1. The Heart & ECGs B5b

2. OBJECTIVES Key Objective Explain how the heart works and is controlled Identify the four chambers (atria, ventricles) of the heart and associated main blood vessels (aorta, vena cava, pulmonary artery and vein) (D) State the use of techniques such as ECG and echocardiograms (C) Interpret data on pressure changes in arteries, veins and capillaries (C) Understand what is meant by a double circulatory system and links to a four chambered heart (B) Describe how the pacemaker cells (SAN and AVN) coordinate heart muscle contraction (A) Interpret data from ECG and echocardiograms (A*)

3. STARTER True or False? 1.All animals have blood. 2.All blood is red. 3.Insect blood does not carry oxygen. 4.Human blood does carry oxygen. 5.Human blood contains red and white blood cells. 6.Blood is the same in different animals. 7.All animal hearts are the same as our heart. 8.You only bleed if a blood vessel is cut or damaged. 1.False 2.False 3.True 4.True 5.True 6.False 7.False 8.True

4. Single Circulation – e.g. fish Blood pressure reduced as blood passes through the gill capillaries - slows down flow to the rest of the body Limits the rate of delivery of O2 and nutrients to cells and removal of waste Efficient for the level of activity of fish but not mammals – also fish do not maintain their body temperature – need to respire relatively less compared to mammals Double Circulation – more efficient - e.g. mammals Heart is composed of two separate pumps – right side pumps blood to the lungs to pick up oxygen; the blood is returned to the left side; the left side pumps oxygenated blood rapidly and at high pressure to the body; the blood is returned to the right side Higher level of activity (energy) and need to maintain their body temperature at 37 0 C – through respiration Need to deliver and remove materials to and from cells rapidly – achieved by delivering blood at high pressure to tissues. Pulmonary – oxygenates blood & removes CO2 Systemic – oxygenated blood from lungs pumped rapidly at an increased pressure by the heart Blood passes through heart TWICE per complete circuit Blood passes through heart ONCE per complete circuit

5. Open Circulatory System Some animals (e.g. insects) have an open circulatory system – the circulating blood is not contained within vessels all the time. It flows freely through the body cavity and is in direct contact with the body cells.

6. Blood circulated in a closed circuit – comprising the heart and blood vessels - It is a CLOSED circulation DOUBLE circulation 2 circuits Pulmonary & Systemic Blood passes through heart twice per complete circuit In lungs O2 diffuses into RBCs Blood oxygenated Hb + O2 HbO2 CO2 diffuses into alveoli In tissues Blood deoxygenated HbO2 Hb + O2 O2 diffuses into cells CO2 diffuses into plasma Hb = haemoglobin

7. Narrow lumen; High pressure Highly elastic – expand and recoil Thick muscular wall – to withstand force; more elastic fibres (recoil) No valves (except aortic and pulmonary semilunar at the start) Oxygenated blood from heart – except pulmonary artery to lungs Pulsatile blood flow (expansion + recoil) Pulse can be felt – e.g. wrist Wide lumen; Low pressure Thin wall - less elastic and less muscular Valves (semilunar) – prevent backflow Deoxygenated blood to heart from tissues - except pulmonary vein from lungs Non pulsatile – smooth flow of blood Capillary – endothelium – large number – large surface area for exchange Wall - one cell thick – short diffusion distance Endothelium is continuous throughout circulatory system Artery Vein Capillary

10. Labels A Right ventricle B Bicuspid (mitral) valve C Tricuspid valve D Right atrium E Pulmonary vein F Pulmonary artery G Vena cava H Aortic semilunar valve I Pulmonary semilunar valve J Chordae tendinae Activity - Label the diagram of the heart

11. Heart relaxed AV valves are open Deoxygenated blood from vena cava flows into RA Oxygenated blood from pulmonary vein flows into LA Blood passes into ventricles passively SA node contracts – sends impulses through atria Atria contract (top downwards) – forces additional blood into ventricles through AV valves Blood from RA to LA; blood from LA to LV Ventricles receive impulses from AVN via Purkinje fibres – ventricles contract (bottom upwards) – force of blood causes AV valves to close (lub)– prevents blood flowing back into atria Blood is forced from RV into PA through pulm. semilunar valves and from LV into aorta through aortic semi lunar valves Heart relaxes – semilunar valves close due to force of blood (dub)- prevent backflow from pulm. artery and aorta into heart - AV valves open Atria fill with blood again to start cycle again Cardiac Cycle

