Drag the labels onto the flowchart to show the sequence of events that occurs on

Under most circumstances, once an axon’s membrane potential reaches threshold (about -55 mV in mammals), an action potential is automatically triggered. The graph below shows the changes in membrane potential that occur in an axon membrane that is initially at resting potential.
 In response to a stimulus, the membrane slowly depolarizes until the membrane potential reaches a particular value, called threshold. At threshold, a rapid depolarization of the membrane occurs and an action potential is initiated.
Drag the labels onto the flowchart to show the sequence of events that occurs once the membrane potential reaches threshold
 
the first box says membrane potential reaches threshold
choices are
membrane potential rises, na ions rush in, many voltage gated na channels open, na ions rush out