Cardiovascular physiology Flashcards
1
Q
The first heart sound occurs at the same time as the ‘P’ wave on an ECG
A
False. The P wave signifies atrial depolarisation which triggers atrial systole hence occurs before the first heart sound.
2
Q
The ‘R’ wave on an ECG coincides with ventricular isovolumetric contraction
A
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.
3
Q
Diastolic pressures in the pulmonary artery are typically lower than those in the right ventricle
A
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.
4
Q
Isovolumetric relaxation is terminated when the atrial pressure exceeds that of the ventricle
A
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.
5
Q
Left atrial pressures typically reach 10mmHg at the onset of atrial systole
A
True. During atrial systole the pressure will transiently rise higher as blood is ejected into the ventricle.
6
Q
Regarding atrial pressure-time waveforms Atrial systole is associated with the ‘c’ wave
A
False. Atrial contraction is associated with the ‘a’ wave on the trace.
7
Q
Regarding atrial pressure-time waveforms Over 90% of left ventricle (LV) filling occurs passively before the onset of atrial systole
A
False. Atrial systole contributes approximately 30% of ventricular filling. This is lost in atrial fibrillation.
8
Q
Regarding atrial pressure-time waveforms The ‘x’ wave occurs as during the phase of ventricular diastole
A
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.
9
Q
Regarding atrial pressure-time waveforms Cannon ‘a’ waves are associated with atrial fibrillation
A
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.
10
Q
Regarding atrial pressure-time waveforms Exaggerated ‘v’ waves are typical of tricuspid regurgitation
A
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.
11
Q
Stroke volume is the left ventricular end-systolic volume divided by the left ventricular end diastolic volume
A
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.
12
Q
The area inside the pressure-volume loop for the left ventricle represents the stroke volume
A
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.
13
Q
Increasing preload typically shifts the pressure-volume loop upwards and to the right
A
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.
14
Q
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
A
True. This is correct. Increasing afterload will increase the gradient of this line.
15
Q
The administration of catecholamines will rotate the Ees contractility line downwards towards the x-axis of the pressure volume loop
A
False. Increasing contractility increases the gradient of the Ees line, hence the line would rotate upwards towards the y-axis.
16
Q
Blood flow during systole continues in the right coronary vessel
A
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.
17
Q
Typical adult coronary blood flow is 500 mls/min at rest
A
False. Typical adult coronary blood flow is 200-250 mls/min (5% cardiac output).
18
Q
The inner surface of the ventricle obtains O2 directly via diffusion from blood within its cavity
A
True. The immediate endocardial layer directly absorbs O2 from the blood within the cavity. The rest of the heart muscle relies on coronary perfusion.
19
Q
Coronary blood flow is inversely related to heart rate
A
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.
20
Q
Aortic systolic pressure is the most significant determinant of coronary blood flow to the left ventricle
A
False. Coronary blood flow to the LV occurs predominantly in diastole, hence is determined by aortic diastolic pressure-intracardiac pressure (LVEDP).
21
Q
Regarding cardiac pacemaker cells
Cardiac pacemaker cells have a stable resting membrane potential
A
False. Cardiac pacemaker cells have a spontaneously decaying membrane potential. This gives the property of automaticity.
22
Q
Regarding cardiac pacemaker cells
Heart rate is determined by the slope of the pre-potential
A
True. The slope of the pre-potential determines the speed at which the cell reaches threshold and depolarises and hence determines heart rate.
23
Q
Regarding cardiac pacemaker cells
Phase 3 is absent from the action potential
A
False. Phase 3 is the repolarisation phase. Phases 1 and 2 are absent.
24
Q
Regarding cardiac pacemaker cells
The action potential will have a plateau phase
A
False. There is no plateau phase (Phase 2) in a pacemaker cell potential. This is a characteristic of a cardiac muscle cell potential.
25
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.
26
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.
27
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.
28
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.
29
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.
30
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.
31
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.
32
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.
33
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
34
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.
35
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.
36
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.
