1
Q
List three adaptations that maximize exchange at capillaries.
A
- Low velocity (0.05-0.1 cm/s vs. 25 cm/s in the aorta)
- Large surface area (6300 m²)
- Thin walls
2
Q
List locations of fenestrated capillaries.
A
- Glomerulus
- Endocrine glands (e.g., thyroid, pituitary)
3
Q
Where are discontinuous capillaries found?
A
In liver sinusoids.
4
Q
Which factors cause precapillary sphincters to dilate, allowing blood flow through the capillary bed?
A
- Nitric oxide
- Decreased PO₂ or increased PCO₂
- Elevated temperature
- Rising K⁺
- Acidosis (e.g., lactate)
- Prostacyclin, thromboxane, and endothelins
5
Q
What colloid oncotic pressure is exerted by albumin in the intravascular space?
A
26 mm Hg
NOTE: interstitial oncotic pressure is around 17 mm Hg
6
Q
State the Starling equation for capillary fluid dynamics.
A
Q = Kf (Pc−Pi)−σ(πc−πi)
Where:
Q → net fluid movement
Kf (K) → filtration coefficient (permeability × surface area)
Pc / Pi → capillary & interstitial hydrostatic pressures
πc / πi → capillary & interstitial oncotic pressures
σ (s) → reflection coefficient (protein leakiness)
7
Q
What does the reflection coefficient for albumin indicate?
A
It indicates how much a membrane restricts the passage of albumin across it.
8
Q
What are the rough capillary hydrostatic pressures at the arteriolar and venous ends of a capillary?
A
Arteriolar: 32 mm Hg
Venous: 15 mm Hg
NOTE: interstitial hydrostatic pressure ranges from - 2 mm Hg in the subcutaneous tissue to +6 mm Hg in the brain.
9
Q
How much fluid is returned to the circulation by the lymphatics every day?
A
2-4 L/day
NOTE: 20 L/day of fluid leaves the capillaries but about 18 L will be reabsorbed into the capillaries (due to oncotic pressure).
10
Q
List some factors that increase capillary permeability.
A
- Substance P
- Histamine
- IL1, IL4 and IL6 (in inflammatory responses)
- Kinins (e.g. bradykinin)
- Accumulation of osmotically active substances in interstitial space
- Burns
- Acute lung injury
- Reperfusion injury
11
Q
What proportion of blood volume is in the venous system?
A
54%
NOTE: heart is 12%, capillaries 5%, arteries 8%, pulmonary 18%.
12
Q
What are the four main functions of the lymphatics?
A
- Return excess fluid to circulation
- Carry chylomicrons from intestines
- Part of the adaptive immune response (APCs will travel to lymph nodes and interact with B and T cells)
13
Q
Which tissues do not have lymphatic drainage?
A
- CNS
- Eyes
- Cartilage
14
Q
What keeps lymphatic vessels open?
A
Collagenous anchoring fibrils hold lymphatics open, generating negative intraluminal hydrostatic pressure for flow.
15
Q
Which factors aid flow within the lymphatics?
A
- Negative intra-thoracic pressure during inspiration
- Suction effect of high velocity flow in the brachiocephalic veins where lymphatics terminate
- Unidirectional valves in major lymph vessels
- Transmitted pulsations from major arteries
IMPORTANT: the main force causing flow is the tissue interstitial pressure (ultrafiltration > reabsorption).
16
Q
What are the contents of lymph?
A
- Neutrophils
- Glucose of 3-5 mmol/L
- Chylomicrons
- Roaming macrophages (act as filter for microbes and foreign particles)
- Protein (mainly in lymph draining the liver and intestine)
17
Q
What are the two main types of junction between cardiomyocytes?
A
- Desmosome Junctional Complex: provide structural integrity and tensile strength.
- Gap Junctions: hexameric proteins (connexons) that span the sarcolemma and allow small molecules to pass.
