6.2 The transport system- objectives 11/24/10 4:05 PM

IB Standard level Biology Dulwich College ShanghaiTopic 6: Human Health and Physiology

The Transport System (pg. 210-216)

Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart (pg. 210-211)

State that the coronary arteries supply heart muscle with oxygen and nutrients (pg. 212)

Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves (pg. 211)

Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline) (pg. 213)

Explain the relationship between the structure and function of arteries, capillaries and veins (pg. 214)

State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets (pg. 215)

State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat (pg. 215)

6.2.1 Heart structure 11/24/10 4:05 PMIB Standard level Biology Dulwich College Shanghai

Topic 6: Human Health and Physiology

The Transport System

Heart StructureDraw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart.

Label the diagram then complete the gap filling exercise.

Orange book pg. 213Green book pg. 97

* This page will be printed and put in your HW bookOn the diagram, use your ruler to draw lines to identify the structures of the heart listed below.Right and left atrium and ventriclePulmonary arteryPulmonary vein

1. 2.

3.

4.

5.

6.

11.

12.

9.

7.

10.

8.

AortaTricuspid valveBicuspid valveAtrioventricular (AV) valves – tricuspid and bicuspid valvesSemilunar (SL) valves – aortic and pulmonary valvesSeptumIndicate with arrows where blood enters and leaves the heart.Indicate with arrows the direction of blood flow through the heart.

You should now be able to try to draw and label the heart without looking at a diagram.

The Anatomy of the Heart - Wisconsin Onlinehttp://www.wisc-online.com/objects/index_tj.asp?objid=AP12504The heart has four chambers. Each one is separated from the other by ___________ ___________. The _______ valves are between the atria and ventricles on each side of the heart. On the right side the AV valve is called the _______________. The left A-V valve is called the _______________. The _______________ ______________ is between the right ventricle and the pulmonary veins, and the _________________ ________________ is between the left ventricle and the aorta. The A-V valves close to prevent blood from flowing ___________ into the atria when the ventricles are contracting. The tricuspid valve has _________ cusps and the bicuspid has _______ cusps. ____________ ______________ are attached to ___________ _____________. When these muscles contract the string like chordae tendinae become taut. It is these chordae tendinae, together with the papillary muscles, that keep the valves shut when the ventricles contract.

6.2.2 Coronary arteries 11/24/10 4:05 PMIB Standard level Biology Dulwich College ShanghaiTopic 6: Human Health and Physiology

The Transport System (pg. 210-216)

Coronary ArteriesState that the coronary arteries supply heart muscle with oxygen and nutrients (pg. 212)

Read the appropriate information and summarise how and why the cells of the heart tissue obtain the nutrients they require.

The heart is a muscle that is continually working. In order for it to contract and relax in its characteristic rhythmic way, the cardiac muscle needs a continual supply of energy. Like any other cell energy is provided by the process of respiration. The cardiac cells need glucose and oxygen to carry out the process of oxygen.

Look at the diagram below. You can see the left and right coronary arteries branching directly off the aorta. These coronary arteries branch all over the surface of the heart bringing glucose and oxygen to the cells and removing carbon dioxide. These coronary arteries are essential for the health of the cardiac cells. Any blockage in a coronary artery deprives the heart muscle of glucose and oxygen and so the cells cannot respire, this leads to cell death and a ‘heart attack’.

6.2.3 Heart action 11/24/10 4:05 PMIB Standard level Biology Dulwich College ShanghaiTopic 6: Human Health and Physiology

The Transport System (pg. 210-216)

Heart ActionExplain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves (pg. 211)

Read the information then draw 2 flow charts to describe the flow of blood through the heart.Then complete the gap filling exercise.

A Journey through the HeartThe heart has four chambers. The two superior chambers are the atria (singular = atrium) and the two inferior chambers are the ventricles.

Right Side

Septum

The right atrium collects deoxygenated blood from the vena cava.

As blood fills the atrium, the pressure rises and causes the tricuspid valve/ atrioventricular (AV) valve to open and blood passes from the right atrium into the right ventricle.

As the ventricle collects blood and fills the tricuspid valve closes. The cusps of the tricuspid valve are connected to tendons, which in turn are connected to muscle. These stop the valve from flipping the wrong way as the ventricle contracts.

The right ventricle is separated from the left ventricle by the septum. This prevents deoxygenated blood from mixing with oxygenated blood.

When the heart contracts, the blood passes from the right ventricle through the pulmonary valve into the pulmonary artery, which carries blood to the lungs to pick up oxygen.

Left SideThe left atrium receives oxygenated blood from the lungs through the pulmonary veins.

