The sodium-potassium pump moves three sodium ions out of the cell for every two potassium ions it moves in. ATP is used to accomplish this because the direction of movement for both ions is against their concentration gradients.

By removing three sodium ions for the entry of every two potassium ions, the pump creates an electrical imbalance: three positive charges exit the cell, but only two enter. There is a net movement of positive charge out of the cell, leading to the electrochemical gradient. The ion imbalance leads to the negative resting potential of the cell.

The question states that the sodium-potassium pump requires ATP, indicating that the pumping action uses energy and is classified as active transport. Recall that active transport involves movement of molecules against their electrochemical gradient. This means that the sodium and potassium ions are moved against their gradients. Since they are moving against their gradients, sodium and potassium ions must move from a region of low concentration to a region of high concentration.

The question states that sodium ions are moving from the inside to the outside of the cell; therefore, there must be a higher concentration of sodium ions outside the cell than inside the cell.

A dendrite carries electrical signals into the cell body of a neuron. This dendrite, however, is typically not myelinated like the axon. There are also frequently many dendrites, while a single axon is the typical rule. Different types of neural cells can carry different arrangements of dendrites depending on their function.

The axon ends in a terminal bud, which transmits signals to target cells by releasing neurotransmitters across the synapse. The soma is the body of the cell and contains the nucleus. This is where the majority of protein synthesis occurs. The dendrites receive electrochemical stimuli from other neurons and cells and transmit the signal to the soma and axon.

Na⁺/K⁺ ATPase always exports three sodium ions out of the cell and imports two potassium ions into the cell. The export of three positively charged sodium ions for the import of only two positively charged potassium ions results in a net -70mV charge across the cell membrane, which is known as the cell membrane resting potential.

All of the following are true characteristics of the neural axon and soma except “increased ribosomal activity in the axon hillock.” The axon hillock is a site of neurotransmitter transport. These molecules are produced and packaged in the soma of the neuron, before being translocated to the axon hillock via microtubule tracks. There is little to no ribosomal activity in the axon of a neuron, since most ribosomes are located near the nucleus of a cell, which is the site of mRNA release.

The enteric nervous system (ENS) is a component of the autonomic nervous system, which is a component of the peripheral nervous system. The ENS is responsible for innervating the digestive organs and, thus, regulating digestion.

The central nervous system is composed of the brain and spinal cord, while the peripheral nervous system prolifertates the body. The somatic nervous system is under voluntary control, while the autonomic is involuntary. The cranial nerves are a set of specialized nerves that branch directly off of the spinal cord.

Along with capillaries, the ependymal cells create the choroid plexus. The choroid plexus is responsible for synthesizing and secreting cerebrospinal fluid around the brain and the spinal cord. 

Calcium is a very common vehicle that drives membrane fusion, including the fusion of synaptic vesicles with the synaptic cell membrane. This allows the ejection of neurotransmitter into the synaptic cleft.

There are two types of synapses: the chemical synapse and the electrical synapse. Chemical synapses are more common than electrical synapses, and use neurotransmitters (chemicals) to propagate action potentials. Electrical synapses have tunnels between cells, called gap junctions, that quickly transmit signals from one cell to the other. Electrical synapses are found extensively in the heart, since it is essential to have quick signal transmission between cardiac cells.

In chemical synapses an action potential reaches the end of a presynaptic neuron, which causes neurotransmitters to be released from the presynaptic neuron. These neurotransmitters bind to receptors on the postsynaptic neuron and initiate a signal transduction pathway in the postsynaptic neuron. The space between the presynaptic and postsynaptic neuron is called the synaptic cleft. Synaptic clefts are important regions where neurotransmitters are released and regulated.

Calcium ions play an important role in chemical synapses. Once an action potential arrives at the presynaptic neuron terminal, calcium ion channels on the presynaptic neuron become permeable to calcium ions. This facilitates the movement of calcium ions into the presynaptic neuron. Influx of calcium ions signals the presynaptic neuron to release neurotransmitters into the synaptic cleft, which eventually bind to receptors on the postsynaptic neuron. The calcium ions do not enter the postsynaptic neuron at the synapse.