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The Central Nervous System Consists Of Two Parts

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Last Updated: 02 July 2021

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Cerebrum is the largest part of the brain and controls voluntary actions, speech, senses, think, and memory. The surface of the cerebral cortex has grooves or infoldings, largest of which are term fissures. Some fissures separate lobes. Convolutions of the cortex give it a wormy appearance. Each convolution is delimit by two sulci and is also called gyrus. Cerebrum is divided into two halves, known as right and left hemispheres. A mass of fibers called corpus callosum link hemispheres. The right hemisphere controls voluntary limb movements on the left side of the body, and the left hemisphere controls voluntary limb movements on the right side of the body. Almost every person has one dominant hemisphere. Each hemisphere is divided into four lobes, or areas, which are interconnect. Frontal lobes are located in front of the brain and are responsible for voluntary movement and, via their connections with other lobes, participate in execution of sequential tasks; speech output; organizational skills; and certain aspects of behavior, mood, and memory. Parietal lobes are located behind frontal lobes and in front of occipital lobes. They process sensory information such as temperature, pain, taste, and touch. In addition, processing includes information about numbers, attentiveness to the position of one's body parts, space around one's body, and one's relationship to this space. Temporal lobes are located on each side of the brain. They process memory and auditory information and speech and language functions. Occipital lobes are located at the back of the brain. They receive and process visual information. The cortex, also called gray matter, is the external layer of the brain and predominantly contains neuronal bodies. Gray matter participates actively in the storage and processing of information. An isolated clump of nerve cell bodies in gray matter is term nucleus. Cells in gray matter extend their projections, called axons, to other areas of the brain. Fibers that leave the cortex to conduct impulses toward other areas are term efferent fibers, and fibers that approach the cortex from other areas of the nervous system are term afferent. Fibers that go from the motor cortex to the brainstem or spinal cord receive names that generally reflect connections. Axons are surrounded in their course outside gray matter by myelin, which has a glistening whitish appearance and thus gives rise to the term white matter. Cortical areas receive their names according to their general function or lobe name. If in charge of motor function, area is called the motor cortex. If in charge of sensory function, area is called the sensory or somesthetic cortex. The Calcarine or visual cortex is located in the occipital lobe and receives visual input. The auditory cortex, localized in the temporal lobe, processes sounds or verbal input.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

divisions of the nervous system

The picture you have in your mind of the Nervous System probably includes the brain, nervous tissue contained within the cranium, and spinal cord, extension of nervous tissue within the vertebral column. That suggests it is made of two organsand you may not even think of the spinal cord as an organbut, 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 is as if the Nervous System is composed of many organs that all look similar and can only be differentiated using tools such as microscope or electrophysiology. In comparison, it is easy to see that the stomach is different than the esophagus or liver, so you can imagine the digestive system as a collection of specific organs. The Nervous System can be functionally divided into 3 actions: sensation, integration, and response. The Nervous System is involved in receiving information about the environment around us and generating responses to that information. The Nervous System can be divided into regions that are responsible for sensation and for response. But there is a third function that needs to be include. Sensory input needs to be integrated with other sensations, as well as with memories, emotional state, or learning. Some regions of Nervous System are term integration or association areas. The process of integration combines sensory perceptions and higher cognitive functions such as memories, learning, and emotion to produce a response. Sensation. The first major function of the Nervous System is sensationreceiving, information about the environment to gain input about what is happening outside the body. Sensory functions of the Nervous System register the presence of change from homeostasis or particular event in the environment, know as stimulus. Sense we think of most are the big five: taste, smell, touch, sight, and hearing. Stimuli for taste and smell are both chemical substances, touch is physical or mechanical stimuli that interact with skin, sight is light stimuli, and hearing is perception of sound, which is a physical stimulus similar to some aspects of touch. There are actually more senses than just those, but that list represents major senses. Those five are all senses that receive stimuli from the outside world, and of which there is conscious perception. Additional sensory stimuli might be from the internal environment, such as stretching of the organ wall or concentration of certain ions in blood. Integration. Stimuli that are received by sensory structures communicate to the nervous system where that information is process. This is called integration. Stimuli are compared with, or integrate with, other stimuli, memories of previous stimuli, or the state of a person at a particular time. This leads to specific responses that will be generate. Seeing a baseball pitch to batter will not automatically cause the batter to swing. The trajectory of the ball and its speed will need to be consider.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Central Nervous System

The Central Nervous System is divided into two parts: brain and spinal cord. The average adult human brain weighs 1. 3 to 1. 4 kg. The brain contains about 86 billion nerve cells and trillions of support cells called glia. The spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about 35 - 40 grams. The vertebral column, collection of bones that houses the spinal cord, is about 70 cm long. Therefore, spinal cord is much shorter than the vertebral column. For the brain weight of other animals, see brain facts and figures.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

What Does the Brain Do?

