16.1:
Organization of the Nervous System
The nervous system is the primary control and communication center of the body.
The nervous system can be divided into two major categories—the central and peripheral nervous systems.
The central nervous system or CNS comprises the brain and spinal cord.
The brain receives incoming sensory information and generates motor output that coordinates movement and behavior. The spinal cord acts as a relay between the brain and the rest of the body, allowing information to flow between the two.
The brain also controls higher cognitive functions like thoughts, memories, and emotions.
The peripheral nervous system or PNS comprises all nervous tissue outside the CNS. This includes cranial nerves that originate from the brain and spinal nerves that originate from the spinal cord, their associated ganglia, and the sensory receptors that are specialized for the sense organs.
The PNS relays sensory signals from the periphery to the CNS and motor signals from the CNS to muscles and glands.
16.1:
Organization of the Nervous System
The nervous system is one of the most complex systems in our body. It is organized into two main divisions: the central nervous system (CNS) and the peripheral nervous system (PNS).
The CNS, comprising the brain and spinal cord, houses billions of neurons. The brain is housed in the skull, while the spinal cord is linked to the brain through the foramen magnum of the occipital bone and is surrounded by the protective structure of the vertebral column. It is responsible for processing various types of sensory information, as well as being the source of thoughts, emotions, and memories. It also initiates signals that trigger muscle contractions and gland secretions.
On the other hand, the PNS includes all nervous tissue outside the CNS. It comprises nerves and sensory receptors—structures that monitor changes in both external and internal environments.
The PNS is further divided into sensory and motor divisions. The sensory division brings input to the CNS from sensory receptors throughout the body, providing sensory information about both somatic and special senses. The motor division, which transmits output from the CNS to effectors like muscles and glands, is divided into the somatic nervous system (SNS) and the autonomic nervous system (ANS). The SNS controls the activity of skeletal muscles, while the ANS controls the activities of smooth muscles, cardiac muscles, and glands.