Feb 27, 2010

Endocrine System

Basic patterns of simple hormonal control pathways. In each pathway, a receptor/sensor (blue) detects a change in some internal or external variable— the stimulus—and informs the control center (gold). The control center sends out an efferent signal, either a hormone (red circles) or neurohormone (red squares). An endocrine cell carries out both the receptor and control center functions.

Graves′ disease, the most common form of hyperthyroidism in humans. Tissue behind the eyes can become swollen and fibrous, causing the characteristic symptom of bulging eyes.

Feb 24, 2010

Good Teaching??

All students have had hundreds of teachers in their lifetimes. A very few of these teachers they remember as being exceptionally good. What are the qualities that combine to create an excellent, memorable teacher? Why do some teachers inspire students to work three times harder than they normally would, while others inspire students to skip class? Why do students learn more from some teachers than others?

If you are trying to become a better teacher, these are important questions. These four essential qualities are important: knowledge, communication skills, interest, and respect for students.

An Experiment
Here's an experiment I have done in a number of my classes. The results may surprise you. Go into one of the classes you are teaching and have your students take out a sheet of paper. Ask them to list for you the qualities they feel are important in a good teacher. Ask them to identify the qualities they admire in the best teachers they have had. Then give the students enough time to think about it and write something down. Five minutes is good, but ten might be better. Let them answer the questions anonymously if they desire.

What you will get if you combine all of the responses is a fascinating collage of ideas. I have found that most of the responses fall into two specific categories: 1) a set of "core qualities" that students recognise in good teachers, and 2) a set of specific skills that are developed by good teachers.

"Core qualities" are the essential characteristics needed to be a good teacher. I would like to concentrate on the core qualities.

In every survey I have given, students consistently and clearly target as the number one quality of a good teacher exactly what you would expect: knowledge of the subject. You must be an expert in your field if you are going to be a good teacher. This is a prerequisite.

The second core quality that good teachers possess is the ability to communicate their knowledge and expertise to their students. You may be the greatest expert ever in your field, but what would happen if you taught in Latin? How much would your students learn?

It is a common misconception at the school level that knowledge of a subject is all that's required to be a good teacher; that the students should be willing and able to extract the meat from what you say regardless of how it is delivered (even if it is delivered in Latin). This might be true at the upper level, but elsewhere it is definitely untrue. It is especially untrue at the school level. The teacher's job is to take advanced knowledge and make it accessible to the students. A good teacher allows students to understand the material, and to understand what it means (because it is one thing to understand how nuclear bombs work, but quite another to understand what nuclear bombs mean).

A good teacher can take a subject and help make it crystal clear to the students. A bad teacher can take that same material and make it impenetrable. Or a bad teacher can devote so little time and effort to preparation that the material presented is intrinsically confusing and disorganised. A good teacher is willing to expend the effort needed to find innovative and creative ways to make complicated ideas understandable to their students, and to fit new ideas into the context available to the student. A good teacher can explain complicated material in a way that students can understand and use.

There is a saying, "Give me a fish and I eat for a day, teach me to fish and I eat for a lifetime." This is the philosophy of a good teacher. Give your students an answer and they can solve one problem, but show students the techniques needed to find the answer for themselves and they can become self-sufficient in the field. Students need to be shown how to apply the new techniques you teach to problem solving.

A good teacher starts with a firm knowledge of the subject, and builds on that with a clarity and understanding designed to help students master the material. The best teachers then go one step further. Because good teachers are interested in the material being taught, they make the class interesting and relevant to the students. Knowledge is worthless unless it is delivered to the students in a form they can understand. But the effort expended making the material understandable is wasted if the students are asleep when it is delivered, or if the students can see no point in learning the material.

Good teachers recognise this, and work hard to make their material relevant. They show students how the material will apply to their lives and their careers. Bad teachers make material "relevant" by threatening students with failure on a test. Good teachers go far beyond this: they make students want to learn the material by making it interesting.

This is one of the things that makes research so important and vital: research makes the ideas discussed in class exciting and important to the teacher, as well as to the students. If the teacher isn't interested in what's being taught, then why should the students be?

Good teachers always possess these three core qualities: knowledge, the ability to convey to students an understanding of that knowledge, and the ability to make the material interesting and relevant to students. Complementing these three is a fourth quality: good teachers have a deep-seated concern and respect for the students in the classroom. Why else would a teacher put in the time and effort needed to create a high quality class?

The creation of a good class requires an immense amount of work. You don't simply come up with clear explanations and examples and experiments for class off the top of your head. You don't create fair, consistent, high quality tests and homework assignments (read "learning experiences") five minutes before you hand them out. You don't figure out ways to integrate new materials and research into a class in an understandable way on the drive in one morning. You work at this sort of quality all the time. You spend time with your students so you can learn about holes in their understanding. You read and write and create to build an exciting and interesting class every day. The only thing that would drive you to do that is a concern and respect for the adults in your classroom.

