What is supernormal conduction?
Abstract. Electrocardiographic manifestation of “supernormal” conduction is defined as conduction that is more rapid than expected or presence of conduction when block is anticipated. It is not supernormal in the sense or being more rapid than normal.
What is supernormal excitability?
The term supernormal excitability refers to a reduced current requirement to excite a tissue at a specific period of its activity cycle. Periods of supernormal excitability were first described for nerve in 1912 by Adrian and Lucas (4) and for heart muscle in 1938 by Hoff and Nahum (158).
What is the supernormal period?
supernormal period in electrocardiography, a period at the end of phase 3 of the action potential during which activation can be initiated with a milder stimulus than is required at maximal repolarization, because at this time the cell is excitable and closer to threshold than at maximal diastolic potential.
What is TMP in action potential?
The transmembrane potential (TMP) is the electrical potential difference (voltage) between the inside and the outside of a cell. When there is a net movement of +ve ions into a cell, the TMP becomes more +ve, and when there is a net movement of +ve ions out of a cell, TMP becomes more –ve.
What is ERP in pharmacology?
In electrocardiography, during a cardiac cycle, once an action potential is initiated, there is a period of time that a new action potential cannot be initiated. This is termed the effective refractory period (ERP) of the tissue.
What is refractory period in action potential?
An important characteristic of the action potential is the refractory period, which is the time after initiation of an action potential when it is impossible or more difficult to generate a second action potential.
What causes the supernormal period?
The supernormal period is always strictly related to the total refractory period and hence, to the duration of the action potential. Accordingly, supernormal excitability will occur earlier within the cardiac cycle with abbreviation of the refractory period at fast rates and later, at slow rates of stimulation.
What does supernormal growth mean?
Supernormal growth is a period of escalating earnings, for one year or more. Supernormal growth periods are unsustainable over the long-term as competition or market saturation eventually result in lower growth levels.
Why does hyperkalemia stop the heart?
High levels of potassium cause abnormal heart and skeletal muscle function by lowering cell-resting action potential and preventing repolarization, leading to muscle paralysis.
What is ERP and ARP?
This is termed the effective refractory period (ERP) of the tissue. This period is approximately equal to the absolute refractory period (ARP), it occurs because the fast sodium channels remain closed until the cell fully repolarizes.
What occurs during refractory period?
By definition, the refractory period is a period of time during which a cell is incapable of repeating an action potential. In terms of action potentials, it refers to the amount of time it takes for an excitable membrane to be ready to respond to a second stimulus once it returns to a resting state.
What is two stage growth model?
The two-stage growth model allows for two stages of growth – an initial phase where the growth rate is not a stable growth rate and a subsequent steady state where the growth rate is stable and is expected to remain so for the long term.
What is the difference between pacemaker potential and action potential?
Pacemaker cells generate spontaneous action potentials that are also termed “slow response” action potentials because of their slower rate of depolarization. These are normally found in the sinoatrial and atrioventricular nodes of the heart.
What is supernormal conduction in ECG?
Electrocardiographic manifestation of “supernormal” conduction is defined as conduction that is more rapid than expected or presence of conduction when block is anticipated. It is not supernormal in the sense or being more rapid than normal.
Is there a difference between supernormality and supernormal conduction?
Therefore, the term relative supernormality or “supernormality” is more appropriate. The mechanism of “supernormal” conduction is conduction during a period of supernormal excitability and conduction associated with altered membrane potential.
What is the gap phenomenon in a–V conduction?
The Gap Phenomenon The term gap in A–V conduction was originally used by Moe and his associates to define a zone in the cardiac cycle during which PAC failed to evoke ventricular responses, while PAC of greater and lesser prematurity conducted to the ventricles.