The components of the central nervous system are the brain and the spinal cord only. The remaining structures of the nervous system belong to the peripheral nervous system. The hemispheres of the brain and the spinal cord are part of the central nervous system. The hippocampus, cerebellum, hypothalamus, thalamus, and cerebral cortex are structures within the brain. The hippocampus is responsible for memory storage and the cerebellum is associated with balance and coordination. The cerebrum is responsible for processing information and higher thought. These structures are also part of the central nervous system.

The cranial nerves attach directly to the spinal cord, but branch out into the periphery. They are not considered part of the central nervous system. The adrenal glands and parathyroid glands are part of the endocrine system. Though they can respond to stimulation from the nervous system, they cannot be classified as part of the peripheral or central nervous system.

The thymus is an endrocrine gland located above the heart and is not part of the nervous system.

Though the pineal gland is found within the skull, it is not composed of nervous tissue and is not considered part of the central nervous system. Instead, it is an endocrine organ that interacts with the nervous tissue of the brain that surrounds it.

The thalamus and cerebellum are both structures of the brain, and are thus part of the central nervous system. Microglia function as macrophages in the central nervous system to prevent infection within the blood-brain barrier.

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 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 spinal cord is found in the central nervous system, and is structurally divided into afferent sensory neurons and efferent motor neurons. Sensory neuron cell bodies are found in the dorsal root ganglion, while somatic motor neurons are found in the ventral horn of the spinal cord.

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.

The somatic nervous system is responsible for chiefly voluntary, conscious behavior, such as choosing a reaction to external stimuli sensed by one of the traditional five senses. The autonomic nervous system is responsible for involuntary bodily function, and can respond to sensations such as gas concentrations in the blood, changes in blood pressure, and slight deviations in body temperature, among many others. 

The parasympathetic nervous system is responsible for the "rest and digest" responses. The sympathetic nervous system, on the other hand, performs the "fight or flight" responses. This question, however, really hinges on knowing the effect of acetylcholine on cardiac muscle. The release of acetylcholine slows the heart rate.

Parasympathetic neurons will only use acetylcholine. Sympathetic neurons signal each other with acetylcholine (preganglionic neurons), but elicit their effects by releasing norepinephrine on their target cells (postganglionic neurons). The effect of norepinephrine on the heart would increase heart rate.

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. Within the autonomic nervous system are the sympathetic and parasympathetic 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 parasympathetic nervous system is responsible for the "rest and digest" actions of involuntary organs, increasing digestive and excretory activity. In contrast, the sympathetic nervous system is responsible for the "fight or flight" response, suppressing these activities and stimulating epinephrine release.

Neuroglia are the support cells of the nervous system, and do not conduct action potentials. The central nervous system is composed of only the brain and spinal cord; not nerves. The somatic system controls voluntary movements, so heart rate would not be under its control. The sympathetic nervous system is commonly assigned the "fight or flight" responses, while the parasympathetic nervous system is responsible for "resting and digesting." Since the body is returning to a rested state by lowering heart rate, we would assign this action to the parasympathetic nervous system.