Cardiac Cycle Research Paper

Oxygen poor blood fills the right atrium from either the superior or inferior vena cava.

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

The Q is the first wave downward, or negative, wave form of the QRS complex. The R wave is the first positive or upward, deflection. The R wave can occur with or without a Q wave. The T wave represents ventricular repolarization. The QT indicated the time from ventricular depolarization to repolarization. The wave of electricity it continues traveling through the myocardium to atrioventricular node. The AV node it coordinates the incoming electrical impulses from the atria and relays the impulse to the ventricles through a bundle of specialized muscle fibers. The atria pump blood into the ventricles and then the ventricles pump blood out of the heart. Chambers of the heart fill with blood during a relaxation phase diastole and eject blood during a contraction phase systole. Atrial

of atria and ventricle. Impulses not being transmitted from atria to the ventricle; no whole number relationship between atrial and ventricular contractions was demonstrated.

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.

Atrioventricular (AV) node: the area of the heart conduction system responsible for receiving impulses from the SA node via intermodal pathways and stimulate the ventricles to contract

Heart contraction is produced by stretching of sarcomere units, which produces strokes between myosin head and actin monomers located in the thin filament of sarcomere (Robinson, Dong et al. 2004). Changes in the resting tension of heart muscle affect the range of heart contraction. The heart has the capacity to adjust its contraction force as result of variations in ventricular filling (end-diastole), this effect is known as the Frank–Starling Law (Sequeira and van der Velden 2015). An increased systolic contraction is the results of the ventricle stretching due to greater end-diastolic volume happens (Schneider, Shimayoshi et al. 2006). However,

“An electrical signal from the ventricles causes an early heart beat that generally goes unnoticed”

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 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.

Cardiac suction- during ventricular systole, the teninous cords pull the Av valve cusps downward, slightly expanding the atrial space. This creates a slight suction that draws blood into the atria and pulmonary veins.

For starters the SA node is set in the posterior wall of the right atrium that is close to the entrance of the superior vena cave. Then with the SA node it contains many pacemaker cells, which establishes the person’s heart rate. Also it is known as the cardiac pacemaker (natural pacemaker). It is connected to the ‘large AV node which is by the internodal pathways within the arterial walls. Also it shows the action takes just about 230 msec to pass through the SA node to AV node the length of these pathways. Once it passes by the conduction cells exceed the motivation of contractile cells of mutually atria. After this action it spreads from one side to the other to the atrial surfaces by cell-to-cell contact. As the stimulus only affects

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.

In invertebrates, the electrical impulses that prompt contraction come directly from the nervous system, however, in vertebrates a group of cells known as the sinoatrial (SA) node is responsible for generating the initial signal. For this reason, the SA node is often referred to as the natural pacemaker. The SA node will begin to be activated when the vena cave fills the right atrium with deoxygenated blood from the body.4 This signal causes the valves to open, the atria to contract which pushes the blood flow to the ventricles and the signal is transferred to the atrioventricular (AV) node.4