Human Neurology

The Human Nervous System

The nervous system is essentially a biological information highway, and is responsible for controlling all the biological processes and movement in the body, and can also receive information and interpret it via electrical signals which are used in this nervous system

It consists of the Central Nervous System (CNS), essentially the processing area and the Peripheral Nervous System which detects and sends electrical impulses that are used in the nervous system

The Central Nervous System (CNS)

The Central Nervous System is effectively the centre of the nervous system, the part of it that processes the information received from the peripheral nervous system. The CNS consists of the brain and spinal cord. It is responsible for receiving and interpreting signals from the peripheral nervous system and also sends out signals to it, either consciously or unconsciously. This information highway called the nervous system consists of many nerve cells, also known as neurones, as seen below.

The Nerve Cell

Diagram of a Neurone - With the Axon and Dendrites projecting from the Cell Body

Each neurone consists of a nucleus situated in the cell body, where outgrowths called processes originate from. The main one of these processes is the axon, which is responsible for carrying outgoing messages from the cell. This axon can originate from the CNS and extend all the way to the body's extremities, effectively providing a highway for messages to go to and from the CNS to these body extremities.

Dendrites are smaller secondary processes that grow from the cell body and axon. On the end of these dendrites lie the axon terminals, which 'plug' into a cell where the electrical signal from a nerve cell to the target cell can be made. This 'plug' (the axon terminal) connects into a receptor on the target cell and can transmit information between cells

The Way Nerve Cells Communicate

The "All-Or-None-Law" applies to nerve cell communication as they use an on / off signal (like an digital signal) so that the message can remain clear and effective from its travel from the CNS to the target cell or vice versa. This is a factor because just like electricity signals, the signal fades out and must be boosted along its journey. But if the message is either 1 or 0 (i.e.) on or off the messages are absolute.

Classification of Neurones

Interneurones - Neurones lying entirely within the CNS

Afferent Neurones - Also known as sensory neurones, these are specialised to send impulses towards the CNS away from the peripheral system

Efferent Neurones - These nerve cells carry signals from the CNS to the cells in the peripheral system

The next page elaborates on how the nervous system works...


The Conscious & Unconscious Nervous System

The Central Nervous System is arguably the most important part of the body because of the way it controls the biological processes of our body and all conscious thought. Due to their importance, they are safely encased within bones, namely the cranium protecting the brain and the spine protecting the spinal cord

Brain Divisions

There are three main components of the brain, namely the brainstem, cerebellum and the forebrain. These are elaborated upon below

The Forebrain

The forebrain has many activities that it is responsible for and is divided into many component parts. The below list elaborates on the localised areas of the forebrain and their functions.

  1. Frontal Lobe - Found at the front of the head, near the temples and forehead, the frontal lobe is essential to many of the advanced functions of an evolved brain. It deals with voluntary muscle movements and deals with more intricate matters such as thought and speech
  2. Parietal Lobe - Situated behind the frontal lobe, this section deals with spatial awareness in the external environment and acts as a receptor area to deal with signals associated with tough.
  3. Temporal Lobe - The temporal lobes are situated in parallel with the ears, they serve the ears by interpreting audio signals received from the auditory canal
  4. Occipital Lobe - This is the smallest of the four lobe components of the cerebrum, and is responsible in interpreting nerve signals from the eye at the back of the brain

The above components of the brain work in tandem in a healthy brain. However, in some cases the brain can be injured in some way, causing brain damage. The next page looks at how brain damage can affect the way we operate.


The Central Nervous System

Myelin Sheath

Myelin is a substance that forms the myelin sheath associated with nerve cells. This sheath is a layer of phospholipids that increases the conductivity of the electrical messages that are sent through the cell. Diseases such as multiple sclerosis are a result in a lack of this myelin sheath, with the resultant effect being that the conductivity of signals is much slower severely decreasing the effectiveness of the nervous system in sufferers.

In total, there are 43 main nerves that branch of the CNS to the peripheral nervous system (the peripheral system is the nervous system outside the CNS. These are the efferent neurones that carry signals away from the CNS to the peripheral system.