Blood passes from the left atrium into the left ventricle through the bicuspid valve/ atrioventricular (AV) valve.

The left ventricle has a much thicker wall than the right ventricle, as it needs to be much stronger to pump blood to the body.

Like the right hand side of the heart, the valve is supported by tendons attached to muscles.

Blood passes from the left ventricle through the aortic valve into the largest artery of the body, the aorta.

Some of the blood in the aorta flows into the coronary arteries, which branch from the aorta and carry blood to the heart muscle.

The remainder of the blood flows in the aorta to be carried around the body.

Heart Blood Flow - Medmovie.comhttp://medmovie.com/mmdatabase/

Blood returns to your heart’s upper chambers (the _____________) from the body and lungs. The ____________________ valves open, the atria contract and blood flows into the _____________________. When the ventricles are full, the ___________________ valves close, creating the first heart sound _______________. The __________________ valves open, your ventricles contract and blood is pumped to your lungs (via the _____________ _____________) and to the body (via the _____________). The semilunar valves close creating the second heart sound ____________.

6.2.4 Control of heart beat 11/24/10 4:05 PMIB Standard level Biology Dulwich College ShanghaiTopic 6: Human Health and Physiology

The Transport System (pg. 210-216)

Control of HeartbeatOutline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline) (pg. 213)

Read the information then complete the tasks below.

Myogenic Stimulation of Heart - The Cardiac CycleCardiac muscle is myogenic, which means that it can contract on its own, without needing nerve impulses. Contractions are initiated within the heart by the sino-atrial node (SAN, or pacemaker) in the right atrium. This extraordinary tissue acts as a clock, and contracts spontaneously and rhythmically about once a second, even when surgically removed from the heart.

The cardiac cycle has three stages:

Atrial Systole (contraction)The sinoatrial node (SAN) contracts and transmits electrical impulses throughout the atria, which both contract, pumping blood into the ventricles.

Ventricular Systole (contraction). The electrical impulse passes to the ventricles via the atrioventricular node (AVN) – located on the wall of the right atrium just above the ventricle.

*The AV node slightly delays sending the impulse onto the Bundle of His. The atrium and ventricles are electrically insulated and so the impulse must pass through the SAN and then the AVN. The delay allows the atria to contact forcing blood into the ventricles to fill them before they in turn contract.

The impulse then passes through the bundle of His (down the septum) and the Purkinje fibres (which spread up around walls of the ventricles). The ventricles contract shortly after the atria, from the bottom up, squeezing blood upwards into the arteries. The blood can't go into the atria because of the atrioventricular valves, which are forced shut

Diastole (relaxed) The atria and the ventricles relax, while the atria fill with blood. The semilunar valves in the arteries close as the arterial blood falls back against them.

Try to complete the following exercises without using the notes too much.On the diagram, label the structures involved in the conduction of the cardiac impulse through the heart.SA nodeAV nodeLeft atriumBundle of HISLeft ventricleRight ventricle

1.

2.

9.

10.

11.

Right atriumApex of the heartPurkinje fibresSeptumTricuspid valve

Briefly bullet-point the events which occur in each of the three stages of the cardiac cycle.

Atrial systole

3.

4.

5. 6.

7.

8.

Ventricular systole

Diastole

Electrocardiogram - Medmovie.comhttp://medmovie.com/mmdatabase/flash/0038a.swfThe _____________ produces an electrical signal, which spreads through the right and left ______________. On the ECG this is recorded as the ____ wave. The signal causes the __________ to contract. The electrical signal reaches the ____ node, where it pauses briefly before continuing through the ____ __________ to the left and right _______________. All the way to the ___________ fibres. As the signal passes from the AV node, to the Bundle of His and purkinje fibres, it is recorded on the ECG as the _______ complex. The signal causes the _____________ to contract and blood is pumped out to your __________ and _________________.

6.2.5 Blood vessels 11/24/10 4:05 PMIB Standard level Biology Dulwich College ShanghaiTopic 6: Human Health and Physiology

The Transport System (pg. 210-216)

Blood VesselsExplain the relationship between the structure and function of arteries, capillaries and veins (pg. 214)

Read the information then take summary notes on the structure and function of each type of blood vessel.

Blood circulates in a series of different kinds of blood vessels as it circulates round the body. Each kind of vessel is adapted to its function.

