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.
As an action potential travels down the axon, there is a change in polarity across the membrane. The Na + and K + gated ion channels open and close as the membrane reaches the threshold potential, in response to a signal from another neuron.At the beginning of the action potential, the Na + channels open and Na + moves into the axon, causing depolarization.he course of the action potential can be divided into five parts: the rising phase, the peak phase, the falling phase, the undershoot phase, and the refractory period. During the rising phase the membrane potential depolarizes (becomes more positive). The point at which depolarization stops is called the peak phase.