REGULATION OF GLUCOSE CONCENTRATION

REGULATION OF BLOOD GLUCOSE CONCENTRATION

What happens if the glucose concentration in the blood increases?

• After having a meal, the glucose concentration in the blood increases (stimulus).
• This increase may caused cells in the body to undergo crenation. For example, the red blood cells in the blood may undergo crenation due to higher water potential in the red blood cells than the blood itself. As a result water molecules in the red blood cells diffuse out of the red blood cells by osmosis.
• This condition needs to be corrected. Because of this increase, the pancreas will secrete insulin into the blood (insulin is a hormone produced by the beta-cells of the islets of langerhans of the pancreas).
• The blood will then transports the insulin to the liver (target organ).
• In the liver, the excess glucose is then converted into glycogen for storage in the liver itself as well as in the muscles.
• This conversion of excess glucose to glycogen slowly lowers the blood glucose concentration (negative feedback).
• Eventually the glucose concentration in the blood will return to normal (Norm).
  

What happens if the glucose concentration in the blood decreases?

• After vigorous exercise, the glucose concentration in the blood decreases due to glucose being oxidised to release energy during cellular respiration (stimulus)
• The decreased may caused the red blood cells to haemolyse. Haemolysis occurs due to passage of water molecules into the red blood cells from the blood from higher to lower water potential by osmosis.
• This condition needs to be corrected. The pancreas responds to this by producing glucagon into the blood (Glucagon is a hormone produced by the alpha cells of the islets of langerhans of the pancreas).
• The glucagon is then transported by the blood to the liver which is the target organ.
• In the liver, the glucagon converts glycogen stored in the liver into glucose.
• This will boost the blood glucose concentration in the blood (negative feedback)
• Eventually the blood glucose concentration will return to normal.
  

Note: Before the insulin and the glucagon can be secreted into the blood, the pancreas must first be triggered or stimulated by the pituitary gland in the brain (Remember: Pituitary gland is a MASTER gland of all the endocrine glands. It controls the activities of other endocrine glands)

THE SKIN

THE ROLE OF THE SKIN IN PREVENTING OVERHEATING

Overheating occurs when too much heat is being produced by the body so the idea here is to remove the excess heat. This then prevent the body temperature to rise above normal. The following are the mechanisms involved in preventing overheating (all occurs within the skin itself):

• The arterioles in the skin vaso-dilate (get wider). As a result of this more blood is directed or transported to the blood capillaries near to the surface of the skin. By this, heat is brought near to the surface of the skin.
• The sweat glands make more sweat. The sweat is then deposited through the sweat pore to the surface of the skin. The heat from the blood is used to evaporate the sweat and at the same time when the sweat evaporates, heat is also removed at the same time.
• The hair erector muscles relax and as a result the body hairs lie flat against the skin allowing air current to get nearer to the skin. As a result more heat will be removed.

(Apart from what happens in the skin the following also occur in order to remove more heat from the body)

• Cellular metabolism in the cells slows down so less heat is produced.
• Breathing rate increases so more heat is removed with the expired air.

THE ROLE OF THE SKIN IN PREVENTING OVERCOOLING
Overcooling occurs when not enough heat is being produced by the body. Therefore the body tries to conserve heat as much as possible so as to prevent the body temperature to drop below normal. The following mechanisms are very important in preventing overcooling:

• The arterioles in the skin vaso-constrict (becomes narrower) and as a result less blood is transported or directed to the blood capillaries. This prevent heat being removed.
• Sweat productions stops or no sweating occurs. Therefore no heat removed.
• The hair erector muscles contract raising the body hairs. This prevents air current from getting near the skin surface when air is trapped in between the hairs (Note: still air is a bad conductor of heat). This prevents heat from being removed.

(Apart from the skin, the following are also involved in conserving the heat available in the body as well as in preventing heat loss)

• Cellular metabolism increases, producing more heat for the blood to distribute around the body.
• The skeletal muscles start contracting regularly which causes shivering. Shivering generates heat.

HYPERTHERMIA AND HYPOTHERMIA

• Hypothermia is a condition where the body temperature falls below normal because too little heat is being generated.
• Hyperthermia is a condition which occurs when the body is unable to shed enough heat to stop the temperature from rising.

THE BRAIN

Central Nervous System

The Central Nervous System (CNS) is composed of the brain and spinal cord. The CNS is surrounded by bone-skull and vertebrae. Fluid and tissue also insulate the brain and spinal cord.

The brain is composed of three parts: the cerebrum (seat of consciousness), the cerebellum, and the medulla oblongata (these latter two are "part of the unconscious brain").