37
Regarding excitation-contraction coupling of a cardiac muscle cell:
A typical resting sarcomere length is 2.2 μm
True.
38
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).
39
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.
40
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.
41
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.
42
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.
43
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.
44
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.
45
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.
46
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.
47
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.
48
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.
49
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.
50
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.
51
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.
52
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.
53
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.
54
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.
55
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.
56
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.
57
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.
58
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.
59
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.
60
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.
61
Which of the following statements about a Valsalva manoeuvre are correct? Can be described as a forced expiration against a closed glottis
True
62
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
63
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
64
Which of the following statements about a Valsalva manoeuvre are correct? Is an example of autonomic control of heart rate
True
65
Which of the following statements about a Valsalva manoeuvre are correct? Is an example of autonomic control of blood pressure
True
66
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.
67
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.
68
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.
69
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.
70
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.
71
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.
72
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.
73
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.
74
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.
75
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.
76
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.
77
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.
78
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).
79
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.
80
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.
81
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.
82
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.
83
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.
84
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.
85
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.
86
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%.
87
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.
88
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.
89
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.
90
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.
91
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.
92
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)).
93
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.
94
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.
95
ADH is secreted from the anterior pituitary gland
False. ADH is a nonapeptide hormone. It is secreted from the posterior pituitary.
96
Coronary blood flow:
| Is approximately 500ml/min at rest
False
97
Coronary blood flow:
| Supplies muscle that extracts 40 ml/l of oxygen per minute at rest
False
98
Coronary blood flow:
| Is altered directly by vagal activity
False
99
Coronary blood flow:
| Ceases in sytole
False
100
Coronary blood flow:
| Undergoes autoregulation
True
101
In the Cardiac cycle:
| Left ventricular volume is maximal at the end of atrial systole
True
102
In the Cardiac cycle:
| The mitral valve closes by contraction of the papillary muscles
False
103
In the Cardiac cycle:
| The left ventricular pressure is maximal just before the aortic valve opens
False
104
In the Cardiac cycle:
| The ejection fraction is normally about 85%
False
105
In the Cardiac cycle:
| The dichrotic notch is due to rebound of the aortic wall
True
106
In a healthy adult human heart the:
| Left ventricular end systolic volume is approximately 30ml
True
107
In a healthy adult human heart the:
| First heart sound coincides with the onset of ventricular systole
True
108
In a healthy adult human heart the:
| Stroke volume is approx 70ml
True
109
In a healthy adult human heart the:
| Left ventricular end-diastolic pressure is about 500 mmHg
False
110
In a healthy adult human heart the:
| Second heart sound is caused by closure of the aortic and pulmonary valves
True
111
Pulmonary vascular resistance:
