d) Cardiovascular System Higher Human Biology

Transcription

1 d) Cardiovascular System Higher Human Biology

2 What can your remember about the heart and blood vessels?

3 What is the Cardiovascular System? The cardiovascular system, also known as the circulatory system, is composed of blood, blood vessels and the heart. The heart functions as a pump to move blood through the blood vessels of the body. A circulatory system is essential for large, multi-cellular organisms, such as humans and animals.

4 Heart Revision

5 Learning Intention Describe the path of blood flow through the heart including the heart valves

6 The heart is a DOUBLE PUMP: 1st - blood is pumped to the lungs & returns to the heart, 2nd - blood is pumped to the body & back to the heart again. 1. Deoxygenated blood from the body is pumped from the heart to the lungs 2. The blood receives oxygen in the lungs and is pumped back to the heart 4. The oxygen leaves the blood to be used by the body and the blood goes back to the heart 3. The oxygenated blood is then pumped by the heart to the body

7 The Structure of the Heart The heart has 4 chamber The upper chambers are called atria (atrium singular) The lower chambers are called ventricles

8 Valves prevent back flow of blood Between the atria and ventricles are atrioventricular (AV) valves Heart Valves Right SL Valve Right AV Valve RA Left SL Valve LA Left AV Valve Between the ventricles and arteries leaving the heart are semilunar (SL) valves RV LV Heart Rap

9 From left ventricle out through the aorta to the body Right SL valve Deoxygenated blood flows from the body into the heart via the VENA CAVA RIGHT ATRIUM RIGHT VENTRICLE Out via the pulmonary artery to the lungs LEFT ATRIUM LEFT VENTRICLE Left SL valve Oxygenated blood flows back from the lungs via the PULMONARY VEIN Left AV valve Right AV valve Parts of heart musical quiz Pig heart dissection

10 Learning Intentions State what is meant by the terms cardiac output, heart rate and stroke volume Explain the calculation of cardiac output

11 Heart Rate (HR) Number of heart beats in one minute Normal values around 72bpm Normal range is between What is your HR?

12 Stroke Volume (SV) Volume of blood pumped out by each ventricle during contraction Normal values are around 70ml

13 Cardiac Output (CO) Cardiac output is the volume of blood pumped out of a ventricle per minute It is calculated by the following equation CO = HR X SV Normal values are around 5 litres/min

14 CO = 200 x 150 = 30000ml/min = 30 litres/min a) At rest: HR = 72bpm SV = 70ml What is the CO of this individual? CO = 72 x 70 = 5040 ml/min = 5 litres/min b) During exercise: HR = 200bpm SV = 150ml What is the CO of this individual?

15 Calculating your CO Use the HR you calculated before and assume your SV is 70ml what is your CO?

16 Some typical values for cardiac output at varying levels of activity: Activity Level Heart rate (bpm) Stroke Volume (ml) Cardiac Output (l/min) Rest Mild Moderate Heavy (athlete)

17 Summary of Cardiac Output The left and right ventricles pump the same volume of blood through the aorta and pulmonary artery. The volume of blood pumped through each ventricle per minute is the cardiac output. Cardiac output is determined by heart rate and stroke volume (CO = HR x SV).

18 Learning Intention Compare the structure and function of arteries, capillaries and veins

19 Blood leaves the heart in arteries It then flows through capillaries in the tissues and organs And returns to the heart in veins There is a decrease in blood pressure as the blood moves away from the heart. Blood Vessels

20 Layers in Blood Vessels The endothelium lining the central lumen of the blood vessels is surrounded by layers of tissue. These surroundings layer differ in each type of blood vessel endothelium

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22 Group Task Use the blood vessel co-op cards to find out more about the structure and function of arteries, veins and capillaries. Use what you find out together to complete your notes and create a mind map / poster

23 Arteries Arteries have an outer layer of connective tissue containing elastic fibres which stretch They have a middle layer containing smooth muscle with more elastic fibres Endothelium lines the central lumen where the blood flows through Connective tissue Muscle tissue Endothelium

24 Arteries The elastic walls of the arteries stretch and recoil to accommodate the surge of blood that enters them after each contraction of the heart. The smooth muscle can contract causing vasoconstriction and less blood to flow The smooth muscle can relax causing vasodilation and more blood to flow

25 Capillaries Transport blood between arteries and veins Exchange of materials between blood and cells Their walls are only one cell thick, allowing nutrients and waste to diffuse through with ease

26 Veins Veins have an outer layer of connective tissue containing elastic fibres but a much thinner muscular wall than arteries. Endothelium lines the central lumen where the blood flows through They contain valves which prevent the backflow of blood into atria Connective tissue Muscle tissue Endothelium

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28 Layers Answers connective tissue muscle tissue endothelium lumen C M E L Can you think of a saying to help you remember the order?

29 Arteries Summary Arteries have an outer layer of connective tissue containing elastic fibres and a middle layer containing smooth muscle with more elastic fibres. The elastic walls of the arteries stretch and recoil to accommodate the surge of blood after each contraction of the heart. The smooth muscle can contract or relax causing vasoconstriction or vasodilation to control blood flow.

