11.2: Organization and functions of the nervous system (2023)

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    At the end of this section you can:

    • Understand the basic structure of a neuron.
    • Distinguish between gray and white matter and relate their differences to the structure of neurons
    • Identify the structural and functional divisions of the nervous system.
    • Identify the organs of the central and peripheral departments of the nervous system.
    • Understand the basic functions and controls of the nervous system.

    The picture you have of the nervous system probably includes thatBrain, the nerve tissue contained in the skull in the cranial cavity and theRückenmark, the expansion of nerve tissue within the spine. This suggests that it is made up of two organs, and you may not even think of the spinal cord as one organ, but the nervous system is a very complex structure. Within the brain, many different and separate regions are responsible for many different and separate functions. It's as if the nervous system were made up of multiple organs that look similar and can only be distinguished with tools like a microscope or an electrophysiology machine. In comparison, it's easy to see that the stomach is distinct from the esophagus or liver, so you can think of the digestive system as a collection of specific organs. For this reason, you first study the organization of nerve tissue and the structures it contains. You will then see the structural divisions of the nervous system by regions where the organs are located, and then the functional divisions by the specific functions performed by the organs within.

    Organization of nerve tissue

    Nervous tissue contains two basic types of cells: neurons and glial cells. FORGliazellenIt is one of several cells that provide tissue structure that supports neurons and their activities. HeNeuron it is the functionally more important of the two in terms of the communicative function of the nervous system. In order to describe the functional areas of the nervous system, it is important to understand the basic structure of a neuron (Figure \(\PageIndex{1}\)). Neurons are cells and therefore have aSoma, Öcell body, but also have cellular extensions; Each extension is commonly denoted as aProceedings. There is an important process that each neuron initiatesAxon, which is the fiber that connects a neuron to its target. Axons are partially insulated by a lipid-rich substance calledMyelin.Another type of process that branches off from soma is thedendrites. Dendrites are responsible for receiving most of the information from other neurons.

    11.2: Organization and functions of the nervous system (2)

    Looking at neural tissue, there are regions that mostly contain cell bodies and regions that mostly consist of axons only. These two regions within the structures of the nervous system are often referred to asgray matter (Regions with many cell bodies and dendrites) orwhite substance(the regions with many axons). Figure \(\PageIndex{2}\) shows what these regions look like in the brain and spinal cord. The colors assigned to these regions are those that would be seen in "fresh" or unstained neural tissue. Gray matter is not necessarily grey. It can be pink or even slightly brownish in color due to blood content, depending on how long the tissue has been stored. But white matter is white because axons are insulated by myelin lipids. Lipids can appear as a white ("fatty") material, similar to the fat in a raw piece of chicken or beef. In fact, this color can be attributed to the gray matter, since it is darker next to the white matter, that is, gray. The cell bodies of neurons are grouped into regions called nuclei or ganglia, depending on their location. The axons of neurons also tend to aggregate into structures called tracts (columns) or nerves (fibers), depending on their location.

    11.2: Organization and functions of the nervous system (3)

    Structural classifications of the nervous system

    The nervous system can be divided into two main areas: the central nervous system and the peripheral nervous system. Hecentral nervous system (CNS)It consists of the brain and the spinal cord and theperipheral nervous system (PNS)it consists of ganglia (structures containing neurons outside the CNS) and nerves (bundles of axons from CNS and PNS neurons) (Figure \(\PageIndex{3}\)). The brain is contained in the cranial cavity of the skull and the spinal cord is contained in the vertebral cavity of the spine. It's a bit simplistic to say that the CNS is what's inside these two cavities and the peripheral nervous system is outside of them, but that's one way of thinking about it. In fact, there are some elements of the peripheral nervous system that are found in the cranial or vertebral cavities. The peripheral nervous system gets its name because it is on the periphery, beyond the brain and spinal cord. Depending on the various aspects of the nervous system, the dividing line between central and peripheral is not necessarily universal.

