Nervous System Vertebrates Vs Invertebrates Physical Education Essay

The nervous system is an organ system composed of a net of cells called neurons in the brain that regulates the animal’s action and sends signals between from the brain to the rest of the body (Northcutt, 2000) . Vertebrates are part of the subphylum of Vertebrata. These animals possesses internal skeleton made of bone (spinal cord) (Northcutt, 2000). Invertebrates are animals without a backbone. A vertebrate nervous is by far more complex than that of an invertebrate. These two phyla of animals are as different as day and light but still possess similar characteristics pasted down by the early animals (invertebrates). The comparison of the nervous systems between these two phyla of animals can be done more intensely with the comparison of mammals and insects.

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Invertebrates are animals that lack a spinal cord (backbone). Invertebrates include animals such as insects, worms, jellyfish, and spiders ect… Invertebrates’ nervous system exhibit cephalization which is an evolutionary process where nervous tissue and sensory structures are concentrated in the front end of the nerve cord (Freeman, 2005). Among the noncoelomate invertebrates, sponges are the only major phylum that lack nerves. The simplest nervous systems occur among cnidarians, in which all neurons are similar and linked to one another in a web, or nerve net. There is no associative activity, no control of complex actions, and little coordination.
The simplest animals with associative activity in the nervous system are the free-living flatworms, phylum Platyhelminthes. Running down the bodies of these flatworms are two nerve cords, from which peripheral nerves extend outward to the muscles of the body. The two nerves cords converge at the front end of the body, forming an enlarged mass of nervous tissues that also contains interneuron with synapses connecting neurons to one another. This primitive “brain” is a rudimentary central nervous system and permits a far more complex control of muscular responses than is possible in cnidarians (Freeman, 2005).
All of the consecutive evolutionary transformation in nervous systems can be considered as a series of amplification on the characteristics already present in flatworms. For example, among coelomate invertebrates, earthworms exhibit a central nervous system that is connected to all other parts of the body by peripheral nerves.
As animals became more complex, so did their nervous systems. The complex nervous system of vertebrate animals has a long evolutionary history. The origin and development of the vertebrate nervous system begins with the primitive brain of vertebrates (Northcutt, 2000). The lampreys and hagfishes are the most primitive living vertebrates. Their brains reveal the most basic and simple vertebrate brain pattern. The myelin sheath on the nerve fibers found in all higher vertebrates is not present in these animals (Northcutt, 2000) . They lack the complexity of the nervous connection of all the higher vertebrates. Although the early vertebrate brain was small it already had three divisions that characterize the brains of all contemporary vertebrates (Webster, 2004) . The Hindbrain or rhombencephalon is composed of the cerebellum and the medulla oblongata (passes thru the spinal cord) which regulate the animal’s balance and movement (Nathan, 1997). The midbrain or mesencephalon is situated behind the thalamus and regulate vision (Nathan, 1997). The forebrain or prosencephalon is the front part of the brain which deals with smell (Nathan, 1997).
The nervous system is the most complex system in the body. The nervous system is divided into the central nervous system and the peripheral nervous system. The brain and the spinal cord form the central nervous system of vertebrates while sensory and motor form the peripheral nervous system.
The central nervous system is the largest and the most complex part of the nervous system. It is the body’s command center. It works to align the activities of all the body parts. The central nervous system composed the brain and spinal cord is cavernous and alveolate and positioned above dorsal to the gut (Webster, 2004). The spinal cord is uniformly gray in color with the nerve cell bodies lying close to the central canal (Webster, 2004). It is responsible for receiving and interpreting signals from the peripheral nervous system and also sends out signals to it, either consciously or unconsciously. The peripheral nervous system (PNS) in vertebrates is divided into the somatic and the autonomic nervous system. Motor neurons that stimulate skeletal muscles to contract make up the somatic nervous system; those that regulate the activity of the smooth muscles, cardiac muscle, and glands compose the autonomic nervous system. The autonomic nervous system is further broken down into the sympathetic and parasympathetic divisions. These divisions counterbalance each other in the regulation of many organ systems.
The honey bee is an invertebrate (insect) which normally have a primitive nervous system (Blankenship and Houck, 2002). However the honey bee possesses a very developed nerve and sensory system. Their Central Nervous System is divided into a brain (in the head) which is located above the pharynx, and a ventral nerve cord (accumulation of nerves in the abdomen) stretching from the head to end of abdomen (Blankenship and Houck, 2002). The brain is the seat of all the mental faculties of a bee. The brain is the bee’s sensory center. A decapitated bee is deprived of any sensory stimuli and the ability to eat (Blankenship and Houck, 2002). However the bee still retains its motor competence which means it can still walk, fly and sting (Blankenship and Houck, 2002). Sensory information travels from the eyes and antennae which transmits the nervous impulses to the motor centers of the ventral nerve cord.
Just like Vertebrates, Invertebrate’s neurons work using an electrochemical process. The honey bee nervous system is similar to that of vertebrates Although Invertebrates nervous system functions basically the same way as that of vertebrates there structure are completely different.
The Honey Bee nervous system is less advanced and complex than humans. Their spineless feature is the main difference between theirs and Humans nervous system. The Honey Bee ‘s nervous system is distributed throughout the body, whereas Humans that have a spine have a central nervous system and a peripheral nervous system, or in other words a central control system and a sensory system. The division of Human’s nervous system into the central and peripheral nervous enhances the complexity of their system. The central nervous system (the brain and spinal cord), is hollow and situated above (dorsal to) the gut (Hörstadius, 2006). This contrasts with the solid ventral nerve cord of the Honey Bee (Hörstadius, 2006). Humans possess a highly developed and larger brain which gives them a more profound intelligence and thinking. With the help of specialized nerve fibers, they can react very quickly to changes in their surroundings, giving them a competitive edge. However unlike other invertebrate the Honey Bee brain is encased in a definite head just like humans.
The nervous systems in animals range from simple nerve nets to paired nerve cords with primitive brains to elaborate brains and sensory systems. Virtually all members of the animal kingdom have at least a rudimentary nervous system. Invertebrate animals show varying degrees of complexity in their nervous systems, but it is in the vertebrate that the system reaches its greatest complexity. The difference between the human and honey bee nervous system is greater than the similarities.
Work Cited
R. Glenn Northcutt, Charles Noback, Ruben Adler, Bengt Kallen, Leon S. Stone, (2000) “Nervous system (vertebrate)”, in AccessScience@McGraw-Hill,, DOI 10.1036/1097-8542.449300
James E. Blankenship, Becky Houck, (2002), “Nervous system (invertebrate)”, in AccessScience@McGraw-Hill,, DOI 10.1036/1097-8542.449210
Walter J. Freeman, (2005), “Brain”, in AccessScience@McGraw-Hill,, DOI 10.1036/1097-8542.093200
Douglas B. Webster, (2004) “Spinal cord”, in AccessScience@McGraw-Hill,, DOI 10.1036/1097-8542.645900
Sven Hörstadius, (2006), “Neural crest”, in AccessScience@McGraw-Hill,, DOI 10.1036/1097-8542.449700
Peter Nathan, (1997), The Nervous system, London : Whurr Publishers, 1997

How Nervous and Hormonal Systems Produce the Fight or Flight Response

How both nervous and hormonal systems interact to produce the ‘fight or flight’ response

The nervous system

Within the body, the nervous system consists of a complex circuit of nerves and cells, which carry messages to and from the brain and spinal cord, which will then be sent out to the other parts of the body to where the message needs to be sent. Within the nervous system there is two more systems, these are the central nervous system and the peripheral nervous system. (News-medicalnet, 2010)

The Central nervous system – is the system, which helps the body to transmit electrical signals to and from the brain to detect things on the receptors on the skin. One part that works within the nervous system is the central nervous system.

