Brain in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials. Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell. Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication,
Electrical conduction system of the heart situated within the myocardium. There is a skeleton of fibrous tissue that surrounds the conduction system which can be seen on an ECG. Dysfunction of the conduction system can cause irregular, fast, or slow heart rhythms. Electrical signals arising in the SA node (located in the right atrium) stimulate the atria to contract. Then the signals travel to the atrioventricular node (AV node), which is located in the interatrial septum. After a delay, the electrical signal diverges and is conducted through the left and right bundle of His to the respective Purkinje fibers for each side of the heart, as