learning outcomes Flashcards
Explain the generation of heart sounds (phonocardiogram).b
the phonocardiogram is a recording of the sounds and murmurs made by the heart using a phonocardiograph. It works by plotting vibrations made by the closure of the atrioventricular valves and the closure of the semilunar valves. It’s more accurate than a stethoscope for tracking heart functions.
Illustrate the sequence of changes in pressure and volume in the chambers of the heart throughout the cardiac cycle.
initially we have the late diastole, in which both sets of chambers are relaxed and fill passively. The next phase is the atrial systole in which the atria contracts and forces a small amount of blood into the already filled ventricle valve through the Atrioventricular valves, but there isn’t sufficient pressure for opening the semilunar valves. The ventricles then contracts, forcing open the semilunar valves and the blood is ejected in ventricular systole, and atria at this point is in diastole. There is the then the isovolumic ventricular relaxation as the ventricles relax, and the pressure falls closing the semilunar valves. Then we go back to the late diastole phase.
closure of the tricuspid and bicuspid valve is S1 which makes the first heart sound, the closure of the semilunar valves is S2 making the two heart sounds.
Explain the significance of Starling forces and the lymphatic system in relation to oedema.
starlings forces varies in capillary bed, due to the osmotic pressure forcing fluid into the capillaries, as fluid if forced out of the capillaries through hydrostatic pressure. Overall 20 litres is lost through this and 17 litres is regained this way, the remaining 3 litres is absorbed by the lymphatic system. An oedema is formed through the accumulation of excess fluid, this may be due to lymphatic obstruction through surgery or filariasis, raised central venous pressure from ventricular failure, hypoproteinaemia from nephrosis, liver failure and nutrition or increased capillary permeability from inflammation or rheumatism
Identify the processes involved in transport between capillaries and tissues.
the gross structure of the capillaries is designed for exchange, with lots of thin walled capillaries with such a small diameter resulted in a large surface area to volume ratio. They had either leaky endothelial junctions, or fenestrated pores to allow for exchange or discontinuous with massive channels. The process itself is either through the self-regulating diffusion, or by carrier mediated transport such as the glucose transporter.
Describe the mechanism that prevents blood clotting in vessels.
clotting involves the formation of a platelet clot and fibrin clot. The fibrin is formed from fibrinogen being activated by thrombin to fibrin which then binds around the platelet plug adhering to the basement membrane. The anti-clotting mechanisms involve stopping blood contacting collagen, the production of prostacyclin and NO which inhibits platelet aggregation, the production of tissue factor pathway inhibitor which prevents thrombin production, the expression of thrombomodulin or heparin which binds to thrombin and inactivates it and the secretion of plasminogen activator which helps form plasmin which breaks down clots
Describe the dominant factors controlling blood flow in cardiac vascular beds
the dominant factors in controlling blood flow are the basic haemodynamics such as Darcy’s law that flow is equal to the change in pressure over resistance, extrinsic effects of neural and hormonal influences, local intrinsic effect.
special areas include coronary circulation as aortic pressure increases, blood flow decreases s it is interrupted by systole, it demonstrate excellent active hyperaemia and many beta 2 receptors.
Justify the importance of Poiseuille’s Law in relation to the control of resistance and blood flow
with darcy’s law and Poiseuille’s law which stated that varying radius controls resistance, therefore the varying radius of arterioles, or the total peripheral resistance and also effects change in pressure or the mean arterial pressure because the change in pressure is equal to flow multiplied by resistance.
Define active hyperaemia,
active hyperaemia in which increasing metabolic activity increased concentration of metabolites such as carbon dioxide, hydrogen and potassium, which triggers the release of EDRF causing arteriolar dilation, the subsequent increase in blood flow is t wash out the metabolites to match blood flow to metabolic needs.
identify the various neural factors affecting arteriolar tone.
neural control of the smooth muscle of arterioles include sympathetic nerves which release norepinephrine binding to alpha1 receptors causing constriction reducing flow and increasing total peripheral resistance.