The central nervous system is made up of 2 main parts. These are the brain and the spinal cord. These are the things that will send the electrical impulses to and from the parts of the body, which they are coming from.

Within the CNS the brain is responsible for the information that it receives both conscious and unconscious functions and is the main center which controls the body and activity which the body doe. This can be from a range of things such as secretion of hormones, sensation and memory. (Medicalnewstodaycom, 2018)   

As well as the brain there is the spinal cord. This is where the motor nurones travel from the brain to the rest of the body sending the electrical signals this is where the relay nutronas are primerally based within the body. The spinal nerves within the body carry information into the spinal cord at diferent levels wihtin the spinal cord.

The preripheral nervous system –  contains all the nerves outside of the centeral nervous system which connects the centeral nervous system to the organs. These nerves are made up of axons which are attached in a reflex arc. The preripheral system is made up of 3 types of nerves; The cranial nerves, the spinal nerves and the preripheral nerves.

The cranial nerves are the nerves that travel from the brain to the top of the body including the head and neck, these casn also incluse the senses such as touch smell and sight. Also controling the facial muscles and glands within the neck.(Msdmanualscom, 2018)

The spinal nerves are wihtin the spine and we have 31 pairs of different nerves that make up all the spinal nerves these are:

8 pairs of cervical nerves

12 pairs of thoracic nerves

5 pairs of lumbar nerves

5 pairs of sacral nerves

1 pair of coccygeal nerves (Antranikorg, 2018)

These spinal nerves carry a rage of motor, sensory and autonomic signals through the spinal cord and into the rest of the body. (Christopherreeveorg, 2018)

The PNS’ main function is to connect the CNS to all the main organs and limbs. The PNS consists of two systems; the motor system and the sensory system. The motor system is there to send responces to the effectors within the reflex arc.

Sensory neurons are converted to a special type of stimulus by the receptors, which are then converted into action potential to be sent to the reflex arc to be converted into an action through the CNS. Motor neurons carry the signal from the CNS to a muscle skin or organ these carry out the sensory neuron signals that was sent to the CNS.

The endocrine system

Within the body, the Endocrine system is made up of many glands that help produce and secrete hormones that help to regulate the bodies systems and functions. Through doing this it will help the body to grow and develop in many ways, one of these is sexual development and sexual function. The hormones from the endocrine system is released into the blood and travels to the necessary organs to be able to be used efficiently. These hormones are then sent through the body by chemical messages to go the right areas within the body. The hormones from the pituitary gland are released by the hypothalamus sending a signal to the pituitary gland telling it to release a specific hormone. This then is released from the pituitary gland in the form of a stimulating hormone. This hormone is then sent to the to the target area to allow it to secrete the hormones. While it is secreting hormones, the hypothalamus and pituitary glands shut down which then means that the target gland slows down as well. This then results in the blood concentrations becoming stable.

The comparison between the endocrine system and the nervous system

One of the main differences between the endocrine system and the nervous systems is that the nervous system uses electrical impulses to be able to send signals around the body using the neurones to and from the brain and other parts of the body. However, the endocrine system is a collection of glands within the body, which produce and secrete hormones and help to develop and to regulate the body’s growth and development throughout the life stages as well as many other different internal functions. The endocrine system sends their signals through chemical messages rather than nervous. Therefore, the endocrine system works a lot slower than the nervous system. This is because the nervous system uses the action potential neurones within the body to transfer the messages, relaying them in a matter of milliseconds. However, the endocrine system responds slower as they secrete the hormones, which goes through the blood to get to the necessary organs or glands.

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As well as this, there is a different kind of response that they both carry out. The nervous system has a localised response, which will only be in a specific area of the body. As well as this, it will only affect the part of the body, which the electrical signals have come from in the first place. However, within the endocrine system the response takes place throughout the whole the full body not just in a specific place.

The nervous system only has a short period where it will affect the body then the changes will change back to how they was before. However, the endocrine system makes a permanent response throughout the body. (Biodifferencescom, 2017)

How are they linked?

The nervous system and the endocrine system both work together to maintain homeostasis. (Quoracom, 2018) All the organs within the bodywork together to get one whole process complete. This is mainly because they are regulated by the nervous system and the endocrine system. The nervous system controls the bodies actions and activities whereas the endocrine system controls the supply of hormones to the different organ systems which will be carrying out these activities. When these function together it helps to keep the bodies temperature, pH and other systems to make sure that they are within the right levels for the body to process. (Quoracom, 2018)

Danger has been detected therefore the body has become prepared to fight off anything that is seen as a threat to them.


This then allows nervous impulses to be sent to the hypothalamus in the brain. Which then sends signals out to the other systems.


The sympathetic nervous system is then activated ready to release the hormones that it needs to help with the response to the stimuli.


The sympathetic nerves then release adrenaline for the body to be able to react quickly.

At the same time as the sympathetic nerves releasing adrenalin the adrenal medulla releases adrenalin also.


Both of these systems work together to help the body to prepare for the danger (stimuli) this will in return help an animal escape from conflict causing the heart rate and glucose levels to increase and the pupils to dilate.

The fight or flight response

When the body is exposed to stress the heart, rate will increase as we as the breathing rate. This will increase the intake of oxygen into the lungs to pump around the body and to decrease the amount of carbon dioxide which is in the lungs. this then causes more oxygenated blood to circulate the body to make sure that all the muscles can react and able to complete respiration faster than normal.

This then causes the eyes to react to the stress neurones; the radial muscles in the iris dilate which then increases the amount of light that can get into the eye to increase visibility.