18
Q
Describe the roles of tropomyosin and troponins.
A
- At rest, tropomyosin blocks myosin binding sites on actin.
- Calcium binds to TnC, triggering tropomyosin to unbind and expose binding sites.
- Myosin heads bind, displacing tropomyosin for more binding.
- Once calcium is sequestered, tropomyosin rebinds to actin.
19
Q
What is the normal flow velocity through the aortic valve?
A
1 m/s
20
Q
What are the phases of the cardiac cycle?
A
- Atrial systole
- Isovolumetric contraction
- Rapid ejection
- Reduced ejection
- Isovolumetric relaxation
- Rapid filling
- Reduced filling
21
Q
What are the different components of the JVP waveform?
A
- A wave: atrial contraction
- C wave: isovolumetric contraction causes AV valves to bulge into atria
- X descent: atrial relaxation + pulling downwards of AV ring during early rapid ejection
- V wave: ventricular systole
- Y descent: AV valves open and blood rapidly leaves the atria into the ventricle during diastole
22
Q
What is the difference between the incisura and the dicrotic notch?
A
- Incisura: sharp downward deflection occurring immediately after the aortic valve closes as blood being ejected from the LV suddenly stops
- Dicrotic Notch: smaller notch caused by brief backflow of blood as the aortic valve closes and the aorta recoils in on itself
23
Q
What causes the third and fourth heart sounds?
A
- 3rd Heart Sound: Occurs during early rapid ventricular filling due to tensing of connective tissues supporting the valve cusps. Associated with ventricular dilation.
- 4th Heart Sound: Occurs during atrial systole, representing vibration of the ventricular wall during atrial contraction. Associated with stiff ventricles.
24
Q
Which part of a left ventricular pressure volume loop denotes stroke work?
A
Area within the loop (pressure x volume)
25
What does the **end-systolic pressure volume relationship (ESPVR)** indicate?
The gradient of the ESPVR and end-diastolic pressure volume relationship (EDPVR) reflects the **ventricle's compliance**. A shallower gradient indicates **greater volume change** for a small pressure change (i.e., more compliant ventricle).
26
How does the **RV pressure volume loop** differ from the **LV** loop?
Ejection from the RV starts earlier in systole before peak pressure. Pulmonary circulation is **high capacitance** and **low pressure**, allowing RV ejection to continue while pressure falls (up to 60% of stroke volume ejected after peak systolic pressure).
27
What are the phases of the **cardiac action potential**?
* **Phase 0**: Depolarization; Na channels open, allowing Na influx.
* **Phase 1**: Na channels close; K channels open, allowing K efflux.
* **Phase 2**: Ca channels open, allowing Ca influx to balance K efflux.
* **Phase 3**: Ca channels close; K efflux continues, causing repolarization.
* **Phase 4**: Na/K ATPase re-establishes resting membrane potential and concentration gradients.
28
Which leads are used to calculate the **cardiac axis**?
**I** and **aVF**; they are at right angles.
Should be -30 to +90 degrees.
29
Describe the phases of the **pacemaker potential**.
* **Phase 4**: Starts at -60 mV; funny sodium channels open, allowing Na influx. At -50 mV, T-type Ca channels open; at -40 mV, L-type Ca channels open, reaching threshold potential.
* **Phase 0**: Continued flow through L-type Ca channels causes depolarization to about +10 mV.
* **Phase 3**: Ca channels close, K channels open, returning to resting membrane potential.
30
What are the normal durations of the **P wave**, **PR interval**, **QRS complex**, and **QTc**?
* **P wave**: < 0.12 seconds
* **PR interval**: 0.12-0.20 seconds
* **QRS complex**: < 0.12 seconds
* **QT interval**:
* Men: < 440 ms
* Women: < 460 ms
31
Describe the effect of **beta-1 stimulation** on the cardiac action potential.