Indicate the factors affecting pressure and flow in veins.
pressure is low and the vessels are distensible and collapsible so they are effected by external factors. Such as gravity which causes venous distension in the legs, decreasing the end diastolic volume, reducing cardiac output and mean arteriolar pressure and causes venous collapse in the neck.
skeletal muscle pump also effects the blood flow, as movement forces blood through the veins. As well as respiratory pump, in that breathing generates a negative upper body pressure and a positive body pressure below it essentially forces the blood up to the heart.
there is venomotor tone, the contraction of smooth muscle around venules and veins, and systemic filling pressure created by ventricles and transmitted through the vascular tree to the veins.
Define systolic pressure, diastolic pressure and pulse pressure.
systolic pressure is the peak pressure of the arteries, the pulse pressure is the difference between the between the systolic and diastolic pressure, and the diastolic pressure is the lowest artery pressure.
Explain the origin of the Korotkoff sounds and their use.
Korotkoff sounds originate from the use of a sphygmomanometer and a stethoscope of the brachial artery, as blood is pumped passed through from the high decreasing pressure of the sphygmomanometer noise is generated. If the pressure of the sphygmomanometer is above or below systolic pressure there is silence, as it is just under systolic, there is a tapping sound and as it decrease is progresses to a thumping, then muffled.
Illustrate the changes in the aortic pressure wave as it passes through the vascular tree
the aortic pressure increases up to systole, the aortic valve closes and then gradually decreases to diastole and repeats. The elastic arteries act as a pressure reservoir dampening decreasing variations. The pressure wave can be altered by stroke volume, velocity of ejection, elasticity and peripheral resistance.
as the pressure flows from the left ventricle to the right atrium the pressure gradually decreases.
Illustrate the changes in blood velocity and total cross-sectional area of the vessels through the vascuar tree.
small drop through the arteries in pressure from 95-90mmHg which is a low resistance conduit, then a large drop through arterioles from 90-40 mmHg as it is the resistance vessels. Pressure is already low when the blood gets to the capillaries for exchange, it then leaves a small pressure difference from 20 – 5 mm Hg for the veins as systemic filling pressure. Pulmonary pressure is then a fifth of that of systemic. As a rule as the cross sectional area decreases, the velocity of the blood flow increases.
Describe the effect of the Valsalva manoeuvre on the cardiovascular system.
the Valsalva manoeuvre refers to an increase in thoracic pressure within the chest cavity due to air being forced against a closed glottis. This increase in pressure results in a drop in the mean arterial pressure, as a result the rate of signals being fired by the aortic baroreceptors decrease. In response the medulla will stimulate a sympathetic signal to increase heart rate and stroke volume, and increasing the total peripheral resistance.
Describe the components and function of the aterial baroreceptor reflex.
the arterial baroreceptor reflex originates from baroreceptors in the aortic arch and the carotid artery sinus’s. if they detect an increase In pressure, they send signals through the vagus nerve and the glossopharyngeal nerves respectively to the cardiovascular centres in the medulla. In response a response parasympathetic in nature is sent through the vagus nerve, it reduces the heart rate and the total peripheral resistance. As a result the cardiac output and blood pressure decrease. If it drops too low, a sympathetic response is sent, stimulating the adrenal gland and the sinoatrial and atrioventricular node to increase the heart rate, the stroke volume, causing increased vasoconstriction increasing the total peripheral resistance and increasing the cardiac output thus the blood pressure.
Describe the effect of changes in posture on the cardiovascular system in relations to baroreceptors
as someone stands up, the blood begins to pool in capacitance veins in the legs. As a result the mean arterial pressure will decreases, reducing the signals being fired by the baroreceptors inducing a sympathetic response by the medulla increasing the heart rate, stroke volume and total peripheral resistance increasing blood pressure. Also as a reflex the vagal tone will decrease, contributing to the increase in heart rate and cardiac output.
what is the relationship between mean arterial pressure, cardiac output and total peripheral resistance?
mean arterial pressure is equal to cardiac output multiplied by the total peripheral resistance.
Identify the reflex pathways involving antidiuretic hormome,
the hypothalamus when stimulated by its osmoreceptors detecting changes in the interstitial fluid, angiotensin 2 or by decreased blood volume detected by baroreceptors in the aortic arch and carotid sinus stimulates the pituitary gland to release ADH which increases permeability of the collecting duct and causing vasoconstriction.