12. OBJECTIVES Key Objective Explain how the heart works and is controlled Identify the four chambers (atria, ventricles) of the heart and associated main blood vessels (aorta, vena cava, pulmonary artery and vein) (D) State the use of techniques such as ECG and echocardiograms (C) Interpret data on pressure changes in arteries, veins and capillaries (C) Understand what is meant by a double circulatory system and links to a four chambered heart (B) Describe how the pacemaker cells (SAN and AVN) coordinate heart muscle contraction (A) Interpret data from ECG and echocardiograms (A*)

13. The cardiac cycle

15. A Atrioventricular (bicuspid / mitral) valve(s) closes (“snaps shut”– makes 1 st louder heart sound “LUB” B Semilunar valve(s) (aortic valve) opens C Semilunar valve(s) closes – makes second softer heart sound “DUB”- shut due to blood accumulating in their pockets D Atriioventricular (bicuspid) valve(s) opens “LUB” “DUB” Atrial Systole Ventricular Systole Diastole Cardiac cycle = 0.8 sec 60/0.8 bpm = 72 bpm

16. Pressures changes in the aorta, left ventricle and left atrium during one heartbeat © Pearson Education Ltd 2008 This document may have been altered from the original

17. Electrocardiogram (ECG) P wave = electrical activity during atrial systole QRS complex = electrical activity during ventricular systole T wave = ventricular repolarisation (recovery of ventricular walls) Q-T interval – contraction time (ventricles contracting) T-P interval – filling time – ventricles relaxed and filling with blood Pattern are studied in different conditions and compared to the standard ECG in order to diagnose heart conditions, such as arrythmias and fibrillation. Fibrillation is stopped by passing a strong electric current through the chest wall – the heart stops for up to 5 seconds after which it begins to beat in a controlled way Electrodes are placed on the skin over opposite sides of the heart, and the electrical potentials generated recorded with time. The result is an ECG.

18. The pathway followed by the wave of excitation

19. A normal ECG trace compared with others indicating an unhealthy heart

20. Hole in the Heart Congenital (at birth) – between atria or ventricles Allows mixing of oxygenated and deoxygenated blood – blood passes from RA to LA Some blood does not enter ventricles Some blood does not enter ventricles and pulmonary artery Reduces systolic pressure Dangerous if not treated Pressure reduced – some blood bypasses lungs Less O2 carried/picked up/loaded Less respiration – decreased O2 supply to cells – less energy Weakness; anaemia;

21. Regulation of the Heart Atria relaxed – fill with blood RA with deoxygenated blood from vena cava LA with oxygenated blood from pulm vein SAN sends out 72 impulses/min over atrial wall – atria contract 72 times/min Atria contract to force blood into ventricles Atria relax Impulse reaches AVN Delayed momentarily Impulse travels through nerve fibres of the atrioventricular bundle and its branches into walls of the ventricles Ventricles contract – from apex upwards to force blood into arteries Oxygenated blood from LV to aorta – to body Deoxygenated blood from RV to pulmonary artery – to lungs (to be oxygenated) Cardiac Output Stroke Volume X Heart Rate = CO 75 X 70 = 5250 ml/min – Normal Factors that increase SV or HR increase CO SV depends on how much blood enters the ventricle during diastole HR is regulated by several factors – Chemical(e.g. CO2; pH) and physical ( blood pressure)

22. Muscles – greater demand for O2 and nutrients (glucose) for energy; increased production of waste – CO2 and lactic acid; excess heat produced - need to be removed. Increase in CO 2 detected by chemoreceptors in aortic arch and carotid artery Accelerator (sympathetic cardiac) nerve releases chemical neurotransmitter (NE) at SAN to increase rate and force of contraction of heart to increase cardiac ouput Adrenaline is released from adrenal gland – stimulates heart (increase rate and force; dilates blood vessels in muscles to increase blood flow) Decelerator (vagus) nerve releases chemical (acetylcholine) at SAN to slow heart Carotid artery Aortic arch Exercise; Stress; Fright

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