What is the function of the refractory period in the myocardial contractile cells?
What is the function of the refractory period in the myocardial contractile cells?
Contractile cells have an action potential with an extended plateau phase that results in an extended refractory period to allow complete contraction for the heart to pump blood effectively.
What is cardiac refractory period?
The functional refractory period (FRP) is the shortest interval between two consecutively conducted impulses out of a cardiac tissue resulting from any two consecutive input impulses into that tissue (i.e., the shortest output interval that can occur in response to any input interval in a particular tissue).
What is the role of calcium in cardiac muscle action potentials?
These calcium ions are responsible for the contraction of the heart. The movement of all of these ions results in the membrane potential remaining relatively constant. This phase is responsible for the large duration of the action potential and is important in preventing irregular heartbeat (cardiac arrhythmia).
What is the significance of the refractory period in an axon?
These transitory changes make it harder for the axon to produce subsequent action potentials during this interval, which is called the refractory period. Thus, the refractory period limits the number of action potentials that a given nerve cell can produce per unit time.
What happens when the bundle of His is completely interrupted?
effect of pacemaker …of conductive fibres called the bundle of His, which induces the contraction of the ventricles. When electrical conduction through the atrioventricular node or bundle of His is interrupted, the condition is called heart block.
What are the two types of cardiac cells?
There are two major types of cardiac muscle cells: myocardial contractile cells and myocardial conducting cells. The myocardial contractile cells constitute the bulk (99 percent) of the cells in the atria and ventricles.
What happens during the refractory period?
In physiology, a refractory period is a period of time during which an organ or cell is incapable of repeating a particular action, or (more precisely) the amount of time it takes for an excitable membrane to be ready for a second stimulus once it returns to its resting state following an excitation.
What happens during effective refractory period?
During phases 0, 1, 2, and part of phase 3, the cell is refractory to the initiation of new action potentials. This is termed the effective refractory period (ERP). During the ERP, stimulation of the cell does not produce new, propagated action potentials.
What is a major difference between depolarization of cardiac cells and depolarization of neurons?
In nerve and muscle cells, the depolarization phase of the action potential is caused by an opening of fast sodium channels. This also occurs in non-pacemaker cardiac cells; however, in cardiac pacemaker cells, calcium ions are involved in the initial depolarization phase of the action potential.
What is the importance of refractory period?
The refractory period limits the rate at which action potentials can be generated, which is an important aspect of neuronal signaling. Additionally, the refractory period facilitates unidirectional propagation of the action potential along the axon.
What would be the effect of the neuron if there was no refractory period?
An important effect of the refractory period is that it regularizes the spike train: i.e., a neuron having a refractory period but otherwise the same mean ISI as a neuron without refractory period will have a more regular spike train.
Why is it called a bundle of His?
These specialized muscle fibers in the heart were named after the Swiss cardiologist Wilhelm His Jr., who discovered them in 1893.
Why does cardiac muscle have a long refractory period?
In contrast, because of the long plateau in the cardiac- muscle action potential, the absolute refractory period of cardiac muscle lasts almost as long as the contraction (250 ms), and the muscle cannot be re-excited in time to produce summation (Figure 14-23).
What is the significance of the refractory period?
After an action potential initiates, the cardiac cell is unable to initiate another action potential for some duration of time (which is slightly shorter than the “true” action potential duration). This period of time is referred to as the refractory period, which is 250ms in duration and helps to protect the heart.
When does the muscle cell return to its resting length?
This returns the cell to its resting, non-contracted, length. During the third stage, repolarization, there is a time period during which the muscle cell cannot respond to any stimulus. This time of non-responsiveness is called the refractory period.
Why are cardiac muscles rich in mitochondria and nuclei?
Cardiac muscles are rich in mitochondria because the heart is always contracted (needs ATP), low nuclei. Action potential in the skeletal muscles has two phases: (1) Depolarization phase due to Na+ influx.