The sphincter muscle in the urethra and anus will relax therefore causing urination and defecation, this is one way to loose excess weight so they can get away much faster than if they didn’t. This means that they will be able to flee as quickly as they can meaning that they will be able to escape the danger. (Howstuffworkscom, 2018)

The arterioles that supply the intestines and the skin will then constrict. This will then cause the blood to go to the more important areas of the body where they will need the blood supply the most; this means that they will divert from the non-essential parts of the body and concentrate on the parts, which will be used within the situation such as digestion. As well as this, the salivary glands will stop producing salivary, as this is not essential when it comes to running away from something this will keep energy stored to be used with its needed, as the body is not doing necessary things to stay alive. This then causes blood pressure to increase causing the heart rate to increase. The arterioles within the skeletal muscles will then dilate allowing more blood to flow through these, as we will be using them to get away from the danger or situation.

This will the cause the blood glucose levels within the body to increase, which will then increase the glucose supply to the muscles to be able to carry out respiration and therefore providing the energy for muscle contraction and to get away. (Howstuffworkscom, 2005)

Consequences when these malfunction

When these systems malfunction, they can cause problems within the body. When the endocrine system fails one of the complications could be diabetes.

There are two main different types of diabetes these are type one and type two

What is type 1 diabetes?

Type 1 diabetes, which is also known as insulin dependent diabetes, is a condition where the body depends on yourself to be able to supply it with the insulin that it needs when it requires it this is all because the pancreas produces little to no insulin to be able to break down the sugars that are in the blood, the insulin also helps the sugar to enter the cells and to produce the energy that we need to be able to get on with our day to day activities.


Hyperglycaemia is where your blood glucose levels have risen too high because you have eaten too much sugar. To be able to treat this you can use your insulin to try and get your levels down to the normal range for them. To be able to prevent this so there isn’t a next time you can be careful with what you eat as then you can manage what you are eating and if and when you might go high. Another way is to monitor your levels, this means that you will be more in control with your diabetes and treat the hyper before you hit it.

Some of the symptoms for hyperglycaemia are:

Increased thirst


Weight loss

Blood glucose levels higher than 180 mg/dL

Needing to urinate more

Some of the causes of hyperglycaemia are:

Forgetting insulin injections

Eating too many carbohydrates



Becoming inactive


Hypoglycaemia is where your blood sugars fall below the range that they are meant to fall below, this means that there isn’t enough sugar in your body and can become dangerous. To be able to treat this you can eat a sugary drink or have a sugary snack to be able to get into your system and bring your sugar back up to normal levels, as well as this you can also test your blood regularly to make sure that you’re not falling too low.

Some of the symptoms of hypoglycaemia are like the symptoms of hyperglycaemia the symptoms are:




Feeling weak

Higher heart rate

Blurred vision

Some of the causes of hypoglycaemia are:

To high dose of insulin


Alcohol consumption

Delaying or non-sufficient meals

The pancreas

The pancreas has an important role within the body which allows the regulation of sugar to take place, when you have eaten your blood glucose level will go up causing the cells in your pancreas also known as the beta cells to start to produce the right amount of insulin to be able to work with the sugar and allow it to work within the body and to be sent around the body to keep your organs working and healthy.  The Endocrine system is the system that involves all the glands in the body that produce hormones, this makes sure that the body can work the way that it is supposed to which will keep you healthy. However, if your Endocrine system isn’t healthy then it won’t be able to function well enough, therefore you might have problems growing and developing, you might gain weight easily and develop osteoporosis, as well as this you could also lack a lot of energy as the sugar stays in the blood instead of going into the cells where it can be used for energy. One of the glands that are in the Endocrine system is the Hypothalamus this gland helps the body to know when to start and stop producing the hormones and sends signals to the pituitary gland to do this. However, hormones are secreted from the islets of langhans these then secrete the hormones such as glucagon to produce insulin.

There is no main cause for type 1 diabetes, however it is thought that it is the body’s own immune system that is there to fight the more harmful bacteria within the body attacks the beta cells within the pancreas as it doesn’t recognise them as part of the body. Another cause is that it could be passed down through genetics and your DNA and that it could develop if you have caught a virus or it could be cause by other environmental factors.

Type 2 diabetes.

Type 2 diabetes is the most common type of diabetes this is when your blood glucose is too high because of the food that you eat. Within type 2 diabetes your pancreas doesn’t use insulin correctly or doesn’t produce enough of it to be able to sustain the blood sugar levels within a healthy amount which then results in your body storing the glucose in the blood and not enough reaches the cells.

Multiple sclerosis

Whereas if the nervous system fails then this can cause problems such as (multiple sclerosis) Ms occurs when the immune system attacks the myelin sheath that is protecting the nerve fibres which then causes communication problems between the brain and the rest of the body. This will then, over time, cause the nerve fibres to become permanently damaged meaning that they wouldn’t be able to function well causing symptoms such as lack of coordination, numbness or weakness in one or more limbs that occurs on one side of the body.   (Uofmhealthorg, 2018) (Mayoclinicorg, 2018)


Biodifferencescom. (2017). Bio Differences. Retrieved 15 December, 2018, from

News-medicalnet. (2010). News-Medicalnet. Retrieved 15 December, 2018, from

Quoracom. (2018). Quoracom. Retrieved 15 December, 2018, from

Howstuffworkscom. (2005). HowStuffWorks. Retrieved 17 December, 2018, from

Howstuffworkscom, . (2018). ENotes. Retrieved 17 December, 2018, from /homework-help/how-does-nervous-system-endocrine-work-together-254816

Quoracom. (2018). Quoracom. Retrieved 17 December, 2018, from 

Uofmhealthorg. (2018). Uofmhealthorg. Retrieved 19 December, 2018, from

Mayoclinicorg. (2018). Mayo Clinic. Retrieved 19 December, 2018, from


A Report Of The Nervous System

The report are divided into two parts. first we will be talking about the Organization of the Nervous System, that includes the Peripheral Nervous system, and the Central Nervous system, then we will move on to the Brain and Behavior part, where we will start to talk about the brain and listing down the three major regions of the brains, and how each brain has its own functions different than the other regions, even though they are all located in the brain.
In this report, you will find information about organs or nervous systems found in the human body, beginning with the definitions, describing its structure and functions in the body, illnesses or disorders that affects that part in the body.
Part 1: Organization of Nervous System:
The Nervous System is a world in itself, we’ve learned only the little tidbits of its secrets, but there are many of what we still do not know, and in this section of the report, we will try to identify the anatomic configuration of the nervous system, its division and branches, and the function of each part of it, and the problems resulting in every part.