The medulla oblongata is closest to the spinal cord, and is involved with the regulation of heartbeat, breathing, vaso-constriction (blood pressure), and reflex centers for vomiting, coughing, sneezing, swallowing, and hiccuping. The hypothalamus regulates homeostasis. It has regulatory areas for thirst, hunger, body temperature, water balance, and blood pressure, and links the Nervous System to the Endocrine System. The midbrain and pons are also part of the unconscious brain. The thalamus serves as a central relay point for incoming nervous messages.

The cerebellum is the second largest part of the brain, after the cerebrum. It functions for muscle coordination and maintains normal muscle tone and posture. The cerebellum coordinates balance.

The conscious brain includes the cerebral hemispheres. The cerebrum governs intelligence and reasoning, learning and memory. While the cause of memory is not yet definitely known, studies on slugs indicate learning is accompanied by a synapse decrease. Within the cell, learning involves change in gene regulation and increased ability to secrete transmitters.

The Medulla Oblongata and the Midbrain

The medulla oblongata controls heart rate, constriction of blood vessels, digestion and respiration.

The midbrain consists of connections between the hindbrain and forebrain. Mammals use this part of the brain only for eye reflexes.

The Cerebellum

The cerebellum is the third part of the hindbrain, but it is not considered part of the brain stem. Functions of the cerebellum include fine motor coordination and body movement, posture, and balance. This region of the brain is enlarged in birds and controls muscle action needed for flight.

The Forebrain

The forebrain consists of the diencephalon and cerebrum. The thalamus and hypothalamus are the parts of the diencephalon. The thalamus acts as a switching center for nerve messages. The hypothalamus is a major homeostatic center having both nervous and endocrine functions.

The cerebrum, the largest part of the human brain, is divided into left and right hemispheres connected to each other by the corpus callosum. The hemispheres are covered by a thin layer of gray matter known as the cerebral cortex.

The cortex in each hemisphere of the cerebrum is between 1 and 4 mm thick. Folds divide the cortex into four lobes: occipital, temporal, parietal, and frontal. No region of the brain functions alone, although major functions of various parts of the lobes have been determined.

The occipital lobe (back of the head) receives and processes visual information. The temporal lobe receives auditory signals, processing language and the meaning of words. The parietal lobe is associated with the sensory cortex and processes information about touch, taste, pressure, pain, and heat and cold. The frontal lobe conducts three functions:

1. motor activity and integration of muscle activity
2. speech
3. thought processes

Most people who have been studied have their language and speech areas on the left hemisphere of their brain. Language comprehension is found in Wernicke's area. Speaking ability is in Broca's area. Damage to Broca's area causes speech impairment but not impairment of language comprehension. Lesions in Wernicke's area impairs ability to comprehend written and spoken words but not speech. The remaining parts of the cortex are associated with higher thought processes, planning, memory, personality and other human activities.

The Spinal Cord

The spinal cord runs along the dorsal side of the body and links the brain to the rest of the body. Vertebrates have their spinal cords encased in a series of (usually) bony vertebrae that comprise the vertebral column.

The gray matter of the spinal cord consists mostly of cell bodies and dendrites. The surrounding white matter is made up of bundles of interneuronal axons (tracts). Some tracts are ascending (carrying messages to the brain), others are descending (carrying messages from the brain). The spinal cord is also involved in reflexes that do not immediately involve the brain.

HORMONES

WHAT ARE HORMONES?

Hormones are chemical substances produced in minute quantities by the endocrine glands and transported by the blood to the target organs where they exert a profound effect. After exerting its effect in the target organ, it is then destroyed in the liver and then transported to the kidneys to be excreted.

DIFFERENCES BETWEEN NERVOUS CONTROL AND HORMONAL CONTROL

• NC involves nervous impulses whereas HC involves hormones

• Impulses are transmitted by neurones in NC whereas hormones are transmitted by blood in HC

• The response is very quick in NC and slower in HC

• Response in NC is usually short-lived whereas in HC it may be short-lived or long-lived

• NC may be voluntary or involuntary whereas HC is always involuntary

• NC is usually localised and in HC it may affects more than one target organ

ADRENALINE

• Adrenaline is a hormone produced by the Adrenal gland located just above each kidney
• Circumstances in which it is secreted: Usually in conditions of fear, anger and anxiety or in any other emergency situation
• Effect 1: Increases metabolic rate. This means that more energy is released in tissue respiration
• Effect 2: Increases in rate of heartbeat and rise in blood pressure so that oxygen and glucose are carried faster to the muscles
• Effect 3: Constriction of arterioles in skin which causes pallor. As a result of this more blood is sent to the muscles
• Effect 4: Causes the conversion of more glycogen stored in the liver into glucose so that the glucose can be used in tissue respiration
• Effect 5: Dilates the pupil of the eye so that more light can enter the eye. Hence this provides clearer vision
• Effect 6: Hair muscles may contract producing "goose pimples"
  