Identify the reflex pathways atrial natriuretic peptide and brain natriuretic peptide in the control of plasma volume.
atrial natriuretic peptide is released by myocardial cells in the due to the increased pressure in the atrium. In response to increased mean arterial pressure it inhibits renin, decreases the permeability of the collecting duct resulting increased secretion of sodium and stimulates the medulla centres to reduce mean arterial pressure.
Identify the reflex pathways involving renin-angiotensin-aldosterone
the release of renin by the juxtaglomerular cells of the kidney occurs in response to a reduced concentration of Chloride and sodium ions, sympathetic nerves or constriction of afferent arterioles in response to the drop-in mean arterial pressure. The renin will convert angiotensin into angiotensin 1 which is then converted into angiotensin 2 which acts as a vasoconstrictor, stimulating the hypothalamus to produce ADH and stimulates the adrenal cortex to produce aldosterone which increases the permeability of the collecting duct to increase the blood volume and reduces diuresis.
identify the various hormonal factors affecting arteriolar tone.
hormonal factors such as epinephrine are released by the adrenal medulla which bind to alpha 1 receptors causing arteriolar constriction, having the same effect as norepinephrine but in some tissue is activates beta 2 receptors such in skeletal muscles increasing flow reducing the total peripheral resistance(TPR). Angiotensin 2 also has a similar effect as epinephrine in response to low blood volume increasing TPR, vasopressin an antidiuretic hormone which like angiotensin is released in response to low blood volume and as a result has a similar effect Atrial natriuretic peptide and brain natriuretic peptide are released in response to high blood volume, having an opposite effect causing dilation and reducing TPR.
Describe the dominant factors controlling blood flow in cerebral vascular beds
the dominant factors in controlling blood flow are the basic haemodynamics such as Darcy’s law that flow is equal to the change in pressure over resistance,
Cerebral circulation is also must be kept stable at all times, shows excellent autoregulation.
As well as the blood brain barrier.
Describe the dominant factors controlling blood flow in pulmonary vascular beds
pulmonary circulation as oxygen decreases there is arteriolar constriction which is the opposite of most tissues because it redirects flow to ventilated areas.
Describe the dominant factors controlling blood flow in renal vascular beds
Renal circulation’s main function is filtration which requires pressure, so it must demonstrate excellent pressure autoregulation otherwise changes in mean arteriolar pressure would have massive effects.
Define autoregulation
pressure autoregulation occurs when mean arteriolar pressure drops, decreasing flow so metabolites accumulate triggering the release of EDRF which causes dilation and flow is restored to maintain supply despite MAP changes.
Define reactive hyperaemia.
Reactive hyperaemia is when the blockage of the blood supply causes a increase in blood flow, this response is essentially and extreme version of pressure autoregulation.
Recognise the role of the kidneys in regulating plasma volume and therefore blood pressure.
The role of the kidneys is for secretion and absorption of plasma fluids, by regulating how much fluid is reabsorbed from the secreted fluid is decided by the osmolarity generated by pumping sodium out. By increasing permeability of the collecting duct, it can increase blood pressure of vice versa.
Identify the receptors involved in sensing plasma volume.
Osmoreceptors in the hypothalamus for the interstitial fluid
baroreceptors in the aortic arch and the carotid sinus’s
juxtaglomerular cells in the kidney
myocardial cells in the atrium
Explain the effects of the sympathetic and parasympathetic systems on heart rate.
sympathetic system releases noradrenaline from nerves and the release of adrenaline from the adrenal medulla, increasing heart rate by acting on beta one receptors on the sinoatrial node. This is called tachycardia.
parasympathetic system the vagus nerve release acetylcholine acting on muscarinic receptors on the sinoatrial node to hyperpolarise cells and reduce heart rate which is called bradycardia.
Explain the effects of the sympathetic and parasympathetic systems on stroke volume.
the sympathetic system nerves release noradrenaline and stimulate the adrenal cortex to secrete adrenaline both operating on beta one receptors increasing contractility making it an inotrope, or a agent which alters contraction by giving a stronger but shorter contraction.
the parasympathetic system has very little effect since the vagus doesn’t innervate the ventricular muscle.