| Is increased in chronic hypoxia
True
112
Pulmonary vascular resistance:
| Has a valve approximately one-sixth that of the systemic circulation
True
113
Pulmonary vascular resistance:
| Can be measured using a flow-directed balloon catheter with a thermistor tip
True
114
Pulmonary vascular resistance:
| Is increased by isoprenaline
False
115
Pulmonary vascular resistance:
| Is decreased by 5-hydroxytryptamine
False
116
In the normal adult heart:
| Mitral Valve closure occurs before tricuspid valve closure
True
117
In the normal adult heart:
| Pulmonary valve closure occurs before aortic valve closure
False
118
In the normal adult heart:
| There is isometric contraction of the left ventricle after the aortic valve opens
False
119
In the normal adult heart:
| Atrial contraction is of more importance to ventricular filling if the heart rate increases
True
120
In the normal adult heart:
| The aortic valve cusps are immobile during ventricular filling
True
121
The pressure:
| Drop across major veins is similar to that across the major arteries
True
122
The pressure:
| Drop across the hepatic portal bed is similar to that across the splenic vascular bed
False
123
The pressure:
| In the hepatic portal vein is approximately 3 times higher than that in the inferior vena cava
False
124
The pressure:
| Drop across the vascular bed in the foot is greater when standing than when lying down
False
125
The pressure:
| Drop across the pulmonary circulation is the same as across the systemic circulation
False
126
In the central venous pressure waveform:
| The c wave occurs after ventricular systole
False
127
In the central venous pressure waveform:
| The v wave is caused by atrial contraction
False
128
In the central venous pressure waveform:
| The a wave is absent in AF
True
129
In the central venous pressure waveform:
| The a wave corresponds with the closure of the aortic valve
False
130
In the central venous pressure waveform:
| The v wave occurs during diastole
True
131
With reference to the mechanical events in the cardiac cycle in a normal adult human:
The left ventricle ejects more blood per beat than the right ventricle
False
132
With reference to the mechanical events in the cardiac cycle in a normal adult human:
The mitral valve opens when the left atrial pressure exceeds the left ventricular pressure
True
133
With reference to the mechanical events in the cardiac cycle in a normal adult human:
During strenuous work, the left ventricular end diastolic volume may be double than at rest
False
134
With reference to the mechanical events in the cardiac cycle in a normal adult human:
The pulmonary valve opens when the right ventricular pressure reaches 20-25 mmHg
False
135
With reference to the mechanical events in the cardiac cycle in a normal adult human:
During diastole, the left ventricular pressure is about 70 mmHg
False
136
Myocardial contractility:
| Is the degree of the ionotropic state of the heart independent of preload, afterload or HR
True
137
Myocardial contractility:
| Determines the rate of development of ventricular pressure
True
138
Myocardial contractility:
| Can be estimated by ventricular pressure-volume loops
True
139
Myocardial contractility:
| Is reduced by hypocalcaemia
True
140
Myocardial contractility:
| Accounts for approx 90% of total myocardial O2 consumption
True
141
On changing from the upright to the supine position:
| Barorecptor firing rate decreases
False
142
On changing from the upright to the supine position:
| Leg vein pressure is reduced
True
143
On changing from the upright to the supine position:
| The blood volume in the pulmonary circulation falls
False
144
On changing from the upright to the supine position:
| Stroke volume increases
True
145
On changing from the upright to the supine position:
| Renin activity increases
False
146
The following are true about the fetal circulation:
| The PaO2 in the descending aorta is lower than that in the aortic arch
True
147
The following are true about the fetal circulation:
| The ductus venosus contains mixed venous blood
False
148
The following are true about the fetal circulation:
| The ductus arteriosus closes due to the rie in the systemic blood pressure
False
149
The following are true about the fetal circulation:
| Closure of the foramen ovale is due to the change in the left and right atrial pressure
True
150
The following are true about the fetal circulation:
| Blood entering the right atrium can reach the systemic circulation without passing through the left side of the heart
True
151
Chemoreceptors in the arterial system:
| Have a higher rate of oxygen consumption per gram than brain tissue
False
152
Chemoreceptors in the arterial system:
| Respond to changes on O2 tension not content
True
153
Chemoreceptors in the arterial system:
| Respond to changes in pH
True
154
Chemoreceptors in the arterial system:
| Conduct afferent information via the glossopharyngeal and vagus nerves
True
155
Chemoreceptors in the arterial system:
| Are found in the carotid sinus
False
156
The following statements are true
| Of the major organs, the heart has the highest A-V O2 difference
True
157
The following statements are true
