Our Brain

The nervous system is your body's decision and communication center. The central nervous system (CNS) is made of the brain and the spinal cord and the peripheral nervous system (PNS) is made of nerves. Together they control every part of your daily life, from breathing and blinking to helping you memorise facts for a test. Nerves reach from your brain to your face, ears, eyes, nose, and spinal cord... and from the spinal cord to the rest of your body. Afferent neurones gather information from the environment, send that info to the spinal cord, which then speed the message to the brain. The brain then makes sense of that message and fires off a response. Efferent neurones deliver the instructions from the brain to the rest of your body. The spinal cord, made of a bundle of nerves running up and down the spine, is similar to a superhighway, speeding messages to and from the brain at every second.

The brain is made of three main parts: the forebrain, midbrain, and hindbrain. The forebrain consists of the cerebrum, thalamus, and hypothalamus (part of the limbic system). The midbrain consists of the tectum and tegmentum. The hindbrain is made of the cerebellum, pons and medulla oblongata. Often the pons, and medulla oblongata are referred to together as the brainstem.

The Cerebrum: The cerebrum or cortex is the largest part of the human brain, associated with higher brain function such as thought and action. The cerebral cortex is divided into four sections, called "lobes": the frontal lobe, parietal lobe, occipital lobe, and temporal lobe.

What do each of these lobes do?

• Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving
• Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli
• Occipital Lobe- associated with visual processing
• Temporal Lobe- associated with perception and recognition of auditory stimuli, memory, and speech

Note that the cerebral cortex is highly wrinkled. Essentially this makes the brain more efficient, because it can increase the surface area of the brain and the amount of neurons within it. We will discuss the relevance of the degree of cortical folding (or gyrencephalisation) later.

A deep furrow divides the cerebrum into two halves, known as the left and right hemispheres. The two hemispheres look mostly symmetrical yet it has been shown that each side functions slightly different than the other. 

Sometimes the right hemisphere is associated with creativity and the left hemisphere is associated with logic abilities. The corpus callosum is a bundle of axons which connects these two hemispheres.

Nerve cells make up the gray surface of the cerebrum which is a little thicker than your thumb. White nerve fibres underneath carry signals between the nerve cells and other parts of the brain and body.

The neocortex occupies the bulk of the cerebrum. This is a six-layered structure of the cerebral cortex which is only found in mammals. It is thought that the neocortex is a recently evolved structure, and is associated with "higher" information processing by more fully evolved animals (such as humans, primates, dolphins, etc).

The Cerebellum: The cerebellum, or "little brain", is similar to the cerebrum in that it has two hemispheres and has a highly folded surface or cortex. This structure is associated with regulation and coordination of movement, posture, and balance.

The cerebellum is assumed to be much older than the cerebrum, evolutionarily. What do I mean by this? In other words, animals which scientists assume to have evolved prior to humans, for example reptiles, do have developed cerebellums. However, reptiles do not have neocortex. 

Limbic System: The limbic system, often referred to as the "emotional brain", is found buried within the cerebrum. Like the cerebellum, evolutionarily the structure is rather old.

This system contains the thalamus, hypothalamus, amygdala, and hippocampus.

Thalamus- a large mass of gray matter deeply situated in the forebrain at the topmost portion of the diencephalon. The structure has sensory and motor functions. Almost all sensory information enters this structure where neurons send that information to the overlying cortex. Axons from every sensory system (except olfaction) synapse here as the last relay site before the information reaches the cerebral cortex.

Hypothalamus - part of the diencephalon, ventral to the thalamus. The structure is involved in functions including homeostasis, emotion, thirst, hunger, circadian rhythms, and control of the autonomic nervous system. In addition, it controls the pituitary. 

Brain Stem: Underneath the limbic system is the brain stem. This structure is responsible for basic vital life functions such as breathing, heartbeat, and blood pressure. Scientists say that this is the "simplest" part of human brains because animals' entire brains, such as reptiles (who appear early on the evolutionary scale) resemble our brain stem. 

Midbrain/ Mesencephalon - the rostral part of the brain stem, which includes the tectum and tegmentum. It is involved in functions such as vision, hearing, eye movement, and body movement. The anterior part has the cerebral peduncle, which is a huge bundle of axons travelling from the cerebral cortex through the brain stem and these fibres (along with other structures) are important for voluntary motor function.