Somatic Nervous System

These efferent fibres are divided into the somatic nervous system and the autonomic nervous system. The somatic fibres are responsible for the voluntary movement of our body, i.e. movement that you consciously thought about doing.

The Autonomic Nervous System

The autonomic nervous system incorporates all the impulses that are done involuntarily, and are usually associated with essential functions such as breathing, heartbeat etc. However this type of system can further be broken down into the sympathetic and parasympathetic systems which keep one another in check in a form of negative feedback such as the release of insulin and glucagon in sugar control of the blood. 

All of the actions executed by the autonomic nervous system are unconsciously done.

These informational pulses executed in our nervous system allow us to do our daily functions. The processing of this information is done in the CNS, the brain, a highly developed mass of nerve cells. The inner workings of the brain are investigated on the next page.


Types and Causes of Brain Damage

Causes of Brain Damage

The brain is a highly specialised tissue, far more complex than today's 21st century supercomputers. Due to this magnificent complexity, even the slightest damage can have extreme consequences

The brain can be damaged in a variety of ways, and depending on the areas damaged and the severity of the damage, it can prove relatively harmless to fatal. Some causes of brain damage are below

Types of Brain Damage

The next page of this neurology tutorial takes a further look at the brain, and the capabilities of it to be used to our advantage in daily life.


IQ, Creativity and Learning

Evolution of Human Intelligence

Human's, as evolved as we are, are the species most capable of exhibiting intelligence and creativity due to our capacity to learn. It is nothing short of remarkable how we, intelligent beings, came to exist.

In light of this snowball effect, and as a continuation of the last bulleted point; we have been able to sustain a rising human population over time. In turn, in accordance with natural selection, more intelligent people may be favoured by our gene pool over the long term, thus making the species as a whole more intelligent as a collective.

Ability to Learn

Humans continually learn from one another and share their information over generations. This is what makes our species a cut above the rest. Our ability to understand the value of learning and to do so gives us the tool to understand more and more about ourselves and our environment.

Intelligence

Intelligence offers us the means to utilise abstract ideas and implement reasoning in our arguments to justify the things we do. The degree of intelligence in people is variable to a number of factors, like genetics, the local environment and even diet.

It is important to note the following

Creativity

It does not take an intelligent person to be creative. It is a popular belief that technically minded people tend to be less creative as others, who, in turn, are not very technically minded.

It is believed that creativity is made possible in the right brain hemisphere while the technical information is processed in the left hemisphere. It is worth noting that many of the famous creative individuals, all the famous writers, artists etc were generally intelligent.

Creativity can rely on a number of factors, some of which are named below

Moreover to the last factor, it is worth considering that any factor in the external environment will be a factor in your creativity. If someone offered you a million euros to write a good poem, you may instantaneously feel more creative!

Moving one step on from the conscious learning mind, we look at the unconscious mind on the next page; via sleep and dreams.


Sleep and Dreams - Neurology

The Falling Asleep Process

During the day when we are a awake, our body and brain are working tirelessly to operate our body, and as they do so they slowly degrade at a cellular level. A person will get progressively tired from this bodily breakdown, because sleep gives us a chance to build and replace the cells and resolve our end of day homeostatic imbalances.

If you have not slept for a while, the decrease in the efficiency and effectiveness of the body begins to tell, and you will begin to feel sleepy as less energy is available to you. The longer we stay up the more likely we will fall asleep.

If certain conditions prevail, like a state of inactivity or relaxing in a warm dry place, there is a higher chance of us falling asleep due to the preferable conditions for us to do so.

Sleeping

When we fall asleep, our metabolic rate slows down, as does almost every other function across the board, we effectively go into hibernation mode. The amount of adrenaline in our body promoting awareness decreases and somatotrophin, controlling the repair of tissue is more abundant. This is effectively the healing process of sleep that revitalises us.

The synaptic nerve connections containing recollections about the last day are also strengthened, hence when you wake up the more you realised you did yesterday. This localised area of memory is what many of our dreams consist of, our past recollections of the day. You may have dreamt something twice, and on the second time it was only because you thought of that first dream the day before you dreamt the second. When looking at it like this, it confirms the reason why you have the same dream, your conscious thought about it accesses that part of the brain thus 'remembers' it at night.

