Cardiac Action Potentials and Conduction System

<p>The attainment of threshold potential (D)</p> Signup and view all the answers

<p>Their inactivation is time-dependent, not voltage-dependent (D)</p> Signup and view all the answers

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

<p>To create a delay between atrial and ventricular contractions (D)</p> Signup and view all the answers

<p>Both A and B (C)</p> Signup and view all the answers

<p>The AV node slowly propagates the AP (D)</p> Signup and view all the answers

<p>Rapid conduction through Purkinje fibers and myocytes (D)</p> Signup and view all the answers

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

<p>By providing specific timing between atrial and ventricular contractions (D)</p> Signup and view all the answers

<p>They contract simultaneously, emptying into the ventricles (A)</p> Signup and view all the answers

<p>Delivery of poorly oxygenated blood to the lungs (C)</p> Signup and view all the answers

<p>L ventricle → aorta → systemic vessels → vena cava (C)</p> Signup and view all the answers

<p>Delivers poorly oxygenated blood to the lungs (A)</p> Signup and view all the answers

<p>Beta1-adrenergic receptors (D)</p> Signup and view all the answers

<p>Left atrium (B)</p> Signup and view all the answers

<p>Acetylcholine (ACh) (B)</p> Signup and view all the answers

<p>Systemic circulation transports oxygenated blood to tissues (A)</p> Signup and view all the answers

<p>Increases heart rate and contractility (C)</p> Signup and view all the answers

<p>Right atrium → right ventricle → pulmonary artery (A)</p> Signup and view all the answers

<p>Pulmonary circulation (C)</p> Signup and view all the answers

<p>Alpha1-adrenergic receptors (A)</p> Signup and view all the answers

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

<p>Decrease heart rate (A)</p> Signup and view all the answers

<p>Mean arterial pressure (MAP) will increase (A)</p> Signup and view all the answers

<p>By detecting atrial stretch and distention (C)</p> Signup and view all the answers

<p>Increases MAP and signals a reduction in MAP through reflex mechanisms (A)</p> Signup and view all the answers

<p>Stimulates parasympathetic signaling to decrease MAP (C)</p> Signup and view all the answers

<p>There is an increase in ventricular chamber pressure (C)</p> Signup and view all the answers

<p>Minimizes deviations from normal but does not return to normal (C)</p> Signup and view all the answers

<p>Closing of the AV valves (D)</p> Signup and view all the answers

<p>Ventricular filling is completed (D)</p> Signup and view all the answers

<p>Closing of the AV valve (C)</p> Signup and view all the answers

<p>After the AV valve closes and before the aortic valve opens (C)</p> Signup and view all the answers

<p>It increases significantly during ventricular contraction (B)</p> Signup and view all the answers

<p>The ventricular pressure decreases (A)</p> Signup and view all the answers

<p>End of systole, beginning of diastole (B)</p> Signup and view all the answers

The movement of blood throughout the body, powered by the heart, delivering oxygen and nutrients while removing waste products.

The circuit of blood flow from the heart to the lungs and back, where oxygen is picked up and carbon dioxide is released.

The circuit of blood flow from the heart to the rest of the body and back, delivering oxygen and nutrients to tissues and removing waste products.

The right ventricle pumps deoxygenated blood to the lungs through the pulmonary artery.

Oxygenated blood returns from the lungs to the left atrium through the pulmonary vein.

The left ventricle pumps oxygenated blood to the rest of the body through the aorta.

Deoxygenated blood from the body returns to the right atrium through the vena cava.

The network of blood vessels, including arteries, veins, and capillaries, that transport blood throughout the body.

The SA node (Sinoatrial node) is a specialized group of cardiac muscle cells located in the right atrium of the heart. It acts as the heart's natural pacemaker, spontaneously generating electrical impulses that trigger the heart beat.

The SA node initiates an electrical impulse that travels rapidly across the atrial myocytes, causing both atria to contract almost simultaneously.

The AV node (Atrioventricular node) is located between the atria and ventricles. It serves as a gatekeeper, slowing down the electrical impulse to allow the atria to finish contracting before the ventricles begin.

The Bundle of His is a specialized pathway that carries the electrical impulse from the AV node to the ventricles. It's located in the septum separating the left and right ventricle.