The brain is the most complex organ in the human body; cerebral cortex contains an estimated 15 - 33 billion neurons, each of which is connected to thousands of other neurons. In total, around 100 billion neurons and 1 000 billion glial cells make up the human brain. Our brain uses around 20 percent of our body's total energy. The brain is the central control module of the body and coordinates activity. From physical motion to secretion of hormones, creation of memories, and sensation of emotion. To carry out these functions, some sections of the brain have dedicated roles. However, many higher functions reasoning, problem - solving, creativity involve different areas working together in networks. Temporal lobe: important for processing sensory input and assigning it emotional meaning. It also involves laying down long - term memories. Some aspects of language perception are also house here. Occipital lobe: visual processing region of the brain, housing visual cortex. Parietal lobe: parietal lobe integrates sensory information including touch, spatial awareness, and navigation. Touch stimulation from the skin is ultimately sent to the parietal lobe. It also plays a part in language processing. Frontal lobe: position in front of the brain, frontal lobe contains the majority of dopamine - sensitive neurons and is involved in attention, reward, short - term memory, motivation, and planning.


What is the central nervous system?

The central nervous system is better protected than any other system or organ in the body. Its main line of defense is the bones of the skull and spinal column, which create a hard physical barrier to injury. Fluid - fill space below bones, called syrnix, provides shock absorbance. Unfortunately, this protection can be a double - edge sword. When injury to the central nervous system occur, soft tissue of the brain and spinal cord swells, causing pressure because of confined space. Swelling makes injury worse unless it is rapidly relieve. Fracture bones can lead to further damage and the possibility of infection.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Sympathetic and Parasympathetic Nervous Systems

Table

FeatureSympathetic NSParasympathetic NS
Summary of responsesFight or flightRest and digest
Spinal cord distributionThoracolumbarCraniosacral
Preganglionic neuroneShortLong
Preganglionic neurotransmitterAcetylcholine (Ach, cholinergic)Acetylcholine (Ach, cholinergic)
Postganglionic neuroneLongShort
Postganglionic neurotransmitterNoradrenaline (NA, adrenergic) in most casesAcetylcholine (Ach, cholinergic)

The Peripheral nervous system is the connection between the central nervous system and the rest of the body. CNS is like power plant of nervous system. It creates signals that control the functions of the body. Pns is like wires that go to individual houses. Without those wires, signals produced by the CNS could not control the body. Pns can be broken down into autonomic nervous system, which controls bodily functions without conscious control, and sensory - somatic nervous system, which transmits sensory information from skin, muscles, and sensory organs to CNS and sends motor commands from CNS to muscles. The autonomic nervous system serves as a relay between CNS and internal organs. It controls lungs, heart, smooth muscle, and exocrine and endocrine glands. The autonomic nervous system controls these organs largely without conscious control; it can continuously monitor conditions of these different systems and implement changes as needed. Signaling to target tissue usually involves two synapses: preganglionic neuron synapses to neuron in ganglion that, in turn, synapses on the target organ, as illustrated in Figure 16. 26. There are two divisions of the autonomic nervous system that often have opposing effects: sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system is responsible for fight or flight response that occur when an animal encounters a dangerous situation. One way to remember this is to think of the surprise person feels when encountering a snake. Examples of functions controlled by the sympathetic nervous system include accelerating heart rate and inhibiting digestion. These functions help prepare organisms ' body for physical strain required to escape potentially dangerous situations or to fend off predator. Most preganglionic neurons in the sympathetic nervous system originate in the spinal cord, as illustrated in Figure 16. 27. Axons of these neurons release acetylcholine on postganglionic neurons within sympathetic ganglia. Acetylcholine activates postganglionic neurons. Postganglionic neurons then release norepinephrine onto target organs. As anyone who has ever felt rush before a big test, speech, or athletic event can attest, effects of the sympathetic nervous system are quite pervasive. This is both because one preganglionic neuron synapses on multiple postganglionic neurons, amplifying the effect of the original synapse, and because adrenal gland also releases norepinephrine into the blood stream. Physiological effects of this norepinephrine release include dilating trachea and bronchi, increasing heart rate, and moving blood from skin to heart, muscles, and brain. Strength and speed of sympathetic response help organisms avoid danger, and scientists have found evidence that it may also increase LTPallowing, animals to remember dangerous situations and avoid them in future. While the sympathetic nervous system is activated in stressful situations, parasympathetic nervous system allows animal to rest and digest.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