Increases **Na** and **Ca** permeability, speeding up pacemaker potential and heart rate. In myocardial cells, increased calcium influx strengthens contraction.
32
Describe the effect of **parasympathetic stimulation** on the cardiac action potential.
**Vagus nerve** releases acetylcholine, stimulating M2 receptors.
This increases membrane **potassium** permeability, hyperpolarizing cells and slowing the rate to reach threshold potential.
33
What does **low central venous oxygen** saturation indicate?
Insufficient oxygen delivery; increased oxygen extraction ratio compensates.
## Footnote
NOTE: Normal is around 75%.
34
What are the **early changes** in response to tissue hypoxia?
* **Local**: Acid accumulation from anaerobic respiration shifts ODC right; increased 2,3-DPG; vasodilation from low pO₂, high pCO₂, low pH.
* **Ventilatory**: Minute ventilation increases when pO₂ < 7 kPa.
* **Cardiovascular**: Chemoreceptor stimulation causes vasoconstriction and tachycardia, improving tissue perfusion by raising blood pressure and heart rate.
35
What is the oxygen extraction of **coronary tissues**?
75% compared to 25% in other tissues. Can increase to 90% during higher demand (e.g., exercise).
36
Which **antihypertensive** affects the autonomic nervous system to reduce blood pressure?
Blocks post-synaptic **β1 receptors** in the autonomic nervous system.
37
How much power does the heart require at rest?
At rest, the heart's mechanical output power is **1.3 W**.
**Efficiency**: 10% of energy is converted to mechanical energy; 90% to heat.
Thus, the heart requires **13 W** to function at rest.
38
What are the effects of an **intra-aortic balloon pump**?
* **Inflation in diastole**: increases early diastolic blood pressure, improving organ perfusion, especially the heart.
* **Deflation as late as possible**: reduces end diastolic pressure in the aorta, lowering afterload and myocardial O₂ demand.
39
Which measurements from **oesophageal Doppler** provide a value for cardiac output?
Area under the velocity-time graph × aortic cross-section × heart rate
## Footnote
NOTE: Area under the velocity-time graph is referred to as stroke distance.
40
How long does a **cardiac action** potential last?
250 ms
41
State the equation for **coronary perfusion pressure**.
CPP = DBP – LVEDP
## Footnote
NOTE: alternatives to LVEDP include RA pressure and coronary sinus pressure
42
How does increased **sympathetic tone** affect the pacemaker potential in the heart?
Increases **sodium** and **calcium** permeability, leading to faster depolarization towards threshold potential during phase 4.
43
What are the three subtypes of **Class I antiarrhythmics**?
* **Class Ia**: **Prolongs** refractory period (e.g., procainamide, quinidine, disopyramide).
* **Class Ib**: **Shortens** refractory period (e.g., lidocaine, phenytoin, mexiletine).
* **Class Ic**: **No effect** on refractory period (e.g., flecainide, propafenone).
44
Which **equation** is used to **calculate cardiac output** from the temperature-time graph for cardiac monitoring via thermodilution?
Stewart-Hamilton equation
45
How does **alpha-1 stimulation** cause **vasoconstriction**?
* Binds to Gq subunit
* Activates cleavage of PIP2 to IP3 and DAG
* Increases calcium entry
46
What information can be ascertained from the gradient of the **upstroke of an arterial line trace**?
* Inotropic component, represents myocardial contractility.
* A slow rise suggests inotropes are needed.
47
What information can be derived from the gradient of the **downstroke** and position of the **dicrotic notch** on an arterial line trace?
Indicates systemic vascular resistance (SVR).
* **Low SVR**: steep downstroke, low dicrotic notch.
* **High SVR**: shallow downstroke, high dicrotic notch.
48
What does the area **under** the systolic component of an **arterial line** trace indicate?
Stroke volume
49
What is the **oculocardiac reflex**?
Stimulation of the **ophthalmic nerve (CN V1)** by traction on extraocular muscles increases **vagal (CN X)** outflow, potentially causing asystole.