30 Capillaries and Veins Summary Capillaries allow exchange of substances with tissues. Veins have an outer layer of connective tissue containing elastic fibres but a much thinner muscular wall than arteries. Veins contain valves to prevent backflow of blood into atria.

31 Learning Intentions Describe the exchange of materials between tissue fluid and cells State how lymph is formed and what happens to it

32 Blood Blood consists of red and white blood cells, platelets and plasma Plasma is a watery yellow liquid containing dissolved substances such as glucose, amino acids, respiratory gases, plasma proteins and useful ions

33 Tissue Fluid Blood at low pressure Blood at high pressure Fluid squeezed out Blood arriving at the arteriole end of a capillary bed is at a higher pressure than blood in the capillaries As blood is forced into the narrow capillaries, it undergoes pressure filtration and much of the plasma is squeezed out through the thin walls

34 Tissue Fluid This plasma which has been squeezed out through the thin walls of the capillaries into the surrounding tissues is called tissue fluid Tissue Fluid The only difference between plasma and tissue fluid is that plasma has proteins and tissue fluids do not Tissue Fluid

35 Tissue Fluid The cells exchange molecules with the tissue fluid by diffusion down a concentration gradient Useful molecules such as food and oxygen diffuse into the cells from the tissue fluid Carbon dioxide and other metabolic wastes diffuse out of the cells and into the tissue fluid to be excreted

36 Lymph Most of the tissue fluid goes back by into the blood capillary by osmosis The fluid that does not return to the blood is now referred to as lymph and is collected by the lymphatic system

37 Lymph passes into lymphatic system Blood leaving in venule low pressure Lymph vessel Blood arriving in the arteriole high pressure Some tissue fluid enters capillary by osmosis Some tissue fluid enters lymphatic system Some plasma forced out of capillary Tissue fluid capillary

38 Lymph Lymph is collected by a vast network of lymph vessels These vessels eventually return their contents to the main circulation near the heart via osmosis The lymphatic system has no pump- the contraction of skeletal muscles squeezes lymph along the vessels Lymphedema

39 Try these questions What is tissue fluid? 2. Name a substance that passes from body cells into tissue fluid 3. Tissue fluid surrounds the muscle cells. Some of this fluid is reabsorbed into the bloodstream. How else is tissue fluid removed from around the cells? 4. Describe the means by which lymph is forced along through the lymphatic system

40 Answers It is the liquid consisting of plasma and small, dissolved molecules that is squeezed out of capillaries during pressure filtration 2. Carbon dioxide 3. It is absorbed into the lymphatic system via thin-walled lymphatic vessels and returned to blood capillaries by osmosis 4. When the vessels are pressed during muscular contraction, the lymph is pushed along the lymph vessels

41 Exchange of Materials Summary Pressure filtration of fluids occurs through capillary walls which squeezes out tissue fluid from the blood plasma into surrounding tissues. Tissue fluid is the same as plasma except it doesn t contain plasma proteins. It supplies cells with glucose, oxygen and other substances. Carbon dioxide and other metabolic wastes diffuse out of the cells and into the tissue fluid to be excreted. Much of the tissue fluid returns to the blood. Lymphatic vessels absorb excess tissue fluid and return the lymph fluid to the circulatory system.

42 Learning Intention Describe the events of the cardiac cycle

43 The Cardiac Cycle The cardiac cycle refers to the pattern of contraction and relaxation of the heart during one complete heartbeat. Contraction of the heart muscle is known as systole while relaxation is known as diastole. This lasts about 0.8 secs (0.3s systole,0.5s diastole)

44 Two Phases of the Cardiac Cycle Systole: contraction of the heart (atrial first, the ventricular). Blood forced out of chambers Diastole: relaxation of all chambers of the heart. The chambers fill with blood

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46 The Cardiac Cycle 1. Atrial & ventricular diastole 2. Atrial systole (ventricular diastole) 3. Ventricular systole (atrial diastole) Animation

47 Atrial and Ventriclar Diastole The atria fill with blood from the vena cava and pulmonary vein, and some of the blood flows into the ventricles. AV valves open

48 Atrial Systole Both atria contract and transfer the remainder of the blood through the open AV valves to the ventricles

49 Semi-lunar valves close when pressure in arteries exceeds pressure in ventricles and the cardiac cycle begins again! Ventricular Systole About 0.1s after atrial systole the ventricles contract Ventricular systole closes the AV valves and pumps the blood out through the open semi lunar (SL) valves to the aorta and pulmonary artery.