INSULIN

• Insulin is a hormone produced by the Islets of Langerhans in the pancreas
• Secretion of insulin is due to an increase in concentration of glucose in the blood
• Effect 1: Causes the conversion of glucose to glycogen for storage in the liver and muscles
• Effect 2: Enables tissue cells to oxidise glucose to produce energy in tissue respiration (Remember the "Gate Keeper")
• Both effects help to control the amount of glucose in the blood
  

THE HUMAN EYES

1. PARTS AND FUNCTIONS

• Sclera - Tough white outer coating (the white part of your eye is actually the sclera. The main function of the sclera is to protect the eyeball.
• Cornea - This is actually the front part of the sclera but unlike the sclera it is transparent. The function of the cornea is to refract light rays into the eye.
• Conjunctiva - This is a thin epithelium which protect the cornea.
• Vitreous humour and aqueous humour - The liquid behind the lens is jelly-like and is called vitreous humour while the aqueous humour in front of the lens is watery. The function of both the vitreous humour and the aqueous humour is to keep the spherical shape of the eyeball. In addition, the aqueous humour also functions in providing nourishment to the non-vascularised lens and cornea.
• Lens - Transparent structure (flexible and can change its shape during accomodation) which refract light rays on to the retina.
• Suspensory ligament - To hold the lens in place. Plays a very important role in accomodation.
  
• Iris - Iris gives colour to your eyes. It consists of the radial and the circular muscles. The iris controls the size of the pupil, thus controlling the amount of light entering the eyes. These muscles of the iris work antagonistically.
• Pupil - Pupil is a hole at the centre of the iris. The function is to allow light to enter the eye.
• Choroid - The second layer of the eye. It is highly vascularised to provide nourishment to the eye. It is also pigmented black (absorbs light) so as to prevent internal reflection in the eye.
• Ciliary body - It produces aqueous humour. It contains circular muscles which helps to alter the size of the lens during accomodation.
• Retina - The internal lining at the back of the eye is the retina. It contains light sensitive cells (the cones and the rods) which respond to light.
• Fovea (yellow spot) - The part of the retina which is very sensitive to light since rods and cones are highly concentrated here. When you focus on an object, the image of the object will fall on to this region.
• Blind spot - This region of the retina contains no light sensitive cells so object will not be seen here if light falls on to this region.
• Optic nerve - This contains nerve fibres which transmit electrical impulses to the brain.
• Tear glands - These are glands present under the top of the eyelid. The function is to produce tear fluid which helps to prevent friction when blinking. The tear fluid also wash away any dust particles or foreign bodies. It contains lysozyme which kills bacteria.

2. ACCOMODATION

• Viewing distant image - Ciliary muscles relax, the suspensory ligaments become taut pulling the lens outwards. As a result the lens becomes thinner. This will in turn, increased the focal length hence enable you to view distant object.
• Viewing near object - Ciliary muscles contract, the suspensory ligaments become slacken. Hence there is no pulling force to pull the lens outwards. As a result the lens becomes thicker and this will decrease the focal length. Hence you are able to focus at near object.
  

3. PUPIL REFLEX

The following figure shows the iris which control the size of the pupil thus controlling the amount of light entering the eye.

In Bright Light AND In Dim Light

• The retina (due to the presence of rods and cones) is very sensitive to light. When light falls on to the retina, the light (stimulus) will stimulates the retina. An electrical impulse will then be transmitted to the brain along the sensory nerve fibres in the optic nerve which contains sensory neurones. At the synapse between the sensory neurones and the relay neurones, acetylcholine will be released which stimulates the relay neurones in the brain to produce an electrical impulse. The electrical impulse is then transmitted along the relay neurones. Again at the synapse between the relay neurones and the motor neurones, acetylcholine will be released which stimulates the motor neurones to produce an electrical impulse. The electrical impulse is then transmitted along the motor neurones to the effector (which in this case are the radial and circular muscles of the iris).
• In dim light, the radial muscles contract and the circular muscles relax. This causes the pupil to dilate and hence allows more light to enter the eye.
• In bright light, the radial muscles relax and the circular muscles contract. This causes the pupil to constrict and hence allows less light to enter the eye (thus protects the delicate light sensitive cells in the retina)