    11.2: Organization and functions of the nervous system (4)

    The cell bodies or axons of neurons can be located in discrete anatomical structures specific to whether the structure is central or peripheral. A localized accumulation of neuron cell bodies in the CNS is known asKern. A group of neuron cell bodies is known in the PNSGanglion. The terminology for bundles of axons also differs by location. A bundle of axons or fibers found in the CNS is calledact(a column) Although that would be called the same in the SNPNerve(the nerve fiber). An important point to note about these terms is that they can both be used to refer to the same bundle of axons. The most obvious example of this is the axons that project from the eye's retina to the brain. These axons are called the optic nerve when they exit the eye, but when they are inside the skull they are called the visual tract. The table \(\PageIndex{1}\) helps to clarify which of these terms applies to the central or peripheral nervous system. There is another classification of nerves based on where they leave the central nervous system:Brain nervesarise directly from the brain whileSpinal nervesThey come from different segments of the spinal cord.

    functional areas of the nervous system

    The nervous system can also be subdivided according to its functions, but the anatomical subdivisions and the functional subdivisions are different. Both the CNS and PNS contribute to the same functions, but these functions may be attributed to different regions of the brain (such as the cerebral cortex or the hypothalamus) or to different ganglia in the periphery. The problem with trying to fit functional differences into anatomical compartments is that sometimes the same structure can serve multiple functions. For example, the optic nerve carries signals from the retina that are used for conscious perception of visual stimuli occurring in the cerebral cortex or for reflex smooth muscle tissue responses processed by the hypothalamus.

    There are two ways to look at how the nervous system is functionally divided. First, the basic functions of the nervous system are perception, integration, and response. Second, body control can be somatic or autonomic, with the divisions being largely defined by the structures involved in the response. There is also a region of the peripheral nervous system called the enteric nervous system that is responsible for a specific set of functions within the area of ​​autonomic control related to gastrointestinal functions.

    basic functions

    The nervous system is involved in receiving information about the environment around us (sensation) and creating responses to that information (motor responses). The nervous system can be divided into regions that are responsible for itSensation (sensory functions) and for theresponder (motor functions). But there is a third feature that needs to be included. Sensory information needs to be integrated with other sensations, as well as with memories, emotional state, or learning (cognition). Some regions of the nervous system are namedIntegration or club areas. The integration process combines sensory perceptions and higher cognitive functions such as memory, learning, and emotion to elicit a response.

    (Video) Chapter 11.1 Functions of the Nervous System BIO201

    Sensation.The first important function of the nervous system is sensation: receiving information about the environment in order to obtain information about what is happening outside the body (or sometimes inside the body). The sensory functions of the nervous system register the presence of a change in homeostasis or a specific environmental event known asStimulus(pl. Reize). The senses we think about most are: taste, smell, sight, hearing and balance. Stimuli to taste and smell are chemicals (molecules, compounds, ions, etc.), vision is light stimuli, hearing is perception of sound, and balance is perception of where your head is in space. . The last two are based on physical stimuli. The above senses are invokedspecial sensesbecause they have specialized organs for perceiving the environment. In fact, there are more senses than just these, for example touch, pain and temperature are sensed through the skin. These are calledgeneral sense. The particular and general senses receive stimuli from the outside world and are consciously perceived, meaning you are aware of them. This conscious sensation of the particular and general senses is called somatic sensation orNo somatosensory. Additional sensory stimuli can come from the internal environment (inside the body), such as B. the stretching of an organ wall or the concentration of certain ions in the blood or pain associated with nerve compression. These are calledvisceral sensesand they are not consciously perceived, meaning you are not aware of them. Somatic and visceral sensory information is sensed by structures within the peripheral nervous system and travels to the central nervous system. This inner direction is calledrelated.

    Integration.Stimuli received from sensory structures are relayed to the nervous system, where this information is processed. Stimuli are compared or integrated with other stimuli, memories of previous stimuli, or a person's state at a particular point in time. This leads to the specific response that is generated. Seeing a baseball thrown at a batsman does not automatically make the batsman swing. It is necessary to take into account the trajectory of the ball and its speed. Maybe the count is three balls and one batter and the batter wants to miss that pitch in hopes of getting to first base. Or maybe the batsman's team is so far ahead that it would be fun to walk away.

    responder.The nervous system produces a response based on sensory stimuli. An obvious answer would be muscle movement, such as B. removing the hand from a hot stove, but there are broader uses of the term. The nervous system can cause all three types of muscle tissue to contract. For example, skeletal muscle contracts to move the skeleton, heart muscle is affected when heart rate increases during exercise, and smooth muscle contracts when the digestive system moves food through the digestive tract. Responses also involve neural control of body glands, such as the production and secretion of sweat by the eccrine and merocrine sweat glands in the skin to lower body temperature. So muscles and glands are the targets of the motor response, they are activated when they are stimulated to perform the response. This is why they are calledeffectors. Responses can be divided into voluntary or conscious (skeletal muscle contraction) and involuntary or unconscious (smooth muscle contraction, heart muscle regulation, gland activation). Voluntary responses are controlled by the somatic nervous system and involuntary responses are controlled by the autonomic and enteric nervous systems, which is discussed in the next section. Motor information is generated by the central nervous system and sent to the peripheral nervous system. This outward direction is alsothey will bring. Afferent and efferent sound the same but are different. One way to remember their differences is to use the acronym SAME, which stands for Sensory Afferent Motor Efferent.

