PHYSIOLOGY OF THE EYE

This is a link to a good lesson on the eye for those interested in learning more about how the eye works. It consist of the anatomy and physiology of the eye with animations.  Click here.

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HAPPY THANKSGIVING TO MY USA FANS!

For all my readers from USA, I want to wish you all

HAPPY THANKSGIVING!

As you eat your turkey, meticulously identify the epithelial tissues, the connective tissues, the muscle tissues, etc. Dissect the turkey with care!

Let your mind wonder about how its proteins were made. PROTEIN SYNTHESIS!

Remember the blood cells are formed in the bone marrow so savor the juicy marrow to derive some iron. IRON is needed for the formation of the hemoglobin in the red blood cells.

Explore the cartilage at the end of the bones and enjoy the sight of its glassy appearance!

Many thanks to you for visiting my blog and making it the best site ever!

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or clicking on some of the associated ads.

Keep this site alive and spread the word about the usefulness of this blog!

HAVE FUN WITH YOUR TURKEY!

CHARLES DARWIN -NATURAL SELECTION AND SURVIVAL OF THE FITTEST

Charles Darwin was one of the famous scientist who set out to discover the origin of life. He set off on a 40,000 mile journey over the course of five (5) years aboard the HMS Beagle to many continents. He observed the patterns of geology and of life both extant and extinct. His discovery led to the writing of his famous book, 'On the Origin of Species'. His study led to the concept of Natural Selection and the ' Survival of the Fittest.

 He was a lover of horses and a keen pigeon fancier. He was sensitive to the power for selective change of careful domestic breeding. Extrapolating from the efficacy of domestication, he stated that, "Why, if man can by patience select variations most useful to himself, should nature fail in selecting variations useful, under changing conditions of life, to her living products..........I can see no limit to this power, in slowly and beautifully adapting each form to the most complex relations of life."

What does survival of the fittest mean? If a trait in a population, such as a dark coat color, confers a survival advantage through more effective camouflage, then those individuals with the darkest coats will have an improved chance of surviving and, therefore, an improved chance of passing their genes to subsequent generations. As time passes, the dark coats will predominate. So over a long time, he claimed that given sufficient change through adaptation, new species will emerge and new forms of life will arise.

He concluded from his study and wrote that "We must, however, acknowledge, as it seems to me, that man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his godlike intellect which has penetrated into the movements and constitution of the solar system - with all these exalted powers - man still bears in his bodily frame the indelible stamp of his lowly origin."

PRACTICE TEST ON KIDNEY FUCTIONS

Click the link below to test yourself on:

1. The kidney functions - Part 1

2. The kidney functions - Part 2

ENZYMES AND CATALYST

A catalyst is any substance that speeds up the rate of any chemical reaction. It does not take part in the reaction itself. It is only there to increase the rate at which the reaction proceed. It can therefore be used over and over again.

In the living organism, the biological catalyst is referred to as an enzyme.
Characteristics of enzymes:

• Enzymes are proteins in nature. They can, therefore, be denatured. That is, they can be destroyed or damaged by extreme conditions of temperature and pH. 
• Enzymes work within a narrow temperature  and pH ranges. 
• Enzymes have active sites when the substrate binds. Substrate is the substance that the enzyme binds to for chemical reaction to occur.
• Enzymes work by lowering the activation energy. Activation energy is the minimum energy that is needed to be overcome before the reactants can be converted into products. 
• Enzyme activity increases with increase in the substrate until saturation is reached and then the rate of activity slows down.
• Enzymes are specific in nature, that is, they work on only specific substances. It is like lock and key. For every lock, there is a particular key that fits it.
• Certain drugs can compete with the substrate for the active site. This can lead to inhibition ot the enzyme. This is referred to as competitive inhibition. 
• There is also non-competitive inhibition where the drug competes for sites other than the active sites. These sites are know as allosteric site. 

PRACTICE QUESTIONS ON THE ENDOCRINE SYSTEM

Click on the link below to test your skills on the endocrine system:

1. Parathyroid gland

2. Endocrine regulation

3. Peptide hormone action

4. Glucose regulation

Click on this link to go back to the lesson on the endocrine system.

THE IMMUNE SYSTEM

The immune system consist of structures and processes that protect the body from infections, diseases, and foreign agents. The immune system should be able to distinguish between self and non-self molecules.

There are two types of immune systems:
1. Innate immune system: This is the part of the immune system present at birth. It consist of the lymphoid system (lymph nodes, spleen, tonsils, adenoids), liver, barriers such as the skin, mucus membranes and its secretions such as tears, gastric juices, cilia and hairs in the respiratory system that trap dirt, etc. It also involves inflammation using the leucocytes (White blood cell) such as neutrophils. Macrophages use the complement system to destroy antigens and micro-organisms. Natural killer cells, a class of lymphocytes, are used to destroy cancer cells.

• Non-specific responses
• Immediate maximum response follows exposure
• Has both cellular and humoral components
• There is no immunological memory

2. Adaptive immune system: This is the part of the immune system that develops following exposure to a foreign substance (antigen). Antigen is a class of foreign molecules. It comes from the word "antibody generators". They stimulate the body to produce antibodies. Antibodies neutralize or fight off the antigens.

• Pathogen and antigen specific responses
• There is a lag phase before maximum response is seen
• Has both cellular and humoral components
• Immunological memory is present

Note:
1. Humoral immunity: This involves antibody response to the antigen. B-lymphocytes are involved here.
2. Cellular immunity: This involves the responses mounted by the T-lymphocytes.

Immunological Memory
This can be classified into:
1. Passive memory: This is a short term memory lasting from few days to months. The antibodies are injected or passed on into the individual. For example, during pregnancy, the mother's antibodies enter the fetus through the placenta to offer protection against infections. The breast milk also contains antibodies. So basically, passive immunity involve the transfer of antibody-rich serum or secretions from one individual to another.
2. Active memory: This is a long term memory acquired during infection by the activation of B-lymphocytes and T-lymphocytes. This is the principle behind vaccination. An antigen is injected into the organism to stimulate it to produce specific antibodies against it. The B-lymphocyte are changed to plasma cells which then produce the antibodies. The T-lymphocytes (called T-Helper cells) produce substances that stimulate the B-lymphocytes to produce the antibodies.

There are five classes of antibodies (immunoglobulins): Ig A, Ig G, Ig M, Ig E, Ig D

You can remember this by using the pneumonic "GAMED"

BIOLOGY PRACTICE QUESTIONS-5

Click on the link to practice on some questions

1. Vision

2. Reflex Arc

3. Action Potential


You can review the reflex arc here.

You can also review the structure of the eye and vision here.