Table2

FeatureSympathetic NSParasympathetic NS
Summary of responsesFight or flightRest and digest
Spinal cord distributionThoracolumbarCraniosacral
Preganglionic neuroneShortLong
Preganglionic neurotransmitterAcetylcholine (Ach, cholinergic)Acetylcholine (Ach, cholinergic)
Postganglionic neuroneLongShort
Postganglionic neurotransmitterNoradrenaline (NA, adrenergic) in most casesAcetylcholine (Ach, cholinergic)
* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Enteric Nervous System

This Nervous System is embed within the lining of the gastrointestinal tract so it can directly control functions of the GI tract. It consists of two plexuses: myenteric plexus located between inner and outer layers of muscularis externa Responsible for increasing tone of gut Controls velocity and intensity of contractions. Submucosal plexus located in the Submucosal layer Responsible for secretions and absorption in the gut Controls local muscle movements as well PNS also stimulates Enteric Nervous System to increase function. Therefore, defecation is not possible during fight or flight mode, as the sympathetic Nervous System inhibits Enteric function.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Synapses and neurotransmission

The nervous system is very complex and toxins can act at many different points in this complex system. The focus of this section is to provide a basic overview of how the nervous system works and how neurotoxins affect it. Due to the complexity of these topics, this section does not include extensive details relating to anatomy and physiology of the nervous system or many neurotoxins in our environment and subtle ways they can damage the nervous system or interfere with its functions. Since the nervous system innervates all areas of the body, some toxic effects may be quite specific and others generalize depending upon where in the nervous system the toxin exerts its effect. Before discussing how neurotoxins cause damage, we will look at basic anatomy and physiology of the nervous system.


Toxic Damage to Nervous System

The nervous system is quite vulnerable to toxins since chemicals interacting with neurons can change critical voltages, which must be carefully maintain. However, nervous system has defense mechanisms that can protect it from toxins. Most CNS are protected by an anatomical barrier between neurons and blood vessels, know as the blood - brain barrier. It is protected from some toxin exposures by tightening junctions between endothelial cells of blood vessels in CNS and having astrocytes surround blood vessels. This prevents diffusion of chemicals out of blood vessels and into intracellular fluid except for small, lipid - soluble, non - polar molecules. Specific transport mechanisms exist to transport essential nutrients into the brain. Another defense mechanism within the brain to counter chemicals that pass through the vascular barrier is the presence of metabolizing enzymes. Certain detoxifying enzymes, such as monoamine oxidase, can biotransform many chemicals to less toxic forms as soon as they enter intercellular fluid. Basic types of changes due to toxins can be divided into three categories - 1 sensory; 2 motor; and 3 interneuronal - depending on the type of damage sustain. Damage can occur to sensory receptors and sensory neurons, which can affect basic senses of pressure, temperature, vision, hearing, taste, smell, touch, and pain. For example, heavy metal poisoning, especially lead and mercury, can cause deafness and loss of vision. Several chemicals, including inorganic salts and organophosphorus compounds, can cause loss of sensory functions. Damage to motor neurons can cause muscular weakness and paralysis. Isonicotinic hydrazide used to treat tuberculosis can cause such damage. Interneuronal damage can cause learning deficiencies, loss of memory, incoordination, and emotional conditions. Low levels of inorganic mercury and carbon monoxide can cause depression and loss of memory.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

What causes paralysis?

There is logical and physical topographical organization to the anatomy of the central nervous system, which is an elaborate web of closely connected neural pathways. This order relationship means that different segmental levels of cord control different things, and injury to particular part of the cord will have an impact on neighboring parts of the body. Paralysis occurs when communication between the brain and spinal cord fail. This can result from injury to neurons in the brain, or in the spinal cord. Trauma to the spinal cord affects only areas below the level of injury. However, poliomyelitis or Lou Gehrig's disease can affect neurons in the entire spinal cord.