Dreams Telling the Future?

Some people believe that dreams tell the future. But, when 6 billion people dream every night, there is bound to be a coincidence when there are trillions of dreams every year. Those people who have dreamed of winning the lottery are one of many.

I, personally don't believe they tell the future, though could be a sign of intelligence, the brain interpreting possibilities in the future from the knowledge of past events. This would be perfectly viable, as it would be a case of the brain 'adapting' to its future environment, and preparing you for the possible future.

REM

REM stands for rapid eye movement and is the points in time during sleep where dreams occur. They occur after periods of deep sleep.

As suggested, rapid eye movement occurs in REM, while the body is under a state of paralysis.

In effect, our brain takes us on a virtual reality of our thoughts while it steadily repairs itself for the next day. The most vivid and deepest dreams will occur in the periods between REM while drowsy, almost conscious dreams occur in the REM stages.

Our Environment Outside Sleep

Have you ever had a dream where someone next door is playing music, and the music is conveniently woven into your dream? This is your body trying to lessen the chances of you awakening while it is repairing itself.

However, sleep deprived people go into much deeper sleep, and may not detect such noises. The overriding point here is, that sleep is essential to the body, and that there are compensations made to our usual behaviour (like paralysis) that enables our body to do what is required for itself.

Sleep Troubles

The older we get, the less sleep we require. Teenagers buck the trends in needing the most sleep of us all, due to the growth spurt occurring at puberty that involves a larger turnover of materials and energy.

Certain drugs are available to induce sleeping, but most are addictive and require controlled and responsible use. The next page looks at the works of famous past neurologists like Carl Gustav Jung and Sigmund Freud, who both actively pursued the way in which we dream as a career in neurology.


Sigmund Freud and Carl Gustav Jung

Sigmund Freud

Sigmund Freud was a famous Austrian neurologist (1856 - 1939), who stated that dreams were the manifestation of the unconscious. Himself and another neurologist, Carl Gustav Jung (1875 - 1961), believed that conscious behaviour derived from unconscious instinct which exists in all of us.

These unconscious thoughts were linked to suppressed sexual desires. Freud identified three key stages in the life cycle where the child's tendency to focus on sexual areas of the body changes over time.

Freud argued that in these stages of unconscious repression, male children are attracted to their mother and become instinctively aggressive towards the father. The father reciprocally injects fear into the child by his male superiority, thus insinuating an essence of competition and games theory. Either way, the prime fact is that the child must grow to become sexually active and mature.

Differences Between Jung and Freud

Jung believed that a persons' brain consisted of the forgotten conscious and a cluster of memories of past experiences. He came to this hypothesis by studying humans suffering a mental disorder, who had hallucinations that were not a past recollection, thus Jung deduced there was another component of the brain adding to this illusion, i.e. the unconscious.

Freud on the other hand believed that the brain was divided into three parts

Essentially, this method of thinking, and approaching the brain from a self-realizing approach, neurology has been able to develop since these initial theories by Jung and Freud.

It also paved advance in psychiatry, and methods of psycho therapy to combat mental disorders, which are investigated upon in the next page.


Psychiatry & Mental Disorders

The Definition of Mad

When someone says 'mental disorder' many people associate it with madness. This is truly not the case. There are many states of mental disorder where the sufferer is not clinically insane.

Madness essentially means psychosis, being out of touch of reality and not being capable of rational and controlled thought. A person in psychosis may have irrational delusions and hallucinations that illustrate this imbalance in conscious and unconscious mind.

Schizophrenia

Schizophrenia can effect mind and personality. In severe cases, the sufferer believes that 'something' is in control of them, and that they have lost control of themselves.

Affective Mood Disorder

Obsessive & Compulsive Disorder

A mental disorder where the sufferer must undergo meticulous rituals to live their normal lives, such as excessive washing of their skin and hair. If the sufferer cannot do this, anxiety kicks in as a "withdrawal symptom" until they allow themselves to repeat the ritual once again.

Phobias

A preconception about a given situation or object, such as a fear of snakes or being in high places. A huge diversity of phobias have been discovered by psychologists.

