"what ion movement changes the membrane potential in a contractile cell from negative to positive? "

INFLUX OF SODIUM IONS changes the membrane potential in a contractile cell from negative to positive.
At rest, the inside of a neuron is negatively charged while the outside is positively charged. The inflow of sodium ions into the neuron will cause the inside of the neuron to become positively charged.

Except hold on to his or her beliefs even if there is no evidence for those beliefs.

Fungi is were it belongs