Wednesday, May 26, 2010

[Science Form 4] The Endocrine System

  • Insulin
    • Convert glucose to glycogen.

  • Pituitary
    • Found at the base of the brain.

  • Pancreas
    • When the cells that produce insulin in one's pancreas are destroyed, he/she gets diabetes.

  • Testosterone
    • Causes the development of men's secondary sex characteristics.

  • Glucagon
    • Break down glycogen to release glucose.

  • Adrenal
    • This gland secretes hormones when one is scared.

  • Ovary
    • Controls the mentrual cycle.

In animal anatomy the endocrine system is a system of glands, each of which secretes a type of hormone into the bloodstream to regulate the body.

The endocrine system is an information signal system like the nervous system.

Hormones regulate many functions of an organism, including mood, growth and development, tissue function, and metabolism.

The field of study that deals with disorders of endocrine glands is endocrinology, a branch of internal medicine.

The endocrine system is made up of a series of ductless glands that produce chemicals called hormones.

A number of glands that signal each other in sequence is usually referred to as an axis, for example, the hypothalamic-pituitary-adrenal axis.

Typical endocrine glands are the pituitary, thyroid, and adrenal glands. Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones.

In contrast, exocrine glands, such as salivary glands, sweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen.

In addition to the specialised endocrine organs mentioned above, many other organs that are part of other body systems, such as the kidney, liver, heart and gonads, have secondary endocrine functions.

For example the kidney secretes endocrine hormones such as erythropoietin and renin.

Saturday, May 22, 2010

10th International APICTA Awards Kuala Lumpur, Malaysia

In conjunction with MSC Malaysia Summit 2010

ALL CAN PARTICIPATE
For more information and enter:
http://www.mscmalaysia.my/topic/APICTA

Sunday, May 16, 2010

Happy Teacher's Day

Teacher's Days are intended to be special days for the appreciation of teachers. Some of them are holidays while others are celebrated during working days.

World Teacher’s Day is celebrated across the world on 5th October, with great verve and enthusiasm.

Ever since the importance of teachers has been recognized by UNESCO, by adopting the “Recommendation concerning the status of teachers”, World Teacher’s Day has been celebrated annually.

This includes celebrations to honor the teachers for their special contribution in a particular field area or the community in general.

In some countries, World Teacher’s Day is celebrated by organizing conferences focused on the importance of teachers and learning.

In many countries, extra training sessions for teachers, recruitment drives for the teaching profession (among university students or other suitably qualified professionals) and events to increase the profile of teachers and the role they play in the media, are undertaken.

In Malaysia, 16 May was chosen as "Hari Guru" because on the same day in 1956, the Federal Legislative Council of the Federation of Malaya endorsed the Razak Report, one of four reports of the Education Committee regarding education in Malaysia.

The document, known as the Razak Report after Tun Abdul Razak who was Education Minister at the time, became the basis of education in Malaysia ever since.

Although it is not an official school holiday, celebrations are usually held on May 16, or earlier, if it falls on a Saturday or Sunday.

Wednesday, May 12, 2010

[Science PMR] Exam Pointers I

A group of students carried out an experiment, using a spring and a set of slotted weights as shown in the diagram below, to investigate the relationship between the length of the spring and the weight.


Number of slotted weights

Extension of spring / cm

1

10

2

20

3

30

4

40

5

50

Table 1
  1. State the variables that are involved in the experiment

    • Manipulated variable => Number of slotted weights.
      Common error: Students only write "weights". You must write out the answer in full.

    • Responding variable => Extension of the spring.
      Common error: Students only write "spring". You must write out the answer in full.

    • Constant variable => The type of slotted weight/type of spring.
      Common error: "Retort stand" is not acceptable. The answer should be the variable that when changed will affect the reading.

    Tutor's comment: Look at the table 1, the first column is the manipulated variable and the second column is the responding variable.

  2. What is the aim of this experiment?
    Answer: To investigate the relationship between the number of slotted weights and the extension of the spring.

    Tutor's comment: It is to investigate the relationship between the manipulated variable and the responding variable.