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The communication in the nervous system is essential to behavior. If you’ve wondered how you are aware of the elements in the environment surrounding you, you hear with your ears and see with your eyes, and be aware of many things by touching and smelling and tasting, following this awareness a response coming from you, so you move or talk or touch and hold things. You receive the influential in a very short time, and this can be done by the nervous system, moreover, the nervous system controls the other organs that works voluntary such as holding up things or the involuntary such as heartbeat rate.
Nervous System chart
Nervous system sections:
The nervous system are divided into two main divisions:
Peripheral Nervous System.
Central Nervous System “CNS”. (the brain and spinal cord)
First comes first. We will start with the peripheral nervous system.
The peripheral nervous system: is made up of all those nerves that lie outside the brain and spinal cord. Nerves are bundled of neuron fibers (axons) that are routed together in the peripheral nervous system.
The peripheral nervous system are made off nerves and neurons that sends and receive information to and from the brain.
The peripheral nervous system are subdivided into two parts, the autonomic nervous system and somatic nervous system.
Let us have a look at the Autonomic Nervous System.
Autonomic Nervous System:
The autonomic nervous system (ANS) is made up of nerves that connect to the heart, blood vessels, smooth muscles, and glands.
The autonomic nervous system function is to maintain the internal environment of the human body in a stable state, sometimes called “homeostasis”. Maintaining and balancing the internal environment by controlling visceral organ functions that people don’t normally think about. like heart rate, blood pressure, digestion and perspiration.
The Autonomic nervous system mobilized bodily resources in times of need. Just as its name, this nervous system works automatically, without the control or conscious of the individuals, these which we do not directly control are like closing your eyes, the increase of heartbeat, sweat or produce saliva by stimulating our salivary glands.
For example, right when you first experience fear, the Autonomic nervous system will start and work on to control the involuntary, visceral functions that are difficult to control consciously. How it does it work: when you see something frightening or threatening your life, and happens to throw fear into you, your heartbeat rate will rise, sweating, pupil dilation, goose bumps and increased respiration.
Even thought the Autonomic nervous system works unconsciously, we can sometimes be aware that our heartbeat rate has increased.
One of the first psychologists to study this reaction is Walter Cannon (1932). He referred it to as the fight-or-light response reaction. Cannon monitored this response from cats after confronting them with dogs. From his observation on the cats response, he concluded that what prepares generally any organisms physiologically for attacking (fight) or fleeing from (flight) the enemy is the response to a threat, or when faced to danger.
Illness and diseases affecting the Autonomic Nervous System:
There are diseases and illnesses affecting the autonomic nervous system, causing a disorder in the system, which this disorder effects the controlling of the heartbeat rate and blood pressure of the body that can lead into causing serious problems to the patient, some of these disorders can be life-threatening when they affect the breathing or heart function of the patient.
Some of these diseases are Diabetes, Alcoholism and Parkinson’s disease. Disorders made by the diseases can either affect the whole system, or a part of it.
The Sympathetic and Parasympathetic Divisions:
The Autonomic Nervous System are subdivided into the Sympathetic division and the Parasympathetic division.
The Sympathetic Division:
The sympathetic division is the branch of the autonomic nervous system that mobilizes the body’s resources for emergencies.
As we stated before, the sympathetic nervous system is a sub part of the Autonomic Nervous System. This system is responsible for controlling functions that mobilize the body’s resources under stress, such as the fight or flight response, and the other energy generation forms as well.
Not only the sympathetic nervous system prepares the body when faced with stress or emergencies, but it also serves other vital purposes. Example, if you stand up after being setting down for a long period of time, your blood pressure will raise, else you may fall unconscious. The sympathetic nervous system also works in increasing your heartbeat rate and perspiration during exercises.
Diseases affecting the Sympathetic nervous system:
A disease affecting the sympathetic nervous system known as reflex sympathetic dystrophy syndrome (RSDS). The signs of this dieses are the heightened sensitivity to heat and cold, excessive sweating, and limbs being warm to the touch. The causes of this dieses are not confirmed, but its seems to be associated with some forms of nerve injury.
The Parasympathetic Division:
Like the sympathetic, it is a sub part of the Autonomic Nervous System, and most what the parasympathetic division controls are visceral and involuntary organs, such as breathing and blood pressure and heartbeat rate, But it differ from the sympathetic division in its activities. The parasympathetic division are responsible in controlling the body organs when in an relaxed or normal state. Some of its activities when the conditions are met, and those condition can be met when the person are calmed and relaxed, is reducing the heartbeat rate, slow down the respiratory rate, increases perspiration and salivation and smaller eye pupils.
The Sympathetic and Parasympathetic divisions activities are the opposite of each other, but they work together to maintain stability in the body when a certain external condition are met and calls for the division that are responsible to act in such situation. Much like an automobile accelerators and brakes.
The Central Nervous System:
The Central Nervous System are responsible of controlling the whole body, regulating the functions of the body. The Central Nervous System are the control center of the body.
The central nervous system (CNS) consists of the brain and the spinal cord. The Central Nervous system lies within the skull and the spinal column, protected by enclosing sheaths known as the meninges, additionally, the central nervous system is covered by the cerebrospinal fluid. The cerebrospinal fluid (CSF) nourishes the brain and provides a protective cushion for it. Ventricles are the hollow cavities in the brain that are filled with CSF.
Diseases affecting the central nervous system:
diseases and infections of the central nervous system are many, some of these diseases are Alzheimer’s disease.
The Spinal Cord and The Brain:
So we know now that the Central Nervous System consists of two things, the brain and the spinal cord. Let us have a look at these two organs:
The Spinal Cord:
Basically, the spinal cord is an extension of the brain. The spinal cord are located at the back of the body and are enclosed by the backbone “Vertebral column”, running from the base of the brain to below the waist, and are covered by the meninges.
The spinal cord connects the brain to the whole body through the peripheral nervous system, conducting sensory information to the brain from the peripheral nervous system, And from the brain, the spinal cord works on conducting motor information to the glands, skeletal, cardiac, and smooth muscles. The Spinal cord also serves as a minor reflex center.
The spinal cord consist of bundles of axons, and these axons carry out the commands from the brain to the peripheral nerves, that relays sensation from the periphery of the body to the brain.
Spinal Cord Injury:
Injury to the spinal cord can damage it, causing a partial or full paralysis to the body. Injury can be a result from a car accident or from a serious fall, or any other form of injury that damages the spinal cord, like a gunshot.
The Brain:
The brain is the part that of the central nervous system that fills the upper part of the brain. The brain is enclosed by the skull. The average weighs of the brain are 1.3 kg, three pounds, and contains billions of nerve cells that links and relays information in and outside the body, Such as coordinating the body actions and movements, talking, thinking, remembering, planning, creating and dreaming.
The brain are covered by the meninges, moreover, the brain contains bundles of axons, that works on receiving sensory information from its own nerves, as well as from the spinal cord.
Brain Injury:
Injuries to the brain can be the result of a car accident, or any other form of damage or hit directed to the head. Children’s or infants can possibly get a brain injury if shaken violently.
Part 2: The Brain and Behavior
The Brain, and how it controls our behavior. All of the body movements, thinking, dreaming, talking, remembering, feeling, and any other actions, are controlled by the brain. The Brain is the control room of your body. From the brain, commands are issued and sent to the whole body, and these commands are carried out, in and out by the nerves.
In this part of the report, we will shed some light on the brain, and how every region in the brain has functions different than the other regions, even though they are located in the same organ.
The Three Regions of the Brain:
The brain has three regions, The Hindbrain, the Midbrain and the forebrain. The location of the three regions are the same, but differ in function and size of region. The Forebrain is taking the largest portion of the brain, then comes the Hindbrain, and smallest is the Midbrain.
Structure and Areas of the Brain:
The Hindbrain:
The hindbrain includes the cerebellum and two structures found in the lower part of the brainstem: the medulla and the pons.
The controlling of essential body function and process, such as heartbeat rate and respiration, is the Hindbrain responsibility. An important part of the Hindbrain, the brainstem, controls functions such as swallowing and breathing, and any other critical functions that affect the life of the living being.
The Medulla are attached to the spinal cord, controls unconscious vital functions, such as blood pressure, heartbeat rate, swallowing, breathing and coughing. The Medulla works without relying on the thoughts of the person, It works by itself.
The pons, sometimes called the “Bridge”, because of its form of structure which looks like a bridge connecting between the medulla and the cerebellum. From its structure form, we can know that it works on sending signals to and from the cerebellum and the cerebrum, a part located in the forebrain. The Pons contains clusters of cell bodies that helps in controlling movements and sleep.
The Cerebellum, which means “Little brain” in Latin, Is a large and a folded structure located rear lower portion of the brain. The role of the cerebellum is providing feedback and fine-tuning for motor output. The cerebellum controls movements and smoothing them up, such as when you bring up your hand and smoothly bring your finger to a stop on your nose, and how you walk, and every action or movement that people make without any thinking about them or concentration, are coordinated by the cerebellum.
The Midbrain:
The midbrain is the segment of the brainstem that lies between the hindbrain and the forebrain.
The Midbrain, The smallest region of the brain regions, are responsible for visual and auditory and motor system information station. motor and sensory functions are directly controlled by the midbrain. An Important system of dopamine- releasing neurons, which originates in the midbrain, projects into various high centers of the brain.
Conscious, voluntary movements has dopamine system are involved in their performance. Degeneration or decline in dopamine synthesis is associated with Parkinson’s’ disease.
The reticular formation, which are located at the central core of the brainstem, is the structure that runs through the hindbrain and the midbrain. The reticular formation contribute in the modulate of breathing, reflexes and pain perception.
The Forebrain:
The forebrain is the largest and most complex region of the brain, encompassing a verity of structures, including the thalamus, hypothalamus, limbic system, and cerebrum.
The three structures, the Thalamus, hypothalamus and the limbic system, form the core of the forebrain. The location of the three structures are near the top of the brainstem. The cerebrum sits above the three structures. The cerebral cortex, the outer layer of the brain, is the wrinkled surface of the cerebrum.
So now we know that the Forebrain, which takes the biggest portion of the brain, and the biggest of the three regions, consists of four structures, the Thalamus, Hypothalamus, Limbic system and cerebrum. Let us have a quick look on each structure and its activities and functions.
The Thalamus:
The thalamus is a structure in the forebrain through which all sensory information (except smell) must pass to get to the cerebral cortex.
The Thalamus which is located at the top of the brainstem, is responsible for relaying sensory information to a particular part of the cortex, and regulating motor control. It also works on receiving information and signals from various brain areas, such as auditory, visual sensory, and samotosensory signals.
The Hypothalamus:
The hypothalamus is a structure found near the base of the forebrain that is involved in the regulation of basic biological needs.