When you strive and work to become a good teacher and to create a good class, the four core qualities are essential: knowledge, the skills to convey that knowledge, the ability to make the material you are teaching interesting and relevant, and a deep-seated respect for the student. Without these four qualities, good teaching will not exist.

Tata titi tutu..........

Feb 23, 2010


A bat using sonar to locate its prey.

An insect ear. The tympanic membrane, visible in this SEM of a cricket′s front leg, vibrates in response to sound waves. The vibrations stimulate mechanoreceptors attached to the inside of the tympanic membrane.

The lateral line system in a fish. Water flowing through the system bends hair cells. The hair cells transduce the energy into receptor potentials, triggering action potentials that are conveyed to the brain. The lateral line system enables a fish to monitor water currents, pressure waves produced by moving objects, and low–frequency sounds conducted through the water.

Feb 21, 2010

Nervous System

The nervous system is an organ system containing a network of specialised cells called neurones that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous system contains the brain and spinal cord. The peripheral nervous system consists of sensory neurones, clusters of neurones called ganglia, and nerves connecting them to each other and to the central nervous system. These regions are all interconnected by means of complex neural pathways. The enteric nervous system, a subsystem of the peripheral nervous system, has the capacity, even when severed from the rest of the nervous system through its primary connection by the vagus nerve, to function independently in controlling the gastrointestinal system.

Neurones send signals to other cells as electrochemical waves travelling along thin fibres called axons, which cause chemicals called neurotransmitters to be released at junctions called synapses. A cell that receives a synaptic signal may be excited, inhibited, or otherwise modulated. Sensory neurones are activated by physical stimuli impinging on them, and send signals that inform the central nervous system of the state of the body and the external environment. Motor neurones, situated either in the central nervous system or in peripheral ganglia, connect the nervous system to muscles or other effector organs. Central neurones, which in vertebrates greatly outnumber the other types, make all of their input and output connections with other neurones. The interactions of all these types of neurones form neural circuits that generate an organism's perception of the world and determine its behaviour. Along with neurones, the nervous system contains other specialised cells called glial cells (or simply glia), which provide structural and metabolic support.

Feb 15, 2010

Synovial Joint

A joint - a place where 2 or more bones meet.
At a joint the bones are held together by tough sheets of elastic fibres called ligaments.
A synovial joint is a joint which has a cavity filled with fluid.
Synovial membrane - secretes synovial fluid into synovial cavity.
Cartilage - cushions joints, absorbs shock and reduces friction between ends of bones.

Feb 13, 2010

Happy Chinese New Year

Chinese Symbol for Happy Chinese New Year (恭禧發財)
Happy Chinese New Year!
How to say Happy Chinese New Year in Chinese?
The most common Chinese ways of saying Happy New Year are Gong Xi Fa Cai (Mandarin) and Gong Hey Fat Choy (Cantonese). Even though the pronunciations are a little different, both are written the same way.
Gong Xi Fa Cai means wishing you to be prosperous in the coming year.
A fun way to respond to someone who greets you with Gong Xi Fa Cai is Hong Bao Na Lai, "Red envelope please!"

Feb 10, 2010

Passive and Active Transport


1. The simplest type of passive transport, diffusion does not require the cell to use energy. Only small molecules can cross the cell membrane by simple diffusion.
2. Diffusion is the movement of molecules from an area of high concentration to one of low concentration.
3. This difference in the concentration of molecules across a space is called the concentration gradient.
4. Diffusion is driven by the kinetic energy of the molecules. Because of their KE, molecules are in constant motion. Diffusion occurs when molecules move randomly away from each other in a liquid or gas.
5. The rate of diffusion depends on the temperature, size and the type of molecules that are diffusing.
6. Molecules diffuse faster at higher temperatures than at lower temperatures, and smaller molecules diffuse faster than large molecules.
7. Most transport of materials into and out of cells occurs by diffusion.

1.Osmosis is “The process by which water molecules diffuse across a partially permeable membrane from a region of higher water potential to a region of lower water potential.”
2. Water moves by diffusion, like any other molecule, from a region of high concentration to one of low concentration, i.e. down its concentration gradient. Confusion occurs because ‘concentration’ normally refers to the solute concentration, whereas, in this case, we are referring to the solvent concentration.
3. For this reason, the use of the term ‘water potential’ is essential; water then simply moves ‘down the water potential gradient’ – easy!
4. The water potential of pure water is zero (0), so, since a solution must always be less than 100% pure water, all solutions (and cells) have a negative (-) water potential.
5. Insoluble molecules do not affect the solute potential (obviously), so have no osmotic effect. Such molecules are used for storage – starch, lipids, and very large proteins (albumin).
6.Water potential is actually a pressure, and is measured in Pascals (Pa), but since these are so small the normal unit is the kilo Pascal (kPa). Typical plant values are -200 to -2000kPa.