  3. What is the inference that you can make based on this experiment?
    Answer: The extension of the spring depends on / is determined by the number of slotted weights.

    Tutor's comment: The changes in the responding variable depends on the changes in the manipulated variable.

  4. What is the relationship between the force applied to the spring and the extension of the spring?
    Answer: When the force applied to the spring increases, the extension of the spring increases.

  5. Based on the data, draw a graph to show the relationship between the length of the spring and the number of slotted weights.


    Tutor's comment: Use a pencil when drawing the graph. If the question did not specify which type of graph to draw, draw a line graph.


  6. Predict the length of the spring if 6 slotted weights are used.
    Answer: 60cm

    Tutor's comment: Draw the corresponding lines on your graph and get the reading from the graph.

  7. What conclusion can be drawn from the experiment?
    Answer: When the number of slotted weights increases, the extension of the spring also increases.

    Tutor's comment: The conclusion will be the same as your hypothesis, that is "When the manipulated variable increase/decreases, the responding variable will increase/decrease."

Tuesday, May 04, 2010

[Chemistry Form 4] Forming Theories

Man's first step in modern chemistry probably dated back to the discovery of fire. Thanks to it, man could cook food, make glass and also extract metals from ores.

Man was so content with the results of what they had done that they did not try to explain what had happened or why something had happened.

Only two thousand and five hundred years ago, philosophers began to question what things are made of, and what happens when things change.

The following is a brief history of chemists who had pondered about matter;
  1. It was the 5th century BC in Greece. Empedocles suggested that all things on Earth are made from four fundamental substances he called elements. What were these four elements?
    • Fire, water, air and earth.

  2. Another Greek philosopher, born at the time Empedocles died, proposed that nature is made up of tiny particles he called atoms, which, in Greek, means indivisible. Who was this Greek philosopher?
    • Democritus.

  3. The atomic hypothesis was contested by the greatest philosopher at the time who remained faithful to the element theory. Because of his great reputation, the false element theory dominated scientific thought for two thousand years. Who was this famous Greek philosopher?
    • Aristotle.

  4. In later years, history has it that the Alexandrians were the first to devote themselves to alchemy, and they were soon followed by the Arabs, who introduced it into Western Europe. When was this?
    • 4th century AD.

  5. Chemistry then made little headway for years. In 1525, a Swiss doctor and scientist challenged his students to tear up their books, which recorded old theories that had been developed through reasoning, and told them to find out for themselves through experiments whether a scientific theory was right or wrong. This scientist had an imposing name. Who was this scientist?
    • Theophrastus Bombastus Paracelsus Von Hohenheim.

  6. Later on, Robert Boyle, an Englishman, succeeded in killing off the old idea of the four elements by establishing that there are other elements - substances that cannot be formed by or broken into other substances. When was this?
    • 1661
A hundred years after Boyle made his discovery, a Swede, Karl Scheele, and an Englishman, Joseph Priestley, succeeded in isolating oxygen. Modern chemistry was thus born.

Monday, May 03, 2010

[Physics Form 4] Quantities Defined

A physical quantity represents any property that can be measured by a scientific device and technique, and given a numerical value.

Classification of quantities

Physical quantities
  1. Base quantities
    • Base quantities cannot be expressed in terms of other physical quantities while derived quantities are combination of two or more base quantities.
    • The five base quantities are current, length, mass, temperature and time.

  2. Derived quantities
    • Derived quantities result from the combination of base quantities through multiplication and divisive operations only.
    • Mathematical operations like subtraction and addition are not involved.
      Eg: Work is a derived quantity because it is obtained through the combination of three base quantities - mass, length and time.

      Work = Force x Displacement
      Work = Mass x Acceleration x Displacement
      Work = (Mass x Velocity x Displacement) / Time
      Work = [Mass x (Displacement)2] / (Time)2

      Note: Displacement is measured in terms of length.

  3. Scalar quantities
    • Scalar quantities describe only the magnitude of physical quantities.

  4. Vector quantities
    • Vector quantities describe both the magnitude and direction of physical quantities.

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