricular filling time.

The Frank-Starling Law describes the heart's intrinsic ability to adapt to changing blood volumes. Increased EDV stretches the heart muscle, leading to a greater force of contraction and increased stroke volume.

Factors that influence the contractile force of the ventricular myocardium. Positive inotropic agents increase stroke volume, while negative inotropic agents decrease it.

The pressure that the ventricle must overcome to open the semilunar valve and eject blood into the aorta. It is influenced by the pressure in the aorta.

The amount of blood ejected from the ventricle with each beat. It is determined by preload, contractility, and afterload.

The percentage of blood ejected from the ventricle with each beat. It is calculated as SV divided by EDV.

Positive ionotropic agents increase stroke volume by enhancing the force of contraction. Examples include norepinephrine and cardiac glycosides.

Norepinephrine (NE) increases the rate of spontaneous depolarization in the SA and AV nodes, leading to faster heart rate.

Norepinephrine (NE) enhances calcium entry into cardiac muscle fibers, increasing contractility and the amount of blood ejected during each heartbeat.

The parasympathetic nervous system, via the vagus nerve, decreases heart rate by slowing the rate of spontaneous depolarization in the SA node.

Acetylcholine released by the vagus nerve causes hyperpolarization of the SA node, leading to a slower heart rate.

Hypoxia, Acidosis, and Alkalosis all negatively affect cardiac function. They decrease heart rate and contractility.

Epinephrine, Norepinephrine, and Thyroid hormones increase heart rate and contractility by enhancing calcium entry into cardiac muscle fibers.

Elevated potassium levels (K+) decrease heart rate and contractility by interfering with the generation of action potentials in the heart.

Moderate calcium levels increase heart rate and strength of contraction, while excess calcium causes spastic contractions, and deficiency leads to weakness and flaccidity similar to high potassium levels.