First of all, calcium channels are the channels that present on the membrane where they have the ability and responsibility to produce the physiological changes in the body and there are many changes that are enhanced from the potential of the channel to form actions on the body physiologically such as the contraction of the muscles, the secretion of the hormones, the ability to regulating the gene expression in the genome and so on.these different physiological actions are depending on the type of the calcium channel and here is the types of the calcium channels.
The types of calcium channels are classified under three classes first class is voltage sensitive calcium channel which has the abbreviation which is (VSCCs) the second class is the receptor-operated-gated ion channel and third and final class in known as the leaky channels. While describing the types of calcium channels is actually undergoes five types which are L-type calcium channel which actually known as the long lasting AKA/DHP receptor.
Secondly is the P-type calcium channel and sometimes the used the letter Q to describe it and the called as Q-type calcium channel, thirdly, will be the N-type calcium channel which is received the name from the Neural where it is describing the specifically the effects on neural properties, fourthly, R-type calcium channel and finally the T-type calcium channel and these are the general types of calcium channels where they are present in the several sites on the body.
While, specifically the types of the upper described types that are present in the cardiovascular system specifically which are the T-type calcium channels which has the full name which is called as the transient type and the L-type which has the full name which is called as low threshold type calcium channels where they are present mainly the muscles of the heart which is called cardiac myocytes ,but the L-type specifically present in the all cardiac or heart cells, while the T-type is actually mainly present in the pacemakers, atrial and also the purkinje cells where is these two types regulating the balance between diastole and systole and also the excitation and contraction of the cells.
The T-type calcium channel which is actually can be inactivated fast or rapidly where is the main reason of that is having the low-threshold which can directly inhibited by Ni and also amiloride and mibefradil. Secondly, the activation and inactivation process that is actually happen in this channel is depending on having or the present of negativity in the action potential in its charge. While, the type L-type calcium channel its activation and inactivation processes is actually depending on the positivity in contrast to the T-type where the positivity is needed for this channel to complete its actions.
The two types of channels that are actually present in the cardiovascular system they are functioning generally to regulate and manage many functions of the body such as the vascular tone which is actually the flexibility of the blood vessels, the signal conduction which means that the signals that electrically reaching the body thorough passing the synapse from one nerve to the other, the function of cardiac pacemaking where these pacemakers are actually such a mass that is specific and formed of muscle which is full of tissues where they are present in the heart as a rhythm to contracting the heart or relaxing the heart to produce the heartbeats that are needed, and finally secreting the specific transmitters intracellularly.
Examples of the transmitters that are secreted in the cardiovascular system are atrial natriuretic peptide which has the abbreviation (ANP) and secondly the brain natriuretic peptide (BNP) and they both work as the cardiac hormones, But specifically, they both have different and specific functions where they play them on the cardiovascular system. First, L-type calcium channel is actually working on the contractility of the muscles which means it is working to make the muscles of the heart which is called as myocardium and vascular muscle are able to be shrink and making the hole smaller in size.
Second, T-type calcium channel is actually working on the pacemaking and conducting of the cardiac cells where the pacemaking is actually the system that is used to send the signals to the heart and providing the rhythm of the heart while conducting is mainly such an electronic device that can be connected another system and reaching the signals there and also works on regulating the remodeling process that is actually happen to some cardiac diseases such as cardiac hypertrophy by regulating the normal and usual growth processes that is happened in the heart.
Generally, the structure of the calcium channels in the cardiovascular system is mainly consist of many of subtypes or in other words subunits which are the alpha subtype and auxiliary subtypes and the alpha subtype is actually the main and the primary subtype which is mainly responsible for the transmembrane pore on the surface of the cardiovascular system and it is actually the one responsible to determine the type of the calcium channels if they either T-type calcium channel or L-type calcium channel while the auxiliary subtypes are actually consist of many or group of subtypes which are β, α2δ, and γ and they known as the secondary subtypes because of their functions that are actually not basic to the channel to be functioning.
