The Pacemaker

If a pacemaker is implanted to control Greg’s heart rate, what life changes will be forced upon him? Do you think Greg will ever play competitive sports again?

In the normal conduction of the heart the electrical impulse starts in the SA node, also called the pacemaker of the heart. The electrical impulse travels through the right atrium and through the Bachmann’s bundle into the left atrium. This stimulates the atria to contract. Next the signal travel to the AV node. The AV node slightly delays the signal. This delay is needed for the heart to beat properly. Without this delay the atria and ventricles would beat at the same time. The electrical signal then travels to the Bundle of His where it is split into the signals going to the right and left ventricle. The signal

In normal heart activity, the ventricles are depolarized by the depolarization wave spreading from the atria.

In a healthy heart, the sinoatrial node sends an electrical impulse through the atria to contract and pump blood into the ventricles. During atrial fibrillation the normal function of the heart is disrupted. It starts with a chaotic electrical discharge in the atria of the heart, which then causes an irregular, rapid atrial contraction – which leads to rapid ventricular conduction in the AV node. Diseases that damage the heart or abnormalities of the heart’s structure are the most common cause of atrial fibrillation.

The heart is able to do this thanks to the specialized cardiac muscle it contains. The contraction of the heart displays excitatory- contraction coupling (EC coupling) similar to skeletal muscles except the action potential in the heart originates spontaneously at the peace maker of the heart (Silverthorn, 2013). Contraction happens when a rapid depolarization occurs due to the influx and opening of sodium voltage gated channels to raise the membrane potential toward the threshold value causing a firing of action potential. The conduction and cardiac cycle starts at a resting distol state for both ventricles and atriums and is initiated with the depolarization at the SA node (Silverthorn, 2013). This causes an action potential which moves rapidly towards the AV node where the signal gets slowed down (Silverthorn, 2013).When the signal reaches this point it causes a contraction/systole stage of the right and left atriums. This causes blood to be pumped into the ventricles through the AV valves (Silverthorn, 2013). The action potential then travels to the ventricles down the bundle branches out towards the Purkinje fibers (Silverthorn, 2013). In terms of the cardiac cycle an isovolumetric contraction occurs during the pause of the signal at the AV node allowing the AV valves to close, followed by ventricular systole where the ventricles expel blood into circulation (Silverthorn, 2013). The final stage in the cardiac cycle occurs between stimulations of action potential when the ventricles and atriums are in diastole and the chambers fill with blood once again (Silverthorn,

The main points are why I have a pacemaker, and how I overcame the obstacle today. This will provide the reader with insight. Understanding how the device helps improve my daily quality of life is a key factor of the essay. The pacemaker became a big deal again last year when my ten-year old pacemaker stopped working and the battery went dead. I had to get a bigger, new device implanted. Both surgeries at age six and sixteen caused me to have a lot of pain. Because I had the surgeries, I was able to thrive and go on energetically with my life. The purpose of this essay is to prove how my pacemaker helps me in life.

There are multiple parts of the heart that plays a role in the electrical conduction of the heart. First off is the SA node which is commonly known as the pacemaker of the heart - this can be found in the right atrium inferior to the superior vena cava. This node sends electrical impulses (to both atria) to tell the heart to expand and contract. On the opposite side of the right atrium is located the AV node which makes sure all the blood is in the ventricle before they

Doctors are able to view a patient’s heart activity through the use of an electrocardiograph or ECG. The ECG is configured with 3 leads that measure changes in electrical voltage; these changes are associated with specific parts of the cardiac excitation process. Doctor’s often look at these ECGs to determine if the heart is functioning properly. A standard sinus rhythm contains P, Q, R, S, and T waves that all occur at specific points and form a defined shape. When there is an abnormality in these waves, physicians know the heart is not functioning correctly and they attempt to diagnose the problem. One abnormality is called sinus arrest. Sinus arrest means the SA node is not firing the initial action potential to depolarize the rest of the heart.

I was in the morning in the operating room observing procedures such as sterilization and pacemaker placement and change of batery of a pacemaker. I evaluated the process post operative and the follow up offered to the patient after reaching the recovery area. I was able to evaluate all the documentation that is done. They explained the importance of the informed consent that must be signed before the surgery and that the patient understands his surgery. Later I went to the emergency room observing and evaluating the realization of triage. Seeing the different types of triage between a patient walking in and sign in and wait to be called and a patient coming in by ambulance.

The SA node is the primary pacemaker of the heart. It starts the heartbeat by spontaneously contracting, causing the rest of the heart to contract in a wave.

The S-A node signal is delayed by the atrioventricular node to allow the full contraction of the atria that allows the ventricles to reach their maximum volume. A sweeping right to left wave of ventricular contraction then pumps blood into the pulmonary and systemic circulatory systems. The semilunar valves that separate the right ventricle from the pulmonary artery and the left ventricle from the aorta open shortly after the ventricles begin to contract. The opening of the semilunar valves ends a brief period of isometric (constant volume) ventricular contraction and initiates a period of rapid ventricular ejection.

An example of a pacemaker potential is shown in Figure 1. The potential goes from slow depolarization to rapid depolarization to a peak and lastly to a repolarization phase. In the slow depolarization phase, funny channels, which are special slow sodium channels found in the pacemaker cells, open and Na+ flows in and depolarizes until threshold is reached. In the rapid

This allows your cardiovascular centres in your brain a little bit more latitude as far as controlling your heart rate. If you were to remove a beating heart from someone's body you would find that the heart is no longer being suppressed by the parasympathetic nervous system and it will accelerate to the same pace as the sinoatrial node. The SA node generates action potentials approximately 100 times per minute due to the physiology of the heart, its own permeability to sodium and calcium via its channels, and a host of other things. Anywhere between 80 to 100 beats per minute is normal for the SA node.

The atria and ventricles are relaxing. The atria are filling with blood from the veins and the ventricles just completed a contraction. The ventricles relax and the right AV valves open. When the heart rate increases atrial systole begins, which causes a contraction that pushes blood into the ventricles. The atria is contracting causing the depolarization wave to move through the cells of the AV node then down the Purkinje fibers to the apex of the heart. Ventricular systole begins as the muscle squeezes the blood toward the base. The blood being pushed along the AV valves cause them to close. This causes a vibration of the AV valve and creates the first heart sound S1. S1 is the lub sound heard when the AV valves close. This indicates

While contraction in skeletal muscle is triggered by motor neurons under central control, certain cardiac muscle variants exhibit autorhythmicity. This means that that they are capable of producing their own depolarizing electrical potential. The cardiomyocytes that are capable of producing their own electrical potentials are found in what is referred to as the electrical condition system of the heart. This system is comprised of specializes cardiomyocytes that are autorhythmic and are able to conduct electrical potentials rapidly. These specialized structures include the sinoatrial node, atrioventricular node and bundle, and Purkinje fibers.