The Main Functions Of The Nervous System

The nervous system is the control and communication system of the body. It sends and receives messages. The nervous system controls all our body movements. It is made up of two parts, the central nervous system (CNS), and the peripheral nervous system (PNS). The central nervous system consists of the brain and the spinal cord, and the peripheral nervous system is made up of the nerves and neurons.
The central nervous system; consists of the brain and spinal cord.
Diagram showing the different structures of the brain.
The brain; it is a large soft mass of nerve tissue that is contained within a vault of bone called the cranium. It is made up of the neurons nerve cells, and other supporting cells. The brain is composed of grey and white matter. The grey matter is the nervous tissues that formed the ‘H’-Shaped structure, and it is surrounded by white matter. The human brains has more than 10 billion nerve cells and over 50 billion other cells, an average weighs 3 1/8 pounds. The brain monitors and regulates our bodily functions and co-ordinates almost all our voluntary movement. The brain is our area of thought, creativity and consciousness.

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The spinal cord; it is an ovoid of column of nervous tissue that average 44 cm in length when flattened. It expands from the medulla oblongata in the brain stem to the second lumbar vertebra in the spinal canal. The spinal cord is the centre of reflexive action. There is a reflex arc that goes from the peripheral nerve to the spinal cord, up to the brain and back down to relay (spread) the action. The spinal cord is contained in a vertebral vault, and it passes down through a hole in each vertebrate. It is surrounded by other tissues, pia mater, cerebrospinal fluid (CSF), arachnoid mater and dura mater. These three maters are called meninges, and they surround the brain. The anterior of the “H” is made up of motor cells from the fibers that make up the motor portion of the peripheral nerves. The sensory neurons enter the posterior of the “H”.
The peripheral nervous system; this is the nerves on the periphery of the body. The autonomic nervous system (ANS) is under the control of central nervous system (CNS) and also part of the peripheral nervous system, these nerves stay inside the body and effect organs and soft tissues. The autonomic nervous system is automatic, and in control of voluntary bodily functions. It is separated into two parts; the sympathetic and parasympathetic nervous system. It regulates the function of the glands, the adrenal medulla, smooth muscle tissue, organs and the heart.
1.2 Explain the functions of each part of the nervous system.
The nervous system is made up large numbers of units known as neurons. They send, receive and process the nerve impulses inside and outside the body. Sensory neurons convert physical stimuli, e.g. smell, light, or sound, into action possibilities, which are then transmitted to the spinal cord or brain. Afferent neurons bring information into the central nervous system. We also have the motor neurons which transmit nerve impulses (sudden urge) away from the brain and spinal cord to muscles or glands, and are known as efferent neurons.
Brain; the cerebral cortex is linked to three main varieties of activity:
Mental activities; this involved in memory, intelligence, sense of responsibility, thinking, reasoning, moral sense and learning. These are accredited to the higher centres.
Sensory perception; this includes the perception of pain, temperature, touch, sight, hearing, taste and smell.
Initiation and control; to initiate and control voluntary muscle contraction.
The nerve cells initiate the contraction of voluntary muscles. Nerve fibres from Betz’s cell move past descending through the internal capsule to the medulla oblongata, and crosses to the opposite side and descends in the spinal cord. The motor region of the right hemisphere of the cerebrum controls voluntary movement of the left side of the body. There is a group of nerve cells called the motor speech (broca’s); it controls the movement essential for speech. The postcentral (sensory) is the area that perceived sensations of pain, temperature, pressure and touch, knowledge of muscular movement and position of joints. The parietal is believed to be connected with obtaining and retaining accurate knowledge of objects. We perceive spoken word from the sensory speech, and the auditory (hearing) receive and interpret transmitted impulses from the inside ear by the auditory nerves. The olfactory (smell) receives impulses from the nose via olfactory nerves and interpret it. Taste is the area where impulses from special nerves endings in taste bud and tongue, and in the lining of the cheeks, palate and pharynx are perceived as taste. The visual is the area which receives and interprets impulses as impressions. There are groups of cells called known as nuclei, they act as relay stations. It passes one neurone to the other in chain. Some important masses of grey matter are:
Basal nuclei; it is thought to influence skeletal muscle tone
Thalamus; this is where sensory input from skin, viscera and special sense organs are transmitted to before redistribution to cerebrum
Hypothalamus; it controls the output of hormones from both lobes of the gland, and it also control the autonomic nervous system, such as thirst, body temperature, hunger, heart and blood vessels defensive reactions.
Spinal cord; it is the centre of reflexive action. The reflex arc is the pathway of nerves through spinal cord. The first step of reflex arc is stimulation of a receptor nerve. They sense heat, coolness, pressure or over-stretching of the muscle. The sensory neuron transmits impulse to spinal cord. The sensory nerves link directly with a motor or glandular nerve, or go through in-between nerve and then to the motor of the glandular nerve, depending on the reflex being stimulated. The nerve sends signals to the muscles or glands to react. Visceral reflexes control heart muscle, glands and organs, and the somatic reflexes control involuntary movement of the skeletal muscles. The spinal cord does the followings:
Support the body and the skull, helps us to stand upright and maintain body balance.
Flexible movement; it allows and helps the head and neck move, and permit the body to stretch, lean, rotate and lean.
It helps protect internal organs, such as heart and lungs.
It provides base for attachment of muscles, ligaments and tendons (tough band connecting muscle to bone).
It has bone marrow inside the bones of the spinal cord that produces red blood cells and also stores minerals.
It connects the upper body to the lower body.
Its intervertebral discs acts like a shock absorber.
Peripheral nervous system; it is the autonomic nervous system which is part of the peripheral nervous system, that control the internal organs; it consists of the motor neurons. It has two systems, the sympathetic nervous system and the parasympathetic system. The autonomic nervous system controls muscles in the heart, the smooth muscle of the intestine, bladder, and uterus. The sympathetic nervous system is involved in the fight or running away response. The parasympathetic is involved in relaxation. Each of the two functions in the reverse of the other (resentment). The two systems act in opposition to maintain homeostasis (state of equilibrium). The sympathetic nervous system promotes the following activities:
It allows blood flow to skeletal muscles and the lungs.
It diverts blood flow away from the gastro-intestinal tract and skin.
It dilates bronchioles of the lung.
Increases heart rate and the ability of cardiac cell (myocytes) to contract.
Dilate pupils (opening in eye) and relaxes the ciliary (surrounding lens of eye) muscle to the lens.
It narrows all intestinal sphincters and urinary sphincter.
It inhibits (adversely affect action of an organ) peristalsis.
