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MICN201 Physiology Cardiovascular Exam With
Complete Solutions
What is the formula for MABP? - Answer CO x TPR
What is the formula for CO? - Answer HR x SV
What are the responses to baroreceptor reflexes? - Answer A decrease in heart rate, reduction in stroke volume and decrease in TPR.
What are baroreceptor reflexes attempting to maintain? - Answer MABP
What are the stages of response to haemorrhage? - Answer Hypotension causes a baroreceptor reflex which decreases heart rate, reduces stroke volume and decreases TPR to reduce the change in MABP. From there, fluid will shift from the capillaries. Finally, fluid volume will be replaced by the function of ADH.
What are the exceptions to the parallel nature of the systemic circulation? - Answer In the renal system, blood is filtered through the glomerulus before it supplies the rest of the kidneys. In the splanchnic system, There is a hepatic artery and splenic artery which lead into the hepatic vein and portal vein respectively. The portal vein then leads into the hepatic vein.
What is the structure of an AV valve? - Answer Chordae tendinae attached to ventricular muscles, ensuring one way flow to the ventricle.
What are the names of the AV valves and which side are they on? - Answer The mitral valve is on the left side and the tricuspid valve is on the right side.
What are the names of the semilunar valves and which side are they on? - Answer The aortic valve is on the left side and the pulmonary valve is on the right side.
Which valves are open in systole and closed in diastole? - Answer The semilunar valves
Which valves are open in diastole and closed in systole? - Answer The AV valves.
What are the 5 phases of the cardiac cycle? - Answer Atrial depolarisation, ventricle depolarisation, isovolumetric contraction, ejection and isovolumetric relaxation.
What happens in the atrial depolarisation phase of the cardiac cycle? - Answer The atrium contracts and the rising pressure ejects blood into the ventricles.
What happens in the ventricular depolarisation phase of the cardiac cycle? - Answer The ventricles contract, developing tension and elevating left ventricular pressure.
What happens in the isovolumetric contraction phase of the cardiac cycle? - Answer Both sets of valves are closed at this point, so the pressure increases with no change in blood volume
What happens in the ejection phase of the cardiac cycle? - Answer When pressure in ventricles is higher than in the aorta and pulmonary arteries, blood is ejected from the ventricles
What happens in the isovolumetric relaxation phase of the cardiac cycle? - Answer All valves are shut and the ventricle is relaxing. This phase is short as the atrium fills quickly from the circulation due to its low pressure, and pressure in the atrium quickly increases.
What are the phases of a Sino-atrial node action potential? - Answer Prepotential, upstroke and repolarisation.
What happens in the plateau phase of myocardial cell contraction? - Answer A sustained depolarisation of the cell competes against outward K+ current. Calcium channels are inactivating more and more.
What happens in the late repolarisation phase of myocardial cell contraction? - Answer The conductance of K+ increases, causing a repolarisation back to the resting membrane potential.
What happens inside a myocardial cell when it is depolarised? - Answer L type Ca2+ channels are opened, causing an influx of Ca2+ into the cell. This also produces a secondary release of Ca2+ from the sarcoplasmic reticulum, which is called Calcium Induced Calcium Release (CICR).
How does Ca2+ cause Calcium induced Calcium Release? - Answer Ca2+ binds to ryanodine receptors in the sarcoplasmic reticulum, near the terminal end of T tubules. This causes vesicles to release stored Ca2+.
How is Ca2+ removed after use? - Answer The SERCA pump pumps Ca2+ into the sarcoplasmic reticulum, and a sodium/calcium exchange pump removes calcium from the cell by exchanging it for Na+.
What is Starling's law of the heart? - Answer The ability of cardiac muscle to increase contractile force leads to an increase in stroke volume. If the end diastolic volume (EDV) increases, the stroke volume increases.
What is the equation for blood flow? - Answer Flow = Change in blood pressure/Resistance to flow
What are the two main patterns of blood flow? - Answer Laminar blood flow is when blood moves faster in the middle of a vessel than at the edge, due to friction with the blood vessel wall. Turbulent blood flow is when blood flow is not focused and there is no discernable pattern of flow.
What can cause turbulent blood flow? - Answer The rate of blood flow is too high, the blood passes an obstruction, blood makes a sharp turn or blood passes over a rough surface.
What is the formula for turbulence? - Answer Re (reynold's number) = vD(rho)/n where v is velocity, d is diameter, rho is density and n is viscosity. Blood is considered turbulent if Re > 2000.
What is Poiseuille's law? - Answer R = 8nL/(pi)r^4 where n is viscosity, L is length of tube and r is the radius.
How are veins different to arteries? - Answer They have thinner walls and often appear collapsed. They have less smooth muscle and elastin. They have high compliance, and one way valves that prevent backflow.
What does changing vascular tone regulate? - Answer Regional blood flow and arterial blood pressure
What are the extrinsic factors controlling vascular tone? - Answer Vasomotor nerves and hormones such as adrenaline, vasopressin and angiotensin II.
Where is adrenaline secreted from? - Answer The adrenal medulla
What happens to vascular tone with increased sympathetic activity? - Answer Vasoconstriction occurs, reducing tissue blood flow. Capillary pressure is reduced which leads to contraction of local resistance vessels, allowing interstitial fluid to be absorbed into the plasma.
