At the end of each heartbeat, calcium is pumped back by a protein called SERCA along with its regulatory protein phospholamban. The calcium is then held within the sarcoplasmic reticulum by a protein called calsequestrin.Fine-tuning of this process can be achieved by phosphorylating these proteins. As an example, during exercise catecholamines activate beta-adrenoceptors on the cell surface, which trigger protein kinase A to phosphorylate the L-type calcium channel, increasing the flow of calcium into the cell. Simultaneously, phosphorylation of the regulatory protein phospholamban causes more calcium to be drawn up into the sarcoplasmic reticulum. The overall effect of this is to generate a larger calcium transient with each beat, leading to a more forceful contraction. Calcium-dependent arrhythmias
Alterations to the proteins involved in excitation-contraction coupling can disrupt this carefully regulated process. In those with CPVT, the normally tight regulation of calcium can become deranged, leading to arrhythmias. While calcium is generally released from the sarcoplasmic reticulum in response to an action potential, calcium sparks can also occur spontaneously. In a healthy heart, a spontaneous calcium spark is generally an isolated event and goes no further, but if ryanodine receptors or the proteins that regulate them are abnormal, these sparks can trigger releases from neighbouring ryanodine receptors which spread throughout the cell as a calcium wave. These calcium waves are much more likely to occur when cardiac muscle cells are stimulated by catecholamines such as adrenaline, which increase the concentration of calcium within the sarcoplasmic reticulum and sensitise the ryanodine receptors.
Popular Culture
A number of films and TV shows have portrayed individuals with a variety of phobic disorders. Movies
Benchwarmers –  Howie Goodman (Nick Swardson), portrayed as being agoraphobic and heliophobic. Television Shows
Monk – Adrian Monk (Tony Shalhoub) is a former homicide detective and a consultant for the San Francisco Police Department. He has an extreme case of OCD and is well known for his various fears and phobias, including (but certainly not limited to) heights, snakes, crowds, glaciers, rodeos, wind, and milk. Shameless (American TV Series) – Sheila Jackson (Joan Cusack) has agoraphobia and mysophobia (fear of germs). Research directions
Before the development of pharmacotherapy, the treatment of phobias and mental health disorders relied solely on therapy such as CBT. Although therapy can be incredibly effective for many, it does not always achieve the desired effect. Interventional psychiatry is an additional branch in medicine that has expanded treatment options, and further research continues to explore effectiveness and applications. Electroconvulsive Therapy (ECT) and Transcranial Magnetic Stimulation (TMS) are two examples of device-based interventions widely utilized. In terms of use in treating phobias and anxiety disorders as a whole, TMS is being explored as an augmentation option for those who do not have the desired response to other therapeutic options or side effects from medications. A majority of research has been conducted exploring the use of TMS in PTSD and generalized anxiety disorder.