50
How does the **Eustachian valve** improve oxygenation of the fetal brain?
* Directs IVC (placental, high-O₂) flow across the foramen ovale → left atrium → left ventricle → carotids.
* Keeps SVC (brain-desaturated) blood in the right heart → pulmonary artery → ductus arteriosus → placenta.
* Net effect: fetus sends most oxygen-rich blood to the brain while shunting lower-O₂ blood back for re-oxygenation.
51
How does **nitric oxide** cause vasodilation?
Nitric oxide **activates guanylate cyclase**, converting GTP to cGMP.
## Footnote
Increased cGMP reduces calcium entry into cells, leading to vasodilation.
52
Outline the **naming convention** for cardiac pacemakers.
* **I:** chamber(s) paced – V (ventricle), A (atrium), D (both), O (none).
* **II:** chamber(s) sensed – V (ventricle), A (atrium), D (both), O (none).
* **III:** mode of response – T (triggered), I (inhibited), D (both), O (none).
* **IV:** programmable functions – R (rate modulated), O (none).
* **V:** multi-site pacing – O (none), A (atria), V (ventricles), D (dual).
53
How do the graphs from **dye dilution** and **thermodilution** techniques for monitoring cardiac output differ?
Dye dilution shows a **recirculation hump** as the dye returns to the heart and is pumped again.
54
How do you interpret flow time corrected on a transoesophageal doppler?
Flow time is the duration of forward blood flow (corrected means adjusted to heart rate by dividing by √cycle time).
* **Low FTC** = impeded filling/emptying (e.g., hypovolaemia, mitral stenosis, PE).
* **High FTC** = vasodilated circulation (e.g., sepsis).
Normal FTC is 330-360 ms.
55
What are the normal ranges for the following pressures observed on a pulmonary artery flotation device:
* Mean right atrial pressure
* Right ventricular pressure
* Pulmonary artery pressure
* Pulmonary capillary wedge pressure (indirect estimate of left atrial pressure)
* Mean right atrial pressure: **0-5 mmHg**.
* Right ventricular pressure: **20-30/0-5 mmHg**.
* Pulmonary artery pressure **20-30/10-20 mmHg**.
* Pulmonary capillary wedge pressure: **6-12 mmHg**.
56
State the **Fick** principle.
Describes how uptake or release of a substance by an organ/system equals **flow multiplied by the difference** between **arterial and venous** concentrations.
## Footnote
Mathematically:
**M = Q x (A-V)**
where M = uptake, Q = flow, A = arterial concentration, V = venous concentration.
57
What are the stages of the **Valsalva manoeuvre**?
* **Phase 1**: Onset increases intrathoracic pressure, raising venous return and BP.
* **Phase 2**: Sustained pressure reduces venous return, causing BP to fall; compensatory tachycardia occurs.
* **Phase 3**: Pressure release leads to blood pooling; BP falls while HR remains elevated.
* **Phase 4**: Increased HR raises BP as venous return normalizes; reflex bradycardia follows.
58
What **proportion of the blood** in the **foetal right heart** is diverted into the descending aorta through the ductus arteriosus?
0.9
59
Why is the **atrial kick** important in patients with **aortic stenosis**?
In aortic stenosis, **up to 40% of preload** comes from atrial contraction. Loss of the atrial kick can significantly reduce cardiac output.
## Footnote
NOTE: Normally, it is less than 10%.
60
What is the **auscultatory gap** in non-invasive blood pressure measurement?
Korotkoff sounds disappear and reappear during cuff deflation, often due to rapid deflation.
61
What is the **anaerobic threshold** and how is it interpreted?
Measured in mL/kg/min of oxygen, it indicates the maximum aerobic work capacity before switching to anaerobic metabolism.
* **>11 mL/kg/min:** Good functional reserve — lower surgical risk.
