 Blood pressure Bt is the pressure of circulating blood on the walls of blood vessels. Used without further specification, blood pressure usually refers to the pressure in large arteries of the systemic circulation. Blood pressure is usually expressed in terms of the systolic pressure maximum during one heartbeat over diastolic pressure minimum in between two heartbeats and is measured in millimeters of mercury MHHG above the surrounding atmospheric pressure. Blood pressure is one of the vital signs, along with respiratory rate, heart rate, oxygen saturation, and body temperature. Resting blood pressure in an adult is approximately 120 millimetres of mercury-16 kPa systolic, and 80 millimetres of mercury-11 kPa diastolic, abbreviated 120 over 80 MHHG. Traditionally, blood pressure was measured non-invasively using the mercury tube's FIG monometer, or an aneroid gauge, which is still generally considered to be the gold standard of accuracy for obscultatory readings. More recently others' amyl-automated methods have become common, largely due to concerns about potential mercury toxicity, although cost and ease of use have also influenced this trend. Early automated alternatives to mercury tube's FIG monometers are often seriously inaccurate, but validated devices allow for an average difference between two standardized reading methods of 5 millimetre HG or less and a standard deviation of less than 8 millimetre HG. Blood pressure is influenced by cardiac output, total peripheral resistance and arterial stiffness and varies depending on situation, emotional state, activity, and relative health-flash disease states. In the short term, blood pressure is regulated by barrel receptors which act via the brain to influence nervous and endocrine systems. Blood pressure that is low is called hypertension, and pressure that is consistently high is hypertension. Both have many causes and may be of sudden onset or of long duration. Long-term hypertension is a risk factor for many diseases, including heart disease, stroke and kidney failure. Long-term hypertension is more common than long-term hypertension, which often goes undetected because of infrequent monitoring and the absence of symptoms.