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6.2 The transport systemTopic 6: Human health & physiology

6.2.1 Draw and label a diagram of the heart

Draw in the route of blood through the heartThe two sides of the heart (left and right) are separated by the septumBlood in the right side is deoxygenated (oxygen-poor)Blood in the left side is oxygenated (oxygen-rich)The right side of the heart is less muscular as the blood is pumped to the nearby lungsBlood is under less pressureThe left side of the heart is more muscular as the blood is pumped to the rest of the bodyBlood is under higher pressureDirection of blood flowTo the heartFrom the heartVesselsPressureOxygen contentVeinsArteriesHighLowLow (exception is the pulmonary vein)High (exception is the pulmonary artery)

Blood is pumped around the body by the heart.

It takes about 30 seconds for blood to go once around the body.

Starting with the left side of the heart, what route does the blood follow to complete one circuit of the body?

4The left side of the heart pumps oxygen-rich blood to the rest of the body.

This blood supplies the bodys cells with oxygen.

What gas does the blood then pick up from the bodys cells and where does the blood go next?

bodyscellsbodyscells5The oxygen-poor blood needs to lose the carbon dioxide and pick up more oxygen. Blood picks up carbon dioxide from the bodys cells.

This oxygen-poor blood then travels back to the right side of the heart.

bodyscellsbodyscells6Next, the right side of the heart pumps oxygen-poor blood to the lungs.

In the lungs the blood gets rid of the waste carbon dioxide and collects more oxygen.

lungslungs

bodyscellsbodyscells7The oxygen-rich blood then returns to the left side of the heart.

This completes the bloods journey around the body.

bodyscellsbodyscellslungslungs8During one complete circuit of the body, blood passes through the heart twice.

The heart has two jobs to do and so the circulatory system involves a double circulation.

bodyscellsbodyscellslungslungs96.2.2 State that the coronary arteries supply the heart muscle with oxygen and nutrients

The heart is full of blood but also needs its own blood supply so that the muscle can keep pumping. blood vessels supply blood to muscle tissueThe blood vessels on the outside of the heart carry oxygen-rich blood to the heart muscle cells. Oxygen-poor blood is then carried away from these cells by outer blood vessels and back into the heart.muscletissue6.2.3 Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves. All the parts of the heart on either side, work together in a repeated sequence.The two atria contract and relax; then the two ventricles contract and relax.This is how blood moves through the heart and is pumped to the lungs and the body. One complete sequence of contraction and relaxation is called a heartbeat. When the heart muscles are relaxed diastoleBlood flows from veins into atriaWhen the heart muscles contract systoleAtria contract first to pump blood into ventricles (valve between atrium and ventricle opens)Ventricles contract to pump blood into the arteries(forces valve to shut)

Normal blood pressure: 120 Systolic pressure 80 Diastolic pressure

The cardiac cycle describes the sequence of events in one heartbeat. It is described in terms of alternate contractions (systole) and relaxations (diastole). There are 3 main stages to the cardiac cycle:

Atrial systole: Blood is collected by the atria, both atria contract and the blood passes down to the ventricles thanks to the atrio/ventricular valves that open due to the pressure of blood against them.

Ventricular systole: The atria relax and the ventricles contract, forcing blood out of the heart into the pulmonary artery and the aorta. Atrio-ventricular valves are closed preventing blood going back to the atria. The oressure of the blood agains the semilunar valves opens them. The pulmonary artery then carries deoxygenated blood to the lungs and the aorta carries oxygenated blood to the different parts of the body.

Diastole: Ventricles relax. Semilunar valves are closed preventing bloodfrom going back into the ventricles. All the muscle in the heart relaxes. Blood from vena cava and pulmonary veins enters the atria and the whole cycle starts again.146.2.4 Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and adrenaline