| Arterial baroreceptors respond to pressure
True
158
The following statements are true
| Each kidney receives about 10% of the cardiac output
True
159
The following statements are true
| On the ECG, lead II is from the left arm to the left leg
False
160
The following statements are true
| LV diastolic compliance fall sharply above a volume of 70ml
False
161
The vagus:
| Innervates the heart primarily via M3 receptors
False
162
The vagus:
| Increases L-type calcium channel opening
False
163
The vagus:
| Slows conduction through the A-V node
True
164
The vagus:
| Lowers the trough potential of he sino-atrial node
True
165
The vagus:
| Is the dominant autonomic effect as rest
True
166
Myocardial contractility is enhanced by:
| Glucagon
True
167
Myocardial contractility is enhanced by:
| Noradrenaline
True
168
Myocardial contractility is enhanced by:
| A decrease in arterial pH
False
169
Myocardial contractility is enhanced by:
| An increase in vagal tone
False
170
Myocardial contractility is enhanced by:
| A fall in extracellular calcium concentration
False
171
Regarding the heart and major vessels:
| The right ventricle is normally about 8-10mm thick
False
172
Regarding the heart and major vessels:
| The right pulmonary artery passes beneath the aortic arch
True
173
Regarding the heart and major vessels:
| The normal pulmonary artery pressure s 25/10 mmHg
True
174
Regarding the heart and major vessels:
| All cardiac valves have three leaflets
False
175
Regarding the heart and major vessels:
| The tricuspid valve is anchroed by chordae tendineae
True
176
The following are normal values:
| Right ventricular presure 25/0 mmHg
True
177
The following are normal values:
| Pulmonary capillary hydrostatic pressure 10 mmHg
True
178
The following are normal values:
| Glomerular capillary hydrostatic pressure 30 mmHg
False
179
The following are normal values:
| Plasma oncotic pressure 25 mmHg
True
180
The following are normal values:
| Right ventricular end-diastolic volume 110ml
True
181
When considering fluid movement at the level of the capillary:
The biggest component of plasma osmotic pressure is generated by electrolytes
True
182
When considering fluid movement at the level of the capillary:
Oncotic pressure is approximately one fifth of total plasma osmotic pressure
False
183
When considering fluid movement at the level of the capillary:
Electrolytes can move freely between plasma and interstitial fluid
True
184
When considering fluid movement at the level of the capillary:
There is net inward movement of fluid at the venous end
True
185
When considering fluid movement at the level of the capillary:
Apporx 2l of fluid per day return via the lymphatic system
True
186
The following produce a fall in systemic vascular resistance:
Hypercapnia
True
187
The following produce a fall in systemic vascular resistance:
Pregnancy
True
188
The following produce a fall in systemic vascular resistance:
Increased intracranial pressure
False
189
The following produce a fall in systemic vascular resistance:
ANP
True
190
The following produce a fall in systemic vascular resistance:
Chnaing from fetal to adult circulation
False
191
Cardiac output increases with:
| Heart rate
True. CO = HR X SV. An increase in heart rate will increase cardiac output until the point where filling time is compromised.
192
Cardiac output increases with:
| Increased systemic vascular resistance
False. Increased SVR results in increased afterload and a reduced cardiac output.
193
Cardiac output increases with:
| A decrease in dp/dt
False. dp/dt represents contractility.
194
Cardiac output increases with:
| Hyperkalaemia
False. Hyperkalaemia has a negative ionotropic effect.
195
Cardiac output increases with:
| An increase in LVEDV
True. LVEDV represents preload.
196
Concerning the cardiac cycle:
| Aortic blood flow is lowest at the end of diastole
False. It is lowest in early diastole.
197
Concerning the cardiac cycle:
| Aortic pressure is highest in mid systole
True
198
Concerning the cardiac cycle:
| Atrial contraction can account for 40% of ventricular filling
True. At rest it is normally closer to 20%, but increases to as much as 40% with tachycardia.
199
Concerning the cardiac cycle:
| The QRS complex on the ECG occurs immediately before the rapid ejection phase
False. The QRS complex occurs immediately before isovolumetric contraction.
200
Concerning the cardiac cycle:
| The aortic valve opens at the start of ventricular systole
False. The initial phase of ventricular contraction is isovolumetiric, with the aortic valve closed. Once LV pressure exceeds aortic pressure, the aortic valve opens.
201
Responses to acute haemorrhage may include:
| Reduced ADH secretion
False. AdH secretion increases
202
Responses to acute haemorrhage may include:
| Increased sympathetic output
True. Initially, sympathetic nerve activity is increased. When blood volume is critically depleted, peripheral sympathetic drive falls steeply.
203
Responses to acute haemorrhage may include:
| Reduced baroreceptor discharge
True. The baroreceptors increase efferent output in response to stretch.
204
Responses to acute haemorrhage may include:
| Increased glucagon release
True.
