The Peripheral Nervous System Is Composed Of – The word peripheral refers to something that is not in the center or that is on the edge of the center. The peripheral nervous system or PNS (see Figure 2.7 and also refer to Figure 2.5) consists of all nerves and neurons outside the brain and spinal cord. It is this system that allows the brain and spinal cord to communicate with the sensory system and allows the brain and spinal cord to control the muscles and glands of the body. The PNS can be divided into two main systems: the somatic nervous system, which consists of the nerves that control the body’s voluntary muscles, and the autonomic nervous system (ANS), which consists of the nerves that control involuntary muscles, organs, and muscles. glands.

One part of a neuron is the soma, or cell body (remember that the word soma means “body”). The somatic nervous system consists of sensory pathways, which are all nerves that carry messages from the senses to the central nervous system (nerves that contain afferent neurons), and motor pathways, which are all nerves that carry messages from the center. the nervous system to the voluntary, or skeletal, other info the muscles of the body that allow people to move the body (nerves composed of efferent neurons). When people walk, raise their hands in class, smell a flower, or direct their gaze to someone they are talking to or look at a beautiful picture, they are using their somatic nervous system. (As seen in the discussion of spinal cord reflexes, although these muscles are called voluntary muscles, they can move involuntarily during a reflex response. They are called “voluntary” because they are

The Peripheral Nervous System Is Composed Of

Involuntary muscles, such as the heart, stomach, and intestines, along with glands such as the adrenal glands and pancreas are all controlled by bundles of neurons located in or near the spinal column. (Word

Nervous System 101

Used quite deliberately here. Neurons inside the spinal column are part of the central nervous system, not the peripheral nervous system.) Large groups of neurons near the spinal column make up the autonomic nervous system.

The word autonomous indicates that the functioning of this system is more or less automatic, which is true. While the somatic division of the peripheral nervous system controls the senses and voluntary muscles, the autonomic division controls everything else in the body—organs, glands, and involuntary muscles. The autonomic nervous system is divided into two systems, the sympathetic division, and the parasympathetic division. (See Figure 2.8).

These young soccer players use their senses and voluntary muscles controlled by the somatic division of the peripheral nervous system. What part of the autonomic nervous system do these girls also use at this time?

The sympathetic division is often called the “fight-or-flight system” because it allows people and animals to deal with all kinds of stressful events. (See Learning Objective 2.7.) Emotions during these events may be anger (hence, the term fight) or fear (the “flight” part, of course) or even excitement or joy. Yes, even joy can be stressful. The job of the sympathetic division is to prepare the body to deal with stress. Many of us have experienced a fight-or-flight moment at least once in our lives. We will look more closely at how the body responds to stress later in the chapter but for now, participate in the survey Do You Fly or Fight? to learn more about how the body responds in certain situations.

Nervous System Overview

What is the special way that this division prepares the body to react? (See Figure 2.8.) Pupils appear larger, presumably to let in more light and, therefore, more information. The heart begins to pump faster and harder, drawing blood from non-essential organs such as the skin (so the person may initially become pale) and sometimes even the brain itself (so the person may faint). The blood needs a lot of oxygen before it goes to the muscles, so the lungs also work overtime (so people can breathe faster). One set of specialized nodes receives specialized instructions. The adrenal glands will be stimulated to release stress-related chemicals (members of a class of chemicals released by the gland called hormones) into the bloodstream. These stress hormones will travel to all parts of the body, but will only affect certain target organs. Just as neurotransmitters fit receptor sites on cells, stress hormone molecules fit receptor sites on various target organs—mainly, the heart, muscles, and lungs. This further stimulates the organs to work harder. But not every organ or system will be stimulated by the activation of the sympathetic division. The digestion of food and the excretion of other waste information do not need to function when dealing with stressful situations, so this system tends to “die” or inhibit. Saliva, which is part of digestion, dries up immediately (when trying to spit when you’re scared?). The food in the stomach sits there like a lump. Usually, the desire to go to the bathroom will be suppressed, but if the person is very afraid, the bladder or intestines can be empty (that’s why people who die due to extreme stress, such as hanging or electrocution, will release urine and waste. ). The sympathetic division will also prompt the body to burn excessive amounts of fuel, or blood sugar.

Now, all these physical arousals occur during stressful situations. When the stress is over, the activity of the sympathetic division will be replaced by the activation of the parasympathetic division. If the stiffness becomes too long or too strong, the person may collapse (as a deer does when it is being chased by another animal). This collapse occurs because the parasympathetic division overresponds to the inhibition of sympathetic activity. The heart slows down, blood vessels open, blood pressure in the brain drops, and fainting can occur.

If the sympathetic division can be called the fight-or-flight system, the parasympathetic division can be called the “eat-drink-and-rest” system. The neurons of this division are located at the top and bottom of the spinal column on either side of the sympathetic division neurons (para means “beyond” or “next” and in this sense refers to the neurons located on either side of the sympathetic division. neurons).

Looking at Figure 2.8, it may seem like the parasympathetic division does pretty much the opposite of the sympathetic division, but it’s a little more complex than that. The task of the parasympathetic division is to restore the body to normal function after the stressful situation is over. It slows the heart and breathing, constricts the pupil, and reactivates digestion and excretion. The signal to the adrenal gland stops because the parasympathetic division does not connect with the adrenal gland. In a sense, the parasympathetic division allows the body to use all the energy it burns – that’s why people are often hungry.

The Nervous System

The parasympathetic division does not only respond to the activity of the sympathetic division. It is the parasympathetic division that is responsible for most of the body’s daily functions, such as regular heart rate and normal breathing and digestion. People spend most of their 24 hours a day eating, sleeping, digesting, and excreting. So the parasympathetic division is normally active. At a certain moment, then, one or the other of these divisions, sympathetic or parasympathetic, will determine whether people are aroused or relaxed. cranium, and the spinal cord, the extension of the nerve network in the vertebral column. In addition, the nerve tissue that extends from the brain and spinal cord to the rest of the body (nerves) is also part of the nervous system. Anatomically, the nervous system can be divided into two main areas: the central nervous system (CNS) is the brain and spinal cord, the peripheral nervous system (PNS) is the nerves (Figure 12.1.1). The brain is in the cranial cavity of the skull, and the spinal cord is in the vertebral canal of the vertebral column. The peripheral nervous system is so named because it is in the periphery—meaning beyond the brain and spinal cord.

Figure 12.1.1 – Central and Peripheral Nervous System: CNS contains brain and spinal cord, PNS includes nerves.

In addition to the anatomical divisions mentioned above, the nervous system can also be divided according to its function. The nervous system is involved in receiving information about our surroundings (sensory function, sensation) and producing a response to that information (motor function, response) and coordinating the two (integration).

. Sensation refers to receiving information about the environment, whether it is happening outside (ie: heat from the sun) or inside the body (ie: heat from muscle activity). These sensations are known as stimuli (singular = stimulus) and different sensory receptors are responsible

Overview Of Neuron Structure And Function (article)

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