What causes cardiac excitability?
Cardiac excitability arises from organized flow of ionic currents through ion-specific channels in the cell membrane, through the myoplasm and gap junctions that connect cells, and through the extracellular space (22).
What is myocardial excitability?
Cardiac excitability, as mentioned, is the ability of cardiac cells regeneratively to depolarize and repolarize during the action potential, as well as the ease with which electrical activity propagates from cell to cell.
What are the four properties of cardiac muscle?
The physiological properties of the cardiac muscle are: 1. Rhythmicity 2. Excitability 3….6.10).
- SA Node: Under normal conditions, electrical activity is spontaneously generated by the SA node, the physiological pacemaker.
- Internodal Tracts:
- AV Node:
- Bundle of His:
- Purkinje Fibers/Ventricular Myocardium:
What is the action potential of cardiac muscle?
The cardiac action potential is a brief change in voltage (membrane potential) across the cell membrane of heart cells. This is caused by the movement of charged atoms (called ions) between the inside and outside of the cell, through proteins called ion channels.
What is paroxysmal arrhythmia?
Paroxysmal supraventricular tachycardia (PSVT) is a type of abnormal heart rhythm, or arrhythmia. It occurs when a short circuit rhythm develops in the upper chamber of the heart. This results in a regular but rapid heartbeat that starts and stops abruptly.
What happens when depolarization occurs in heart?
Pacemaker Cells Phase zero is the phase of depolarization. This phase starts when the membrane potential reaches -40 mV, the threshold potential for pacemaker cells. There is the opening of voltage-gated Ca2+ channels on reaching the threshold, causing the influx of Ca2+ ions.
What is the supernormal phase of excitability?
The supernormal phase is that stage of enhanced excitability near the end of the relative refractory period in both nerve and myocardium when subthreshold stimuli can elicit a response. This condition of higher excitability which follows the vulnerable phase coincides with the negative after-potential.
What are the function of cardiac muscle?
12.1. 1.1 Cardiac muscle. Cardiac muscle tissue forms the muscle surrounding the heart. With the function of the muscle being to cause the mechanical motion of pumping blood throughout the rest of the body, unlike skeletal muscles, the movement is involuntary as to sustain life.
What is cardiac muscle and its function?
Cardiac muscle tissue is a specialized, organized type of tissue that only exists in the heart. It is responsible for keeping the heart pumping and blood circulating around the body. Cardiac muscle tissue, or myocardium, contains cells that expand and contract in response to electrical impulses from the nervous system.
What are the phases of the cardiac action potential?
The action potential in typical cardiomyocytes is composed of 5 phases (0-4), beginning and ending with phase 4.
- Phase 4: The resting phase.
- Phase 0: Depolarization.
- Phase 1: Early repolarization.
- Phase 2: The plateau phase.
- Phase 3: Repolarization.
What are the phases of action potential?
An action potential is caused by either threshold or suprathreshold stimuli upon a neuron. It consists of four phases: depolarization, overshoot, and repolarization. An action potential propagates along the cell membrane of an axon until it reaches the terminal button.
What does paroxysmal AFib feel like?
Paroxysmal AFib You may feel your heart palpitating or get the sensation that your heart is skipping a beat every now and then. This kind of AFib tends to be unpredictable. Paroxysmal AFib can sometimes go away if you make the right lifestyle adjustments or get the right medication from your doctor.
What is cardiomyopathy and what are the symptoms?
Cardiomyopathy refers to diseases of the heart muscle. These diseases have many causes, signs and symptoms as well as treatments. In most cases, cardiomyopathy causes the heart muscle to become enlarged, thick or rigid.
How does hypertrophic cardiomyopathy affect the heart?
The thickened heart muscle can make it harder for the heart to work properly. Hypertrophic cardiomyopathy can develop at any age, but the condition tends to be more severe if it becomes apparent during childhood. Most affected people have a family history of the disease, and some genetic mutations have been linked to hypertrophic cardiomyopathy.
What is restrictive cardiomyopathy?
Restrictive cardiomyopathy. In this type, the heart muscle becomes rigid and less elastic, so it can’t expand and fill with blood between heartbeats. This least common type of cardiomyopathy can occur at any age, but it most often affects older people.
Is there a cure for cardiomyopathy?
For other people, the disease develops quickly, symptoms are severe, and serious complications occur. Treatments for cardiomyopathy include lifestyle changes, medicines, surgery, implanted devices to correct arrhythmias, and a nonsurgical procedure.