Spinal Cord

A common set of biological events take place following spinal cord injury: cells from the immune system migrate to the injury site, causing additional damage to some neurons and death to others that survive initial trauma. Death of oligodendrocytes causes axons to lose their myelination, which greatly impairs conduction of action potential, messages, or renders remaining connections useless. The Neuronal information highway is further disrupted because many axons are sever, cutting off lines of communication between the brain and muscles and between the body's sensory systems and the brain. Within several weeks of initial injury, area of tissue damage has been cleared away by microglia, and a fluid - filled cavity surrounded by glial scar is left behind. Molecules that inhibit regrowth of severed axons are now expressed at this site. Cavitation is called syrinx, which acts as a barrier to reconnection of two sides of the damaged spinal cord. Although spinal cord injury causes complex damage, surprising amount of basic circuitry to control movement and process information can remain intact. This is because the spinal cord is arranged in layers of circuitry. Many of the connections and neuronal cell bodies forming this circuitry above and below the site of injury survive trauma. An important question for research scientists is, how much do these surviving neurons know? Can they regenerate and make new, correct connections?


What is the central nervous system?

Nervous SYSTEM is a collection OF CELLS, tissues, and organs. It can be split into two separate divisions: Central Nervous SYSTEM and peripheral Nervous SYSTEM. The Central Nervous SYSTEM acts as the command center of the body. It interprets incoming sensory information, then sends out instructions on how the body should react. Cns consists of two major parts: BRAIN and spinal cord. The Peripheral Nervous SYSTEM is Part OF Nervous SYSTEM outside OF CNS. It consists mainly of nerves that extend from the BRAIN and spinal cord to areas in the rest of the body. Cranial nerves carry impulses to and from BRAIN while spinal nerves carry impulses to and from the spinal cord. Pns can be divided into two systems: somatic Nervous SYSTEM and autonomic Nervous SYSTEM. Somatic Nervous SYSTEM controls voluntary movements of skeletal muscles. Autonomic Nervous SYSTEM controls activities in the body that are involuntary or automatic. These include actions of the heart, glands, and digestive organs and associate parts. Autonomic Nervous SYSTEM can be divided further into two subdivisions: parasympathetic and sympathetic Nervous systems. These two subdivisions work against each other. Parasympathetic Nervous SYSTEM regulates involuntary activities that keep the body running smoothly under normal, everyday conditions. Sympathetic Nervous SYSTEM controls involuntary activities that help the body respond to stressful situations.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

The information pathways

Neurons connect with one another to send and receive messages in the brain and spinal cord. Many neurons working together are responsible for every decision make, every emotion or sensation felt, and every action take. The complexity of the central nervous system is amazing: There are approximately 100 billion neurons in the brain and spinal cord combine. As many as 10 000 different subtypes of neurons have been identify, each specializing in sending and receiving certain types of information. Each neuron is made up of a cell body, which houses nucleus. Axons and dendrites form extensions from the cell body. Astrocytes, kind of glial cell, are primary support cells of the brain and spinal cord. They make and secrete proteins called neurotrophic factors. They also break down and remove proteins or chemicals that might be harmful to neurons. Astrocytes aren't always beneficial: after injury, they divide to make new cells that surround the injury site, forming a glial scar that is a barrier to regenerating axons. Microglia are immune cells for the brain. After injury, they migrate to the site of injury to help clear away dead and dying cells. They can also produce small molecules called cytokines that trigger cells of the immune system to respond to injury site. This clean - up process is likely to play an important role in recovery of function following spinal injury.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Voluntary and involuntary movement

The central nervous system is made up of the brain and spinal cord, which process sensory input and provide instructions to the body. The central nervous system is one of two major subdivisions of the nervous system. Cns include the brain and spinal cord, which together comprise the body's main control center. Together with the peripheral nervous system, CNS performs fundamental functions that contribute to organisms ' life and behavior. The nervous system has three main functions: gathering sensory information from external stimuli, synthesizing that information, and responding to those stimuli. Cns is mainly devoted to information synthesizing function. During this step in the process, brain and spinal cord decide on appropriate motor output, which is computed based on type of sensory input. CNS regulates everything from organ function to high - level thinking to purposeful body movement. Thus, CNS is commonly thought of as the control center of the body. Cns is comprised of the brain, brain stem, and spinal cord.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Autonomic Nervous System

The autonomic nervous system is a network of nerves and ganglia that control involuntary physiologic actions and maintain internal homeostasis and stress responses. Ans innervate structures within cardiovascular, pulmonary, endocrine, exocrine, gastrointestinal, genitourinary, and central nervous systems and influences metabolism and thermal regulation. Ans is divided into two parts: sympathetic and parasympathetic nervous system. When stimulate, effects of SNS are widespread across the body. In contrast, PNS stimulation tends to produce localized, discrete effects. Sns and PNS generally have opposing effects on end - organs, with either SNS or PNS exhibiting dominant tone at rest and without exogenous stimulating events. In general, function of PNS is homeostatic, whereas stimulation of SNS prepares organism for some stressful event.Sss

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Sources

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

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