Pons- part of the metencephalon in the hindbrain. It is involved in motor control and sensory analysis... for example, information from the ear first enters the brain in the pons. It has parts that are important for the level of consciousness and for sleep. Some structures within the pons are linked to the cerebellum, thus are involved in movement and posture. 

Medulla Oblongata - this structure is the caudal-most part of the brain stem, between the pons and spinal cord. It is responsible for maintaining vital body functions, such as breathing and heart rate.

Kidney Failure

Kidney failure occurs when your kidneys are not working well. The kidneys cannot filter out toxins from your blood and will build up. The worse the kidney failure the more the toxins will build up

Kidney failure is detected by checking the blood for toxins normally cleared by the kidneys such as Urea and Creatinine. In kidney failure, the level of Urea and Creatinine in the blood will be raised. Ultrasound is usually done to check the size and texture of the kidneys as well as to look for stones or blockage to the kidneys. If both kidneys are shrunken, it usually means that the kidney failure has been present for sometime and the kidney damage is irreversible.

Ultrasound is not sensitive to detect early kidney failure. The kidneys will shrink only after the kidney damage has been present for a long time so a normal ultrasound does not always mean that the kidneys are normal.

If both kidneys failed, toxins build up in your blood.

Often people with mild kidney failure do not feel unwell. The condition is sometimes detected only during medical examination, urine or blood tests. In chronic kidney failure the kidney fails slowly and most patients do not feel ill until the kidneys have failed almost completely.

Symptoms of kidney failure are unfortunately vague and happen late. Often kidney failure does not cause any problems until the kidneys have almost completely failed. You may feel tired, less energetic, have poor appetite, nauseated and itchy. You also become more pale and your skin may darken and develop swelling in the feet or may be puffy in the face. Eventually you may start to vomit and become breathless. You can become pale and your skin may darken.

Most patients can still pass urine even when the kidney failure is very bad. It can take several years for dialysis patients to completely stop passing urine.

There are two types of kidney failure - acute kidney failure and chronic kidney failure. In acute kidney failure the kidney stops functioning suddenly. In many cases the kidney will recover if treated quickly. In chronic renal failure however there is long-standing kidney damage and scarring and it cannot be reversed even with medication.

Discuss with your doctor about definitive treatment for your kidney disease. However many kidney diseases cannot be cured and treatment will not cure any damage already present in the kidneys.

Heart beat

Mechanism?

The cardiac muscle is myogenic.

The heart beat starts at sinoatrial node/pacemaker.

The impulse from the pacemaker spread across both atria.

Both atria contract.

The impulse reach atrioventricular node.

Impulse travel through bundle of His to purkinje tissues/purkyne tissues.

And then spread to all parts of both ventricles.

Both ventricles contract/ventricular systole.

Control?

Cardiovascular centre is located in the medulla oblongata.

The heart is supplied by two nerves : vagus/parasympathetic and sympathetic nerves.

Impulse from cardiac inhibitory centre is transmitted to sinoatrial node through vagus nerve.

Vagus/parasympathetic nerve slows down the rate of heart beat.

Impulse from cardiac acceleratory transmitted to sinoatrial node through sympathetic nerves.

Sympathetic nerves increase/speed up the rate of heart beat.

Adrenaline/Epinepherine/Thyroxine also increases/speeds up the rate of heart beat.

The production of extracellular enzymes

In the nucleus, the DNA double helix unwinds & exposes its two strands for the synthesis of mRNA strand.

The mRNA (messenger RNA) leaves the nucleus through the nuclear pore and moves to a ribosome.

The mRNA attaches itself to the ribosome.

Proteins are synthesised & transported through the space within the rough ER.

Proteins depart from rough ER wrapped in vesicles (transport vesicle) that bud off from the membrane.

The transport vesicle then fuse with Golgi apparatus. The proteins are further modified, packaged, sorted (eg. carbohydrates are added to proteins --> glycoproteins)

Secretory vesicles then bud off from the Golgi apparatus & travel to plasma membrane.

They then diffuse with the plasma membrane before being released outside. 