205
Responses to acute haemorrhage may include:
| Increased interstitial fluid formation
False. Fluid enters the capillaries from the interstitium as a result of reduced hydrostaic capillary pressure.
206
In the fetal circulation at birth:
| The pulmonary vascular resistance halves
False. With the first gasp, PVR falls by > 80%.
207
In the fetal circulation at birth:
| Systemic vascular resistance rises
True. Largely due to intense vasoconstriction of the umbilical vessels.
208
In the fetal circulation at birth:
| Left atrial pressure rises
True. Due to increase pulmonary blood flow.
209
In the fetal circulation at birth:
| The ductus arteriosus should close within 48 hours
True. A High PaO2 appears to initiate closure. Prostaglandins maintain its patency.
210
In the fetal circulation at birth:
| The foramen ovale fuses
False. It closes as left atrial pressure rises, but does not fuse for around 48 hours.
211
The following increase the movement of fluid out of capillaries:
Venous hypertension
True.
212
The following increase the movement of fluid out of capillaries:
Decrease in oncotic pressure
True.
213
The following increase the movement of fluid out of capillaries:
Arteriolar vasoconstriction
False.
Factors which increase flow out of capillaries are increased capillary hydrostatic pressure, increased interstitial colloid osmotic pressure, reduced interstitial hydrostatic pressure or reduced colloid oncotic pressure. In certain conditions (eg sepsis) the permeability coefficient may be altered.
214
The following increase the movement of fluid out of capillaries:
Hypotension
False.
Factors which increase flow out of capillaries are increased capillary hydrostatic pressure, increased interstitial colloid osmotic pressure, reduced interstitial hydrostatic pressure or reduced colloid oncotic pressure. In certain conditions (eg sepsis) the permeability coefficient may be altered.
215
The following increase the movement of fluid out of capillaries:
Decrease in hydrostatic pressure in capillaries
False.
Factors which increase flow out of capillaries are increased capillary hydrostatic pressure, increased interstitial colloid osmotic pressure, reduced interstitial hydrostatic pressure or reduced colloid oncotic pressure. In certain conditions (eg sepsis) the permeability coefficient may be altered.
216
The a-wave in the jugular venous pulse:
| Is caused by atrial filling during ventricular systole
False. This would be the v-wave. The a-wave is due to atrial contraction.
217
The a-wave in the jugular venous pulse:
| Is elevated in tricuspid stenosis
True.
218
The a-wave in the jugular venous pulse:
| Is elevated in atrial fibrillation
False. It is absent in atrial fibrillation due to the lack of atrial contraction.
219
The a-wave in the jugular venous pulse:
| Is elevated in tricupid regurgitation
False. The v-wave is elevated in tricupid regurgitation.
220
The a-wave in the jugular venous pulse:
| When enlarged are known as canon waves
True. Canon waves are large waves corresponding to atrial contraction against a closed tricuspid valve. They are seen in complete heart block or junctional arrhythmias.
221
In cardiac ventricular muscle:
| Cells exhibit automaticity
False. This behaviour is exhibited primarily by pacemaker cells allowing spontaneous depolarisation. However if this apparatus is disrupted an escape rhythm may originate from in/below the AV node in a junctional escape rhythm, or in the Purkinje fibres in a ventricular escape rhythm.
222
In cardiac ventricular muscle:
| The cells membranes are largely impermeable to negatively charged ions
True. These include proteins, sulphates and phosphates which thus remain intracellularly and contribute to the negative RMP.
223
In cardiac ventricular muscle:
| Depolarization is followed by a plateau potential lasting about 200 ms
True. Due to Calcium influx via slow L-type calcium channels
224
In cardiac ventricular muscle:
| Rapid depolarzsation is mainly due to calcium influx throught transient (T-type) calcium channels.
False. Rapid depolarization of myocardial cells is due to sodium influx. Depolarisation of slow-response action potentials of pacemaker cells is due to calcium influx throught transient (T-type) calcium channels.
225
In cardiac ventricular muscle:
| Cannot be tetanized
True. The prolonged refractory period prevents tetany.