Responsible for the stimulation of orgasm.
The parasympathetic nervous system promotes:
The expansion of blood vessels leading to the gastro-intestinal tract, increasing blood flow.
The constriction of bronchiolar diameter when the need for oxygen has diminished.
The constriction of the pupil (opening in the eye) and contraction of the ciliary (surrounding lens of eye) muscle to the lens.
The stimulation of salivary gland secretion, and speed up peristalsis (muscle contraction).
The erection of genitals.
The stimulation of sexual arousal.
The control of the myocardium (heart muscle).
3.2 Explain the transmission of an impulse across a synapse.
A synapse is the junction where communication between neurons and neurons between muscles takes place. Synaptic transmission starts when nerve impulse arrives at the pre-synaptic axon terminal. The depolarisation (less polarity) of the pre-synaptic membrane starts series of events leading to transmitter release, and the activation of receptors that is on the post-synaptic membrane. Synaptic vesicle lives in different pool; attached to the cytoskeleton in a reverse pool, or free in the cytoplasm. A number of the free vesicles make their way to the plasma membrane for docking, and sequence of primary reactions prepares the vesicular and plasma membranes for fusion. The membranes of the synaptic vesicles are drawn together passing through protein complexes that are articulated on the vesicle and pre-synaptic membranes. A depolarised axon terminal open voltage calcium channel and calcium ions run into the axon terminal and some of the calcium ions attach to a protein on the synaptic vesicle membrane known as synaptotagmin. The vesicles are drawn closer to the pre-synaptic membrane, when calcium attach to synaptotagmin on the synaptic vesicles adjacent to the active region. Transmitter cargo is release into the synaptic cleft when the vesicles combine with the axon membrane. Some transmitter molecules attach to receptor molecules in the post-synaptic membrane. Post-synaptic cell response depends on neurotransmitter and receptor combination. After attaching acetylcholine, the channel opens and sodium ions enter the post-synaptic cell, and generate an exciting post-synaptic response. The transmitters are removed or inactivated quickly from the synaptic cleft. Acetylcholine, an enzyme in the synaptic cleft, acetylcholinesterase (AChE), breaks down Ach into choline and acetate. The transmitter released from the receptor causes the channel to close. Some transmitters are not broken down by enzymes and many transmitters rapidly clear from the synaptic cleft and taken into the pre-synaptic terminal by special proteins known as transporters. This process is called reuptake, it not only cut off synaptic activity quickly, but also allow the terminal to recycle transmitter molecules. Membrane needed for the creation of synaptic vesicles, is also recycled passing through endocytosis of the pre-synaptic membrane. The recycled vesciles which are now filled with neurotransmitter molecules are ready for another circle of synaptic transmission.
4.1 Describe the main parts of the brain and explain their functions.
The brain; it is a large soft mass of nerve tissue that is contained within a vault of bone called the cranium. It is made up of the neurons nerve cells, supporting cells. The brain is composed of grey and white matter. The grey matter is the nervous tissues that formed the ‘H’-Shaped structure, and it is surrounded by white matter. The human brains has more than 10 billion nerve cells and over 50 billion other cells, an average weighs 3 1/8 pounds. The brain monitors and regulates our bodily functions and co-ordinates almost all our voluntary movement. The brain is our area of thought, creativity and consciousness.
Functions of the brain; the functions of the three main parts of the brain are the followings:
The cerebrum; this is the largest portion of the brain, it occupies about 2/3 fractions of the human brain. The cerebral hemisphere is separated into two by a longitudinal fissure. The two hemispheres are joined by a fibre called corpus callosum that consists of long bundles of closely packed nerve fibres of about 10cm long. The corpus callosum has about 200 million of nerve fibres.
The cerebral hemisphere is divided into four lobes by three deep grooves called fissures. From the front part of the brain to the back is known as the Frontal lobe, the Temporal lobe, Parietal lobe and Occipital. The right part of the brain controls the left part of the body while the left part of the brain controls the right.
Frontal lobe- It is involved in inner monitoring of complex thoughts, actions and creative ideas. The anterior (front) portion of the frontal lobe is called the prefrontal cortex. The posterior (back) of the frontal lobe consists of the motor and premotor areas. Nerve cells that produce movement are located in the motor areas.
Temporal lobe- it helps in the decoding and interpretation of sounds. It is the centre for memory and emotions. It also helps in language comprehension.
Occipital lobe – it decodes and interprets the visual information, such as shapes and colours.
Parietal lobe- it is the main area for feelings, touch, hot, cold and pain. It takes different bits of information from the surroundings, organises it and communicates it to other part of the brain.
The cerebral cortex; this is the outside surface of the cerebrum with a layer of 2-4mm thick. It has a greyish brown look, and it is referred to as the gray matter. The surface of cerebral cortex is divided into large number of folds, which increases the surface area of the brain.
The Diencephalon – it is made up of mainly subcortical nuclei, thalamus and hypothalamus. .
Thalamus – it lays crossway to the cerebrum. The thalamus plays an important part in the link between the sense organs and cerebral cortex. It receives bulk of incoming signal from the sense organs. It also determines the source of signals, evaluates their importance integrates them and passes them to the cerebrum.
Hypothalamus – it lies in the base of thalamus, weighs about 4 gm with a small vascularised structure. It is only about 1/300 of the total brain mass. It incorporates and manages visceral activities. It maintains homeostasis and the body’s internal equilibrium. The hypothalamus corrects the rate of heart beat and respiration whenever they go wrong. It is known as the control centre for fight and flight (Control Mind, 2010).
The mid brain; this component forms the middle part of the brain. It controls the activity of voluntary muscles. It is made up of four small lobes called the corpora quadrigemina. The upper part is colliculi which receives sensory informations from eyes and muscles of the head; it controls all the visual reflexes and coordinates the movements of the head and eyes. The lower part control part of colliculi and receives sensory impulses from the ears and muscles of the head. (Control Mind, 2010).
The hind brain; It is made up of the followings:
Cerebellum; it is the second largest part of the brain and it consists of two cerebral hemispheres. They are located at the cerebral hemisphere and the brain stem. The cerebellum assists in the maintenance posture and balance of the body. It plays an important role in controlling the fast muscular activities of the brain, e.g., running and talking.
Medulla Oblongata; this is the posterior part of the brain which links the other parts of the brain to the spinal cord. The medulla controls the subconscious activities, e.g., digestion and breathing.
Brain stem; it is part of the brain that controls basic functions that are necessary for maintaining blood pressure, eye movements, heartbeat, swallowing and breathing.
Pons Varoli; it is the base of the brain stem. It connects the cerebral cortex to the cerebellum. It relays the information between cerebrum and cerebellum. It is the part of the brain that controls arousal and control respiration (Quizlet, 2010).

