Exercise physiology loss of integrity to the blood brain barrier. Hyperthermia also can lower cerebral blood flow, and raise brain temperature. Researchers once attributed fatigue to a build-up of lactic acid in muscles. However, this is no longer believed. Rather, lactate may stop muscle fatigue by keeping muscles fully responding to nerve signals. The available oxygen and energy supply, and disturbances of muscle ion homeostasis are the main factor determining exercise performance, at least during brief very intense exercise. Each muscle contraction involves an action potential that activates voltage sensors, and so releases Ca ions from the muscle fibre’s sarcoplasmic reticulum. The
Hard currency its short history, however the European sovereign debt crisis has partially eroded that confidence. The Swiss franc (CHF) has long been considered a hard currency, and in fact was the last paper currency in the world to terminate its convertibility to gold. In the summer of 2011, the European sovereign debt crisis led to rapid flows out of the euro and into the franc by those seeking hard currency, causing the latter to appreciate rapidly. On September 6, 2011, the Swiss National Bank announced that it would buy an "unlimited" number of euros to fix an exchange rate at 1.00