226
Concerning coronary blood flow:
| It is increased during hypoxia
True. Hypoxia increases coronary blood flow 2-3 fold.
227
Concerning coronary blood flow:
| It is approximately 25% of the cardiac output at rest
False. Normal coronary blood flow at rest is approximately 250 ml/min or 5% of the cardiac output.
228
Concerning coronary blood flow:
| Significant right coronary artery perfusion occurs during systole
True. Unlike the left ventricle, the right ventricle receives most perfusion during systole due to its lower wall pressures.
229
Concerning coronary blood flow:
| The coronary cirulation has the highest A-V oxygen difference of all the major organs
True. The myocardium extracts 70% of oxygen
230
Concerning coronary blood flow:
| Coronary blood flow is regulated via the baroreceptor reflexes
True. Aortic pressure provides the main driving force for coronary blood flow and this pressure is controlled by baroreceptor reflexes. Flow is also affected by many local factors, including systolic compression and local metabolic factors.
231
Cardiac excitation in the normal heart:
| Is initiated spontaneously in the sino-atrial (SA) node
True.
232
Cardiac excitation in the normal heart:
| Transmission through the atrium takes 0.4 s
False. Transmission through the atrium and the AV node to the venticular myocardium takes 0.2 s.
233
Cardiac excitation in the normal heart:
| The AV node allows rapid transmission of electrical excitation to the ventricle
False. Transmission is slowest at the AV node.
234
Cardiac excitation in the normal heart:
| The preferential route of transmission from right to left atrium is via Bachmann's bundle
True. Also known as the anterior interatrial band.
235
Cardiac excitation in the normal heart:
| Gap junctions allow the myocardium to act as a single contractile unit
True. Gap junctions are located at the intercalated disc and allow electrical impulses to propagate freely.
236
The Valsalva Manoeuvre:
| At the onset of the Valslava manouvre arterial pressure rises
True. Due to the the effect of increased intrathoracic pressure on the aorta.
237
The Valsalva Manoeuvre:
| The reduced arterial pressure seen during the Valslva manouvre will be exagerated in hypovolaemia
True. After the initial rise, BP then falls due to the effect of raised intrathoracic pressure on venous return - this will be more pronounced in the hypovolaemic and can result in cardiovascular collapse.
238
The Valsalva Manoeuvre:
| Heart rate changes are mediated via the aortic chemoreceptors
False. Pressure changes are detected by baroreceptors.
239
The Valsalva Manoeuvre:
| The bradycardia seen after the termination of the manouvre is absent in most long-standing diabetics
False. Autonomic neuropathy results in an absence of heart rate changes, but this is seen in only 20-40% of long-standing diabetics.
240
The Valsalva Manoeuvre:
| Increases the intensity of the heart mumur associated with aortic stenosis.
False. It increases the murmur of mitral regurgitation, but most other mumurs are decreased.
241
At birth:
| The foramen ovale closes because of a reversal of the pressure gradient between the left and right atria
True.
At birth, pulmonary vascular resistance falls markedly as the lungs expand and fill with air. This decreases pulmonary artery pressures and increases blood flow to the left atrium.
242
At birth:
| The ductus arteriosus closes because of a respiratory acidosis
False. The ductus arteriosus closes functionally soon after birth (usually within 24 hours) due to exposure to oxygenated blood and reduced prostaglandin-E2.
243
At birth:
| Blood flow in the IVC falls
True.
Umbilical vessels constrict and placental circulation ceases resulting in increased systemic vascular resistance and arterial pressure.
244
At birth:
| Hypoxia will favour a right to left shunt
True. Any stimulus increasing Pulmonary Vascular Resistance will favour a right to left shunt and hence a Persisitent Fetal Circulation. These stimuli include hypoxia, hypercarbia, acidosis and hypothermia.
245
At birth:
| The first breath generates a negative pressure of about 50 cmH2O
True.
