Av Node Analysis

When a stimulus is applied to smooth muscle, it causes an action potential, depolarizing the plasma membrane. Voltage gated calcium channels open allowing calcium into the cell. This increases calcium levels in smooth muscle cells.

Early doctors were researching arrhythmia in heart beat as a result of unknown abnormal neuro-cardio mechanisms of the heart, one of theories was that SA and AV nodes were interfering with each other’s bio-electrical impulses another theory was that the right side of the septum was hypersensitive to electrical impulse, all were more else on the right track because we know now that SVT is a result of a faulty electrical connections of the heart.

Next, to determine if contraction via the EMC pathway requires extracellular or intracellular calcium, the second type of stimulus was used and the tissue was stimulated using calcium free K+-depolarising solution. The bathing solution in this experiment was calcium free solution to make sure all extracellular calcium was eliminated, as without calcium, the EMC pathway is expected to produce no response.

The effects of a ligature around the AV groove presented no difference in the contraction of atria or ventricle after the first tightening. After the string was tightened further, the ventricular contractions were lost and the atria beat alone at 60 BPM. The AV signal between the chambers was blocked.

This stage is called repolarisation. The K+ channels then close, the sodium-potassium pump restarts, restoring the normal distribution of ions either side of the cell surface membrane and thus restoring the resting potential. In response to this the Na+ channels in that area would open up, allowing Na+ ions to flood into the cell and thus reducing the resting potential of the cells. If the resting potential of the cell drops to the threshold level, then an action potential has been generated and an impulse will be fired.

In a normal human being the heart correctly functions by the blood first entering through the right atrium from the superior and inferior vena cava. This blood flow continues through the right atrioventricular valve into the right ventricle. The right ventricle contracts forcing the pulmonary valve to open leading blood flow through the pulmonary valve and into the pulmonary trunk. Blood is then distributed from the right and left pulmonary arteries to the lungs, where carbon dioxide is unloaded and oxygen is loaded into the blood. The blood is returned from the lungs to the left

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

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

A: Each of the atrial paced impulses (S1) conducts anterogradely over the slow AVN pathway. The last paced impulse also conducts retrogradely up the fast AVN initiate typical AVNRT with RBBB. B: Each of the atrial paced impulses conducts anterogradely over the slow AVN pathway with a long PR interval resulting in crossing over, which can mimic a 1:2 AV. Following anterograde conduction down the slow pathway, the last paced impulse also conducts retrogradely over the fast pathway, initiating typical AVNRT. C: Atrial pacing from the coronary sinus ostium (CS os) induces typical AVNRT. The last paced impulse conducts over both the fast and slow AVN pathways resulting in a 1:2 response (i.e., 2 ventricular responses); this is followed by induction of typical AVNRT with RBBB (Issa et al,

When a membrane is excited depolarization begins. When the membrane depolarizes the resting membrane potential of -70 mV becomes less negative. When the membrane potential reaches 0 mV, indicating there is no charge difference across the membrane. the sodium ion channels start to close and potassium ion channels open. By the time the sodium ion channels finally close. The membrane potential has reached +35 mV. The opening of the potassium channels allows K+ to flow out of the cell down its electrochemical gradient ( ion of like charge are repelled from each other). The flow of K+ out of the cell causes the membrane potential to move in a negative direction. This is referred to as repolarization. ( Marieb & Mitchell, 2009). As the transmembrane potential comes back down towards its resting potential level and the potassium channels begins to close, the trasmembrane potential level goes just below -90mV, causing a brief period of hyperpolarization (Martini, Nath & Bartholomew, 2012). Finally, as the potassium channels close, the membrane turns back to its resting potential until it is excited or inhibited again.

The wave spreads through the atria before reaching the atrioventricular node, or AV node, located just above the right ventricle. The AV node focuses the wave into the ventricles, contracting the ventricles. Should the SA node fail, the AV node can take over as the primary pacemaker at a rate of forty to sixty beats per minute.

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.

• sinoatrial node- is the impulse-generating (pacemaker) tissue located in the right atrium of the heart, and thus the generator of normal sinus rhythm.

Action potentials in the heart start in the sinoatrial node and move to the atrioventricular node and to

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.