50 Cardiac Cycle Summary Cardiac cycle song Video

51 Cardiac Cycle Summary

52 Ventricular Volume Graph Atrial systole Ventricular systole

53 Heart Sounds The opening and closing of the AV and SL valves are responsible for the heart sounds heard with a stethoscope (lubb dubb)

54 Cardiac Cycle Summary During diastole blood returning to the atria flows into the ventricles. Atrial systole transfers the remainder of the blood through the atrioventricular (AV) valves to the ventricles. Ventricular systole closes the AV valves and pumps the blood out through the semi lunar (SL) valves to the aorta and pulmonary artery. In diastole the higher pressure in the arteries closes the SL valves. The opening and closing of the AV and SL valves are responsible for the heart sounds heard with a stethoscope.

55 Learning Intention Describe the structure of the cardiac conducting system

56 Conducting System of Heart The heart beat starts in the heart itself Heart muscle cells are selfcontractile. This means they are able to contract and produce an electrochemical signal, which is passed on to other cardiac muscle cells, causing them to contract. It is regulated by the nervous system and hormones which ensures that it beats in a coordinated manner. Inside human body

57 SA Node The SAN is found at the top of the right atrium. It sends out a electrical impulses which are carried through the muscular walls of both atria This ensures that both atria contract simultaneously and results in atrial systole The electrical impulse is then passed to the atrioventricular node (AVN) Bundle of HIs

58 AV Node The AVN is found lower part of the right atrium When the impulse reaches the AVN it is passed into a bundle of conducting fibres. These fibres split left and right into the ventricles. This causes the ventricles to contract at the same time.

59 Pathway SAN (1) Impulse is generated in the SA node (2)The AVN then picks up the impulse from SAN (3)Passes to bundle of conducting fibres and travels down the septum (4)Passes to the bundle branches (right & left) (5)Passes to the ventricles contract from bottom up AVN septum Bundle of conducting fibers

60 Conducting System Summary The autorhythmic cells of the sinoatrial node (SAN) or pacemaker set the rate at which cardiac muscle cells contract. The timing of cardiac cells contracting is controlled by the impulse from the SAN spreading through the atria and then travelling to the atrioventricular node (AVN) and then through the ventricles.

61 Learning Intention Describe the autonomic and hormonal regulation of the cardiac conducting system

62 Regulation of Heart Rate The SAN alone initiates each heartbeat, and the timing of each of controlled by the impulse from the SAN travelling to the AVN and then through the ventricles. However, heart rate is not fixed as it is altered by nervous and hormonal activity

63 Nervous System Factsheet Questions 1. What are the 2 branches of the nervous system called and what do they consist of? 2. Compare the 2 branches of the peripheral nervous system 3. Give an example of the somatic nervous system 4. Give an example of the autonomic nervous system 5. Compare the 2 branches of the autonomic nervous system

64 Autonomic Nervous System Regulation The medulla regulates the rate of the SAN through the antagonistic action of the autonomic nervous system (ANS) The autonomic nervous system consists of 2 opposing (antagonistic) branches Sympathetic pathway Parasympathetic pathway

65 Sympathetic Nerve An increase in the number of nerve impulses at the SAN via the sympathetic nerve increases heart rate Sympathetic accelerator nerves release norepinephrine (noradrenaline)

66 Parasympathetic Nerve An increase in the number of nerve impulses at the SAN via the parasympathetic nerve decreases heart rate Parasympathetic nerves release acetylcholine

67 Hormonal Regulation of the Heart Under certain circumstances e.g. stress or exercise the sympathetic nervous system causes the adrenal glands to produce the horomone adrenaline This travels in the blood to act on the SAN, which generates impulses at a higher rate, increasing heart rate

68 Autonomic Nervous System & Hormonal Regulation Control centre in medulla adrenalin

69 Electrocardiogram In an ECG(electrocardiogram) test, the electrical impulses made while the heart is beating are recorded and shown on a piece of paper It can show any problems with the heart's rhythm, and the conduction of the heart beat through the heart which may be affected by underlying heart disease

70 Abnormal ECG Ventricular tachycardia Ventricles beat rapidly and independently of the atria

71 Abnormal ECG Ventricular fibrillation Unco-ordinated electrical activity Pumping cannot take place Fatal if not corrected by defibrillation

72 Control of Conducting System Summary The heart beat originates in the heart itself but is regulated by both nervous and hormonal control. The medulla regulates the rate of the SAN through the antagonistic action of the autonomic nervous system (ANS). Sympathetic accelerator nerves release adrenaline (epinephrine) and slowing parasympathetic nerves release acetylcholine.

73 Learning Intention Discuss the measurement and typical readings for blood pressure

74 Blood Pressure The blood needs to be under pressure to travel round the body and for pressure filtration (as mentioned at the capillaries) As the heart contracts and relaxes blood pressure rises and falls. Measure 2 values systolic BP (pressure during ventricular contraction) and diastolic BP (pressure during ventricular relaxation)

75 Measurement of BP Both systolic and diastolic BP can be measured by an inflatable instrument called a sphygmomanometer which is wrapped around the upper arm. Normal values are around 120mmHg for systolic pressure and 70mmHg for diastolic pressure (120/70)

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77 Hypertension High blood pressure is called hypertension Hypertension is a major risk factor for many diseases including coronary heart disease.