Functions of the Nervous System: The nervous system’s functions include sensory input, integration, control of muscle and glands, homeostasis, and mental activities. For sensory input, the nervous system detects external and internal stimuli through sensory receptors. Some of the stimuli result in sensations we are aware of, such as vision, hearing, smell, touch, pain, body position, and temperature. Other stimuli, such as blood pH, blood gases, or blood pressure are processes at an unconscious level. During integration, the brain and the spinal cord are the major organs for processing sensory input and initiating responses. The input may produce an immediate response, it may be stored as memory, or perhaps even ignored. In this stage, the integration process is practically where the sensory information is translated from raw information to interpreted information. The controlling of muscles and glands is when skeletal muscles normally contract when stimulated by the nervous system. Thus, through the control of skeletal muscle, the nervous system controls the major movements of the body. The nervous system also participates in controlling the cardiac muscle, smooth muscle, and many glands. Additionally, the nervous system also plays an important role in the maintenance of homeostasis. This function depends on the ability of the nervous system to detect, interpret, and respond to changes in internal and external conditions. In response, the nervous system stimulates or inhibits activities of other systems to help maintain a constant internal environment. Lastly, the nervous system is the center of mental activities. It regulates mental activities, including consciousness, abstract thought, memory, and emotions.

Divisions of the Nervous System: The nervous system has two anatomical divisions that which includes the central nervous system and the peripheral nervous system. The central nervous system or the CNS consists of the brain and spinal cord and is encased in bone. In this system, the CNS receives, integrates information, initiates responses, and carries out mental activity. The peripheral nervous system or the PNS, is the nervous tissue outside of the CNS, consisting of sensory receptors and nerves that detects and transmits stimuli to the CNS. Furthermore, the PNS has two divisions that includes the afferent and the efferent responses. Afferent responses is the sensory division that transmits action potentials from sensory receptors towards the CNS, which in other words means that the afferent response processes the information coming in. Whereas, the efferent responses is the motor division that carries action potentials away from the CNS, which means that it responds to the stimuli. On that note, there are also two types of efferent responses: somatic and autonomic. Somatic responses are voluntary responses carried out by the skeletal muscle. The autonomic responses, however, are the involuntary responses that are carried out by the cardiac muscle, smooth muscle, and many glands. Additionally, the autonomic can be subdivided into the sympathetic division and the parasympathetic division. The sympathetic division is essentially the fight or flight response, which is most active during physical activity. In contrast, the parasympathetic response regulates resting functions, which aids in returning the body back to homeostasis, digestion, and rest.

Glial Cells of the CNS and the PNS Glial cells support and aid the neurons of the central nervous system (CNS) and the peripheral nervous system (PNS). In the CNS, there are four types of glial cells: astrocytes, ependymal cells, microglia, and oligodendrocytes. Astrocytes provide structural support for neurons and blood vessels; influencing the permeability of the blood-brain barrier and process substances that pass through it. Additionally, cells are vital for the formation of functional synapses. Secondly, the ependymal cells lines ventricles of the brain and central