Note: TIME WAITS FOR NO MAN

SKELETON

FUNCTIONS OF THE SKELETON:

• Support - The skeleton holds the body off the ground and keeps its shape even when muscles are contracting to produce movement.
• Protection - The brain is protected from injury by being enclosed in the skull. The heart, lungs and liver are protected by the rib cage and the spinal cord is enclosed inside the backbone.
• Movement and Locomotion - Many bones of the skeleton acts as levers. When muscles pull on these bones, they produce movements such as the raising of the ribs during breathing or the chewing action of the jaws. For a skeletal muscle to produce movement, both its ends need to have a firm attachment. The skeleton provides suitable points of attachment for the ends of muscles. The skeleton with the help of muscles also helps to move the body from one place to another. This is called locomotion.
• Production of blood cells - The red bone marrow of some bones produce both red and white blood cells.

Note: You should be able to identify the humerus, ulna, radius, femur, tibia, fibula, pelvic girdle, pectoral girdle and of course the skull, ribs and rib cage, sternum and skull.JOINTS:

• Where two bones meet they form a joint.
• In the syllabus, you only have to know the hinge and the ball and socket joints.

THE HINGE JOINT

THE BALL AND SOCKET JOINT

• Where can these joints be found? Hinge joints are found at your elbows and your knees whereas the ball and socket joint are usually found at your shoulder and your hip.
• The differences between these two types of joints are: hinge joints only allow movement in one direction only (for example bending your knee and your arm) whereas the ball and socket joints allow movement in all direction.

THE CARTILAGE, LIGAMENT, SYNOVIAL MEMBRANE AND SYNOVIAL FLUID

• The cartilage functions in reducing friction between two bones as shown in the figure above.
• Friction is further reduced by the synovial fluid which is produced by the synovial membrane.
• The function of the ligaments is to hold bones in position thus preventing dislocation. Dislocation may occurs if the ligaments are torn.
  

ANTAGONISTIC ACTION OF THE BICEPS AND TRICEPS IN THE ARM

• You need to know the role the biceps and triceps (these are known as skeletal muscles) in your arm which helps in bringing about movement such as when you are flexing or stretching your arm.
• Arm flexing - Biceps contracts while triceps relaxes.
• Arm stretching - Biceps relaxes while triceps contracts.

TRANSPORT IN MAMMALS PART 7: ORGAN TRANSPLANT AND TISSUE REJECTION

Organ or tissue transplant is when a damaged or diseased organ or tissue is replaced by a healthy or functional one. This healthy or functional organ or tissue may come from another person or the patient himself.

PROBLEM:
If the healthy organ or tissue to be donated comes from another person (donor), the organ or tissue may be treated by the patient's (recipient's) immune system as foreign body. As a result the lymphocytes may respond to this transplanted organ or tissue by producing antibodies which destroy the transplanted tissue or organ. This results in TISSUE/ORGAN REJECTION.



Tissue or organ rejection may not be a problem if the tissue or organ to be transplanted comes from the patient himself. For example, a blocked coronary artery may be replaced by an artery form another part of the patient's body.

PREVENTION OF TISSUE REJECTION:

• Tissue match: the tissue of both the donor and recipient must be genetically as close as possible. Therefore the likely candidate should be the brother, sister, parents and close relatives of the patient.
• Using immuno-suppressive drugs: this drug inhibits the activity of the recipient's immune system. Problem: the patient is prone to many kind of infection and he has to continue treatment of this drug for the rest of his life.
• X-ray radiation of the bone marrow and lymphoid tissue: this method inhibits the production of blood cells which slows down the rejection process.
  

TRANSPORT IN MAMMALS PART 6: THE FUNCTION OF BLOOD

The blood has two important functions: the transport function and the protective function.

THE TRANSPORT FUNCTION OF BLOOD
Blood acts as a transport medium carrying various substances from one part of the body to another. The blood transport the following:

• Digested food nutrients from the ileum to all parts of the body (via plasma).
• Excretory products from the tissues to the excretory organs for removal (via plasma).
• Hormones, from the endocrine glands to the target organs (via plasma).
• Heat, from the respiring tissues to other parts of the body, hence maintaining constant body temperature (via plasma).
• Oxygen, from the lungs to all parts of the body (via the red blood cells).