    control the body

    The nervous system can be divided into two parts mainly based on a functional difference in responses. Hesomatic nervous system (SNS)It is responsible for conscious perception (somatosensory) and voluntary motor responses (also called somatic responses). Voluntary motor response involves skeletal muscle contraction, but these contractions aren't always voluntary in the sense that you have to want them. Some somatic motor responses are knee-jerk and often occur without a conscious decision to perform them. When your friend jumps around a corner and says "Boo!" he is startled and may scream or jump back. You didn't choose to do it, and you might not want to give your friend anything to laugh about, but it's a reflex that involves skeletal muscle contractions. Other motor responses become automatic (in other words, unconscious) when a person learns motor skills (known as "habit learning" or "procedural memory").

    Isautonomic nervous system (ANS)It is responsible for the involuntary control of the body, usually for the purpose of homeostasis (regulation of the internal environment). Sensory information for autonomic functions can come from sensory structures that are attuned to external or internal environmental stimuli. Motor performance extends to cardiac and smooth muscle and glandular tissue. The role of the autonomic system is to regulate the body's organ systems, which usually means controlling homeostasis. The sweat glands, for example, are controlled by the vegetative system. When you're hot, sweat helps cool your body. This is a homeostatic mechanism. But if you're nervous, you can also start sweating. This is not homeostatic, it is the physiological response to an emotional state.

    There is another division of the nervous system that describes functional responses. Heenteric nervous system (ENS)It is responsible for controlling smooth muscle and glandular tissue in your digestive system. It is a large part of the PNS and is not CNS dependent. However, it is sometimes valid to view the enteric system as part of the autonomic system, since the neural structures that make up the enteric system are a component of the autonomic output that regulates digestion. There are some differences between the two, but for our purposes there will be a good amount of overlap here. See table \(\PageIndex{2}\) for a schematic representation of the different departments based on their basic functions and control mechanisms.

    interactive connection

    progressive weakness

    read thisArticle progressive weaknessabout a woman who notices her daughter having trouble climbing stairs. This leads to the discovery of an inherited disease affecting the brain and spinal cord. Electromyography and MRI scans showed defects in the spinal cord and cerebellum (region of the brain), both of which are responsible for controlling coordinated movements. What functional area of ​​the nervous system would these structures belong to?


    Answer: They are part of the somatic nervous system responsible for generating voluntary movements such as walking or climbing stairs.

    DAILY CONNECTION: How much of your brain do you use?

    Have you ever heard the statement that humans only use 10% of their brains? Perhaps you've seen an ad on a website that says there's a secret to unlocking your mind's full potential, like 90% of your brain is idle, waiting for you to use it. If you see such an ad, do not click on it. It is not right.

    (Video) Neurons - Structure & Function - 7 Minutes! (11.2)

    A simple way to see what part of the brain a person is using is to measure brain activity while they are performing a task. An example of this type of measurement is functional magnetic resonance imaging (fMRI), which creates a map of the most active areas that can be created and displayed in three dimensions (Figure \(\PageIndex{4}\)). This procedure differs from the standard MRI technique because it measures changes in tissue over time with an experimental condition or event.

    11.2: Organization and functions of the nervous system (5)

    Figure \(\PageIndex{4}\): Image map of functional magnetic resonance imaging (fMRI). This image represents a cross-sectional view of the brain with the posterior side on the left and the anterior side on the right. The orange colored areas represent highly active regions. In this particular example, the fMRI map shows activation of the visual cortex in response to visual stimuli. (Image credit:"1206 FMRI"by OpenStax is licensed underCC POR 4.0)

    The underlying assumption is that active nerve tissue will have increased blood flow. By having the subject perform a visual task, activity throughout the brain can be measured. Consider this possible experiment: The subject is instructed to look at a screen with a black dot in the center (a fixation point). A photo of a face is projected off-center on the screen. The person needs to look at the photo and figure out what it's about. The subject is instructed to press a button if the photo is of someone they recognize. The photo can be of a celebrity, so the subject presses the button, or it can be of a random person unknown to the subject, so the subject does not press the button.