Explain the effects of preload and afterload on stroke volume.
an important component of preload is that the energy of contraction is as a result of the initial length of muscle. Preload thus is affected by the end diastolic volume, increasing it increases stroke volume and vice versa. Therefore, it is restricted to the influence of the capacitance vessels such as veins.
afterload is the load against what the muscle has to contract, this is determined by the cardiac output and the total peripheral resistance. Therefore, afterload is restricted to the arterioles. Increasing total peripheral resistance decreases stroke volume.
Recognise the effectiveness of treatment for hypertension in the young population.
hypertension treatment varies for young people with their main source of treatment consisting of ACE inhibitors or angiotensin receptor antagonists if not suitable then beta blocker, if this is ineffective they are then moved up to diuretics, then calcium channel blockers, normally though a younger person with high blood pressure will be referred to a specialist for treatment and screened for underlying causes
Recognise the effectiveness of treatment for hypertension in the elderly population.
For elderly people they are normally put onto calcium channel antagonists, then thiazide-type diuretic, if this is ineffective a combination of ACE inhibitors if viable, and anti-diuretics will be considered as well, then beta blockers. As well as less commonly used drugs in small doses. Co-morbidities have to be taken into account, and their target goal is higher than young people being <145/85.
define hypertension
the official definition is that saying when the benefits of treatment outweigh the risks in terms of morbidity and mortality.
hypertension is defined as an elevated normal blood pressure on a daily basis. There are several stages, with the first being stage one with 140/90mm Hg clinically or 135/85 daily, stage two 160/100 mm Hg clinically and 150/95 mmHg daily and stage three being anything above 180/110 mm Hg.
Know the aetiology of hypertension.
hypertension is one of the most leading causes of death in the world, It can be primary in nature as a result of lifestyle and idiopathic causes or it can be secondary due to renal or endocrine disease. Many factors are involved such sodium intake, environmental such as stress, genetic, lifestyle, smoking, alcohol intake, age or even birth weight etc.
Be able to discuss the outcome of untreated hypertension.
The outcome of untreated hypertension is severe muscle damage that increase exponentially the longer it is untreated and can likely lead to death either as the primary or secondary cause. Organs commonly effected are the kidneys through renal failure or renal arteriolar stenosis, retinopathy, left ventricular hypertrophy, cardiac heart disease, congestive heart failure, peripheral vascular disease, stroke, proteinuria, haemorrhage, MI and impaired cognitive abilities.
Define ischaemia, hypoxia and infarction.
ischaemia refers to the lack of oxygen to a tissue to meet its demands.
Hypoxia is either low oxygen level or low partial pressure of oxygen. It can be anaemic, with abnormal blood, stagnant hypoxia due to occlusion or shock and cytotoxic with abnormal transport of oxygen at tissues.
Explain the relationship between atheroma and ischaemia.
an atheroma, a localised accumulation of lipids encapsulated in fibrous tissue within the intima of arteries can reduce the flow of blood to an area altering the vessel structure resulting in ischaemia due to the fact oxygen is no longer reaching the tissues. It if it established this results in stable angina however any complications result in instability, ulceration, ischaemia, infarction and if it occurs in the aorta an aneurysm.
Describe the consequences of ischaemia
the consequences include infarction of the brain or heart, a transient Ischaemic attack (stroke like symptoms) cardiac failure, abdominal aneurysm, or peripheral vascular disease. This is because of the reduced oxygen to meet energy demands, often resulting in dysfunction, pain and cellular damage.
Recognise the supply and demand issues affecting the heart and coronary blood flow and the relevance of these issues to ischaemic heart disease
factors effect oxygen supply includes the percentage of air being inspired, the pulmonary function, the constituent and flow of blood, vessel structure and oxygen transport at tissues. Tissue’s requiring the oxygen have varying demands depending of their activity.
specifically, for the heart cardiac failure or atheroma disrupting the flow, or anything altering the pulmonary function such as an oedema or myocardial infarcture can reduce supply or anaemia.
This is the issue because the heart has a high intrinsic demand due to its constant exertion.
Understand the difference between subendocardial and transmural infarction of the myocardium and the clinical significance of the two types of infarct.
death of the myocardial tissue that extends from the endocardium to the epicardium as a result of myocardial infarction and it referred to as transmural, also known as a STEMI. A subendocardial infarction involves the innermost layer of the myocardium but doesn’t extend to the epicardium and is also referred to as a non-Stemi. With a STEMI complications such as a papillary muscle rupture are more likely.
