During excitatory synaptic transmission, the electrical signal carried along the axon of a presynaptic neuron causes the release of neurotransmitters into the synapse and its subsequent reception by receptors on the postsynaptic neurons. The activation of receptors on the postsynaptic neurons then triggers the generation of the new action potential in that neuron.Both chemical and electrical neuronal signals are mediated by the movement of ions across the neuronal membrane. Which of the following correctly describes the movement of ions across neuronal membranes as an action potential is conducted down the neuron?- **A**: At rest, the internal side of the membrane has an overall positive charge, but as the action potential moves down the neuron, more ions flow out of the neuron to neutralize the membrane.- **B**: At rest, the internal side of the membrane has an overall positive charge, but as the action potential moves down the neuron, more ions flow into the neuron making the membrane more positive.- **C**: At rest, the internal side of the membrane has an overall positive charge, which intensifies the action potential.- **D**: At rest, the internal side of the membrane has an overall negative voltage. As the action potential moves down the neuron, the internal membrane becomes positive as ion channels open and ions flow into the neuron.

The point of electric nerve impulse transmission between two nerve cells (neurons), or between a neuron and a gland or muscle cell, is referred to as a synapse. It is also known as a neuronal junction (effector). A neuromuscular junction is a synaptic link between a neuron and a muscle cell. The receptors' shape is altered by the chemical binding action, which sets off a chain of events that causes channel-shaped protein molecules to open. The channels then allow electrically charged ions to enter or exit the neuron. The postsynaptic potential, or PSP, is the result of this abrupt alteration in the electric polarisation of the postsynaptic membrane. The PSP is excitatory if the net flow of positively charged ions into the cell is sufficient; in other words, it can cause the formation of a fresh nerve impulse known as an action potential.(d) At rest, the internal side of the membrane has an overall negative voltage. As the actionpotential moves down the neuron, the internal membrane becomes positive as an ionchannels open and ions flow into the neuron, is the correct statement.