Cardiovascular physiology Flashcards
The first heart sound occurs at the same time as the ‘P’ wave on an ECG
False. The P wave signifies atrial depolarisation which triggers atrial systole hence occurs before the first heart sound.
The ‘R’ wave on an ECG coincides with ventricular isovolumetric contraction
True. Isovolumetric contraction occurs when both the mitral and aortic valves are closed. This pressure generating phase occurs with ventricular contraction triggered by excitation contraction coupling.
Diastolic pressures in the pulmonary artery are typically lower than those in the right ventricle
False. When a pulmonary artery catheter is floated diastolic pressure is seen to rise as the catheter tip leaves the RV and enters the pulmonary artery. Typical values PA= 25/15 vs RV = 25/8.
Isovolumetric relaxation is terminated when the atrial pressure exceeds that of the ventricle
True. Isovolumetric means both the inflow and outflow valves for that chamber are closed, hence the volume cannot change. When the pressure in the ventricle falls below that of the atria then the mitral valve will open and blood will flow down its pressure gradient to commence ventricular filling.
Left atrial pressures typically reach 10mmHg at the onset of atrial systole
True. During atrial systole the pressure will transiently rise higher as blood is ejected into the ventricle.
Regarding atrial pressure-time waveforms Atrial systole is associated with the ‘c’ wave
False. Atrial contraction is associated with the ‘a’ wave on the trace.
Regarding atrial pressure-time waveforms Over 90% of left ventricle (LV) filling occurs passively before the onset of atrial systole
False. Atrial systole contributes approximately 30% of ventricular filling. This is lost in atrial fibrillation.
Regarding atrial pressure-time waveforms The ‘x’ wave occurs as during the phase of ventricular diastole
False. The ‘x’ is a descent which corresponds to falling pressure within the atria during atrial relaxation. This occurs during ventricular systole where ventricular muscle contraction pulls the atrio-ventricular rings towards the apex of the heart, this “lengthens” the atria and causes pressure to fall within the atria.
Regarding atrial pressure-time waveforms Cannon ‘a’ waves are associated with atrial fibrillation
False. ‘a’ waves are absent in atrial fibrillation. Cannon waves are associated with heart block where there is dissociation between atrial and ventricular contraction and the atria contract against a closed tricuspid/ mitral valve.
Regarding atrial pressure-time waveforms Exaggerated ‘v’ waves are typical of tricuspid regurgitation
True. The ‘v’ wave is formed by passive filling of the atria. Regurgitant blood flowing back into the atria across the tricuspid valve increases the volume in the atria and exaggerates the ‘v’ wave.
Stroke volume is the left ventricular end-systolic volume divided by the left ventricular end diastolic volume
False. Stroke volume is defined as the volume of blood ejected from the ventricle. In an equation format = LV end diastolic volume – LV end systolic volume.
The area inside the pressure-volume loop for the left ventricle represents the stroke volume
False. The area inside the pressure-volume loop is the work done by the ventricle. The Stroke Volume is taken from the horizontal dimension of the loop as read from the x-axis.
Increasing preload typically shifts the pressure-volume loop upwards and to the right
True. Increasing preload increases the volume in the LV hence loop moves to the right. It also moves upwards due to the shape of the LV elastance curve.
Afterload may be indicated by the slope of a line joining the left ventricular end diastolic volume with the end-systolic point on a pressure-volume loop
True. This is correct. Increasing afterload will increase the gradient of this line.
The administration of catecholamines will rotate the Ees contractility line downwards towards the x-axis of the pressure volume loop
False. Increasing contractility increases the gradient of the Ees line, hence the line would rotate upwards towards the y-axis.
Blood flow during systole continues in the right coronary vessel
True. Flow is reduced (compared to diastolic flow) but continues in the right coronary during systole as the RV pressures are much lower than the left side of the heart.
Typical adult coronary blood flow is 500 mls/min at rest
False. Typical adult coronary blood flow is 200-250 mls/min (5% cardiac output).