Learn about the patho-physiology of mitral stenosis
when the valve becomes less than 2 cm2. The Left atrial pressure increases as well as pulmonary venous, and capillary increases. Pulmonary vascular resistance increases as well as pulmonary arterial pressure resulting in pulmonary hypertension. Right heart dilation occurs with tricuspid regurgitation and pulmonary regurgitation.
Learn about the patho-physiology of mitral regurgitation
effective regurgitation orifice not fixed, annular enlargement of contractility, afterload and preload. Left ventricular compensation. Acute has reduced end systolic pressure and volume as well as a drop-in tension. Chronically end diastolic volume increases and left ventricular hypertrophy develops. There is a reduction in left ventricle compliance due to thickening of the myocardium In response to increased pulmonary vascular resistance and remodelling, or it can be increased compliance due to enlargement but with atrial fibrillations.
Learn about the patho-physiology of aortic stenosis
if rheumatic there is adhesion/fusion of commissures and stiffening of cusp margins. However if degenerative lots of inflammation, thickening and calcification. As a result there is increased LV systolic pressure which results in hypertrophy increasing the left atrial pressure and left ventricular end diastolic pressure. This leads to increased myocardial oxygen consumption and eventually ischaemia leading to left ventricular failure.
Learn about the patho-physiology of aortic regurgitation
increased Left ventricular end diastolic volume systolic pressure, leading to hypertrophy and dilation. This results in increased oxygen consumption then ischaemia and heart failure.
Recognise the symptoms of mitral stenosis valve disease and natural progression of the disease
mitral stenosis; dyspnoea, haemoptysis, pulmonary oedema, systemic embolization, Left atrium enlargement, Chest pain, hoarseness due to compression of the Left recurrent laryngeal nerve and infective endocarditis
Recognise the symptoms of aortic stenosis valve disease and natural progression of the disease
aortic stenosis: asymptomatic but chest pain, syncope, breathlessness, heart failure.
Recognise the symptoms of mitral regurgitation valve disease and natural progression of the disease
mitral regurgitation: acute includes breathlessness, cardiogenic shock and pulmonary oedema. Chronically it can induce fatigue, exhaustion and right heart failure as well as dyspnoea or palpitations.
Recognise the symptoms of aortic regurgitation valve disease and natural progression of the disease
aortic regurgitation; chronic exertional breathlessness, acute is poorly tolerated.
Learn about the diagnostic investigations for mitral stenosis
: LA CXR enlargement, echocardiography (thickening and scarring, fusion of commissures)
Learn about the diagnostic investigations mitral regurgitation
ECG LA enlargement, Right ventricular hypertrophy. CXR shows cardiomegaly, Left atrium enlargement and calcification of mitral annulus.
Learn about the diagnostic investigations aortic stenosis
calcification of atrioventricular valves. Echocardiography demonstrates Lv hypertrophy, pressure gradient and AV cusp mobility.
Learn about the diagnostic investigations aortic regurgitation
ST wave changes on ECG, cardiomegaly in CXR. Echocardiography demonstrates thickening of cusps and vegetations, dilation, hypertrophy of LV and regurgitant flow.
treatment for aortic stenosis
aortic valve replacement or repair.
treatment for aortic regurgitation
vasodilator therapy to delay surgery. Aortic valve replacement or repair.
treatment for mitral stenosis
diuretics, NA restriction, sinus rhythm restoration or ventricular rate control. Anticoagulation. Interventional treatment includes a valvotomy or a mitral valve replacement
treatment for mitral regurgitation
acute MR requires preload/afterload reduction through sodium nitroprusside and dobutamine. Intervention requires mitral valve repair or replacement.
Describe the pathophysiology of stable angina
stable angina is the result of possible arteritis, artery spasm, anaemia, thyrotoxicosis, or structural changes in the heart such as left ventricular hypertrophy due to hypertension resulting in an increased oxygen and metabolite demand in which the supply cannot meet. More commonly it is the result of atheroma, a lipid encased in a fibrous shell that occludes a blood vessel, reducing blood flow in the coronary arteries to the heart. The lack of oxygen supply becomes increasing symptomatic upon aggravation through stress or exercise resulting in chest pain due to the section of the heart suffering from ischaemia not necrosis.