What are the intrinsic factors controlling vascular tone? - Answer Autoregulation, NO production, Humoral control, Autacoid regulation.
What are factors affecting NO production? - Answer Exercise and drugs such as Glyceryl trinitrate.
What laws do fluid exchange and solute exchange in capillaries follow? - Answer Fluid exchange follows Starling's law and solute exchange follows Fick's law of diffusion.
What are the metabolic consequences of diabetes? - Answer Increased reliance on fatty acid oxidation and decreased reliance on carbohydrate oxidation.
What are the metabolic consequences of a reperfused heart? - Answer Increased reliance on fatty acid oxidation and decreased reliance on carbohydrate oxidation.
What are the metabolic consequences of a hypertrophied heart? - Answer Decreased FA oxidation and increased glycolysis
What are the metabolic consequences of an ischaemic heart? - Answer Decreased oxidation and increased glycolysis
What are the metabolic consequences of a hypoxic heart? - Answer Decreased oxidation and increased glycolysis
What is the function of the coronary circulation? - Answer To maintain a high supply of oxygen to the heart at all times, to increase coronary blood flow in proportion to demand, and to allow vasodilatation to limit damage by coronary artery disease.
How does the coronary circulation deal with ischaemia or increased demand? - Answer ATP is broken down to adenosine, a powerful vasodilator. The more energy is required, the more ATP is broken down, so the more vasodilation occurs.
What are the main difficulties the coronary circulation faces? - Answer Atheromas, Coronary stenosis.
What is an atheroma? - Answer Because there are end-arteries, plaques called atheromas can form in the tunica intima, bulging into the lumen and leading to angina and thrombosis.
What is coronary stenosis? - Answer When metabolic hyperaemia can no longer match myocardial perfusion to O2 demand, stenosis (abnormal narrowing) occurs.
What are the main methods of assessing coronary arteries? - Answer Coronary angiography and Isotope imaging of the ventricular wall.
What can you learn from coronary angiographies? - Answer The locations of coronary obstructions.
What can you learn from isotope imaging of the ventricular wall? - Answer Perfusion defects in the heart wall, to assess the extent of an infarct or aid diagnosis of angina.
What are the special features of the Cutaneous ciculation? - Answer Anastomoses at extremities to serve as backup supply if a pathway is blocked, ability to control temperature through vasodilation and sweating.
What are the problems with Cutaneous circulation? - Answer Severe cold causes paradoxical vasodilation due to paralysis of noradrenaline, as well as prostacyclin release.
What are the special features of the Cerebral circulation? - Answer A high blood flow rate, where pressure is safeguarded by brainstem regulation of other regions.
What are the problems with Cerebral Circulation? - Answer Blood brain barrier can breakdown, allowing contents of blood to damage the brain. Postural hypotension can cause syncope upon standing up. Dilation of arteries can produce migrane headaches.
What are the factors controlling MABP? - Answer Arterial Baroreceptor Reflex, Posture, Exercise, Response to Blood Loss.
What happens to cause orthostatic hypotension upon standing up suddenly? - Answer
What is the major effect of ischaemia of the heart? What causes this? - Answer A reduction in contractility of myocardial cells. This is caused by a decrease in ATP and CP, as well as accumulation of lactic acid and extracellular K+. The current is not as negative as in healthy tissue, and so some Na+ channels remain inactive. This reduces the upstroke produced, making smaller action potentials and decreasing their likelihood to propagate.
What stops ischaemia being as bad as it could be? - Answer The lack of contractility means that the heart fills up with blood. This causes stretch receptors on the ventricular wall to be activated, activating the sympathetic nervous system and increasing the force of contraction.
How is cardiac function in ischaemic patients maintained in the long run? - Answer Lack of perfusion causes the renin-angiotensin-aldosterone system to be activated. This causes retention of Na+ and water, increasing end diastolic volume and, through starling's law, returning cardiac output to normal.
What are the two main electrocardiographic features of a myocardial infarction? - Answer ST elevation and a Current of Injury.
How is ejection fraction calculated? - Answer EF = SV/EDV
What is heart failure? - Answer Inability of the heart to maintain adequate perfusion of the tissues at a normal filling pressure.
Why does ejection fraction decrease massively in heart failure? - Answer The sympathetic nervous system is impaired due to a downregulation of Beta-1 receptors, so that stroke volume will not change but EDV will dramatically increase.
Why does pulmonary oedema occur from heart failure? - Answer An increase in EDV increases EDP. This means that the pressure of the ventricles will eventually be greater than that of the atrium, so that blood will not travel from the atrium to the ventricles. As volume increases in the atrium, the pressure also increases here and through a similar process, the pulmonary veins also fill up with blood. Eventually, this causes the lungs to
fill up with fluid causing oedema.
What can cause referred pain? - Answer The first mechanism is that myocardial ischaemia can send visceral signals to the spinal cord. The sympathetic nervous system has mixed fibres, so the somatic sensory nerve will get stimulated causing pain in the T1-T4 regions, therefore sending pain to the chest and left arm.
The second mechanism is that pericardial problems can signal phrenic nerve pain (C3-C5) which will refer pain to the neck and shoulder.