The inner surface of the ventricle obtains O2 directly via diffusion from blood within its cavity
True. The immediate endocardial layer directly absorbs O2 from the blood within the cavity. The rest of the heart muscle relies on coronary perfusion.
Coronary blood flow is inversely related to heart rate
True. Coronary blood flow occurs predominantly during distole. As heart rate increases the absolute time for diastole shortens. This is compounded further by a relative shortening of diastole:systole ratio from typical 66:33 to 50:50. The shorter diastolic time therefore reduces time for coronary blood flow.
Aortic systolic pressure is the most significant determinant of coronary blood flow to the left ventricle
False. Coronary blood flow to the LV occurs predominantly in diastole, hence is determined by aortic diastolic pressure-intracardiac pressure (LVEDP).
Regarding cardiac pacemaker cells
Cardiac pacemaker cells have a stable resting membrane potential
False. Cardiac pacemaker cells have a spontaneously decaying membrane potential. This gives the property of automaticity.
Regarding cardiac pacemaker cells
Heart rate is determined by the slope of the pre-potential
True. The slope of the pre-potential determines the speed at which the cell reaches threshold and depolarises and hence determines heart rate.
Regarding cardiac pacemaker cells
Phase 3 is absent from the action potential
False. Phase 3 is the repolarisation phase. Phases 1 and 2 are absent.
Regarding cardiac pacemaker cells
The action potential will have a plateau phase
False. There is no plateau phase (Phase 2) in a pacemaker cell potential. This is a characteristic of a cardiac muscle cell potential.
Regarding cardiac pacemaker cells
Stimulation of the 10th cranial nerve causes increased potassium efflux during phase 4 of the pacemaker cell action potential
True. Stimulation of the 10th cranial nerve equates to parasympathetic stimulation. Increased potassium efflux renders the intracellular potential more negative and hence reduces the gradient of the pre-potential. This slows heart rate.
Regarding cardiac action potentials:
Adrenaline increases the slope of Phase 4 in an action potential from a cell in the sinoatrial node
True. Sympathetic stimulation increases the pre-potential gradient, leading to more frequent depolarisations and generating a faster heart rate.
Regarding cardiac action potentials:
The rapid depolarization in a cardiac ventricular muscle cell is due to the movement of sodium ions
True. The rapid depolarization (Phase 0) is due to the opening of voltage gated sodium channels.
Regarding cardiac action potentials:
The absolute refractory period of a ventricular muscle cell lasts until the action potential returns to the resting membrane potential
False. The absolute refractory period is the time at which the membrane potential lies above the threshold potential. This is followed by the relative refractory period where by potential is between threshold and the resting membrane potential. Further depolarisation is impossible during the absolute period but with an adequately strong stimulus could be generated during the relative period.
Regarding cardiac action potentials:
The phase 2 ‘plateau’ of a ventricular muscle cell action potential lasts for approximately 200 μs
False. The plateau phase lasts approximately 200-250 ms.
Regarding cardiac action potentials:
The resting membrane potential is maintained by a sodium-calcium pump
False. The resting membrane potential is maintained by an ATP driven sodium-potassium pump.
Regarding the action potential of a cardiac muscle cell:
At resting membrane potential (RMP) the cell membrane is more permeable to potassium than sodium
True. The membrane is approximately 100 fold more permeable to potassium than sodium at RMP.
Regarding the action potential of a cardiac muscle cell:
At RMP the ATP pump extrudes 2 sodium ions from the cell per 3 potassium ions pumped into the cell
False. The ATP pump extrudes three sodium ions in exchange for two potassium ions into the cell.
Regarding the action potential of a cardiac muscle cell:
Closure of L-type calcium channels in the plateau phase is a timed inactivation process.
True. L-type calcium channel closure is a time rather than a voltage triggered event
Regarding the action potential of a cardiac muscle cell:
Closure of L-type calcium channels in the plateau phase is a voltage triggered event.
