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Higher Human Biology

Higher Human Biology. Unit 2 Physiology & Health. KEY AREA 6: Structure and Function of the heart. Higher Human Biology. We are going to build on the knowledge and skills that you developed during N5 and will learn about the following Physiology & Health key areas : -

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Higher Human Biology

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  1. Higher Human Biology Unit 2 Physiology & Health KEY AREA 6: Structure and Function of the heart

  2. Higher Human Biology We are going to build on the knowledge and skills that you developed during N5 and will learn about the following Physiology & Health key areas : - Key Area 1 – Reproductive Organs Key Area 2 –Hormonal Control of Reproduction Key Area 3 – Biology of Controlling Fertility Key Area 4 – Ante- and Postnatal Screening Key Area 5 – Structure and Function of Arteries, Capillaries and Veins Key Area 6 – Structure and Function of the heart Key Area 7 – Pathology of Cardiovascular Disease (CVD) Key Area 8 – Blood Glucose Levels and Obesity

  3. N5 Revision - Circulatory System Blood is transported in the Circulatory System. The heart is made up of cardiac muscle tissue. The 4 chambers of the heart are:- Right Atrium Right Ventricle Left Atrium Left Ventricle The right ventricle pumps blood to the lungs. The left ventricle pumps blood to the WHOLE BODY! Therefore the muscle of the left ventricle is much thicker than the right ventricle muscle

  4. 1. Blood from the Body 2. Vena cava vein 3. Right Atrium 4. Right Ventricle 5. Pulmonary Artery 6. LUNGS 7. Pulmonary Vein 8. Left Atrium 9. Left Ventricle 10. Aorta artery 11. Blood to the Body 12. Arteries 13. Capillaries 14. Veins N5 Revision - Pathway of Blood Vena Cava Vein

  5. N5 Revision - Heart Structure Semi-lunar Valves Tricuspid Valve Bicuspid Valve Valves STOP the blood from flowing backwards Bitesize Heart Function (0:40) Bitesize animation of heart

  6. N5 Revision - Coronary Arteries Coronary Arteries supply the heart muscle with blood containing oxygen and nutrients (e.g. glucose) Coronary Veins take carbon dioxide and wastes away from the heart

  7. Physiology & Health Learning Intentions KEY AREA 6 – Structure & Function of the Heart • Cardiac output • Cardiac Cycle • Structure and function of the Cardiac Conducting System • Blood pressure

  8. 6a) Structure and function of the heart Atrio-ventricular (AV) valves prevent back flow of blood from ventricles to atria Semi-lunar (SL) valves prevent backflow of blood at the entrance of the pulmonary and aorta arteries. These valves open during ventricular contraction allowing blood into the arteries, and close when arterial pressure exceeds ventricular pressure

  9. 6b) Cardiac Output At each contraction of the heart, the right ventricle pumps the same volume of blood through the pulmonary artery (and round to the lungs) as the left ventricle pumps through the aorta (and round the body) Heart Rate (Pulse) is the number of heartbeats that occurs per minute Stroke Volume is the volume of blood expelled by each ventricle on contraction. The stronger the contraction, the greater the stroke volume. Cardiac output is the volume of blood pumped through each ventricle per minute. Thus:- CARDIAC OUTPUT (CO) = HEART RATE (HR) X STROKE VOLUME (SV)

  10. 6c) Cardiac Cycle The cardiac cycle refers to the pattern of contraction (systole) and relaxation (diastole) shown by the heart during one complete heartbeat The average cardiac cycle is 0.8seconds, which is based on a heart rate of 75 beats per minute

  11. 6d) Atrial and Ventricular Diastole (relaxing) The blood returning from the vena cava and pulmonary veins going into the atria causes the volume of blood in the atria to increase and some of the blood flows into the ventricles AV valves opening SL valves closed – caused by the higher pressure in the arteries

  12. 6e) Atrial systole (atria contracting) Atrial systole transfers the remainder of the blood to go through the AV valve to the ventricle. This is due to the fact that atrial pressure exceeds ventricle pressure, so the AV valves are pushed open and blood then enters the ventricles. During atria systole the two atria contract simultaneously and send the remainder of the blood down into the ventricles through the open AV valves. The ventricles fill up with blood and the SL valves remain closed AV valves open SL valves closed

  13. 6f) Ventricular systole (ventricles contracting) Closes the AV valves and pumps the blood out through the SL valves to the aorta and pulmonary artery AV valves closed SL valves open Pressure changes It is the opening and closing of the AV and SL valves that are responsible for the heart sounds heard with a stethoscope