Role of Non-adrenergic, Non-cholinergic Transmitters in the Autonomic Nervous System

The transmission of electrical signals from presynaptic junction to postsynaptic terminal that bring about action potentials through depolarization of cells between nerve and muscle are generally powered by neurotransmitters. The contraction and relaxation of smooth muscle cells of the visceral organs are under the control of autonomic nervous system. The neurotransmitters other than acetylcholine and noradrenaline of sympathetic and parasympathetic nervous systems play important roles in synaptic junction transmission, and these neurotransmitters are generally called Non-Adrenergic, Non-Cholinergic (NANC) neurotransmitters.  Currò D et al (1) stated that at around 1960s Burnstock and his team were the first set of neurophysiologists that discovered NANC neurotransmission and inhibitory junction potentials (IJP). The effect of NANC motor functions cut across cardiovascular, genitourinary, respiratory and most especially gastrointestinal system.  Joos GF (4) stated that most bronchodilation of the airway are as a result of inhibitory NANC transmitters, predominantly VIP and NO. Major NANC neurotransmitters with their inhibitory and excitatory roles in smooth muscle will be discussed in categories in this term paper as below:
Adenosine triphosphate (ATP)
According to Currò D et al (1), ATP as a neurotransmitter performs the inhibition of motor response in the proximal gastric region of the stomach. However, the relaxation effect of ATP particularly on the smooth muscle is usually temporary sustained, because ATP also simultaneously stimulate the release of contraction dependent prostaglandin in the body. This is a chemical agent that serves as an antagonist to the relaxation effect of ATP creating a short live effect of ATP on the smooth muscle. Additionally, cyclooxygenase inhibitors that hinder production of prostaglandin often time has little effect on ATP function. The effect of ATP is usually abridged by the ATP receptor antagonist including apamin, that block Ca2+, leading to influx of K+ into the cell with resultant hyperpolarization. However, except α-β-methylene ATP, apamin ( and not suramin) has no effect on the relaxation produced by electrical field stimulation (EFS) at the stomach proximal gastric region, especially EFS high frequency relaxation (2, 3). De Man JG (2) added that the inhibitory mediated effect of ATP occurs when ATP binds to purine receptors on the  intestinal smooth muscle and  nerve majorly P2Y1 and P2X1and 3 respectively. Nevertheless, Jenkinson KMet al(3) opined that this relaxant induced function of ATP can be blocked by action of P2-purinoceptor antagonist. Like wisely, Matsuda et al (5) explained the ATP mechanism of action that leads to its hyperpolarization of cells resulting in relaxation of smooth muscle. Firstly, ATP binds to purinergic G-protein receptor (P2Y), activates soluble apamin molecules. This chemical causes Ca2+ conduction through opening of K+ channels in the cell, activating adenylate cyclase enzyme and raising cyclic adenosine monophosphate (cAMP) level. Eventually, the cell is hyperpolarized with IJP leading to smooth muscle relaxation.
Mechanism of Action of ATP by Matsuda et al (5)
Vasoactive Intestinal Polypeptide (VIP) and Related Peptide
Currò D et al (1) described VIP, a sister of co-synthetized 27-amino-acid peptide histidine isoleucine (PHI), as a 28-amino-acid peptide that function in contraction-dependent relaxation of the gastric fundus. Peptides induced relaxation are not immediate, start after certain delay period and gradually increase in intensity; and they are long lasting contrary to latency deprived EFS induced relaxation that is autonomous of the frequency involved.  On the other hand, peptides play some major roles in the sustained length of relaxation induced by high frequency EFS of the proximal gastric region. In addition, high frequency EFS stimulation enhance the synthesis of VIP- like immunoreactivity (LI) from the stomach. In contrary, peptidergic component function becomes apparent for low frequency produced relaxation when there is an adequate and prolonged stimulation of neurons. However, the inhibitory motor function of VIP; low and intermediate frequency-EFS relaxation can be antagonized by anti-VIP sera including α-chymotrypsin and trypsin- peptidase (6). Matsuda et al (5) buttressed the fact that VIP serves as an inhibitory motor neurotransmitter principally in mesenteric motor neurons that leads to extended interval of relaxation of gastric smooth muscles.
VIP-Mechanism of Action
VIP transmitter which mixed with G-protein, binds to its VPAC-2 receptor on the fundus smooth muscle leading to increase in cAMP and activation of adenylate cyclase with resultant relaxation of smooth muscle. This relaxation effect is mediated when ATP-dependent K+ channel become activated with influx of Ca+ into the cell. The substance then prolongs the effect of voltage gated K+ channel leading to hyperpolarization, with no action potential generated. Eventually, the process potentiates inhibition and relaxation of gastric smooth muscle (5).
Also, Matsuda et al (5) stated that peptide inhibitory neurotransmitter including Pituitary Adenylate Cyclase-Activating Peptide (PACAP) participates as IJP in the relaxation of gastric smooth muscle. PACAP inhibitory effect often seen concurrently with VIP’s in the gastrointestinal tract (GIT)
PACAP-Mechanism of Action
