c) What is the main mechanism contributing to the absolute refractory period in neurons: a) potassium ions can only flow outside the neurons. b) autoreceptors are inhibiting the opening of ionotropic...

Extracted text: c) What is the main mechanism contributing to the absolute refractory period in neurons: a) potassium ions can only flow outside the neurons. b) autoreceptors are inhibiting the opening of ionotropic sodium channels, c) the voltage-dependent sodium channels cannot be opened. d) the voltage-dependent potassium channels cannot be opened. e) there are too many sodium ions inside the cell to permit another action potential. f) undershoot hyperpolarization