Common problems among students (majority)

1. Poor memory
2. Procrastination
3. Laziness
4. Addicted to computer games, TV, internet
5. Difficulty in understanding what is taught
6. Easily distracted
7. Short attention span
8. Day-dreaming
9. Exam anxiety
10. Making careless mistakes
11. Pressure stress from parents
12. Too much to study and not enough time
13. Lack of motivation
14. Give up easily
15. Boring teachers
16. No interest in what they are learning

A Successful Student

Introduction

The school is a friendly place; but it is also a competitive environment. The education you receive there, and the attitudes you develop, will guide you in futute. Your grades will be important. To be a successful student requires certain skills; but, these are skills that can be learned.

The Basics of Being a Good Student

- Prioritise your life: Doing well in school should be your top priority.

- Study: There is no substitute.

- Always attend class.

- Do all of the homework and assigned reading.

- Develop self-discipline.

- Manage your time.

Self-Discipline Made Easy

Human beings are creatures of habit. Therefore, form a habit of doing what you reason you should do. Is it not foolish for your behaviour to contradict your own reasoning? And what could be more harmonious than finding yourself wanting to do what you know you should?

Train yourself so there is an immediate reaction-mechanism within you:

You reason that you should do something, and thus you do it.

Other people who seem to have less difficulty with self-discipline probably have simply had more practice at it, thereby making it less difficult; because, practice is what it takes. 

Time Management

No matter how you slice it, there are only 24 hours in a day. Good time-management requires:
1. Note taking on more than you can handle.
2. Reasonably estimating the time required to perform each of the tasks at hand.
3. Actually doing what needs to be done.

Only you can do these things. A couple of thoughts, though, that may help spur you on:
- A minute now is as precious as a minute later. You can't put time back on the clock.
- If you're not ahead of schedule, then you're behind schedule. Because, if you try to remain right on  schedule, then any mishap or misjudgment will cause you to fall behind---perhaps right at the deadline, when no recovery is possible. 

Introspection
- Understand, and be honest with, yourself. All else follows from this.
- Be both athlete and coach: Keep one eye on what you are doing, and one eye on yourself.
- Take command of, and responsibility for, yourself.
- Face your insecurities head-on. Some common signs of insecurity: Asking a question to which you already know the answer; being artificially social with teachers or other students, when the real reason is to temporarily kill the pain.
- Form a positive self-image: Those students who are first entering secondary school will probably have doubts about how well they will do. Try to do well immediately to instill an expectation of continuing to do well. Settle for nothing less. Nevertheless, try not be restricted by your past performance and experiences, good or bad. Learn from the past, but don't be bound by it. Seek out your weaknesses and attack them. Be realistic about your limitations; but, don't let this lead to becoming satisfied with them.

Taking a Course

Each student's attitude is some mixture of the following:
- He/She wants to learn the material.
- He/She wants to get a good grade.
- He/She doesn't care.

Each teacher's attitude is some mixture of the following:
- He/She wants students to learn the material.
- He/She wants grading to be fair and reflect students' knowledge and abilities.
- He/She doesn't care.

In order to do well, it is up to you (the student) to do two things:
- Learn the material.
- Learn the teacher.

As for the latter, pay attention in class to the teacher's patterns, to what he/she emphasises, etc. Gather information about the teacher from other students. A good teacher, however, will present their subject in such a way that it will be of little benefit for the student to try to learn him/her, thereby forcing their students to learn the material.