Arteries

Arteries carry blood from the heart to every tissue in the body. They have thick, elastic walls to withstand the high pressure of blood from the heart. The arteries close to the heart are particularly elastic and expand during systole and recoil again during diastole, helping to even out the pulsating blood flow. The smaller arteries and arterioles are more muscular and can contract (vasoconstriction) to close off the capillary beds to which they lead; or relax (vasodilation) to open up the capillary bed. These changes are happening constantly under the involuntary control of the medulla in the brain, and are most obvious in the capillary beds of the skin, causing the skin to change colour from pink (skin arterioles dilated) to blue (skin arterioles constricted).

Veins Veins carry blood from every tissue in the body to the heart. The blood has lost almost all its pressure in the capillaries, so it is at low pressure inside veins and moving slowly. Veins therefore don’t need thick walls and they have a larger lumen than arteries, to reduce the resistance to flow. They also have semi-lunar valves to stop the blood flowing backwards. It is particularly difficult for blood to flow upwards through the legs to heart, and the flow is helped by contractions of the leg and abdominal muscles:

The body relies on constant contraction of these muscles to get the blood back to the heart, and this explains why soldiers standing still on parade for long periods can faint, and why sitting still on a long flight can cause swelling of the ankles and Deep Vein Thrombosis (DVT or “economy class syndrome”), where small blood clots collect in the legs.

Capillaries Capillaries are where the transported substances actually enter and leave the blood. No exchange of materials takes place in the arteries and veins, whose walls are too thick and impermeable. Capillaries are very narrow and thin-walled, but there are a vast number of them (108 m in one adult!), so they have a huge surface area: volume ratio, helping rapid diffusion of substances between blood and cells. Capillaries are arranged in networks called capillary beds feeding a group of cells, and no cell in the body is more than 2 cells away from a capillary.

Practice QuestionsState two features of capillaries that enable tissue fluid to be formed.

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6.2.6 Blood 11/24/10 4:05 PMIB Standard level Biology Dulwich College ShanghaiTopic 6: Human Health and Physiology

The Transport System (pg. 210-216)

BloodState that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets (pg. 215)

Read the information then complete the exam question at the end of the document.

Introduction to BloodMost adults have 4 to 6L of blood. It consists of plasma (the fluid part), erythrocytes (red blood cells), leucocytes (white blood cells) and platelets.

 Blood CellsErythrocytes = red blood cellsPlatelets = cell fragments from white blood cellsLeukocytes = white blood cells (phagocytes and lymphocytes)

*On the diagram below you do NOT need to know the names of the different white blood cells – just recognise the difference between a white blood cell and a red blood cell.

Red Blood CellsErythrocytes (red blood cells) have no nucleus and so are biconcave discs (the sunken centre is where the nucleus used to be) that carry oxygen around the body. A pigment called haemoglobin combines with the oxygen in the lungs to form oxyhaemoglobin. New red blood cells (RBC) are produced in the red bone marrow .

The main function of RBC is the transport of respiratory gases. Oxygen is picked up from the lungs and delivered to the tissues. Carbon dioxide is picked up from respiring cells and transported to the lungs to be exhaled.Oxygen is carried in RBC bound to the protein haemoglobin. A haemoglobin

molecule consists of four polypeptide chains, with a haem group at the centre of each chain. Each haem group contain one iron atom, and one oxygen molecule binds to each iron atom. Therefore haemoglobin can bind up to four oxygen molecules. RBC have specific features (listed below) that make it efficient in absorbing and transporting respiratory gasses: They have a small size - They are much smaller than most other cells in the body. This means that all the haemoglobin molecules are close to the surface, allowing oxygen to be picked up and release rapidly.

Shape - RBC are biconcave shapes discs. It allows the cell to contain a lot of haemoglobin while still allowing efficient diffusion through the plasma membrane.

Organelles – RBC do not contain either nuclei or mitochondria. This allows more space inside the cell for haemoglobin. As they do not contain a nucleus there is nothing to control the functioning of a RBC and so they usually only live for approximately 120 days. A lack of mitochondria means they cannot carry out aerobic respiration. This also prevents them from consuming the oxygen they are transporting to other cells.

White Blood Cells

Leukocytes, or white blood cells (WBCs), play a number of roles in the body’s defence against pathogens. They are easily distinguished from erythrocytes in stained blood films because they contain conspicuous nuclei that stain from light violet to dark purple with the most common blood stains.

Two WBC types –

Phagocytes:Phagocytosis (engulf and digest) of bacteria

LymphocytesSecrete antibodies

Practice QuestionsGive an account of the structure and functions of mammalian blood cells.

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6.2.7 Transport of substances 11/24/10 4:05 PMIB Standard level Biology Dulwich College ShanghaiTopic 6: Human Health and Physiology

The Transport System (pg. 210-216)

Transport of SubstancesState that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat (pg. 215)

* You just need to be able to list the substances that are carried in the blood as stated in the objective. The notes given below should provide a recap of other parts of the course where the substances that are carried in the blood have been mentioned.