THE PROTECTIVE FUNCTION OF BLOOD

• Phagocytosis by the phagocytes: The phagocytes engulf and ingest foreign particles (mainly bacteria) at the site of the wound or cut. Some of the phagocytes are killed in the process. These dead phagocytes at wound, together with the dead foreign particles, form pus.
• Production of antibodies by the lymphocytes: The production is triggered when foreign particles produce toxins. The antibodies neutralise the poisonous effect of the toxins. The antibodies can also kill the foreign particles by causing the foreign particles to clump together (agglutination). The agglutinated bacteria are then ingested by the phagocytes.
• Blood clotting: This seals wound, prevents entry of foreign particles and prevents excessive loss of blood.

IMPORTANT:

• In the lungs, haemoglobin in the red blood cell combines loosely with oxygen to form oxyhaemoglobin.
• The blood containing oxyhaemoglobin is called OXYGENATED BLOOD.
• The oxyhaemoglobin is then transported to all body tissues.
• The oxyhaemoglobin then releases its oxygen as the blood passes through tissues containing very little oxygen.
• The blood containing little oxygen is called DEOXYGENATED BLOOD.
• The deoxygenated blood is then transported back to the lungs

OXYGENATED BLOOD TENDS TO BE BRIGHT RED IN COLOUR WHEREAS DEOXYGENATED BLOOD TENDS TO BE BLUISH. HENCE ARTERIES WHICH GENERALLY TRANSPORT OXYGENATED BLOOD IS RED IN COLOUR WHILE THE VEINS WHICH GENERALLY TRANSPORT DEOXYGENATED BLOOD IS BLUISH IN COLOUR.

TRANSPORT IN MAMMALS PART 5: PLATELETS (THROMOBOCYTES)

Thrombocytes are actually not true cells. They are fragments of cytoplasm from certain bone marrow cells. Together with fibrin, they play a very important role in BLOOD CLOTTING. Blood clotting is very important because it helps to seal wound and cut, thus preventing excessive loss of blood. Apart from this it also stops foreign particles like bacteria from entering the blood stream.

The following figure shows how blood clot clogged wound thus preventing blood loss.
MECHANISM OF BLOOD CLOTTING

• At cut or wound, an enzyme called thrombokinase is released by the damaged tissues and blood platelets.
• The thrombokinase together with calcium ions, then convert the (inactive) protein prothrombin to thrombin (Calcium ions as well as vitamin K must be present, otherwise blood clotting will not take place - hence one of the importance role of calcium in your diet).
• The thrombin (which is also an enzyme) then catalyses the conversion of soluble protein fibrinogen to a meshwork of insoluble threads of fibrin.
• The fibrin threads formed entangle the red blood cells which results in the formation of BLOOD CLOT. White blood cells can also be found together with the blood clot to fight against foreign particles like bacteria at the cut or wound.
  

The following figures show how the fibrin entangle the red blood cells to form BLOOD CLOT.

The following figure summarises the mechanism of blood clotting. It heps a lot if you remember the flow.


Vitamin K? Where is Vitamin coming from? It is actually produced by bacteria (NOT HARMFUL!!!) in your intestines.

TRANSPORT IN MAMMALS PART 4: WHITE BLOOD CELLS (LEUCOCYTES)

Characteristics of white blood cells:

• Colourless
• Irregular in shape
• Contains nucleus
• Contains no haemoglobin
• Larger in size than red blood cells
• Fewer in number than red blood cells
• The ratio of red to white blood cells is 700:1

There are two main kinds of white blood cells

• Lymphocytes
• Phagocytes

LYMPHOCYTES

• Produced by the lymph glands or the lymph nodes.
• Has large rounded nucleus with small amount of non-granular cytoplasm.
• Nearly round in shape.
• Show limited movement.
• Function: to produce antibodies which fight against micro-organisms other than bacteria (mainly viruses).

A Lymphocyte

PHAGOCYTES

• Produced by the bone marrow.
• Has lobed nucleus with granular cytoplasm.
• Irregular shape.
• Able to move.
• Function: to fight against foreign particles (mainly bacteria) by means of phagocytosis.
  

A Phagocyte

The following figure shows phagocytosis. In phagocytosis, first the phagocyte moves with the help of its pseudopodia towards the foreign particles (bacteria). Upon reaching the foreign particles, it will then engulf the foreign particles by surrounding them using the pseudopodia. A vacuole is formed as a result. Digestive enzyme is then secreted into the vacuole which digests the foreign particles. The products of digestion is then absorbed into the cytoplasm and when the phagocyte died, pus will be formed at the infected area.

TRANSPORT IN MAMMALS PART 3: RED BLOOD CELLS (ERYTHROCYTES)

The following are the characteristics of a mammalian red blood cell:

• Shape: biconcave (provides large surface area for more absorption of oxygen).
• No nucleus (this enables the red blood cell to accommodate more haemoglobin so that more oxygen molecules can be transported and to make the red blood cell more flexible so that it can squeeze itself through the blood capillaries).
• Produced by the bone marrow as shown below.