Homework
- Keep in mind that your work is being graded by a human being. Thus:
Write legibly, orderly, and coherently.
Supply any commentary necessary to make it clear what you are attempting to do.
- Making the teacher's job easier will more likely lead to you getting the benefit of doubt when it occurs.
- Don't think that getting the right answer to a homework problem implies that you have mastered the corresponding material. All you have done is solve one particular problem; that does not mean you have necessarily learned how to solve all such problems (such as the ones to appear on your exams). It's up to you to view the homework problems from this wider perspective.
- If available, always go over the solutions provided by the teacher, even if you did well on the assignment. He/She may demonstrate methods (perhaps more efficient) or provide useful information that you hadn't thought of.
Exams
- Preparation:
Roughly prioritise material as to its importance (primary, secondary, tertiary), and concentrate your studying on the most significant topics. Remember, the teacher only has a limited amount of time to test what you know and can do. Thus, keep in mind when preparing for an exam that the problems cannot be too complicated if they are to fit within the allotted time.
- Study in ways that are suited to you.
Study with a group or alone based upon which is really best for you.
Do your most strenuous and important work during those times of the day that you work best.
Summarise or outline the course or text material in your own words. Writing a summary not only forces you to examine the subject matter in detail, but provides a compendium to review just prior to the exam.
Play it safe: Memorise somewhat more than what the teacher says is required. Bring a calculator even if it's not suggested. Etc.
Study old exams if the teacher is known to give similar exams. But, don't be fooled into thinking that since you were able to work through an old exam, it means you understand all the course material in general, and can perform in a test situation.
Bring your own paper and a watch.
Fighting exam anxiety: Convince yourself that all you can do is all you can do; but, don't let that lead you to become complacent. Just be determined to be "on" for the duration of the exam. (Give yourself a pep-talk to this effect prior to each exam.)
- Starting the exam:
Read the instructions thoroughly and carefully.
Skim over the entire exam prior to beginning work.
Don't necessarily do the problems in order. Instead, get those problems out of the way you feel confident you can do quickly and well. Observe how the problems are weighted, and direct your efforts to where you believe you can pick up points most easily. This does not necessarily mean attempting the most heavily weighted problem first; rather, it means first doing the problem for which you can accumulate points at the fastest rate. Indeed, there is a good chance that this is not the most heavily weighted problem, since many instructors dislike giving any one problem significantly greater or fewer points than the average, thereby underweighting the harder problems and overweighting the easier ones.
Before writing on any given problem, think. A small investment in time at the beginning can save time overall (for you might thereby choose a more efficient method of solving the problem).
Do precisely what is requested. In particular, don't waste time doing things that will not receive credit. For example, unless explicitly required, do not rewrite the exam problems on your paper.
Pace yourself through the exam. Example: On a 50-minute exam worth a 100 points, you should be accumulating 2 points per minute; thus, a 26-point problem should be completed in 13 minutes. Do this calculation at the start of the exam if the problem weights are given.
Show your work and make clear your reasoning in order to have a chance to receive partial credit.
As with homework, and even more importantly, neatness counts.
Always check over your answers if you have time.

Further Suggestions

• Unify and simplify your knowledge: A textbook presents the subject in a particular form, as does a teacher. By their very natures, however, textbooks and teachers tend to present subjects sequentially. Take the extra step of understanding the material in your terms, which may involve recognising relationships that could not be conveniently expressed in the order presented in the text(s) and lessons.
• Remember, almost every logically consistent topic is simple at its foundation. Try to recognise the simple underlying relationships in the subject at hand; these are often left unstated by instructors and textbooks.
• Try to learn general principles and methods. Learning by examples (putting the new in terms of the familiar) can only take you so far.
• Learn as many methods of problem-solving as you can. This is especially helpful for exams, when time is of the essence.
• Ask yourself questions. Why didn't the teacher or text(s) do this or that? Explore your own ideas. Try to understand the subject content in detail.
• It is often said that the best way to learn something is to teach it. Do you know the subject matter well enough to explain it clearly and completely to someone else?
• Learn by observing others. Notice what works for them and consider incorporating those methods into yourself. Ask yourself "Why didn't I think of that?", and try to develop the related ability.
• Attempt to be methodical, neat, legible, deliberate, precise, knowledgeable, and reliable on the one hand, and creative, spontaneous, imaginative, smart, clever, articulate, and flexible on the other. The first mentality thrives on order, and inherently tries to do well what it already knows how to do; the second mentality thrives on disorder, and inherently tries to expand upon its abilities. Adopt the best of these two mentalities. Remember, every tool is a potential crutch. The first mentality may rely too heavily on already-mastered skills; but, the second mentality may fail to carefully apply those same skills.
• Think about and question everything, even the statements appearing here (and, yourself!). But, realise that it is equally foolish to be different merely for the sake of being different, as it is to mindlessly conform to the norm.
• For maximum efficiency, have several projects going at once. Then, if you get tired, frustrated, or bored working on one item, you can easily move onto something else, thereby staying productive as well as giving pending problems a chance to work themselves out subconsciously.
• Anticipate. For example, you may need to ask the instructor about the present assignment, but he/she is only guaranteed to be available at certain times; therefore, you should look over the assignment early.
• Forget pulling "all-nighters". These merely amount to borrowing from tomorrow, at which time you will find yourself considerably less functional. All-nighters are really an indication of not having properly planned your activities.
• If possible, bring your textbook(s) to class.
• Take your lessons notes in pencil, since any modifications can then be made quickly and neatly.

Closing

Overall, there is one basic trait that distinguishes successful students from those that are not:

Successful students force themselves to understand.

