Organization of the Nervous System: Videos & Practice Problems

The nervous system consists of the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS, comprising the brain and spinal cord, acts as the control center for thoughts, emotions, and motor commands. The PNS connects the body to the CNS and includes the somatic nervous system, which governs voluntary movements, and the autonomic nervous system (ANS), which regulates involuntary functions. The ANS is further divided into the sympathetic nervous system, responsible for the fight or flight response, and the parasympathetic nervous system, which promotes rest and digestion, demonstrating antagonistic effects on shared organs.

The Nervous System

The nervous system is a sophisticated network of neurons responsible for transmitting electrochemical information throughout the body. It is divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS, which includes the brain and spinal cord, serves as the control center for the body, managing thoughts, emotions, memories, sensations, perceptions, and motor commands. You can visualize the CNS as the headquarters of the human body, orchestrating all activities and responses.

In contrast, the PNS consists of nerves located outside the CNS, connecting the body to the brain. This system is crucial for both sensation and movement. Sensory nerves within the PNS relay information about external stimuli, such as pain or pressure, back to the CNS. In response, the CNS sends motor signals through motor nerves to initiate movement, allowing actions like picking up a foot or moving a hand. This collaboration between the CNS and PNS is essential for the body's overall functionality.

While the CNS is straightforward in its structure, the PNS has several subdivisions that play specific roles in sensory and motor functions. Understanding these components is vital for grasping how the nervous system operates as a whole.

Organization of the Nervous System Example 1

The nervous system is divided into two main components: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). Understanding the distinctions and functions of each is crucial for grasping how the body processes information and responds to stimuli.

The PNS is characterized by its composition of nerves that are located outside the brain and spinal cord. This system is responsible for connecting the CNS to the limbs and organs, facilitating communication between the central command center and the rest of the body.

In contrast, the CNS serves as the control center for most bodily functions. It includes the brain and spinal cord, acting as the primary hub for processing sensory information, coordinating responses, and managing cognitive functions such as thinking and feeling.

Both the CNS and PNS utilize electrochemical signals for communication. This fundamental mechanism allows for the rapid transmission of information throughout the nervous system, enabling reflexes and complex behaviors.

In summary, the CNS includes the brain and spinal cord, while the PNS consists of nerves outside these structures. Both systems work together, using electrochemical signals to ensure effective communication and coordination within the body.

True or False: If false, choose the answer that best corrects the statement.
The peripheral nervous system is comprised of nerves outside the brain and the spinal cord.

• A. True.
• B. False; the peripheral nervous system includes nerves, the spinal cord, and the brain.
• C. False; the peripheral nervous system includes the brain and the spinal cord.
• D. False; the peripheral nervous system is a system of organs and muscles that coordinate with the brain.

Answer: (A)

Subdivisions of the PNS

The peripheral nervous system (PNS) is a crucial component of the nervous system, divided into two primary subsystems: the somatic nervous system and the autonomic nervous system. The somatic nervous system, represented in green, is responsible for controlling voluntary movements. It achieves this by innervating skeletal muscles, which are the muscles attached to the skeleton. Activities such as writing, stirring a pot, picking up a pet, or kicking a ball are all examples of voluntary movements governed by this system, as they require conscious thought and intention.

In contrast, the autonomic nervous system, depicted in purple, manages involuntary movements—functions that occur without conscious awareness or control. This system primarily innervates internal organs, including the heart and lungs, as well as glands and blood vessels. It regulates essential bodily functions such as heart rate, blood vessel constriction or dilation, and hormone release from glands. A helpful way to remember the autonomic nervous system is to associate it with the term "automatic," as it oversees all automatic bodily functions.

While the somatic nervous system remains a singular entity, the autonomic nervous system is further divided into two subdivisions, which will be explored in subsequent discussions. Understanding these systems is vital for grasping how the body coordinates both voluntary and involuntary actions, ensuring a balanced and responsive physiological state.

Organization of the Nervous System Example 2

In this exercise, we explore the two subdivisions of the peripheral nervous system (PNS): the somatic nervous system and the autonomic nervous system. Understanding the distinction between these systems is crucial for recognizing how our body responds to different stimuli.

The somatic nervous system is responsible for voluntary movements and the control of skeletal muscles. For instance, when you consciously decide to pick up your dog, your biceps contract, indicating the involvement of the somatic nervous system. Similarly, when you jump over a puddle, the contraction of your calf muscles is also a voluntary action, again reflecting the somatic system's role.

On the other hand, the autonomic nervous system manages involuntary functions, controlling organs and glands without conscious effort. For example, when your heart rate increases after walking up a flight of stairs, this response is regulated by the autonomic nervous system, as it involves the heart, an organ that operates automatically. Additionally, the contraction of salivary glands upon smelling fresh cookies and the dilation of pupils when entering a bright room are both involuntary actions governed by the autonomic nervous system.

In summary, the somatic nervous system is engaged during voluntary movements, while the autonomic nervous system regulates involuntary physiological responses. Recognizing these distinctions enhances our understanding of how the body functions in various scenarios.

Which of the following statements is true about the autonomic nervous system?
I) It is a division of the central nervous system.
II) It primarily innervates organs, glands, and vessels.
III) It controls involuntary movement.

• A. I & II only.
• B. I & III only.
• C. II & III only.
• D. I, II, & III.