http://drugline.org/img/term/sa-node-13124_3.jpgThe beating of the heart is due to myogenic muscle contraction... This means that the myoctye (muscle cell) is the origin of the contraction and it is not controlled externally.A region of myocytes, called the sinoatrial node (SA node) controls the rate of the heartbeat. This region is also called the pacemaker.A wave of excitations is sent from the SA nose, causing the atria to contract. This excitation is conducted to the atrioventricular (AV) node, where it is passed through the nerves to the muscles of the ventricles, causing them to contract. The heart muscle is indefatigable.The heart is myogenic, that is, it can contract and relax without having to receive impulses from the nervous system. If one heart muscle cells contracts, it stimulates any other cells that is tuching, so they also contract. A group of cells therefore contracts almost simultaneously at the rate of the fastest. The region of the heart that sets the overall pace of contraction is the pacemaker (a small group of cells in the wall of the right atrium). The pacemaker can respon to signals from outside the heart. Branches of two nerves are connected to it, which bring signals from a region in the medulla of the brain. Impulses from one of the nerves cause the pacemaker to increase the rate, and the impulses from the other nerve decrease the rate, rather like the throttle and the brake of a car. The pacemaker also responds to the hormone adrenaline, by increasing the heart rate.156.2.4 Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and adrenaline (epinephrine)

Heart rate can be controlled by the autonomic nervous system the part of the nervous system that responds automatically to changes in body conditions.Where mycocardial contraction maintains the beating of the heart, we may need to speed up or slow down heart rate.When exercising, more CO2 is present in the blood. This is detected by chemoreceptors in the brains medulla oblongata, resulting in a nerve signal being sent to the SA node to speed up the heart rate.When CO2 levels fall, another nerve reduces heart rate.The hormone adrenaline causes a rapid increase in heart rate in fight-or-flight reponses, preparing the body for action. This effect can be mimicked by stimulant drugs.6.2.5 Explain the relationship between the structure and function of the arteries, capillaries and veins.

Arteries have a thick outer layer of longitudinal collagen and elastic fibers to avoid leaks and bulges. They have a thick wall which is essential to withstand the high pressures. They also have thick layers of circular elastic fibres and muscle fibres to help pump the blood through after each contraction of the heart. In addition the narrow lumen maintains the high pressure inside the arteries.Veins are made up of thin layers with a few circular elastic fibres and muscle fibres. This is because blood does not flow in pulses and so the vein walls cannot help pump the blood on. Veins also have thin walls which allows the near by muscles to press against them so that they become flat. This helps the blood to be pushed forwards towards the heart. There is only a thin outer layer of longitudinal collagen and elastic fibres as there is low pressure inside the vein and so little chance of bursting. Finally, a wide lumen is needed to accommodate the slow flowing blood due to the low pressure.Capillaries are made up of a wall that is only one cell layer thick and results in the distance for diffusion in and out of the capillary being very small so that diffusion can occur rapidly. They also contain pores within the their wall which allow some plasma to leak out and form tissue fluid. Phagocytes can also pass through these pores to help fight infections. In addition, the lumen of the capillaries is very narrow. This means that many capillaries can fit in a small space, increasing the surface area for diffusion

17ArteriesCarry blood away from the heartExcept for the pulmonary artery, transport oxygenated bloodArtery walls are thick and elastic so they can stretch under the high pressure of blood As the arteries stretch, they pulse

thick outer wall thick inner layerof muscle and elastic fibresnarrow central tubeVeins

thin outer wall thin inner layerof muscle and elastic fibreswide central tubeCarry blood to the heartExcept for the pulmonary vein, carry deoxygenated bloodWider than arteries, with thinner wallsBlood under lower pressureValves prevent the back-flow of blood

CapillariesCapillaries are the tiny blood vessels that carry a blood supply to and from the bodys cells.

arteryvein

Capillaries are the only blood vessels where substances can be exchanged between the blood and body cells.

6.2.6 State that blood is composed of plasma, erythrocytes, leucocytes and plateletsThe liquid part of the circulatory systemBlood cells are suspended in plasmaAn adult human has about 5.5L of blood in their body

Plasma [55%]Leucocytes (WBCs) and platelets [0.09%]Erythrocytes (RBCs) [44.91%]The four components of blood

red blood cellwhite blood cellplateletBlood plasma carries three types of blood cells. They have different shapes and carry out different functions. Components of bloodMicrographs of blood

Scanning electron micrograph of bloodErythrocyte (RBC)Lymphocyte (WBC)Platelet6.2.7 State what is transported by the blood

http://www.webmd.com/heart/anatomy-picture-of-blood nutrients, oxygen, carbon dioxide, hormones, antibodies, urea, heat