  14. 6g) Cardiac Conducting System The sequence of events that occurs during each heartbeat is brought about by the activities of the pacemaker and the conducting system of the heart The auto-rhythmic cells of the sino-atrial node(SAN)/Pacemaker is located in the wall of the right atrium and sets the rate at which the cardiac muscle cells contract

  15. 1. Impulses from the SAN spreads through the muscle cells in the wall of the two atria making them contract simultaneously (atrial systole). 2. The impulses then travel to the Atrio-Ventricular node (AVN) which is located in the centre of the heart (near the base of the atria) 3. The impulses pass from the AVN down fibres in the central wall of the heart and then up through the walls of the ventricles, causing contraction of the two ventricles (ventricular systole) **This ensures that ventricle systole occurs slightly later than atrial systole – which allows for the ventricles to fill completely before they contract** 4. The timing of cardiac cells contracting is controlled by the impulse from the SAN spreading through the ventricles – these impulses generate currents that can be detected by an electrocardiogram (ECG) The heart beat originates in the heart itself but is regulated by both nervous and hormonal control 6h) Cardiac Conducting System

  16. 6i) Autonomic Nervous Control of the Heart • Control centres in the medulla of the brain regulate the rate of the SAN through the antagonistic action of the autonomic nervous system (ANS)

  17. 6j) Autonomic Nervous Control of the Heart • The cardio-accelerator centre sends its nerve impulses via sympathetic nerves to the heart • The cardio-inhibitor centre sends its information via a parasympathetic nerve to the heart 3. The two pathways are antagonistic to one another in that they have opposite effects on heart rate:- a)An increase in the number of nerve impulses arriving at the SAN (pacemaker) via the sympathetic nerve results in an increase in heart rate due to the sympathetic accelerator nerves releasing the neurotransmitter noradrenaline b)An increase in the number of nerve impulses arriving at the SAN (pacemaker) via the parasympathetic nerve results in a decrease in heart rate due to the slowing parasympathetic nerves releasing the neurotransmitter acetylcholine

  18. 6k) Hormonal Control of the Heart During exercise or stress, the sympathetic nervous system acts on the adrenal glands in the kidneys, making them release the hormone epinephrine (adrenaline) into the bloodstream. On reaching the SAN (pacemaker), this hormone causes the pacemaker to generate cardiac impulses at a higher rate, and brings about an increase in heart rate

  19. 6l) Interpretations of Electrocardiograms • The electrical activity of the heart generates tiny currents that can be picked up by electrodes placed on the skin surface, this creates an electrocardiogram • Normal ECG pattern consist of 3 waves:- • P wave – is the electrical impulses spread over the atria from the SAN (Atrial systole) (2) QRS wave complex – is the electrical impulses passing through the ventricles (Ventricular systole) • T wave – is the electrical recovery of the ventricles near the end of ventricular systole (Diastole) ECGs can be used to calculate heart rate: What would this person’s heart rate be?

  20. 6m) Blood Pressure Changes • Blood pressure is the force exerted by blood against the walls of the blood vessels • BP is measured using a sphygmomanometer in units of millimetres of mercury (mmHg) (see figure 12.10) • As the heart goes through systole and diastole during each cardiac cycle, the arterial pressure rises and falls • During ventricular systole, the pressure of blood in the aorta/pulmonary artery rises to a maximum e.g. 120mmHg • During ventricular diastole, the pressure of blood in the aorta/pulmonary artery drops to a minimum e.g. 80mmHg • Typical blood pressure for a young adult is: 120/80 mmHg

  21. 6n) Measurement of blood pressure Using a sphygmomanometer • The inflatable cuff stops blood flow in the artery 2. The cuff is allowed to deflate gradually until the blood starts to flow (detected by a pulse) at systolic pressure (120mm/Hg) 3. More air is released from the cuff until no pulse detected – this is a measure of diastolic pressure (80mm/Hg)

  22. 6o) Measurement of blood pressure Hypertension (high blood pressure) is the prolonged elevation of blood pressure when at rest e.g. above 140/90mmHg Hypertension is a major risk factor for many diseases that have a relatively high incidence later in life e.g. coronary heart disease, strokes Hypertension is commonly found in people that are: - overweight - not taking enough exercise - eating high fat diet - eating too much salt - drinking alcohol to excess regularly - under continuous stress

  23. Physiology & Health Questions KEY AREA 6 – Structure and function of the heart • Testing Your Knowledge 1 Page 172 Q’s 1-4 2. What you should know Page 172 Q1-15 2. Quick Quiz

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