Specifically, the T-type calcium channel where its structure is consist of alpha subtype where it is actually consist of four domains and these domains are consisting of six transmembrane segments and the pore of alpha subtype in T-type is actually present between the fifth and sixth segments and this pore is lipophilic in nature while the fourth segment contains lots of amount of the positive charges and also work by these charges as a sensor to be opened or closed which means doing its function while the auxiliary subtypes which are α2δ where it is present in the extracellular part and the beta subtype is actually present in the intracellular part of the transmembrane and finally the lemda subtype which is responsible for the sensitivity of the channel where there is something touches the channel this subtype already working.
The L-type calcium channel where its structure is calles as heterotetrameric polypetide and it is called like that because of the prescence of four subtypes or subunits which are α1, α2/δ, β and they are the main subtypes of the L-type while the lemda subtype is known as secondary subtype so it is not present in the all tissues of the cardiovascular system and all bound tightly and strongly to the alpha one subtype which is the primary subtype. There are many of the activators which is actually the drugs that is called as the agonist of the calcium channels that is present in the cardiovascular system such as the 1,4-dihydropyridine
Which is a drug that is discovered lately or recently and has similar structure of the nifedipine which is work as an antagonist of the calcium channels ,but the drugs that have similar structures of either nifedipine or1,4-dihydropyridine so they said to be as a derivative that designed to be an activator of the calcium channels specifically on the L-type calcium channel such as Bay K8644 where it is open the calcium channel and allowing the ions to passed through.
As a result the calcium enters the cell and the amount or concentration of calcium is increased and sending many signals to producing many functions such as gene transcription, proliferation and cell migration while the calcium channel antagonist or in other words the blockers such as verapamil, diltiazem and nifedipine which are specifically inhibiting the L-type calcium channel in cardiovascular system where it can be useful in treat many of cardiac diseases or disorders such as cardiac arrythmia, angina of the heart, hypertension, peripheral vascular diseases, cardio protection and finally cardiomyopathy. These CCBs treat hypertension by relaxing the vascular smooth muscle of the cardiovascular system and that is done by decreasing the resistance where it is directly lowering the blood pressure.
Secondly, the mechanism of action that is done to treat the angina is by using the antianginal effects which are the vasodilator and cardiopressent actions by decreasing both the afterload and oxygen demand and finally treating the arrythmia its mechanism of action that is done by decreasing the firing rate and conduction velocity and then prolonging the repolarization phase of it. For the summarization the regulation is done by identifying the need of the cells to the calcium to be inside so depend on the disease if it needs the calcium to cause contraction by joining the myosin and actin or not needed.
The channel structure which is composed or consist of protein is actually related to the calcium channel functioning which are the subtypes of the channel and the channel is actually bounding to the receptor which is called as ryanodine receptor which allow the entering of calcium ions intracellularly where it is control or regulate the electrophysiological factors or properties of the cardiovascular system which basically controlling the cardiac contractility by a process called as excitation-contraction coupling process. Also, the inositol triphosphate is actually activating this process that is responsible to regulate the diastolic tone of the heart and activating it cause the contractility and the inositol triphosphate activation is really important for the signal transduction which is responsible mainly in the growth of the cells.
The calcium ions that enter the cells specifically by L-type calcium channel the is present in the sinoatrial node or SA node enhances the activity of the pacemaker while the ones that is present in the atrioventricular node or AV node is mainly enhancing the conduction of the AV. While these actions are less clear in the other type which is T-type calcium channel. Pathophysiology of calcium channels are coming where there is damaging of the channel as a result the functions that done normally in the cardiovascular system will be oppositely and harmfully done.
First, the calcium channels are responsible for generating the cardiac pacemakers actions which are actually done by SA node where they enhancing the diastolic depolarization having abnormal calcium channels and this abnormality is come because of the ankyrin B dysfunction as a result the SA node directly becomes abnormally functioning and then causing SAN diseases which is a cardiovascular disease.
Also, the dysregulation of the calcium channels of the cardiac myocytes which causes the overload of the calcium ions and then causing the plateau phase to become disrupted as a result the pacemaker will be directly does not work in the SA node where it will causes many of the cardiovascular diseases such as cardiac arrythmia, hypertension and angina pectoris ,too.