• Lifespan: 3 to 4 months (when they are worn out, they are destroyed in the liver).
• Contains haemoglobin (a speial kind of protein containing iron): this pigment enables red blood cell to transport oxygen from the lungs to all cells in the body (mind you carbon monoxide combines readily with haemoglobin than oxygen).
• When haemoglobin is broken down in the liver, the iron is released and stored in the liver (hence liver is very rich source of iron). Bile pigments are also produced during the breakdown of haemoglobin (bile pigments are excreted into the colon and gives faeces its colour - brownish and sometimes greenish depending on the amount of bile pigments being excreted).

BLOOD APPEARS RED IN COLOUR BECAUSE OF THE RED BLOOD CELLS

TRANSPORT IN MAMMALS PART 2: THE BLOOD

The average person has about 5.5 litres of blood. Although blood is liquid, about 45% of it is made up of solid particles held in suspension. The remaining 55% is a straw-coloured fluid called PLASMA. The solid matter in blood consists of:

• Red blood cells (erythrocytes)
• White blood cells (leucocytes)
• Platelets (thrombocytes)

THE PLASMA
The plasma is a pale yellowish liquid. About 90% of plasma is water in which a complex mixture of various substances is dissolved. These substances are:

• Soluble proteins: serum albumin, serum globulin, fibrinogen, prothrombin and antibodies (fibrinogen and pro-thrombin play an important role in blood clotting whereas antibodies are involved in fighting diseases).
• Dissolved mineral salts: chlorides, bicarbonates, and sulphates and phosphates of sodium and potassium. All these occur as ions in the plasma. CALCIUM SALTS are also present which are essential for blood clotting.
• Food substances such as glucose, amino acids, fats and vitamins.
• Excretory products such as urea, uric acid and carbon dioxide.
• Hormones such as Insulin, Glucagon, Adrenaline and Anti-Diuretic Hormone.
  

TRANSPORT IN MAMMALS PART 1: WHY DO WE NEED ONE?

WHY DO WE NEED A TRANSPORT SYSTEM?

• To distribute the absorbed useful substances like oxygen and food substances (particularly products of digestion - simple sugars, amino acids and fats) throughout the body of the animal (example: glucose is distributed to all respiring cells to generate energy).
• To remove waste products such as carbon dioxide and urea from the body of the animal before these waste products accumulate to harmful levels.

TRANSPORT SYSTEM IN MAMMALS
In mammals, the transport system consists of the:

• Blood system for transporting blood
• Lymphatic system for transporting lymph

(Note: Both blood and lymph are fluids in which substances are distributed all over the body)

The main transport system in mammals is its Blood System (also called the Vascular System). It consists of three important components:

• The Blood
• The Blood Vessels
• The Heart (a pump which keep the blood flowing through the blood vessels)

The following figure shows the general layout of the transport system (blood system) of a human as seen from the front.

Notice that the figures above show that the human transport system consists of the SYSTEMIC CIRCULATION and the PULMONARY CIRCULATION. The systemic circulation transports blood all over the body (except the lungs) whilst the pulmonary circulation transports blood only to the lungs.

If you follow the arrows, beginning at the lungs, you can see that the blood flows into the left-hand side of the heart, and then out to the rest of the body. It is brought back to the right hand side of the heart, before going back to the lungs again. This is called a DOUBLE CIRCULATORY SYSTEM because the blood travels through the heart TWICE on one complete journey around the body.

The following figure shows the lymphatic system:


(Note: there is no "pump" in the lymphatic system as in the blood system)


Now, because there is no pump in this system, lymph is prevented from flowing backward by having VALVES along the lymph vessels. The following figure shows the valves in the lymph vessels.



The following figure shows the relationship between the BLOOD SYSTEM and the LYMPHATIC SYSTEM:

PLANT NUTRITION PART 16: MORE ON THE RATE OF PHOTOSYNTHESIS

As mentioned in the previous post, any factor that directly affects a process if its quantity is changed is called the LIMITING FACTOR.



By looking at graph 1, we can see that the rate of photosynthesis increases as the light intensity increases (0 to A). We say that light intensity is the LIMITING FACTOR. Beyond point A, light intensity is no longer the LIMITING FACTOR since the rate remains constant even though the light intensity increases. In this case we have to consider other factors that could cause the rate to become constant (A to B).