False. Channel opening is a voltage triggered event however, closure is a time driven process.
Regarding the action potential of a cardiac muscle cell:
During the plateau phase movement of calcium is into the ventricular muscle cell
True. Calcium flows into the muscle cell through voltage gated calcium channels.
Regarding excitation-contraction coupling of a cardiac muscle cell:
Tetanic contraction is prevented by the relative refractory period
False. Tetanic contraction is prevented by the absolute refractory period, where by the membrane potential is above threshold and even a supra-maximal stimulus would be unable to generate further contraction.
Regarding excitation-contraction coupling of a cardiac muscle cell:
A typical resting sarcomere length is 2.2 μm
True.
Regarding excitation-contraction coupling of a cardiac muscle cell:
Calcium binds to Troponin-I
False. Calcium binds to Troponin -C. (Troponin-I binds to Actin and Troponin-T binds to Tropomyosin).
Regarding excitation-contraction coupling of a cardiac muscle cell:
Beta adrenergic stimulation increases calcium flow through L type channels
True. This is the mechanism by which sympathetic stimulation generates positive inotropy.
Regarding excitation-contraction coupling of a cardiac muscle cell:
The return of calcium from the cytoplasm back into the sarcoplasmic reticulum is an ATP dependent process
True. At the end of the plateau phase calcium is pumped back into the sarcoplasmic reticulum and out into the T-tubules by ATP driven calcium-magnesium pump.
Concerning electrocardiography:
CM5 configuration uses ECG electrodes in the V1, V5 and V6 positions
False. The electrode positions for CM5 configuration are: left clavicle, manubrium and V5. This view is very sensitive for detecting changes due to left ventricular ischaemia.
Concerning electrocardiography:
A normal cardiac axis is between
-90o and +30o
False. A normal cardiac axis is between -30° and +90°. (0° is taken as the lead I viewpoint). Anything +90° is termed right axis deviation.
Concerning electrocardiography:
Standard recording speed on an ECG is 25 mm/min
False. Standard recording speed on an ECG is 25 mm/s, not mm/min.
Concerning electrocardiography:
J waves may be seen in an ECG from a hypothermic patient
True. J waves are associated with hypothermia and are characterized by a ‘dome’ in the terminal portion of QRS complexes. The size of the wave often correlates with the severity of the hypothermia. May also be seen in hypercalcaemia, massive head injury and sub-arachnoid haemorrhage.
Concerning electrocardiography:A negative deflection is created by an electrical impulse travelling away from the recording electrode
True. An electrical impulse travelling directly towards the ECG electrode produces an upright (positive) deflection relative to the isoelectric baseline, whereas an impulse moving directly away from an electrode produces a downward (negative) deflection.
Concerning aortic valvular heart disease:
Anaesthetic management should favour peripheral vasodilation for a patient with aortic stenosis, to minimize resistance against which the LV ejects
False. It is important that peripheral vasodilatation is avoided in a patient with aortic stenosis. Coronary perfusion gradient must be preserved and is dependent on aortic diastolic pressure. Judicious use of peripheral vasoconstrictors to maintain aortic diastolic pressure is vital.
Concerning aortic valvular heart disease:
Critical aortic stenosis cannot be diagnosed unless the transvalve gradient exceeds 80 mmHg
False. The gradient that is achieved across the valve depends on the reduction in valve area and also the degree of LV pump function. If the LV function is poor a high gradient may not occur despite critical aortic stenosis. Valve area (cm2) is therefore a more reliable indicator of disease severity.
Concerning aortic valvular heart disease:
Angina is a recognized feature of aortic stenosis
True. Angina, heart failure and syncope make up a triad of symptoms associated with aortic stenosis.
Concerning aortic valvular heart disease:
An area of 1-1.5 cm2 is normal for an adult aortic valve
False. A normal adult aortic valve has an area of 2.5-3.5 cm2.
