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Phase 1A Andrew Hu + Elaine Pang

Cardiovascular Physiology. Phase 1A Andrew Hu + Elaine Pang. The Peer Teaching Society is not liable for false or misleading information…. Aims and Objectives. The tiniest amount of heart anatomy Activation and Contraction Cardiac Cycle Control of MAP.

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Phase 1A Andrew Hu + Elaine Pang

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  1. Cardiovascular Physiology Phase 1A Andrew Hu + Elaine Pang The Peer Teaching Society is not liable for false or misleading information…

  2. Aims and Objectives • The tiniest amount of heart anatomy • Activation and Contraction • Cardiac Cycle • Control of MAP The Peer Teaching Society is not liable for false or misleading information…

  3. Anatomy The Peer Teaching Society is not liable for false or misleading information…

  4. Anatomy The Peer Teaching Society is not liable for false or misleading information…

  5. Sino-atrial node • Called the pacemaker • P-wave • Located in the right atrium • Transmits across both atria • Transmission goes to AV node The Peer Teaching Society is not liable for false or misleading information…

  6. Atrioventricular node • Specialised myocytes • Base of the right atrium • Transmit impulse deliberately slowly (0.1s) • Purely there to allow for atrial contraction The Peer Teaching Society is not liable for false or misleading information…

  7. Atrioventricular node • Impulse then travels down the IVS • Initially as AV bundle (His) • Splits into RBB and LBB • Splits into the Purkinje fibres at base of ventricles • Spreads upwards and outwards • Contract from base • 20-40 bpm The Peer Teaching Society is not liable for false or misleading information…

  8. Actin and Myosin Troponin C – calcium binds to cause conformational change in Troponin I Troponin T – Binds to tropomyosin forming a tropomyosin troponin complex Troponin I – binds to actin, to hold the tropomyosin – troponin complexes in place The Peer Teaching Society is not liable for false or misleading information…

  9. Contraction • Excitation • L Type Ca channels in T tubules open causing influx of Ca • Ca binds to sarcoplasmic opening lateral sacs releasing more Ca • Ca binds to TnC moving tropomyosin • Allows energized myelin to bind to actin • Repolarization and Ca reuptaken The Peer Teaching Society is not liable for false or misleading information…

  10. Myocyte Contraction Energised cross-bridge binds to actin Cross-bridge moves ATP binds to myosin → cross bridge detaches Hydrolysis of ATP → cross-bridge becomes energised The Peer Teaching Society is not liable for false or misleading information…

  11. Events of the Cardiac Cycle VENTRICULAR FILLING (DIASTOLE) • Passive filling of the ventricles – Ventricular volume and pressure increases • AV valves are open • Semi lunar valves are closed ISOVULUMETRIC CONTRACTION (SYSTOLE) • Ventricular pressure> Atrial pressure • Causing the AV valves to close EJECTION (SYSTOLE) • Ventricular pressure> Atrial pressure • Causing the semi lunar valves to open. ISOVOLUMETRIC RELAXATION (DIASTOLE) • Both semi lunar and AV valves are closed • When ventricular pressure < atrial pressure, AV valves open http://www.beltina.org/pics/cardiac_cycle.gif The Peer Teaching Society is not liable for false or misleading information…

  12. Heart Sounds • Four heart sounds. • Usually only the first two can be heard – ‘LUBB DUBB’ • 1st heart sound = due to the closure of the AV valves • 2nd heart sound = due to the closure of the semi lunar valves • 3rd heart sound = due to the sudden rapid flow of blood into the ventricles during diastole • 4th heart sound = due to the flow of blood into the ventricles due to atrial contraction The Peer Teaching Society is not liable for false or misleading information…

  13. ECG Representation http://www.google.co.uk/imgres?hl=en&sa=X&biw=518&bih=273&tbm=isch&tbnid=1aB0RS0FWjHX0M:&imgrefurl=http:// The Peer Teaching Society is not liable for false or misleading information…

  14. Mean Arterial Pressure Mean Arterial Pressure (MAP) MAP = the average arterial blood pressure over an entire cardiac cycle Total Peripheral Resistance (TPR) Cardiac Output (CO) = x The Peer Teaching Society is not liable for false or misleading information…

  15. Cardiac Output CO = the volume of blood each ventricle pumps Therefore, CO = the volume of blood flowing through either the systemic (or pulmonary) circuit per minute Cardiac Output (CO) Heart Rate (HR) Stroke Volume (SV) x = The Peer Teaching Society is not liable for false or misleading information…

  16. Total Peripheral Resistance TPR = the sum of the resistances to flow offered by all the systemic blood vessels The arterioles are the principle site of resistance to vascular flow (their radii can be changed by vascular smooth muscle contraction/relaxation) Therefore, TPR is essentially the same as the Total Arteriolar Resistance The Peer Teaching Society is not liable for false or misleading information…

  17. So, to summarise… Heart Rate (HR) Stroke Volume (SV) Cardiac Output (CO) Total Peripheral Resistance (TPR) Mean Arterial Pressure (MAP)

  18. Sensors of MAP Arterial baroreceptors • Stretch-sensitive receptors • Blood vessel wall stretch → pressure within blood vessel • Located in the carotid sinus and aortic arch • Send neurons to the Medullary Cardiovascular Centre The Peer Teaching Society is not liable for false or misleading information…

  19. Arterial Baroreceptor Reflex ↑ MAP ↓ MAP ↑ Arterial Baroreceptor Firing ↓ Arterial Baroreceptor Firing Medullary Cardiovascular Centre Medullary Cardiovascular Centre ↑ MAP ↓ MAP The Peer Teaching Society is not liable for false or misleading information…

  20. Effectors of MAP Heart Rate (HR) Stroke Volume (SV) Cardiac Output (CO) Total Peripheral Resistance (TPR) Mean Arterial Pressure (MAP)

  21. Effectors of CO Heart Rate (HR) Stroke Volume (SV) Activity of sympathetic nerves to heart Plasma adrenaline End-diastolic ventricular volume (preload) Dependent on venous pressure • Activity of sympathetic nerves to heart • Activity of parasympathetic nerves to heart • Plasma adrenaline

  22. Effectors of TPR Vasoconstrictors (↑ TPR) Vasodilators (↓ TPR) Local ↓ O2 (hyperaemia) CO2 NO Inflammatory mediators Neural Neurons that release NO Hormonal Atrial Natriuretic Peptide • Local • Endothelin-1 • Neural • Sympathetic nerves • Hormonal • Adrenaline • Anti-Diuretic Hormone • Angiotensin II The Peer Teaching Society is not liable for false or misleading information…

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