What is the path of the electrical impulse that travels through the heart causing the atrial-ventricular contraction?

What do scientists need to look at before developing an argument

What did hunter gathers do to alter the environment?

'which of these statements about the scientific method is not true? all experiments must follow the same number of steps in the procedure. experiments may be repeated several times. some unexpected results can be beneficial. experimental results may or may not support the hypothesis.