Concerning aortic valvular heart disease:
A wide pulse pressure is a feature of aortic regurgitation
True. Regurgitant flow back across the aortic valve into the LV causes a reduced diastolic pressure. This widens the pulse pressure (systolic - diastolic pressure) and is a classic feature of aortic regurgitation. By contrast, aortic stenosis is associated with a narrowed pulse pressure.
The correct position for the V1 electrode is the 4th intercostal space to the left of the sternum
False. V1 is positioned at the 4th intercostal space to the right of the sternum. It is V2 that is positioned at the 4th intercostal space to the left of sternum.
Lead II represents +60° on the axial referencing system
True. Lead II is at 60°, Lead I is termed 0° and Lead III at +120°. Knowledge of how the leads relate to the axial reference system allows the clinician to use ECG morphology in various leads to determine the cardiac axis.
Lead I is an example of a unipolar lead
False. The limb leads (I, II and III) are all bipolar leads. This means they record the potential difference between two active electrodes, e.g. for lead I this is between the left arm and right arm electrodes. The augmented limb leads (aVR, aVL, aVF) are unipolar leads. They record the potential difference between one active limb electrode and a composite reference electrode made by averaging the signals from the other limb leads at the centre of Einthoven’s triangle.
An inferior territory infarct is typically characterized by the mirror rule with deep ST depression noted in V1 to V4 leads
False. This is characteristic of a posterior territory infarct. Other changes include dominant R wave in V1-2 and upright T waves in V1-2. These changes are the most difficult of all the ischaemic territory changes to detect on ECG. Consider use of posterior ECG leads. Inferior territory infarcts typically affect leads II, III and aVF.
Mobitz type 1 block is characterized by progressive lengthening of the P-R interval
True. Mobitz type 1 is also called Wenckebach. It is associated with high vagal tone and may also occur following myocardial infarction. A repeating pattern of progressive P-R interval lengthens until a ventricular complex does not conduct and an isolated P wave occurs.
A regurgitant fraction of >0.3 indicates severe mitral regurgitation
False. In mitral regurgitation, the regurgitant fraction is measured as the ratio of the flow that leaves the left ventricle and enters the left atrium versus that which enters the aorta. A ratio of 0.3 indicates mild regurgitation and 0.6 indicates severe pathology.
NYHA Heart Failure Functional Class IV means that symptoms occur at rest and the patient is unable to carry out any physical activity without discomfort
True. Class IV is a functional assessment implying severe heart failure. Class III (moderate) means there is marked limitation of physical activity and less than ordinary activity causes fatigue, palpitation or dyspnoea.
Avoiding bradycardia is a key management principle when anaesthetising patients with severe mitral regurgitation
True. At slower heart rates, the increased systolic time means there is more time per cardiac cycle for regurgitation across the mitral valve.
Atrial fibrillation is often associated with mitral valve disease
True. In mitral regurgitation, the left atrial dimensions increase. This increases the chance that ectopic foci will discharge and atrial fibrillation occur. Because the atrial fibrillation is caused by a structural problem, the condition is often refractory to treatment that aims to maintain cardioversion to sinus rhythm.
30% of patients with aortic stenosis and normal coronary arteries have angina
True. In aortic stenosis, there is an increase in wall tension and increased myocardial oxygen demand. Coronary blood supply does not increase in proportion to the hypertrophied muscle mass and sub-endocardial ischaemia often occurs despite normal coronary vessels.
Which of the following statements about a Valsalva manoeuvre are correct? Can be described as a forced expiration against a closed glottis
True
Which of the following statements about a Valsalva manoeuvre are correct? Generates a decrease in intrathoracic pressure of 50 mmHg
False
It increases intrathroacic pressure by
40 mmHg
Which of the following statements about a Valsalva manoeuvre are correct: Generates an increase in intrathoracic pressure of 50 mmHg
False
It increases intrathroacic pressure by
40 mmHg
Which of the following statements about a Valsalva manoeuvre are correct? Is an example of autonomic control of heart rate
True
Which of the following statements about a Valsalva manoeuvre are correct? Is an example of autonomic control of blood pressure
True
Which of the following are appropriate uses of the Valsalva manoeuvre?
