The nervous system is a network of nerve cells that transmit nerve impulses between different parts of the body. The two divisions of the nervous system are central nervous system and peripheral nervous system. The central nervous system is composed of the brain and spinal cord. The peripheral nervous system is made up of various types of nerves. The brain is the control system of the nervous system, which sends information throughout the entire body. It receives information about internal and external changes of the body from various sense organs.
Key Areas Covered
1. What is Nervous System
– Definition, Components
2. How Does the Nervous System Work with Other Systems
– Sensory Organs, Voluntary Control, Involuntary Control
Key Terms: Central Nervous System, Involuntary Responses, Peripheral Nervous System, Sensory Responses, Voluntary responses
What is Nervous System
The nervous system is a bodily system in vertebrates, which carries signals to and from the brain and spinal cord to the various parts of the body. The two main components of the nervous system are central nervous system and peripheral nervous system.
Central Nervous System
The central nervous system is composed of the brain and spinal cord. The brain is responsible for integrating most of the sensory information. It coordinates bodily functions both consciously and unconsciously. It also performs some complex congenital functions such as thinking and feeling. The main function of the spinal cord is to transmit signals between the brain and the rest of the body. It also controls muscular-skeletal reflexes independently from the brain.
Peripheral Nervous System
The peripheral nervous system is composed of nerves and ganglia outside of the brain and spinal cord. It includes the roots and the branches of the cranial nerves, spinal nerves, peripheral nerves, and neuromuscular junctions. The main function of the peripheral nervous system is to transmit nerve impulses to and from the central nervous system. Therefore, the two main divisions of the peripheral nervous system are sensory (afferent) and motor (efferent) divisions.
How Does the Nervous System Work with Other Systems
The nervous system interacts with three main types of body systems. They are sensory organs, somatic systems controlled by voluntary responses, and autonomic systems controlled by involuntary responses.
Sensory Organs
The brain receives both internal and external sensory stimuli through the afferent division of the peripheral nervous system and the spinal cord. Various types of receptors are responsible for responding to these stimuli: exteroceptors, interoceptors, and proprioceptors.
Exteroceptors
Most exteroceptors that respond to external stimuli are found in the skin. The receptors in the skin respond to external stimuli such as temperature, touch, pressure, and pain. In addition to the skin, complex organs also serve as receptors. Some of these are:
- Light receptors in the retina of the eye
- Sound receptors in the ear
- Position receptors in the ear
- Chemical receptors in the nose and tongue
- Secreting cells in the glands
- Muscle cells
- Different internal organs
The connection between the sensory system and the central nervous system is shown in figure 1.
Figure 1: Sensory System
The brain receives information about the five senses (seeing, smelling, taste, touch, and hearing) from the sensory organs.
Interoceptors
The changes in the internal organs are also detected by various types of internal receptors known as interoceptors. Peripheral chemoreceptors (detect the chemical changes in the blood), nociceptors (detect damaging stimuli), and stretch receptors (detect increase in blood pressure in the aorta and carotid artery and filled bladder with urine) are some of the interoceptors.
Proprioceptors
Proprioceptors are found in muscles, tendons, and joints and determine the position and movement of structures.
Somatic Systems
The sensory information received by the brain are processed and transmitted in the form of voluntary responses to the somatic system of the body. This transmission occurs through the somatic nervous system, a part of the peripheral nervous system, exerting the voluntary movements of the body. The somatic system consists of skeletal muscles that are controlled consciously. The skeletal muscles are innervated by both afferent and efferent nerves. The sensory information is transmitted to the body through the afferent nerves, and the processed information is transmitted to the skeletal muscles through efferent nerves. Various functional areas of the brain are shown in figure 2.
Figure 2: Functional Areas of the Brain
Autonomic Systems
The autonomic nervous system, the other part of the peripheral nervous system, unconsciously control the functions of the internal organs. It innervates the smooth muscles, glands, and internal organs. This system controls functions such as heart rate, breathing, digestion, urination, etc. The functions of the autonomic nervous system are shown in figure 3.
Figure 3: Autonomic Nervous System
The two divisions of the autonomic nervous system are sympathetic nervous system and parasympathetic nervous system. The sympathetic nervous system promotes flight-or-fight response while parasympathetic nervous system promotes rest-and-digest response.
Conclusion
The nervous system controls the functions of the entire body through the central nervous system. The peripheral nervous system is involved in the transmission of nerve impulses between the central nervous system and the body. Primarily, nervous system deals with three types of body systems, while coordinating the functions of the body. They are sensory organs, somatic systems, and autonomic systems. The nervous system receives information from the sensory organs, and the processed information is transmitted to the somatic and autonomic systems.
Reference:
1.“Types of Receptors.” Anatomy & Physiology; Nervous System, Available here.
2.“Somatic system.” Nature News, Nature Publishing Group, Available here.
3.“How does the nervous system work?” National Center for Biotechnology Information, U.S. National Library of Medicine, 19 Aug. 2016, Available here.
Image Courtesy:
1. “Structure of sensory system (4 models) E” By Shigeru23 – Made by uploader (ref:岩堀修明著、『感覚器の進化』、講談社、2011年1月20日第1刷発行、ISBN 9784062577120、21頁) (CC BY-SA 3.0) via Commons Wikimedia
2. “Blausen 0102 Brain Motor&Sensory (flipped)” By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia
3. “The Autonomic Nervous System” By Geo-Science-International – Own work (CC0) via Commons Wikimedia
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