Graph 2 shows that the rate does not increase so much despite the temperature being increased from 20 to 30 degree celsius (with the carbon dioxide being kept constant). This means that temperature is not the actual LIMITING FACTOR. But if the conditions are reversed, the temperature being constant and the carbon dioxide being increased from 0.03% to 0.13%, the rate increases (Look at graph 3). Both of these indicate that carbon dioxide concentration is the LIMITING FACTOR in A to B (Graph 1).

The LIMITING FACTOR in E to F (Graph 3) is the temperature. Increasing the temperature from 20 to 30 degree celsius causes an increase in the rate of photosynthesis (Look at graph 4) though the carbon dioxide concentration remains constant at 0.13%.

END OF CHAPTER 6

PLANT NUTRITION PART 15: FACTORS AFFECTING PHOTOSYNTHESIS

The rate of photosynthesis is affected by the following factors:

• LIGHT INTENSITY

• CONCENTRATION OF CARBON DIOXIDE

• TEMPERATURE

When we consider light intensity, immediately we would think that, the higher the light intensity, the higher would the rate of photosynthesis be, right? That's right actually. But at certain point even if the light intensity is increased, the rate will not increase any further. This is because, the chlorophyll in the chloroplasts can only absorb so much energy from sunlight. It's just like pouring water into a glass. The more you pour in water the higher will the water level be in the glass but if the level is already reaching the brim of the glass, no matter how much water you pour in, the water level will not increase any further. UNDERSTAND?

In the above analogy, when the water level reaches the brim of the glass, we can say that the glass is the LIMITING FACTOR because despite the availability of water, the glass can only take so much. Now, lets consider light intensity which is a factor affecting the rate of photosynthesis. In this case, the LIMITING FACTOR is the chlorophyll right? Right you are, if you consider the absorption of light at a point at which the chlorophyll can no longer absorb more than it should. Because, no matter how much light energy there is available, the chlorophyll can only absorb so much. So at this point, increasing the light intensity will not increase the rate of photosynthesis any further.

But mind you, before reaching that particular point where the graph levels off, light intensity is actually the LIMITING FACTOR because the rate of photosynthesis depends on it. Meaning, before this particular point (where the graph levels off), the rate of photosynthesis will only increase, when the light intensity is increased.


Now, lets consider the effect of carbon dioxide concentration. By looking at the graph below, the rate of photosynthesis increases as the concentration (%) of carbon dioxide is increased. We say that carbon dioxide is the LIMITING FACTOR since the rate depends on it. But at certain point, even after increasing the concentration of carbon dioxide, the rate remain constant. After this point, carbon dioxide concentration is no longer the LIMITING FACTOR.



Temperature may also affect the rate of photosynthesis. Since photosynthesis is an enzyme-controlled reaction, the rate depends on the temperature at which the reaction takes place. As can be seen from the graph, as the temperature is increased, the rate will also increased. We say that the temperature is the LIMITING FACTOR since the rate really depends on it. But at the optimum temperature, the reaction decreased and eventually stops at 45 degree celsius because at high temperature the enzyme catalysing photosynthesis is denatured. So, after the optimum temperature, temperature is no longer the LIMITING FACTOR.

PLANT NUTRITION PART 14: WATER CULTURE EXPERIMENT

The water culture experiment is used to find out whether nitrogen, phosphorus and magnesium are essential for plant growth.


HOW TO MAKE A COMPLETE CULTURE SOLUTION?

• 1000cc distilled water
• 0.25g potassium nitrate
• 0.25g magnesium sulphate
• 0.25g potassium acid phosphate
• 1g calcium nitrate
• 2 drops iron(III) chloride solution

(Important: The chemicals should be added to the water in the order shown above)

To investigate whether Nitrogen is really needed for plant growth, omit the nitrates and use potassium chloride and calcium sulphate.

To investigate whether Magnesium is really needed for plant growth, omit magnesium sulphate and use potassium sulphate.

PRECAUTIONS

• Before setting up the experiment, all apparatus are to be sterilize to ensure that the apparatus is free from micro-organisms which might interfere with the growth of the seedlings.
• The outside of the gas jars are to be covered completely with black papers to prevent light from entering the gas jars. This prevents algae from growing around the roots and hinder their normal functioning.
• The gas jars are to be placed in such a way that they receive enough sunlight but be very careful not to place the gas jars in direct sunlight as it may caused the leaves of the seedlings to scorch and heat up the culture solutions.
• Keep the cotton wool around the seedling dry to prevent the stem from rotting.
• Renew the culture solution every 2 weeks (Remember: Depletion).
• Aerate the solution by blowing air through the delivery tube to supply oxygen for root respiration.
  