The bundle branches are a group of fibers that spread from the Bundle of His, delivering the electrical impulse to the left and right ventricles, ensuring they contract effectively.

The Purkinje fibers are a network of specialized fibers that transmit the electrical impulse to the inner portions of the left and right ventricles, enabling a coordinated and powerful contraction.

The specialized conduction system of the heart, which includes the SA node, AV node, Bundle of His, Bundle branches, and Purkinje fibers, ensures that each heartbeat follows a specific sequence, allowing for efficient pumping of blood.

The coordinated action of the specialized conduction system results in a specific sequence of contractions in the heart: 1. Both atria contract, 2. A brief pause (slow propagation in AV node), 3. Both ventricles contract, 4. Relaxation and refilling of the heart.

A reflex that helps to regulate blood pressure by detecting changes in blood pressure within the cardiovascular system.

The baroreceptor reflex cannot restore normal blood pressure values, but it can minimize deviations from the norm.

A reflex that helps regulate blood volume by sensing changes in atrial stretch caused by variations in blood volume.

The AVRR helps restore blood volume to normal levels by regulating fluid intake and output.

The AVRR works by sending signals to the CNS, which then adjusts autonomic nervous system activity and impacts blood pressure.

The initial phase of an action potential in cardiac cells, characterized by a rapid rise in membrane potential due to the opening of voltage-gated sodium channels, leading to a large influx of sodium ions into the cell.

The brief plateau phase after the initial depolarization, caused by the inactivation of voltage-gated sodium channels and the opening of voltage-gated potassium channels, which allows potassium to exit the cell, slightly reducing membrane potential.

The period where voltage-gated potassium channels remain open, resulting in a sustained outflow of potassium ions, further decreasing the membrane potential closer to resting potential.

The final stage of the action potential where the membrane potential returns to its resting level, mainly due to the closure of potassium channels and the return of sodium channels to their resting state.

The state where the membrane potential remains at its resting level, ready for the next action potential. The sodium-potassium pump actively pumps sodium ions out of the cell and potassium ions back in, maintaining the concentration gradients essential for the next action potential.

A rapid increase in the electrical potential across the cell membrane during an action potential. This phase is primarily driven by the influx of sodium ions into the cell.

The period during the cardiac cycle when the heart muscle relaxes, allowing the chambers to fill with blood.

The period during the cardiac cycle when the heart muscle contracts, pumping blood out of the chambers.

The first heart sound, a 'lub' sound, that occurs when the atrioventricular (AV) valves close at the start of ventricular contraction.

The second heart sound, a 'dub' sound, that occurs when the semilunar valves close at the end of ventricular contraction.

The contraction of the heart muscle without a change in the volume of the ventricle. This happens briefly before the semilunar valves open.

Sympathetic nervous system activation increases heart rate and contractility through norepinephrine (NE) and epinephrine binding to beta1-adrenergic receptors on cardiac muscle cells. These receptors are Gs-linked G protein-coupled receptors (GPCRs), leading to increased cAMP production and activation of PKA, which ultimately enhances heart function.

Sympathetic nervous system activation leads to vasoconstriction in most blood vessels, particularly in the skin and internal organs, through alpha1-adrenergic receptors on vascular smooth muscle cells. These receptors are Gq-linked GPCRs, resulting in the activation of the phospholipase C pathway, ultimately leading to vasoconstriction.

Parasympathetic nervous system activation decreases heart rate through acetylcholine (ACh) binding to M2 muscarinic receptors on cardiac muscle cells. These receptors are Gi-linked GPCRs, leading to a decrease in cAMP production and inhibition of PKA, ultimately slowing down heart rate.

Parasympathetic nervous system activation can lead to vasodilation in certain blood vessels, particularly in the skeletal muscles, through acetylcholine (ACh) binding to M3 muscarinic receptors on endothelial cells. These receptors are Gq-linked GPCRs, resulting in the activation of the phospholipase C pathway, ultimately leading to nitric oxide (NO) production and vasodilation.

The autonomic nervous system, composed of the sympathetic and parasympathetic branches, plays a crucial role in regulating blood pressure by influencing heart rate, contractility, and blood vessel diameter. However, it doesn't initiate heart muscle contraction.