into many parts depending on its location or Fig. . : Transmission of Nerve Impulse through Synapse Terminal button Synaptic vesicles Synaptic cleft Neurotransmitter Dendrite Fig. .
: Schematic Representation of the Nervous System Spinal Cord (Ascending Pathways, Interneurons, and Descending Pathway) Somatic Nervous System (SNS) (Sensory and Motor Nerves, Voluntary) Brain (Hindbrain, Midbrain, and Forebrain) Sympathetic Division (Trouble Shooter) Parasympathetic Division (Housekeeping) Autonomic Nervous System (ANS) (Internal System, Involuntary) Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS) (Neural Tissue outside Brain and Spinal Cord) Endocrine System The Peripheral Nervous System The PNS is composed of all the neurons and nerve fibers that connect the CNS to the rest of the body. The PNS is divided into Somatic Nervous System and Autonomic Nervous System. The autonomic nervous system is further divided into Sympathetic and Parasympathetic systems. The PNS provides information to the CNS from sensory receptors (eyes, ears, skin, etc.) and relays back motor commands from the brain to the muscles and glands.
The Somatic Nervous System This system consists of two types of nerves, called cranial nerves and spinal nerves. There are twelve sets of cranial nerves which either emanate from or reach different locations of the brain. There are three types of cranial nerves - sensory, motor, and mixed. Sensory nerves collect sensory information from receptors of the head region (vision, audition, smell, taste, touch, etc.) and carry them to the brain.
The motor nerves carry motor impulses originating from the brain to muscles of the head region. For example, movements of the eyeballs are controlled by motor cranial nerves. Mixed nerves have both sensory and motor fibers, which conduct sensory and motor information to and from the brain. There are thirty one sets of spinal nerves coming out of or reaching to the spinal cord.
Each set has sensory and motor nerves. Spinal nerves have two functions. The sensory fibers of the spinal nerves collect sensory information from all over the body (except the head region) and send them to the spinal cord from where they are then carried out to the brain. In addition, motor