To test autonomic function
Correct. You use the Valsalva manouoevre to test autonomic function. It may also be useful if you suspect autonomic neuropathy, e.g. in diabetic patients.
Which of the following are appropriate uses of the Valsalva manoeuvre?
For cardioversion of a supra-ventricular tachyarrhythmia
Correct. You use the Valsalva manouoevre for cardioversion of a supra-ventricular tachyarrhythmia due to vagal slowing of heart rate in Phase IV of the manoeuvre.
Which of the following are appropriate uses of the Valsalva manoeuvre?
In diagnostic assessment of cardiac murmurs
Correct. The Valsalva manouoevre can help in the diagnostic assessment of cardiac murmurs. All heart murmurs decrease in loudness during a Valsalva, apart from the murmurs associated with mitral valve prolapse and hypertrophic obstructive cardiomyopathy which become more prominent.
Which of the following are appropriate uses of the Valsalva manoeuvre?
To reduce intrathoracic or intra-abdominal pressure
Incorrect. You use the Valsalva manouoevre to achieve elevated intra-thoracic and intra-abdominal pressures during ‘straining’ or for vaginal delivery.
Which of the following are appropriate uses of the Valsalva manoeuvre?
To clear middle ear congestion
Correct. Clearing middle ear congestion was the original descriptor of the technique by Valsalva, in 1704.
Baroreceptors are located in the carotid bodies
False. Baroreceptors respond to tension across a structure. They are located in the carotid sinus, aorta and heart. The carotid sinus is an enlargement of the internal carotid artery and lies just above the carotid bifurcation.
The glossopharyngeal nerve is one of the stimulating pathways linking baroreceptors to the vasomotor centre
True. The afferent neuronal pathway from the carotid sinus baroreceptors to the vasomotor centre is via the Nerve of Hering, a branch of the glossopharyngeal nerve. Baroreceptors from the aorta and heart project via the Vagus nerve.
In response to the sudden loss of 1000 ml of blood in an adult, Starling forces can mobilize 1 ml/kg/min from the interstital volume to the intravascular volume
False. Mobilization of interstitial fluid back into the intravascular compartment in response to a fall in capillary hydrostatic pressure in sudden haemorrhage can generate approximately 0.25 ml/kg/min fluid volume. This is one of the compensatory mechanisms to try and maintain an effective circulating volume.
A true Valsalva requires the generation of 40 mmHg intrathoracic pressure
True. The defining characteristic of a Valsalva manoeuvre is the generation of raised intra-throacic pressure of at least 40 mmHg.
High reticulocyte count is a late feature of compensation for haemorrhage
True. Late features of compensation for haemorrhage include restoration of red blood cell and haemoglobin levels. Reticulocytes are released from bone marrow and levels typically peak at the tenth day post haemorrhage. Erythropoetin secretion and liver synthesis of plasma proteins also occurs.
Which of the following statements concerning the sympathetic pathways involved in blood pressure control are true?
Pre-ganglionic fibres in the sympathetic nervous system are typically long and unmyelinated
False. Pre-ganglionic sympathetic fibres are typically short. They are myelinated structures and are classed as B fibres in the Erlanger and Gasser classification system. Other nerve fibre types in this classification are: Aα, Aβ, Aγ, Aδ, and C fibres.
Which of the following statements concerning the sympathetic pathways involved in blood pressure control are true?
Synaptic transmission between pre- and post-ganglionic sympathetic fibres use noradrenaline as the neurotransmitter
False. Synaptic transmission between pre- and post-ganglionic fibres in both the sympathetic and parasympathetic nervous system uses ACh. This acts on nicotinic receptors.
Which of the following statements concerning the sympathetic pathways involved in blood pressure control are true?
