The frontal lobe contains most of the dopamine-sensitive neurons in the cerebral cortex. The dopamine system is associated with reward, attention, short-term memory tasks, planning, and motivation. Dopamine tends to limit and select sensory information arriving from the thalamus to the forebrain.
Na + concentration is lowered, indicating that Na + in-flux is responsible for the rising phase of the action po-tential. Their data also suggested that the falling phaseof the action potential was caused by a later increase inK+ permeability.
The Na+ leaking into the cell (called the Na+ influx) causes the membrane potential to increase (become less negative). When the membrane potential crosses a threshold value (usually about -65mV), suddenly a whole lot more of Na+ channels are opened.There is a sudden rush of Na+ into the cell causing a rapid spike in the membrane potential. This can go up to 20mV. This influx of Na+ is the start of the action potential/impulse.When the voltage reaches the peak, Na+ channels are closed off due to the voltage. At the same time, these closed Na+ channels are inactivated temporarily and cannot be stimulated to open again. This is known as the absolute refractory period.ust think of it sitting there doing nothing. =p All cells have a membrane potential, which is the voltage across it's membranes. This is due to the difference in concentrations of ions inside and outside of the cells.