1. Passive transport across a membrane requires no energy input from the cell and always goes down the concentration gradient. Simple diffusion and osmosis are examples of passive transport.
2. However, most molecules cannot cross the membrane by simple diffusion; to do so, the molecule must either be very small (water, carbon dioxide) or be soluble in both water and lipid (ethanol).
3. Some molecules are carried across the membrane by carrier proteins which are embedded in the cell membrane.

4. Carrier proteins often change shape when molecules attach to them, and this change in shape enables the molecule to cross the membrane.
5. Because the carrier protein has to fit around the molecule, it is specific to one molecule, or related class of molecules.
6. This use of carrier proteins to cross the membrane is known as facilitated diffusion, and can be used by those molecules to cross the membrane in either direction – into or out of the cell.
7. Like simple diffusion, facilitated diffusion always goes down the concentration gradient, and therefore continues until equilibrium is reached, for that molecule.
8. A good example of facilitated diffusion is the transport of glucose into the cell. Once inside the cell, the glucose is immediately turned into glucose phosphate, for which no carrier protein exists. Glucose will thus continue to enter the cell, since equilibrium can never be reached!
9. Facilitated diffusion is therefore another form of passive transport, since it requires no energy input from the cell.
10. Some molecules, mainly ions (e.g. Na+, K+) cross the membrane through tunnels made of protein called ion channels.
11. Some ion channels are always open, but others (e.g. in neurones) have ‘gates’ that open to allow ions to pass or close to stop their passage.
12. Gates open and close in response to conditions in the external environment, or in the cell. It is the opening and closing of the sodium and potassium gates that allows a nerve impulse to be formed and passed along a neurone.
1. Cells often move molecules across the membrane against the concentration gradient, i.e. from an area of low concentration to an area of high concentration.
2. This requires energy (uses ATP), and is known as active transport.
3. Active transport involves the use of carrier proteins, similar to those of facilitated diffusion, but these carrier proteins act as pumps, using the energy from splitting ATP to pump specific molecules against the concentration gradient.
4. These carrier proteins are known as membrane pumps, and are particularly important in maintaining the Na+ /K+ ion balance between Eukaryotic cells and their external environment.
5. The sodium/potassium (Na+ /K+) pump maintains a high concentration of Na+ ions outside the cell, and a high concentration of K+ ions inside the cell. This is particularly important in muscle contractions, nerve impulses and the absorption of nutrients from the gut.
6. The Na+/K+ ion pump moves Na+ ions out of the cell, and K+ ions into the cell, against their concentration gradient, using ATP to supply the energy needed.

7. In plants, active transport enables roots to absorb mineral ions from the soil, which are therefore more concentrated inside plant cells than in the soil.
8. This requires ATP energy from aerobic respiration, and therefore roots need oxygen to allow mineral uptake and a waterlogged (thus anaerobic) soil will kill most roots.

Hypertonic, Isotonic and Hypotonic

In a hypertonic solution, the concentration of solutes in the solution is higher and so it has a lower water potential. Therefore, when placed in a hypertonic solution, water leaves the cell by osmosis, until equilibrium is established.
If the cell loses too much water, the cell will shrivel and shrink. Eventually they die, as their metabolism is disrupted i.e. badly wilted plants never recover fully.

Conversely, cells in a hypotonic solution will absorb water by osmosis until equilibrium is reached, since the cell has the lower water potential, and water ‘flows downhill’.
This flow of water into a cell causes it to swell:
a. Animal cells placed in a hypotonic solution will swell and often burst because of osmosis.
b. Plant, fungal and bacterial cells do not burst because of their cell wall. The pressure that the cell exerts against the cell wall is its pressure potential. These cells are normally in this state, i.e. turgid.

In an isotonic solution, the concentration of solutes on both sides of the membrane is the same and so the net movement of water is zero. This is the normal position inside an animal’s body.

Feb 6, 2010

Human Skeleton

The human skeleton consists of 206 bones. We are actually born with more bones (about 300), but many fuse together as a child grows up. These bones support your body and allow you to move. Bones contain a lot of calcium (an element found in milk, broccoli, and other foods). Bones manufacture blood cells and store important minerals.