Depressive Neurosis

The classic case of depression where depression is the primary emotion in the sufferer, resulting in a lack of motivation and self-esteem to be functional in society and to themselves.

Physical Disease

Not only can the way the brain works be affected by disorders, the physical components of the brain can also be infected by pathogens. Dementia is such a physical disease, where the long term memory of the sufferer is broken down due to the physical components of the brain and nervous synapses degrading over time.

Drugs for Mental Disorders

A wide range of drugs are now available for those suffering mental disorders, though many people face a psychological barrier when it comes to taking medication to cure their 'soul'. Many of the drugs used prove addictive which in turn can also lead to further psychiatric problems.

However, psychotherapy is an alternative communicative treatment designed to get the patient to understand themselves better. This can be combined with drugtherapy, and eventually develop the patients' self realisation into a moreproductive and positive state. Medicinal neurology is a fairly new area of medicine.

The next page investigates perception and two people can interpret the same thing differently.


Human Perception - Neurology

A better understanding of human perception unlocks the key to how the mind works, an advantage when working with people with mental disorders.

Visual Perception

The below diagram is an illustration as to how we all perceive things in our own way, as suggested by the theories of Jung and Freud.

Human Perception in Action

What do you see? Some of you may see 2 green faces, other may see a white chalice. This all depends on your initial perception of the diagram. You may find that when you look again, you may see the alternate picture within the diagram.

The retina is responsible for interpreting visual stimuli such as this, where it picks up photons of light via the 130 000 000 rods and cones situated on it. In pre-modern times it was considered that visual perception simply encompassed what was seen by the eye on the outside. This external stimuli would in turn produce a perception in the brain caused by the stimulus.

However this is not the case. Modern medicine now knows that information from the eye is simply a physiological process that does not actually process the signals it receives. This job is left to the brain.

The senses simply act as a messenger to a particular stimulus that is seen, the brain is the place where external stimuli is actually perceived.

Spatial Awareness

The environment we live in is 3 dimensional, thus needs a 3 dimensional approach to understand it. Therefore height, width and depth must be measured by the eyes

This is possible by the way the eyes are situated on the head. Positioned either side of the nose, the right eye picks up vision on the left hemisphere and the left eye picks up vision in the right hemisphere.

The images picked up by the eyes are projected upside down on each of the eyes retina. This in turn will be perceived the right way up by the brain, which will interpret the three dimensional values of the external environment at a very fast and effective rate

Illusions

It is possible for the physiological state of the brain to deviate from the norm and trigger of a mental disorder. Illusions are a symptom of such mental disorders.

However it is also possible to trick the senses of a perfectly functional healthy brain. Illusions, such as the mirages that appear in the desert are caused by trickery of the sense, leading us to believe there is something out there when this is not the case.

More information on illusions and mind trickery are looked upon in the next page


Neurology of Illusions

As mentioned in the previous page looking at perception, illusions can be caused by mental disorders or misreading of the sensory data obtained from the external environment. For now we will look at the latter.

Visual Illusions

Auditory Illusions

One of the most famous of these is the Doppler Effect, where a noise situated close to you has a higher pitch of sound to that of a sound further away. This is the case if you should and get an echo, your voice will always sound more deeper in the echo when it is not. This is effectively an illusion.

The Study of Illusions

As mentioned previously, the study of illusions in sufferers of a mental disorder provide a key into a deeper understand of what is going on in their mind. This is also the case of a healthy brain, where the study of illusions can work out the parameters at which it compensates for its own lack of ability

It is worth noting that the trial and error the sensory organs function have, they are as just as foolproof as any other conscious human thought. The chances of your brain not being able to guess the spatial distance of a fuzzy moving object is the same lack in ability that people have in typing an error free document

In this sense, illusions is studying the perceptions and sensory data obtained from situations where human error prevents us from seeing the real deal.

Another interesting fact is that the retina is read by the brain every 0.1 seconds, meaning that you are not actually seeing anything in the present, but something that just happened a fraction of a second ago.


http://www.biology-online.org/8/1_nervous_system.htm