NutrientsSmall simple soluble products of digestion are absorbed across the intestinal wall and into the blood. These nutrients include: glucose (from digestion of carbohydrates), amino acids (from protein digestion) and fatty acids and glycerol (from lipid digestion). The nutrients are carried to the liver in the hepatic portal vein where many of them are processed e.g. excess glucose will be converted to glycogen for storage. Nutrients are carried to all cells of the body where they can be absorbed for assimilation.

OxygenDeoxygenated blood leaves the right hand side of the heart via the pulmonary arteries and goes to the lungs to pick up oxygen. In the capillaries of the lungs oxygen combines loosely with haemoglobin to form oxyhaemoglobin.

The word equation below shows the reaction of haemoglobin with oxygen.

oxygenationhaemoglobin + oxygen oxyhaemoglobindeoxygenation

Oxygenated blood returns to the left hand side of the heart in the pulmonary veins. It is pumped out of the left ventricle into the aorta to be carried around the body in the arteries providing all cells with oxygen needed for respiration. Oxygen combines with haemoglobin to form oxyhaemoglobin and this is the form in which it is carried around the body.

Carbon DioxideCarbon dioxide is produced in cells due to the process of respiration. The carbon dioxide diffuses through the walls of the blood capillaries and into the blood. In the red blood cells an enzyme called carbonic anhydrase greatly accelerates the chemical combination of carbon dioxide with water to form carbonic acid:

carbonic anhydrasecarbon dioxide + water carbonic acid CO2 + H2O H2CO3

The carbonic acid partially dissociates into hydrogen (H+) and hydrogen carbonate (HCO3-) ions:

carbonic acid hydrogen ions +hydrogencarbonate ions H2CO3 H+ HCO3-

The HCO3- ions readily diffuse out of the red blood cells and into the plasma. It is as HCO3- ions that most of the carbon dioxide is carried to the lungs to be excreted. In the lungs the reactions described above are reversed and the carbon dioxide gas formed diffuses into the alveoli and is breathed out.

HormonesA hormone is a messenger molecule, which is released in one part of the body but regulates activity of cells in other parts of the body. Most hormones enter the blood stream to be carried to their target organ. Hormones exert their effects by binding to receptors on or in their “target” cells.

This table shows some of the main endocrine glands and their hormones that you have encountered during the IB course.

Gland Hormone Target Organ ResponsePituitary FSH

LHADH

OvariesOvariesKidneys

Mature an ovaOvulationWater homeostasis

Adrenal Adrenaline Manye.g. heart

‘Fight-or-Flight’ responseincreases heart rate

Pancreas InsulinGlucagon

LiverLiver

Converts glucose to glycogenConverts glycogen to glucose

Ovaries OestrogenProgesterone

UterusUterus

Thickens uterus liningMaintains uterus lining

Testis Testosterone Manye.g. testis

Male characteristicsSperm production

Once a hormone has diffused into the blood stream it is carried all round the body to all organs. However, it only affects certain target organs, which can respond to it. These target organs have specific receptor molecules in their cells to which the hormone binds. These receptors are protein molecules, and they form specific hormone-receptor complexes, very much like enzyme-substrate complexes. Cells without the specific receptor will just ignore a hormone.

Antibodies (covered in next topic)An antibody is a globular protein found in the blood plasma and body secretions. Antibodies are secreted by white blood cells called lymphocytes. The immune system is thought to produce as many as 2 million different antibodies!

UreaUrea is produced by the breakdown of excess amino acids in the body. After a protein rich meal, the protein is digested to amino acids in the digestive system, which are then absorbed into the blood. The excess amino acids are carried in the blood to the liver. In a process known as deamination the amino acids are broken down to form urea. The amino (nitrogen containing) part is combined with CO2 to form urea. The urea is carried to the kidneys in the blood where it will be filtered out and combined with water to form urine before being removed from the body.

HeatHeat is released during the process of respiration carried out by cells. In cells, which are very metabolically active, a lot of heat will be produced. The liver is a very metabolically active organ and produces a lot of heat. This heat warms the blood and as the blood flows round the body it distributes the heat throughout the body. During exercise the muscles are metabolically very active and produce a lot of heat. Again this heat enters the blood and is spread around the body. The blood can also be used to cool the body down as blood vessels in the skin can vasodilate (expand) and so more blood flows through the vessels at the surface of the skin and heat can radiate away from the body to help cool the body down. This explains why you turn red when you exercise.2.7