* **9–11 mL/kg/min:** Borderline — moderate fitness; may need tailored perioperative care.
* **<9 mL/kg/min:** Poor fitness — higher risk of complications, slower recovery, and prolonged rehab.
62
# Define:
lusitropy and dromotropy
* **Lusitropy** refers to the ability of the heart to relax
* **Dromotropy** refers to the ability of the heart to conduct electrical impulses
63
How is **nitric oxide** produced?
Produced from L-arginine by **nitric oxide synthase**. Formed by vascular endothelium in response to hemodynamic stress, leading to smooth muscle relaxation.
64
What proportion of total body weight is **water**?
60%
## Footnote
NOTE: In obese individuals, ECF proportion is smaller.
Rule: 60-40-20: TBW 60% - ICF 40% - ECF 20%.
65
List the pressures in a **pulmonary artery catheter** for a normal patient.
* **Right atrium**: 0-12 mm Hg
* **Right ventricle**: 2-25 mm Hg
* **Pulmonary artery**: 12-25 mm Hg
* **Occlusion pressure**: 8-12 mm Hg
66
State the **equation** for calculating **systemic vascular resistance**.
SVR = (MAP-CVP)/CO x 80
67
By what mechanism does **ventricular stretch** increase contraction force according to **Frank-Starling law**?
* Greater actin-myosin interaction
* Increased sensitivity of myofibrils to calcium
68
What is the best measure of **LV contractility**?
Ejection fraction
69
What is the most important physiological change during **exercise** for maximizing oxygen delivery to tissues?
Relaxation of pre-capillary sphincters increases oxygen delivery by **20-30** times.
70
Describe the **Fick method** for **cardiac output studies**.
Calculates **blood flow to an organ** using a marker substance, based on the amount taken up by the organ per unit time and the arterio-venous difference.
71
What does a **pulmonary artery catheter** trace indicate?
It provides information about **heart function and pressures** within the pulmonary artery.
## Footnote
This trace is used to monitor hemodynamics and assess cardiac performance.
72
What are key differences between **cardiac** and **skeletal muscle action potentials**?
* **Calcium influx** through L-type channels balances K efflux, creating a plateau phase.
* **Cardiac AP** lasts longer for complete ventricular depolarization and ejection.
* Longer refractory period prevents tetany.
73
What are the pressure changes during the cardiac cycle in the **aorta**, **left atrium**, and **left ventricle**?
During **atrial** systole, atrial pressure exceeds ventricular pressure; during **ventricular** systole, ventricular pressure exceeds aortic pressure.
## Footnote
These pressure changes are crucial for understanding the phases of the cardiac cycle.
74
What is the main difference in blood flow during the cardiac cycle between **left** and **right coronary circulation**?
During **systole**, increased LV pressure occludes blood flow in the left coronary artery, so most perfusion occurs in **diastole**. The right ventricle, operating at lower pressure, has less impedance to blood flow during systole.
75
What aspect of a left ventricular pressure-volume loop represents **afterload**?
Slope linking **LVEDV** and **LVESV**. An increase in afterload results in a steeper gradient.
76
Explain key differences in **Starling forces** between glomerular and pulmonary capillaries.
* **Glomerular**: high capillary hydrostatic pressure (55 mm Hg) with fenestrated capillaries allows significant fluid movement for filtrate production.
* **Pulmonary**: lower pressure system (10 mm Hg) results in minimal fluid leaving the capillaries.
77
What effect does high serum **K** have on **cardiomyocyte membrane potential**?
* It reduces the K⁺ concentration gradient, making the resting membrane potential (RMP) less negative (**depolarized**).
* This affects **cell excitability**, inactivating voltage-gated Na⁺ channels, impairing action potential initiation and conduction, weakening cardiac contractility, and leading to **flaccid, dilated myocardium**.
78
What is the **square wave response** to a **Valsalva maneuver**?
Phases II and IV are **blunted or absent**; BP remains **flat and high**.