246
Left ventricular end diastolic pressure (LVEDP):
| Gives an index of preload
True. The best measure of preload in LVEDV, however this will correlate with LVEDP - the exact numerical relationship being dependent on left ventricular compliance.
247
Left ventricular end diastolic pressure (LVEDP):
| Will be raised if left ventricular compliance increases
False. Pressure will be lower for a given volume if compliance is increased (Complaince = Vol/Pressure)
248
Left ventricular end diastolic pressure (LVEDP):
| Is increased in aortic regurgitation
True. Because regurgitant blood re-enters the ventricle increasing volume and pressure.
249
Left ventricular end diastolic pressure (LVEDP):
| Is a determinent of myocardial oxygen consumption
True. Raised LVEDP increases myocardial work and therefore oxygen requirement.
250
Left ventricular end diastolic pressure (LVEDP):
| Is measured using a pulmonary artery flotation catheter
False. A pulmonary artery flotation catheter can measure the left atrial pressure (wedge pressure).
251
An increase in right atrial pressure:
| Decreases systemic arterial pressure
False. An increase in preload will increase LVEDV and therefore stroke volume and consequently cardiac output and arterial blood pressure (unless in heart failure).
252
An increase in right atrial pressure:
| Will increase type A atrial stretch receptor discharge during atrial systole
True. Atria have Type A stretch receptors that discharge predominantly during atrial systole and Type B receptors that discharge predominantly during atrial diastole.
253
An increase in right atrial pressure:
| Causes an increase in urine volume
True. Stimulation of atrial stretch receptors causes the release of atrial naturetic peptide (ANP) which has a diuretic action.
254
An increase in right atrial pressure:
| Can increase the heart rate via the Bainbridge reflex
True
255
An increase in right atrial pressure:
| Can decrease the heart rate via the baroreceptor reflex
True. Increasing RA filling produces 2 opposing reflexes that control HR. The resultant increased blood pressure can decrease HR via the baroreceptor reflex, however the atrial stretch receptors can increase HR via the Bainbridge reflex. Whether the HR increases of decreases after a sudden increase in intravascular volume is thought to be related to the initial heart rate (decreasing if it is high and increasing if it is low).
256
In diastole:
| Myocardial relaxation is metabolically active
True. Myocardial relaxation is a metabolically active phase when calcium re-uptake occurs by the sarcoplasmic reticulum.
257
In diastole:
| Hypercalcaemia causes positive lusitropy
False. Lusitropy is a term that decribes myocardial relaxation. Catecholamines have a positive lusitropic action (allowing rapid relaxation) whilst hypercalcaemia inhibits relaxation due to incomplete calcium reuptake (an essential process in diastole).
258
In diastole:
| Left atrial contraction occurs just before right atrial contraction
False. RA contration preceeds LA contraction, however LV contaction precedes RV contraction.
259
In diastole:
| The greater part of left coronary artery blood flow occurs during diastole.
True. Whereas in the Right Coronary Artery, the greater part of blood flow occurs during systole.
260
In diastole:
| Diastasis shortens first with increasing heart rate
True. Diastasis is the slow ventricular filling phase of diastole. There is only a small increase in ventricular volume during this time.
261
In the first 24 hours after major trauma:
| Sodium is retained
True. Aldosterone levels increase, promoting sodium reabsorption.
262
In the first 24 hours after major trauma:
| Glomerular filtration rate increases
False. GFR decreases.
263
In the first 24 hours after major trauma:
| Patients will be immunosuppressed
False. Immunusuppression is a late feature following trauma.
264
In the first 24 hours after major trauma:
| Urinary nitrogen levels will rise
True. Due to protein breakdown in the initial catabolic phase.
265
In the first 24 hours after major trauma:
| Insulin secretion is decreased
True. Glucagon secretion also increases briefly.
266
Afterload:
| Equals systemic vascular resistance
False. Afterload is the tension developed in the LV wall during systole. SVR is however the commonest index of afterload used clinincally, but it is only one component that determines afterload.
267
Afterload:
| If increased, will result in decreased LVEDV
False. If afterload increases, SV initially falls. SV is then (partially) restored by an increase in LVEDV. This is known as the Anrep effect.
