Heart rate persons with coronary artery disease. The heart rate is rhythmically generated by the sinoatrial node. It is also influenced by central factors through sympathetic and parasympathetic nerves. Nervous influence over the heartrate is centralized within the two paired cardiovascular centres of the medulla oblongata. The cardioaccelerator regions stimulate activity via sympathetic stimulation of the cardioaccelerator nerves, and the cardioinhibitory centers decrease heart activity via parasympathetic stimulation as one component of the vagus nerve. During rest, both centers provide slight stimulation to the heart, contributing to autonomic tone. This is a similar concept to tone in skeletal muscles. Normally, vagal stimulation
Brain heart infusion settings. A number of fastidious organisms, including some bacteria, yeasts, and other fungi, grow well on BHI. It can also be used to differentiate between enterococci and group D streptococci. The earliest version of brain heart infusion media was made in 1919 when Edward Rosenow combined dextrose broth with calf brain tissue to grow streptococci. This was modified in 1923 by Russell Haden while working on dental pathogens. Modern BHI typically uses an infusion from porcine brains and hearts rather than calf brain tissue, and uses disodium phosphate as a buffer, rather than the calcium carbonate used by Rosenow and