Cardio 2
- Created by: Mohsin
- Created on: 08-04-18 14:46
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- Cardio Therapeutics 2
- Cardiac Anatomy
- Double circulatory system
- LV thicker muscle
- Left side pumps blood into systemic circulation
- Lots of resistance to flow which the heart has to overcome
- Left side pumps blood into systemic circulation
- Pressure is Pulmonary circulation LOWER than systemic
- At rest blood flow = 5L/min
- SYSTEMIC circulation
- Arteries = carry oxygenated blood AWAY from the left side of the heart
- Veins = carry de-oxygenated blood to the right side of the heart
- Parallel - allows finer control of blood flow
- Kidney - needs high blood flow to allow adequate excretion of urea
- Distribution of cardiac output is not constant - changes to maintain internal environment
- Most of the blood is held in the veins
- Blood pressure (BP)
- Normal BP = 120/80; sys/dia
- Systolic = contraction
- Diastolic = relaxation
- Electrical conduction in the heart
- SA generates AP (action potential)
- Initiates rise in intracellular Ca+ which activates contraction
- Causes depolarisation across the atria = contraction
- Ventricles contract bottom upwards
- Causes depolarisation across the atria = contraction
- Initiates rise in intracellular Ca+ which activates contraction
- At rest = 60/70 BPM
- SA generates AP (action potential)
- Myocardium and myocyte structure
- Desmosomesjoin adjacent myocytes
- Provide mechanical strength
- Junction transmit ionic currents (electrical excitation) between myocytes
- Gap made of protein (connexion) allows flow of ion
- Ensures myocytes in ventricles activated together
- Gap made of protein (connexion) allows flow of ion
- Myocytes filled with myofibrils - consist if sarcomeres
- T-tubules transmit electrical stimulus into cell - activate myofibrils
- Shortening of sarcomere - contraction of the heart
- Desmosomesjoin adjacent myocytes
- Electro -cardiograph
- P wave = atrial fill with blood - atria depolarise
- P-Q wave = atrial contraction
- QRS wave = firing of AV node and ventricular de-polarisation
- S wave = last phase of ventricular de-polarisation
- ST wave = ventricles contract and eject blood
- ST segment is isoelectric
- If region of the ventricular myocardium is damaged by ischaemia (immediately after an MI)
- causes ST elevation
- in chronic myocardium ischaemia the ST segment is depressed
- the myocyte in an ischaemic zone have:
- smaller resting potential
- smaller action potential
- If region of the ventricular myocardium is damaged by ischaemia (immediately after an MI)
- ST segment is isoelectric
- T wave = ventricular diastole
- PR interval = time taken for excitation to spread through atria, AV node and His-Purkinje system into the ventricle
- PR interval mainly caused by the delay at the AV node
- Cardiac Anatomy
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