    In this task, the visual sensory areas would be active, the integrating areas active, the motor areas responsible for moving the eyes, and the motor areas responsible for pressing the button with the finger. These areas are distributed throughout the brain, and fMRI images would show activity in over 10% of the brain (some evidence suggests that around 80% of the brain uses energy, depending on tissue perfusion) for well-defined tasks. . similar to the one suggested above). This task does not even include all the functions that the brain performs. There is no speech response, most of the body is immobile in the MRI machine and does not account for the autonomic functions that would be going on in the background.

    concept review

    Nervous tissue consists of neurons and glial cells. The basic structure of a neuron consists of a soma (cell body) and processes. Processes can be divided into dendrites, which receive information, and axons, which carry information. Axons are partially covered by a lipid-rich sheath called myelin. Due to the high fat content of myelin, myelin-covered axons appear white. Therefore, based on its appearance in unstained tissue, neural tissue can also be described as gray matter and white matter. The cell bodies of neurons are grouped into regions called nuclei or ganglia, depending on their location. The axons of neurons also tend to aggregate into structures called tracts (columns) or nerves (fibers), depending on their location.

    The nervous system can be divided into departments based on anatomy and physiology. The anatomical regions are the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. In the CNS there is a localized collection of neuron cell bodies called nuclei in the gray matter and bundles of axons called tracts in the white matter. The PNS is made up of collections of neuron cell bodies called ganglia and bundles of axons called nerves. A single axon can be part of a nerve when in the PNS and then become a tract when crossing the CNS.

    Functionally, the nervous system can be divided into regions responsible for sensation, regions responsible for integration, and regions responsible for generating responses. All of these functional areas are found in both the central and peripheral anatomy. The nervous system can also be divided according to how it controls the body. The somatic nervous system (SNS) is responsible for the functions that lead to the movement of skeletal muscles. Any sensory or integrative function that results in skeletal muscle movement would be considered somatic. The autonomic nervous system (ANS) is responsible for functions that affect heart tissue, smooth muscle, or that cause glands to produce their secretions. Autonomic functions are distributed between the central and peripheral regions of the nervous system. The sensations that lead to autonomic functioning may be the same sensations that are part of the triggering of somatic responses. Somatic and autonomic integrative functions can also overlap. A special part of the nervous system is the enteric nervous system, which is responsible for controlling the digestive organs. Parts of the autonomic nervous system overlap with the enteric nervous system. The enteric nervous system is found exclusively in the periphery as it is the nervous tissue in the organs of the digestive system.

    review questions

    Q. Which of the following cavities contains a central nervous system component?

    for abs

    B's pelvis

    C Craneal

    D. Chest cavity

    (Video) BIOL 20 11.1-11.2 Intro to Nervous Tissue


    Answer: C

    Q. What structure is predominant in the white matter of the brain?

    A. myelinized Axon

    B. neuronal cell bodies

    C. Autonomous ganglia

    D. Dendritic bundles of the enteric nervous system


    answer to

    Q. Which part of a neuron transmits an electrical signal to a target cell?

    A. Dendriten

    Soma B

    C. Cell body

    D. Axon


    Answer : D

    Q. What term describes a bundle of axons in the peripheral nervous system?

    A. Kern

    (Video) A&PI Chapter 11 Nervous Tissues = terminology

    B. ganglio

    Griff c

    Nerv D


    Answer : D

    Q. Which functional division of the nervous system would be responsible for the physiological changes observed during exercise (e.g. increased heart rate and sweating)?

    A. somatic

    B. autonomous

    enterisches C.

    D central



    Critical thinking questions

    Q. What reactions does the nervous system produce when you run on a treadmill? Include an example of each type of tissue that is under the control of the nervous system.


    A. Running on a treadmill involves contraction of the skeletal muscles in the legs via the somatic nervous system, increased contraction of the cardiac muscle of the heart, and the production and secretion of sweat in the skin to keep it cool via the autonomic nervous system. .

    Q. What anatomical and functional areas of the nervous system are involved in the perceptual experience of eating?


    A. The taste sensation associated with food is perceived by peripheral nerves involved in sensory and somatic functions. Chewing is somatic motor, utilizing skeletal muscle, while swallowing is somatic motor (first upper phase) and autonomic motor (second lower phase).

