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.
â¢ When the axon hillock is depolarized to threshold, an action potential is generated. Voltage-gated. channels open, thereby increasing permeability of the neuron first to sodium and then to. potassium. â¢ As sodium moves rapidly into the neuron, it produces the rising phase of the action potential. â¢ As the inward movement of sodium slows and the outward movement of potassium increases, the. membrane repolarizes.