The uncontrolled wave of calcium can be forced out through the cell membrane via the sodium-calcium exchanger, causing an electric current known as a delayed afterdepolarisation. Afterdepolarisations, if large enough, can trigger additional action potentials, premature ventricular contractions, or sustained arrhythmias. Causes
CPVT can be caused by mutations in several genes, all of which are responsible for regulating the concentrations of calcium within cardiac muscle cells. The most commonly identified genetic mutation in CPVT is a mutation in the RYR2 gene that encodes the cardiac ryanodine receptor, responsible for releasing calcium from the sarcoplasmic reticulum. Mutations associated with CPVT have also been identified in the CASQ2 gene which encodes calsequestrin, a protein that binds calcium within the sarcoplasmic reticulum. Other genes associated with rarer, atypical forms of CPVT include TECRL encoding Trans-2,3-enoyl-CoA reductase-like protein, CALM1, CALM2 and CALM3 all encoding Calmodulin, and TRDN encoding Triadin. CPVT1: RYR2 mutations
The most commonly identified genetic mutations in those with CPVT occur in the RYR2 gene which encodes the cardiac ryanodine receptor. Mutations in this gene lead to an autosomal dominant form of typical CPVT known as CPVT1. While the precise effect differs between specific mutations in this gene, many RYR2 mutations cause the ryanodine receptor to open in response to lower concentrations of calcium—the threshold for calcium release is lower. As a result, the sarcoplasmic reticulum spontaneously releases calcium through these abnormal ryanodine receptors when the concentration of calcium within the sarcoplasmic reticulum rises, a process known as store-overload induced calcium release.
Along with this path, there will be high-draw, high-impulse items that will influence the consumer to make purchases which they did not originally intend. Service areas such as restrooms are placed in a location which draws the consumer past certain products to create extra buys. Necessity items such as bread and milk are found at the rear of the store to increase the start of circulation. Cashiers desks are placed in a position to promote circulation. In most supermarkets, the entrance will be on the right-hand side because some research suggests that consumers who travel in a counter-clockwise direction spend more. However, other researchers have argued that consumers moving in a clockwise direction can form better mental maps of the store leading to higher sales in turn.The second principle of the layout is coordination. Coordination is the organized arrangement of product that promotes sales. Products such as fast-selling and slow-selling lines are placed in strategic positions in aid of the overall sales plan. Managers sometimes place different items in fast-selling places to increase turnover or to promote a new line. The third principle is consumer convenience. The layout of a supermarket is designed to create a high degree of convenience to the consumer to make the shopping experience pleasant and increase customer spending. This is done through the character of merchandising and product placement. There are many different ideas and theories in relation to layout and how product layout can influence the purchases made.