PACAP neurotransmitter binds to its VCAP-1 and raise cAMP level, and PACAP type-1 receptor (PAC1). This joining increase influx of intracellular Ca2+, which then activates K+ channel, a apamin friendly channel (SKCa2+). The resultant efflux of K+ trigger hyperpolarization and relaxation of smooth muscle.
Mechanism of Action of VIP and PACAP
The figure explaining how the hyperpolarization, due to voltage gated Ca+ influx and K+ efflux, potentiates NANC VIP and PACAP inhibitory mediated effect on smooth muscle relaxation (5).
Joos GF(4) also emphasized that the nerves of upper and lower respiratory track including larynx and lung respectively are supplied with VIP and PACAP, functioning as vasodilator of bronchiolar tree. Moreover, innate immune cells including neutrophils and macrophages secrete VIP which specializes in decreasing the function of acquired immune cell including activated T-cells. This chemical simultaneously reduces the effect of proinflammatory cytokines, a signaling substance that increase inflammation, and increases anti-inflammatory cytokines in the circulatory system.
Nitric oxide (NO)
NO forms main NANC peripheral neurotransmitter of peripheral nervous system that ensure the immediate commencement of relaxation of GIT muscle and is well known as Endothelium-derived relaxing factor (EDRF). Currò D et al (1, 5) also point out the three main Ca2+ and calmodulin reliant isoforms of NO synthase (NOS) including endothelial’s (eNOS), neuronal’s (nNOS) and inductible’s (iNOS).  The relaxant mediated effect of NO is very diminutive due to its short half-life. The inhibitory function of NO often time demonstrated by quick onset of smooth muscle relaxation, as NOS inhibitors can eliminate the low frequency EFS relaxation and but has no power on relaxation secondary to high-frequency EFS. Even though NO works for beginning of gastric muscle relaxation, the relaxant function can be sustained by nonstop nitrergic nerve stimulation while peptidergic effects can leads to low or high frequency EFS. Additionally, Matsuda et al (5) shows that NO is produced from amino acid L-arginine by NOS, and nNOS isomer is more abundant in the neurons of GIT.
NO-Mechanism of Action.
NO originates from L-arginine asynthetized by the action of enteric nervous system (ENS) when gastric nerve is stimulated. This chemical which then lead to activation of soluble guanylate cyclase (sGC) and subsequent rise in cyclic guanosine monophosphate (cGMP). Thereafter, Protein kinase G acted upon by cGMP also activate K+ pathway, with increase Ca2+ influx that  eventually lead to hyperpolarization and relaxation of smooth muscle
Mechanism of Action of NO by Matsuda et al (5)
Irie K et al (6) also enunciated that the relaxation of smooth muscle is made possible by the action of endogenous NO, found in the myenteric plexus of the GIT, produced by L-arginine. However, an antagonist of NOS, majorly NG-nitro-L-arginine (L-NOARG) elicits some opposing effect; just as Tetrodotoxin (TTX) competes against the relaxant effect of ATP and VIP. More so, localized effect of endogenous NO in this plexus is often due to its short life span and this make it function as a neuromodulator, when secreted by action of [Met5] enkephalin (ENK), regulating the release of NANC neurotransmitters. Joos GF(4) expressed also that the nNOS isomer is predominant in the nerves of tracheobronchial pathway serving as inhibitory NANC neurotransmitter.
Carbon monoxide (CO)
Just like NO, CO is a gaseous neurotransmitter and chief hyperpolarizing factor that influence the relaxation of gastric smooth muscle. Oxidation of heme degradation through Nicotinamide adenide dinucleotide phosphate (NADPH) propelled by heme oxygenase (HO) leads to the production of CO endogenously. HO-2 Isoform produced CO in the GIT while HO-1 is mainly formed at the site of injury or inflammation. Activation of sGC raised the cGMP level, the increase K+ efflux results in hyperpolarization of cells and subsequent relaxation of the smooth muscle (5).
Mechanism of Action of CO by Matsuda et al (5)
Conclusively, relaxation of gastric smooth muscle is controlled by the functions of some NANC neurotransmitters including ATP, VIP, NO and CO among others through hyperpolarization of postsynaptic junction resulting in inhibition of action potentials. These chemicals often work in synergy as effect of one enhance the action of the other. Mainly, through activation of K+ channels that trigger hyperpolarization of cells resulting in smooth muscle inhibition (8)
1. Currò D and Preziosi P. REVIEW: Non-adrenergic Non-Cholinergic Relaxation of the Rat Stomach. Gen.Pharmacol. 31: 697-703, 1998.
2. De Man JG, Seerden TC, De Schepper HU, Pelckmans PA, Herman AG and De Winter BY. Functional evidence that ATP or a related purine is an inhibitory NANC neurotransmitter in the mouse jejunum: study on the identity of P2X and P2Y purinoceptors involved. Br.J.Pharmacol. 140: 6: 1108-1116, 2003.
3. Jenkinson KM and Reid JJ. Evidence that adenosine 5 ‘-triphosphate is the third inhibitory non-adrenergic non-cholinergic neurotransmitter in the rat gastric fundus. Br.J.Pharmacol. 130: 7: 1627-1631, 2000.
4. Joos GF. The role of neuroeffector mechanisms in the pathogenesis of asthma. Curr Allergy Asthma Rep 1: 2: 134-143, 2001.
5. Matsuda NM and Miller SM. Non-adrenergic non-cholinergic inhibition of gastrointestinal smooth muscle and its intracellular mechanism(s). Fundam.Clin.Pharmacol. 24: 3: 261-268, 2010.
6. Irie K, Fujii E, Uchida Y, Muraki T. Involvement of endogenous nitric oxide in non-adrenergic, non-cholinergic contraction elicited by [Met5]-enkephalin in rat isolated duodenum. Neuropharmacology. 1994 Nov 1;33(11):1333-8.