268
Afterload:
| Is likely to be low in heart failure
True. Afterload is the tension developed in the LV wall during systole and as such can be related to pressure by Laplaces law. Thus in the failing heart afterload is likely to be low due to low intraventricular pressure.
269
Afterload:
| Will be low in a dilated ventricle
False. Using Laplaces law, the inreased radius will increase tension
270
Afterload:
| Is decreased in mitral regurgitation
True. The left ventricle requires less tension to eject blood through this low pressure pathway.
271
Concerning the splanchnic circulation
| The adult liver normally receives approximately one third of its blood supply from the coeliac axis
True. The hepatic artery is a branch of the coeliac axis. There is an inverse ratio of the flow between the hepatic artery and portal vein but under normal conditions 1/3 of hepatic blood comes from the hepatic artery.
272
Concerning the splanchnic circulation
| Beta 1 adrenergic receptors cause mesenteric arteriolar vasodilatation
False. Beta 2 adrenergic receptors mediate vasodilation.
273
Concerning the splanchnic circulation
| Positive end expiratory pressure (PEEP) decreases portal blood flow
True. Portal blood flow does not autoregulate well. PEEP increases hepatic venous pressure and reduces portal flow.
274
Concerning the splanchnic circulation
Arcades of arterioles supplying mucosal villi terminate and branch at the tip supplying well oxygenated blood to the mucosa
False. The countercurrent exchange of oxygen between parallel arterioles and submucosal venules makes oxygen delivery to the tips of mucosal villi poor.
275
Concerning the splanchnic circulation
| The splanchnic venous system can contain 1/3 of the total blood volume
True. The splanchnic and skin circulations are the major reservoirs of available blood in times of stress.
276
Concerning cardiac tissue:
| Myocardial cells have a RMP of -60mV
False. This is the RMP of pacemaker cells. Myocardial cells have a RMP of -90 mV.
277
Concerning cardiac tissue:
| Myocardial cells do not possess gap junctions
False. Gap junctions connect the cytosol of adjacent myocardial cells allowing rapid transmission of electrical cells.
278
Concerning cardiac tissue:
| Conduction velocity of action potentials is greatest in the bundle branches and Purkinje system
True
279
Concerning cardiac tissue:
| Calcium within the sarcoplasmic reticulum is released in response to rising intracellular sodium levels
False. It is released in response to rising intracellular calcium levels.
280
Concerning cardiac tissue:
| Both the SA and AV nodes blood supply is derived from the right coronary artery
True
281
During moderate exercise:
| Cerebral blood flow increases
False. Caridac output by upto seven times resting values, but cerebral blood flow is maintained at normal levels.
282
During moderate exercise:
| Increased cardiac output is achieved mainly from an increased heart rate
True.
283
During moderate exercise:
| Central venous pressure rises
False. At moderate levels of exercise, increased venous return matched increased cardiac output and thus CVP does not significantly change. CVP does rise at maximal exertion.
284
During moderate exercise:
| Intravascular volume is usually reduced
True. Due to increased insensible losses and increased capillary filtration.
285
During moderate exercise:
| Haematocrit tends to fall
False. There is often a slight rise in haematocrit due to the reasons in Part D.
286
Regarding electrolyte changes:
| Hypokalaesmia increases automaticity
True. Hypokalaemia makes the cardiac muscle RMP more negative, resulting in it being less excitable but with increased automaticity.
287
Regarding electrolyte changes:
| Hypokalaemia increases the QT interval
True.
288
Regarding electrolyte changes:
| Hyperkalaemia brings the RMP closer to the threshold potential
True. Hyperkalaemia makes the RMP less negative.
289
Regarding electrolyte changes:
| Hypercalcaemia makes the threshold potential more negative
False. Hypercalcaemia makes the threshold potential less negative, decreases conduction velocity and shortens the refractory period.
290
Regarding electrolyte changes:
| Hypermagnesemia prolongs the PR interval
True. Hypermagnesemia delays AV conduction.