The human skeleton consists of both fused and individual bones supported and supplemented by ligaments, tendons, muscles and cartilage. It serves as a scaffold which supports organs, anchors muscles, and protects organs such as the brain, lungs and heart. The biggest bone in the body is the femur in the upper leg, and the smallest is the stapes bone in the middle ear. In an adult, the skeleton comprises around 14% of the total body weight and half of this weight is water.

Axial skeleton

The axial skeleton (80 bones) is formed by the vertebral column (26), the thoracic cage (12 pairs of ribs and the sternum), and the skull (22 bones and 7 associated bones). The axial skeleton transmits the weight from the head, the trunk, and the upper extremities down to the lower extremities at the hip joints, and is therefore responsible for the upright position of the human body. Most of the body weight is located in back of the spinal column which therefore have the erector spinae muscles and a large amount of ligaments attached to it resulting in the curved shape of the spine. Only the parts of the skeleton that are directly affected by the exercise will benefit. Non weight-bearing activity, including swimming and cycling, has no effect on bone growth. control the minute and complex facial movements.

Appendicular skeleton

The appendicular skeleton (126 bones) is formed by the pectoral girdles (4), the upper limbs (60), the pelvic girdle (2), and the lower limbs (60). Their functions are to make locomotion possible and to protect the major organs of locomotion, digestion, excretion, and reproduction.


The skeleton has six main functions:

The skeleton provides the framework which supports the body and maintains its shape. The pelvis and associated ligaments and muscles provide a floor for the pelvic structures. Without the ribs, costal cartilages, and the intercostal muscles the lungs would collapse.

The joints between bones permit movement, some allowing a wider range of movement than others, e.g. the ball and socket joint allows a greater range of movement than the pivot joint at the neck. Movement is powered by skeletal muscles, which are attached to the skeleton at various sites on bones. Muscles, bones, and joints provide the principal mechanics for movement, all coordinated by the nervous system.

The skeleton protects many vital organs:
The skull protects the brain, the eyes, and the middle and inner ears.
The vertebrae protect the spinal cord.
The rib cage, spine, and sternum protect the lungs, heart and major blood vessels.
The clavicle and scapula protect the shoulder.
The ilium and spine protect the digestive and urogenital systems and the hip.
The patella and the ulna protect the knee and the elbow respectively.
The carpals and tarsals protect the wrist and ankle respectively.

Blood cell production
The skeleton is the site of haematopoiesis, which takes place in red bone marrow. Marrow is found in the center of long bones.

Bone matrix can store calcium and is involved in calcium metabolism, and bone marrow can store iron in ferritin and is involved in iron metabolism. However, bones are not entirely made of calcium, but a mixture of chondroitin sulfate and hydroxyapatite, the latter making up 70% of a bone.

Endocrine regulation
Bone cells release a hormone called osteocalcin, which contributes to the regulation of blood sugar (glucose) and fat deposition. Osteocalcin increases both the insulin secretion and sensitivity, in addition to boosting the number of insulin-producing cells and reducing stores of fat.

Sex-based differences
An articulated human skeleton, as used in biology educationThere are many differences between the male and female human skeletons. Most prominent is the difference in the pelvis, owing to characteristics required for the processes of childbirth. The shape of a female pelvis is flatter, more rounded and proportionally larger to allow the head of a fetus to pass. Men tend to have slightly thicker and longer limbs and digit bones (phalanges), while women tend to have narrower rib cages, smaller teeth, less angular mandibles, less pronounced cranial features such as the brow ridges and external occipital protuberance (the small bump at the back of the skull), and the carrying angle of the forearm is more pronounced in females. Females also tend to have more rounded shoulder blades.


There are many disorders of the skeleton. One of the most common is osteoporosis.

Osteoporosis is a disease of bone, which leads to an increased risk of fracture. In osteoporosis, the bone mineral density (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered. Osteoporosis is defined by the World Health Organization (WHO) in women as a bone mineral density 2.5 standard deviations below peak bone mass (20-year-old sex-matched healthy person average) as measured by DXA; the term "established osteoporosis" includes the presence of a fragility fracture. Osteoporosis is most common in women after the menopause, when it is called postmenopausal osteoporosis, but may develop in men and premenopausal women in the presence of particular hormonal disorders and other chronic diseases or as a result of smoking and medications, specifically glucocorticoids, when the disease is craned steroid- or glucocorticoid-induced osteoporosis (SIOP or GIOP).

Osteoporosis can be prevented with lifestyle advice and medication, and preventing falls in people with known or suspected osteoporosis is an established way to prevent fractures. Osteoporosis can also be prevented with having a good source of calcium and vitamin D. Osteoporosis can be treated with bisphosphonates and various other medical treatments.

Feb 1, 2010

Frog Dissection