Blood vessels in skeletal muscle have noradrenergic post-ganglionic transmission
False. The majority of blood vessels receive noradrenergic stimulation from the post-ganglionic sympathetic fibres, however there are a few groups which have different neurotransmitters. Blood vessels in skeletal muscle typically have post-ganglionic sympathetic cholinergic transmission (on to muscarinic receptors) and some renal vessels have dopaminergic transmission (D1 receptors).
Which of the following statements concerning the sympathetic pathways involved in blood pressure control are true?
The adrenal medulla receives sympathetic stimulation directly from a pre-ganglionic nerve fibre
True. The adrenal medulla receives sympathetic stimulation directly from a pre-ganglionic nerve fibre. This releases ACh, which acts on nicotinic receptors to stimulate the adrenal gland to release adrenaline and noradrenaline into the blood stream.
Which of the following statements concerning the sympathetic pathways involved in blood pressure control are true?
Sympathetic ganglia are typically located near to or in the walls of the organs they innervate
False. The majority of pre-ganglionic sympathetic fibres synapse with post-ganglionic fibres in the paravertebral chain. This means that pre-ganglionic sympathetic fibres are typically short, the ganglia are located far away from the target organ and the post-ganglionic fibres are long structures. The reverse is true in the parasympathetic nervous system where pre-ganglionic fibres are typically long with respect to the length of their post-ganglionic counterparts and the ganglia are found close to or often within the walls of the target organ.
The Valsalva ratio describes the ratio of the maximum heart rate in Phase IV divided by the minimum heart rate of Phase II
False. One of the methods by which the Valsalva ratio can be calculated is to divide the maximum heart rate in Phase II by the minimum heart rate in Phase IV.
A Valsalva manoeuvre may assist in the diagnosis of hypertrophic obstructive cardiomyopathy
True. Almost all cardiac murmurs decrease in intensity during a Valsalva manoeuvre; apart from the murmurs associated with mitral valve prolapse and hypertrophic cardiomyopathy.
A patient who is alpha-blocked has an exaggerated blood pressure rise in phase IV of a Valsalva manoeuvre
True. Alpha blockade prevents vasoconstriction during the body’s attempt to restore cardiac output in Phase II therefore there is an exaggerated increase in heart rate. When strain is released and venous return is restored to the heart, the elevated heart rate increases cardiac output and causes overshoot in blood pressure.
Standing from the supine position will lead to reduced renin secretion
False. Standing from the supine position leads to a fall in renal perfusion pressure. The effect of this would be to stimulate renin secretion.
The blood volume in the pulmonary circulation falls when a patient stands up from the supine position
True. The lungs and liver both act as reservoirs of circulating volume. When a change in posture or haemorrhage occurs then sympathetic stimulation triggers venoconstriction which mobilizes blood in these areas into the effective circulating volume.
Class II haemorrhage implies a blood volume loss of between 30-40%
False. Class II haemorrhage is between 15-30% volume loss. Clinical features of this are likely to include anxiety, tachycardia, tachypnoea and a narrowed pulse pressure. Urine output <0.5 ml/kg/h. Class III haemorrhage is a volume loss of 30-40%.
Volureceptors and baroreceptors are efferents in the body’s response to haemorrhage
False. Volureceptors are located in the right atrium and great veins. Baroreceptors are found in the carotid sinus. They are afferents because they respectively sense a change in volume or pressure status and relay this via neuronal pathways. To respond to these changes, various efferent pathways, including sympathetic activation and endocrine signalling, are triggered.
Regarding haemorrhage and the body’s response to haemorrhage:
Aldosterone secretion is suppressed
False. Aldosterone secretion is stimulated by haemorrhage. The reduced blood volume leads to a fall in renal perfusion pressure. This triggers the secretion of renin from the juxta-glomerular apparatus which via the renin-angiotensin-aldosterone cascade triggers aldosterone secretion. Aldosterone promotes renal retention of sodium (and hence water) at the expense of potassium excretion.