PLANT NUTRITION PART 13: MINERAL NUTRITION

And you think photosynthesis is enough for plants to make food right? Nope.... there is more to it actually. After carbohydrate (glucose) is synthesized, some of them need to be converted into amino acids and later from amino acids, proteins are synthesized. For this to occur, plants need minerals. The minerals needed by plants are divided into two groups: Macronutrients and Micronutrients.

MACRONUTRIENTS: Needed in large amount. Examples are Nitrogen, Phosphorus, Sulphur, Magnesium, Potassium and Calcium.

MICRONUTRIENTS: Needed in small amount. Examples are Iron, Manganese, Boron, Cobalt, Zinc, Copper and Molybdenum.

THE ROLE OF MACRONUTRIENTS IN PLANT GROWTH
Do you need to know all these? Hold your horses. In the Biology syllabus, you are required to know the functions and deficiency symptoms of Nitrogen and Magnesium only.


NITROGEN

• Plants generally dependent on nitrogen in the form of nitrate ions or ammonium ions.
• Symptom of deficiency: Chlorosis and stunted growth (Why? Nitrogen is a component of chlorophyll and amino acids and hence proteins are needed for growth. Therefore if plants lack Nitrogen, chlorophyll formation will be affected and there will be insufficient proteins for growth, hence stunted growth)

MAGNESIUM

• Magnesium is also a component of chlorophyll.
• Deficiency symptoms: Chlorosis develops upward from the base of the plant. Unlike in Nitrogen deficiency, yellowing is only in-between the veins (the veins remain green). Chlorosis is accompanied by death of the entire leaf or portions of it.

PLANT NUTRITION PART 12: RATE OF PHOTOSYNTHESIS

The following set up can be used to investigate the effect of different light intensities, different temperatures and different carbon dioxide concentrations on the RATE of photosynthesis.
MODIFICATIONS

• For investigating the effect of different light intensities on the rate of photosynthesis, the distance of the light source should be altered. For example, 50cm, 40cm, 30cm, 20cm and 10cm away from the plant. Air bubbles are given out from the cut end of the plant. Allow some time for the plant to adapt to the conditions provided before taking readings. When they are coming at a regular rate, count the number of air bubbles over a period of time, say five minutes. Repeat this a few times to obtain the average rate (Note: the bubbles produced are oxygen gas released as a result of photosynthesis). The readings may be tabulated like the one shown in the following figure (The heat from the light source may affect the temperature of the water bath, so throughout the investigation, the temperature should be monitored so that it is always constant)

• To investigate the effect of different temperature on the rate of photosynthesis, the temperature of the water bath may be altered by using hot water and ice cubes.
• To investigate the effect of different carbon dioxide concentrations, sodium hydrogen carbonate solutions of different concentrations may be used. For example, 0.01M, 0.02M, 0.03M up to 0.1M.

EXPECTED OBSERVATIONS:

• Effect of different light intensities: The closer the light source to the plant, the higher the light intensity and the more bubbles will be produced and this means that the higher the rate of photosynthesis. Likewise, the further the light source away from the plant, the lower the light intensity and the less bubbles will be produced and this means that the lower the rate of photosynthesis.
• Effect of different temperatures: The lower the temperature the less bubbles will be produced and this means that the lower the rate of photosynthesis. As the temperature is increased, more and more bubbles will be produced and this indicates that the rate of photosynthesis increases with the increase in temperature. WHAT DO YOU THINK HAPPENED IF THE TEMPERATURE IS ABOVE 40 DEGREE CELSIUS? WILL THE RATE INCREASE? OR DECREASE?
• Effect of different carbon dioxide concentrations: The lower the carbon dioxide concentration, the less bubbles will be produced and this means that the lower the rate of photosynthesis. The higher the concentration of carbon dioxide, the more bubbles will be produced and this means that the higher the rate of photosynthesis.
  

CHROMOSOMES

Chromosomes consist of one DNA molecule. Each somatic cell of your body has 23 pairs of chromosomes, one member of each pair contributed by your mother and the other by your father. (In egg and sperm cells - there are 23 individual chromosomes, not chromosome pairs.) One pair are the sex chromosomes, which can come in two forms, X and Y. A pair of X's gives a female, and an XY results in a male.

CELL DIVISION

Cell divides!!! Yes, cell divides constantly. This is important for growth, replacing dead cells and gamete formation. Cell divides in two ways: MITOSIS and MEIOSIS. The following figure shows the difference between mitosis and meiosis.

NOTICE ANY DIFFERENCES? WHICH TYPE INVOLVES IN GROWTH? WHICH TYPE INVOLVES IN GAMETE FORMATION?