There are two major criteria that can be used to define nervous system categorizations. The first is location in the body. The central nervous system consists only of the brain and spinal cord, while the peripheral nervous system extends throughout the rest of the body. The central nervous system is enclosed by the blood-brain barrier, separating it from the rest of the body. The second classifier is mechanism of control. Some nervous pathways can be controlled voluntarily (somatic), while others are involuntary (autonomic).

The sympathetic and parasympathetic divisions are both peripheral autonomic pathways.

The correct answer is Schwann cells. Schwann cells are cells that produce the myelination present on the outer covering of the axon of the neuron. This lipid-rich material helps facilitate the movement of the action potential along the axon from the axon hillock to the axon terminal branches.

Neurons have many dendrites, one cell body, and a single axon with several terminal branches. A dendrite receives an external stimulus and causes an electrical disturbance in the cell body. This electrical disturbance is transmitted to the axon, where an action potential is generated if the stimulus is large enough. The action potential is propagated through the axon and is transmitted to a neighboring neuron at the synapse.

A large enough electrical disturbance will generate an action potential in the axon, but no magnitude of stimulus can create an action potential in the dendrites. Neurons do contain multiple dendrites, but they only contain one cell body and one axon. Finally, neurons transmit electrical signals to other neurons at the synapse, not at the cell body.

The correct answer is Schwann cells. Schwann cells are cells that produce the myelination present on the outer covering of the axon of the neuron. This lipid-rich material helps facilitate the movement of the action potential along the axon from the axon hillock to the axon terminal branches.

The resting potential of a cell is roughly –70mV. When the potential rises above this level, the cell is considered "depolarized." When the potential delves below this level, the cell is considered "hyperpolarized." If the cell is depolarized above –55mV, the threshold potential, then an action potential is triggered.

Hyperpolarization occurs because potassium channels are slow to open and close, and thus the cell polarizes itself beyond its usual membrane potential. After an action potential depolarizes a cell there is a build-up of positive charge in the cell interior. The late opening of potassium channels causes an abrupt rush of potassium out of the cell, propelled by its electrochemical gradient. This rush lowers the cell potential below its normal resting state, resulting in hyperpolarization. The cell then returns to its resting state via repolarization. Sodium is removed from the cell and potassium is reintroduced through action of the sodium-potassium pump.

There are two major criteria that can be used to define nervous system categorizations. The first is location in the body. The central nervous system consists only of the brain and spinal cord, while the peripheral nervous system extends throughout the rest of the body. The central nervous system is enclosed by the blood-brain barrier, separating it from the rest of the body. The second classifier is mechanism of control. Some nervous pathways can be controlled voluntarily (somatic), while others are involuntary (autonomic).

The sympathetic and parasympathetic divisions are both peripheral autonomic pathways.

The resting potential of a cell is roughly –70mV. When the potential rises above this level, the cell is considered "depolarized." When the potential delves below this level, the cell is considered "hyperpolarized." If the cell is depolarized above –55mV, the threshold potential, then an action potential is triggered.

Hyperpolarization occurs because potassium channels are slow to open and close, and thus the cell polarizes itself beyond its usual membrane potential. After an action potential depolarizes a cell there is a build-up of positive charge in the cell interior. The late opening of potassium channels causes an abrupt rush of potassium out of the cell, propelled by its electrochemical gradient. This rush lowers the cell potential below its normal resting state, resulting in hyperpolarization. The cell then returns to its resting state via repolarization. Sodium is removed from the cell and potassium is reintroduced through action of the sodium-potassium pump.

The nervous system has two principle divisions for function and two principle divisions for structure. Structurally, there are the central and peripheral nervous system divisions. Functionally, there are the somatic and autonomic divisions.

The somatic nervous system is responsible for voluntary actions, namely the innervation of skeletal muscle. The autonomic nervous system is responsible for all involuntary actions, including smooth muscle contraction, glandular stimulation, and other functions.

The peripheral nervous system carries both somatic and autonomic signals, innervating the entire periphery (not just skeletal muscle). The sympathetic and parasympathetic divisions of the nervous system are both autonomic. Though they innervate some skeletal muscles, they also play keys roles in other bodily functions, such as heart rate and blood pressure regulation.

The somatic nervous system is the only division to only innervate skeletal muscle.

Neurons have many dendrites, one cell body, and a single axon with several terminal branches. A dendrite receives an external stimulus and causes an electrical disturbance in the cell body. This electrical disturbance is transmitted to the axon, where an action potential is generated if the stimulus is large enough. The action potential is propagated through the axon and is transmitted to a neighboring neuron at the synapse.

A large enough electrical disturbance will generate an action potential in the axon, but no magnitude of stimulus can create an action potential in the dendrites. Neurons do contain multiple dendrites, but they only contain one cell body and one axon. Finally, neurons transmit electrical signals to other neurons at the synapse, not at the cell body.

The nervous system has two principle divisions for function and two principle divisions for structure. Structurally, there are the central and peripheral nervous system divisions. Functionally, there are the somatic and autonomic divisions.

The somatic nervous system is responsible for voluntary actions, namely the innervation of skeletal muscle. The autonomic nervous system is responsible for all involuntary actions, including smooth muscle contraction, glandular stimulation, and other functions.

The peripheral nervous system carries both somatic and autonomic signals, innervating the entire periphery (not just skeletal muscle). The sympathetic and parasympathetic divisions of the nervous system are both autonomic. Though they innervate some skeletal muscles, they also play keys roles in other bodily functions, such as heart rate and blood pressure regulation.

The somatic nervous system is the only division to only innervate skeletal muscle.