Answer: (C)

Subdivisions of the Autonomic Nervous System

The autonomic nervous system (ANS) is crucial for regulating involuntary bodily functions and is divided into two main branches: the sympathetic nervous system and the parasympathetic nervous system. These divisions play distinct roles in how the body responds to various stimuli, adapting to environmental changes and emotional states.

The sympathetic division is often referred to as the "fight or flight" system. It becomes dominant during stressful situations, such as when facing a threat or experiencing anxiety. This activation triggers a series of physiological responses designed to prepare the body for immediate action. For instance, when the sympathetic nervous system is engaged, heart rate increases to pump more blood, bronchioles in the lungs dilate to enhance oxygen intake, and pupils dilate to improve vision. Conversely, non-essential functions, such as digestion, are temporarily suppressed to prioritize energy for survival.

In contrast, the parasympathetic division is known as the "rest and digest" system. It becomes more active when the body is relaxed and at rest, allowing for recovery and maintenance of bodily functions. During this state, heart rate decreases, bronchioles constrict, and gastrointestinal activity increases to facilitate digestion. The pupils also constrict, as there is no immediate need for heightened visual acuity.

Both divisions innervate many of the same organs but typically have opposing effects, a phenomenon known as antagonistic effects. This means that when one division is active, the other is suppressed, ensuring that the body can efficiently respond to varying demands. For example, while the sympathetic division prepares the body for action, the parasympathetic division promotes recovery and homeostasis.

Understanding the balance between these two systems is essential for recognizing how the body manages stress and relaxation, ultimately influencing overall health and well-being.

Organization of the Nervous System Example 3

The nervous system is a complex network that can be organized into two primary divisions: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord, serving as the main control center for processing information. In contrast, the PNS encompasses all the nerves outside the CNS and is further divided into several branches.

Within the PNS, there are two main divisions: the somatic nervous system and the autonomic nervous system. The somatic nervous system is responsible for voluntary movements, allowing individuals to control their actions consciously. On the other hand, the autonomic nervous system manages involuntary functions, such as reflexes and the movement of internal organs, which occur without conscious control.

The autonomic nervous system is further categorized into two divisions: the sympathetic and parasympathetic systems. The sympathetic division is often referred to as the "fight or flight" response, becoming active during stressful situations or threats, preparing the body for rapid action. Conversely, the parasympathetic division is known as the "rest and digest" system, promoting relaxation and recovery when the body is at rest.

This organization of the nervous system highlights the intricate balance between voluntary and involuntary control, as well as the body's ability to respond to varying stimuli through its different divisions.

The ________ system is likely active during a difficult exam while the _______ system is likely active while relaxing.

• A. Central; peripheral.
• B. Sympathetic; parasympathetic.
• C. Autonomic; somatic.
• D. Sympathetic; somatic.

Answer: (B)

Parasympathetic activation would _________ heart rate while sympathetic activation would ______ heart rate.

• A. Increase; decrease.
• B. Not affect; increase.
• C. Decrease; not affect.
• D. Decrease; increase.

Answer: (D)

Here’s what students ask on this topic:

What are the main divisions of the nervous system?

The nervous system is divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord and acts as the control center for thoughts, emotions, and motor commands. The PNS connects the body to the CNS and includes all the nerves outside the brain and spinal cord. The PNS is further divided into the somatic nervous system, which controls voluntary movements, and the autonomic nervous system (ANS), which regulates involuntary functions. The ANS is further subdivided into the sympathetic nervous system, responsible for the fight or flight response, and the parasympathetic nervous system, which promotes rest and digestion.

What is the role of the central nervous system (CNS)?

The central nervous system (CNS) comprises the brain and spinal cord and serves as the control center for the body. It processes and interprets sensory information, generates thoughts and emotions, stores memories, and coordinates voluntary and involuntary motor commands. Essentially, the CNS integrates and responds to information from the entire body, making it crucial for overall functioning and behavior.

How does the peripheral nervous system (PNS) connect the body to the brain?

The peripheral nervous system (PNS) connects the body to the brain through a network of nerves that extend from the CNS to various parts of the body. Sensory nerves in the PNS transmit sensory information (e.g., pain, pressure) from the body to the CNS, while motor nerves convey motor commands from the CNS to muscles and glands, enabling movement and responses. This bidirectional communication allows the brain to monitor and control bodily functions effectively.

What is the difference between the somatic and autonomic nervous systems?

The somatic nervous system controls voluntary movements by innervating skeletal muscles, allowing conscious actions like writing, walking, and speaking. In contrast, the autonomic nervous system (ANS) regulates involuntary functions, such as heart rate, digestion, and respiratory rate, by innervating organs, glands, and blood vessels. The ANS operates without conscious control and is further divided into the sympathetic nervous system, which activates the fight or flight response, and the parasympathetic nervous system, which promotes rest and digestion.

What are the functions of the sympathetic and parasympathetic nervous systems?

The sympathetic nervous system prepares the body for stressful or threatening situations by activating the fight or flight response. It increases heart rate, dilates bronchioles for more oxygen intake, decreases gastrointestinal activity, and dilates pupils for better vision. Conversely, the parasympathetic nervous system promotes relaxation and recovery by activating the rest and digest response. It decreases heart rate, constricts bronchioles, increases gastrointestinal activity, and constricts pupils. These systems have antagonistic effects on shared organs, ensuring the body can respond appropriately to different situations.