    (Video) Chapter 11 Lecture Video Part 1


    drive or drive into or into something
    autonomic nervous system (ANS)
    functional division of the nervous system responsible for homeostatic reflexes that coordinate the control of cardiac and smooth muscle and glandular tissue
    unique process in the neuron that transmits an electrical signal (action potential) from the cell body to a target cell
    the large organ of the central nervous system, composed of white and gray matter, contained in the skull and connected to the spinal cord
    cell body
    in neurons, the part of the cell that contains the nucleus, as distinguished from the cellular processes (axons and dendrites). Also called sum
    central nervous system (CNS)
    anatomical division of the nervous system within the cranial and vertebral cavities, d. H. of the brain and spinal cord
    Brain nerves
    one of twelve nerves connected to the brain responsible for sensory or motor functions of the head and neck
    one of many branches that emanate from the cell body of the nerve cell and function as a contact for input signals (synapses) from other nerve cells or sensory cells
    a body tissue, structure, or organ (such as a gland or muscle) that is activated in response to stimulation
    they will bring
    directed or driving away or driving away from something
    enteric nervous system (ENS)
    Neural tissue connected to the digestive system and responsible for nerve control through autonomic connections
    localized accumulation of neuron cell bodies in the peripheral nervous system
    common sense
    any sensory system distributed throughout the body and integrated into the organs of many other systems, such as B. the walls of digestive organs or the skin
    one of several types of neural tissue cells responsible for maintaining tissues and largely supporting neurons
    gray matter
    Regions of the nervous system containing neuronal cell bodies with few or no myelinated axons; In fact, it may be more pink or brown, but it is referred to as gray as opposed to white matter
    Function of the nervous system that controls sensory perception and higher cognitive functions (memories, learning, emotions, etc.)
    lipid-rich insulating substance that surrounds the axons of many neurons and allows for faster transmission of electrical signals
    Bundles of cord-like axons in the peripheral nervous system that carry sensory information and response output to and from the central nervous system
    A cell of nervous tissue primarily responsible for generating and transmitting electrical signals inside, inside, and outside the nervous system.
    in the nervous system, a localized collection of neuronal cell bodies that are functionally related; a "hub" of neural function
    peripheral nervous system (PNS)
    anatomical division of the nervous system that lies largely outside the cranial and vertebral cavities, d. H. all parts except brain and spinal cord
    in cells, an extension of a cell body; in the case of neurons, this includes the axon and dendrites
    Nervous system function that causes a target tissue (muscle or gland) to produce an event in response to stimuli
    Function of the nervous system, which takes in information from the environment and translates it into electrical signals in nerve tissue
    in neurons, the part of the cell that contains the nucleus, as distinguished from the cellular processes (axons and dendrites). Also called cell body.
    somatic nervous system (SNS)
    functional division of the nervous system concerned with conscious perception, voluntary movement, and skeletal muscle reflexes
    No somatosensory
    general body-related senses, usually referred to as touch, which include pain, temperature, and proprioception
    Organ of the central nervous system located in the vertebral cavity and connected to the periphery by spinal nerves; mediates reflex behavior
    special meaning
    any sensory system associated with the structure of a particular organ, d. H. smell, taste, vision, hearing and balance
    one of the 31 nerves connected to the spinal cord
    an event in the external or internal environment that is registered as activity in a sensory neuron
    Bundles of axons in the central nervous system with the same function and origin
    common sense
    Senses connected to internal organs
    white substance
    Regions of the nervous system that contain mostly myelinated axons, causing the tissue to appear white due to the high lipid content of myelin

    employees and tasks


    What is the organization and function of the nervous system? ›

    The CNS is comprised of the brain, cerebellum and spinal cord. Remaining neurons, and associated cells, distributed throughout the body form the PNS. The nervous system has three broad functions: sensory input, information processing, and motor output.

    What is the 11 nervous system? ›

    The nervous system is the human organ system that coordinates all of the body's voluntary and involuntary actions by transmitting electrical signals to and from different parts of the body. Specifically, the nervous system extracts information from the internal and external environments using sensory receptors.

    What is the structure and organization of the nervous system? ›

    The nervous system consists of two divisions; Central nervous system (CNS) is the integration and command center of the body. Peripheral nervous system (PNS) represents the conduit between the CNS and the body. It is further subdivided into the somatic nervous system (SNS) and the autonomic nervous system (ANS).

    What are the three primary functions of the nervous system 11? ›

    Key Points

    The nervous system has three overlapping functions based on sensory input, integration, and motor output.


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