Divisions of the Nervous System

| Home | | Anatomy and Physiology | | Anatomy and Physiology Health Education (APHE) |

Chapter: Anatomy and Physiology for Health Professionals: Control and Coordination: Neural Tissue

The nervous system controls all body functions, maintains homeostasis, and allows the body to respond to many varieties of changing conditions. Information is carried to the brain and spinal cord, which then stimulate the body’s responses.

Divisions of the Nervous System

Divisions of the Nervous System

The nervous system controls all body functions, maintains homeostasis, and allows the body to respond to many varieties of changing conditions. Information is carried to the brain and spinal cord, which then stimulate the body’s responses. The nervous system has millions of sensory receptors that monitor changes (sensory input) outside and inside of the body.

The nervous system processes and interprets this information to determine how it should react (integration­).The effector organs of the body are the muscles and glands, which are activated by the ner-vous system to respond. The responses are collectively termed motor output.

The CNS consists of the brain and spinal cord, located in the dorsal body cavity. The CNS is the con-trol center of the nervous system, integrating all its activities. Reflexes, past happenings, and current con-ditions determine how it will interpret sensory input and control motor output. The PNS consists of the peripheral nerves connecting the CNS to other parts of the body (FIGURE 11 -1). Primarily, it is made up of nerves extending from the brain and spinal cord to the rest of the body. The cranial nerves transmit impulses to and from the brain. Likewise, the spinal nerves transmit impulses to and from the spinal cord.


The CNS and PNS work together to provide sen-sory, integrative, and motor functions to the body. The two functional subdivisions of the PNS are the afferent (sensory) division and the efferent (motor) division. The afferent division carries impulses toward the CNS from the body’s sensory receptors. Somatic sensory fibers transmit impulses from the joints, skeletal muscles, and skin. Visceral sensory fibers transmit impulses from the visceral organs of the ventral body cavity. This sensory divi-sion informs the CNS of all events happening inside and outside the body. The efferent division carries impulses from the CNS to the effector organs, acti-vating muscles to contract and glands to secrete. They affect (cause) motor responses. The two main parts of this motor division are the somatic nervous system and the autonomic nervous system (ANS).

The somatic nervous system is made up of somatic motor fibers transmitting impulses from the CNS to the skeletal muscles. It is also called the voluntary nervous system because our skeletal muscles are under conscious control. However, the somatic ner-vous system also controls involuntary contractions, such as those involved in reflexes. The ANS contains visceral motor nerve fibers regulating glandular, car-diac muscle, and smooth muscle activity. In general, the ANS is not under conscious control, and thus is also called the involuntary nervous system. The two subdivisions of the ANS are the sympathetic and parasympathetic divisions. Their actions usually oppose each other. When one division causes stimula-tion, the other inhibits its actions.

Major subdivisions of the nervous system are summarized in FIGURE 11-2.



1. What is the mechanism of integration in the nervous system?

2. Describe the divisions of the nervous system.

Contact Us, Privacy Policy, Terms and Compliant, DMCA Policy and Compliant

TH 2019 - 2022 pharmacy180.com; Developed by Therithal info.