Regarding haemorrhage and the body’s response to haemorrhage:
ADH is a vasoconstrictor
True. ADH triggers thirst, promotes renal conservation of water in the collecting ducts and at higher concentrations is a potent vasoconstrictor.
Regarding haemorrhage and the body’s response to haemorrhage:
Arterial constriction mobilizes blood from reservoirs in the lungs, liver and muscle beds
False. Blood held in reservoirs in the lungs, liver and muscle beds can be mobilized into the circulation to form part of the effect circulating volume. This is achieved by venoconstriction because it is the venous system that acts as the reservoir volume in these organs.
Transfusion of 1 litre of 0.9% saline into a healthy normovolaemic adult should trigger volureceptor stimulation
False. Volureceptor stimulation requires a change of 8-10% for the threshold to be exceeded. A transfusion of 0.9% saline distributes throughout the whole of the ECF compartment. The ratio of the fluid compartment sizes within the ECF is 25% intravascular:75% interstitium. This means that out of the 1000 ml infused, only 250 ml remains in the intravascular space and 750 ml moves into the interstitium. This 250 ml increase in intravascular volume is less than the 8-10% threshold (400-500 ml) that is required for volureceptor stimulation.
Transfusion of 1 litre of 5% glucose into a healthy normovolaemic adult results in approximately 250 ml remaining in the intravascular space
False. 5% glucose distributes freely across all of the fluid body compartments. The glucose is taken up into the cells and metabolized, which leaves free water. Per 1000 ml infused, only 85 ml remains intravascularly (660 ml intraceullar fluid, 340 ml extracellular fluid; of which 25% intravascular (85 ml) and 75% interstitial (255 ml)).
The threshold change for osmoreceptor activation is 5%
False. The threshold change for osmoreceptor activation is 1-2%. This is because the body needs to be able to closely regulate alterations in serum osmolality.
A fall in serum osmolality suppresses ADH release
True. A fall in serum osmolality inhibits ADH secretion. ADH inhibition promotes diuresis and tries to normalize the serum osmolality.
ADH is secreted from the anterior pituitary gland
False. ADH is a nonapeptide hormone. It is secreted from the posterior pituitary.
Coronary blood flow:
Is approximately 500ml/min at rest
False
Coronary blood flow:
Supplies muscle that extracts 40 ml/l of oxygen per minute at rest
False
Coronary blood flow:
Is altered directly by vagal activity
False
Coronary blood flow:
Ceases in sytole
False
Coronary blood flow:
Undergoes autoregulation
True
In the Cardiac cycle:
Left ventricular volume is maximal at the end of atrial systole
True
In the Cardiac cycle:
The mitral valve closes by contraction of the papillary muscles
False
In the Cardiac cycle:
The left ventricular pressure is maximal just before the aortic valve opens
False
In the Cardiac cycle:
The ejection fraction is normally about 85%
False
In the Cardiac cycle:
The dichrotic notch is due to rebound of the aortic wall
True
In a healthy adult human heart the:
Left ventricular end systolic volume is approximately 30ml
True
In a healthy adult human heart the:
First heart sound coincides with the onset of ventricular systole
True
In a healthy adult human heart the:
Stroke volume is approx 70ml
True
In a healthy adult human heart the:
Left ventricular end-diastolic pressure is about 500 mmHg
False
In a healthy adult human heart the:
Second heart sound is caused by closure of the aortic and pulmonary valves
True
Pulmonary vascular resistance:
Is increased in chronic hypoxia
True
Pulmonary vascular resistance:
Has a valve approximately one-sixth that of the systemic circulation
True
Pulmonary vascular resistance:
Can be measured using a flow-directed balloon catheter with a thermistor tip
True
Pulmonary vascular resistance:
Is increased by isoprenaline
False
Pulmonary vascular resistance:
Is decreased by 5-hydroxytryptamine
False
In the normal adult heart:
Mitral Valve closure occurs before tricuspid valve closure
True