They do not merely go through the motions of attending class, reading the text(s), and doing the homework, expecting these actions to necessarily suffice. Rather, they are continually asking, "Do I really understand what's going on here?" They ask this question of themselves honestly, applying an internal barometer formed from experience to detect the slightest lack of understanding, be it ignorance or confusion. And, if the answer is "No", then the situation is viewed as unacceptable, and more effort is the response.

Facts about cell

Cells are the fundamental units of life. Whether they be unicellular or multicellular life forms, all living organisms are composed of and depend on cells to function normally. Scientists estimate that our bodies contain anywhere from 75 to 100 trillion cells. Cells do everything from providing structure and stability to providing energy and a means of reproduction for an organism. The following facts about cells will provide you with well known and perhaps little known tidbits of information about cells.

1. Cells are too small to be seen without magnification.

Cells range in size from 1 to 100 micrometers. The study of cells, also called cell biology would not have been possible without the invention of the microscope. With the advance microscopes of today such as the Scanning Electron Microscope and Transmission Electron Microscope, cell biologists are able to obtain detailed images of the smallest of cell structures.

2. There are two primary types of cells.

Eukaryotic and prokaryotic cells are the two main types of cells. Eukaryotic cells are called so because they have a true nucleus. Animals, plants, fungi and protists are examples of organisms that are composed of eukaryotic cells. Prokaryotes include bacteria and archaeans.

3. Prokaryotic single-celled organisms were the earliest and most primitive forms of life on earth.
Prokaryotes can live in environments that would be deadly to most other organisms. They are able to live and thrive in various extreme habitats. Archaeans for example, live in areas such as hydrothermal vents, hot springs, swamps, wetlands, and even animal intestines.

4. There are more bacterial cells in the body than human cells.
Scientists have estimated that about 95% of all the cells in the body are bacteria. The vast majority of these microbes can be found within the digetive tract.

5. Cells contain genetic material.

Cells contain DNA (deoxyribonucleic acid), the genetic information necessary for directing cellular activities. DNA is a type of molecule known as a nucleic acid. In prokaryotic cells, the single bacterial DNA molecule is not separated from the rest of the cell but coiled up in a region of the cytoplasm called the nucleoid region. In eukaryotic cells, DNA molecules are located within the cell's nucleus. DNA and proteins are the major components of chromosomes. Human cells contain 23 pairs of chromosomes (for a total of 46). There are 22 pairs of autosomes (non-sex chromosomes) and one pair of sex chromosomes. The X and Y sex chromosomes determine gender.

6. Cells contain structures called organelles which carry out specific functions.

Organelles have a wide range of responsibilities within a cell that include everything from providing energy to producing hormones and enzymes. Eukaryotic cells contain several types of organelles, while prokaryotic cells contain a few organelles (ribosomes) and none that are bound by a membrane. There are also differences between the kinds of organelles found within different eukaryotic cell types. Plant cells for example, contain structures such as a cell wall and chloroplasts that are not found in animal cells. Other examples of organelles include:

• Nucleus
• Mitochondria
• Endoplasmic Reticulum
• Golgi Complex
• Ribosomes

7. Different types of cells reproduce through different methods.
Most prokaryotic cells reproduce by a process called binary fission. This is a type of cloning process in which two identical cells are derived from a single cell. Eukaryotic organisms have a similar type of reproductive method known as mitosis. Some eukaryotes also have the ability to reproduce sexually, which involves the fusion of sex cells or gametes. Gametes are produced by a process called meiosis.

8. Groups of similar cells form tissues.
Tissues are groups of cells with both a shared structure and function. Cells that make up animal tissues are sometimes woven together with extracellular fibers and are occasionally held together by a sticky substance that coats the cells. Different types of tissues can also be arranged together to form organs. Groups of organs can in turn form organ systems.

9. Cells have varying life spans.
Cells within the human body have different life spans based on the type and function of the cell. They can live anywhere from a few days to a year. Certain cells of the digestive tract live for only a few days, while some immune system cells can live for up to six weeks. Pancreatic cells can live for as long as a year.

10. Cells commit suicide.

When a cell becomes damaged or undergoes some type of infection, it will self destruct by a process called apoptosis. Apoptosis works to ensure proper development and to keep the body's natural process of mitosis in check. A cell's inability to undergo apoptosis can result in the development of cancer.