## Footnote
Associated with **heart failure** due to:
* Elevated baseline sympathetic tone
* Reduced preload sensitivity (impaired Frank-Starling response)
* Higher than average CVP
* Blunted baroreflex
Other causes include: constrictive pericarditis, cardiac tamponade, mitral stenosis.
79
Describe how **cardiac output** changes during **pregnancy**.
* **End of 2nd Trimester:** 50% increase
* **Labour:** 60% increase
* **Immediate post-partum:** 80% increase
## Footnote
NOTE: SVR decreases by 20% and HR increases by 25%.
80
What is the **Bowditch** phenomenon?
**Contractility** increases when HR increases, because higher HR causes **more calcium** to accumulate in **cardiomyocytes**, thereby enhancing ability to contract.
81
What is the **Anrep** effect?
Contractility increases in response to a **sudden increase in afterload**. It helps maintain stroke volume despite the increased resistance.
82
What is the **Bezold-Jarisch** reflex?
* Bradycardia, hypotension, and vasodilation triggered by mechano- and chemoreceptor stimulation in the **left ventricle**.
* **LOW PRELOAD**: A sudden drop in preload (e.g., spinal anesthesia) slows HR, allowing more time for ventricular filling.
* **MI**: Bradycardia reduces myocardial oxygen consumption during ischaemia.
## Footnote
Reflex helps protect the heart under stress.
83
What proportion of **total body water** is intracellular vs extracellular?
* **Intracellular:** 2/3
* **Extracellular:** 1/3 (of this 1/3, 25% is intravascular)
84
What ECG changes are associated with **hypermagnesaemia**?
* **Initially:** prolonged PR, broad QRS
* **Severe:** sinoatrial and AV node block, complete heart block
85
Which **afferent nerves** convey signals from the **carotid body** and **aortic arch** chemoreceptors?
* Carotid Body: **Glossopharyngeal Nerve**
* Aortic Arch: **Vagus Nerve**
86
What is the partial pressure of oxygen and oxygen saturation in the **umbilical vein**?
pO₂: 4.7 mmHg
SpO₂: 80-90%
87
What is the **Bainbridge reflex**?
An increase in heart rate due to **atrial stretch**. It aims to **clear excess volume** from central circulation and normalize atrial and ventricular pressures.
88
Which indicators are used in **dilution techniques** to estimate fluid volumes?
* **Deuterium oxide**: Total body water
* **Inulin**: Extracellular fluid
* **Plasma**: Radiolabelled albumin, Evan's blue
* **Red cell volume**: Radiolabelled red cells
89
What are the effects of **ANP**?
* Reduced sodium reabsorption in the collecting duct
* Reduced renin secretion (and, hence, reduced aldosterone activity)
* Reduced pulmonary capillary wedge pressure
* Vasodilation of the afferent arteriole (increase glomerular filtration)
90
What is the estimated blood volume of a term **neonate**?
80-90 mL/kg
91
Describe the stimulation of **nitric oxide** generation and its role in vasodilation.
NO production starts with inflammatory mediators activating endothelial **NO synthase**. This enzyme converts L-arginine to L-citrulline, **producing NO**.
NO then stimulates guanylate cyclase, increasing cGMP in smooth muscle cells, leading to **blood vessel dilation**.
92
Describe the **synthesis pathway** for adrenaline and noradrenaline.
The synthesis pathway begins with the amino acid **tyrosine**, which is converted to **L-DOPA** and then to **dopamine**. Dopamine is further converted to **norepinephrine**, which can then be converted to **epinephrine** in the adrenal medulla.
## Footnote
This pathway involves several enzymes, including tyrosine hydroxylase and dopamine β-hydroxylase.
93
What's the difference between **high-pressure** and **low-pressure** baroreceptors?
* **High-pressure**: located in the aortic arch and carotid body; involved in rapid short-term blood pressure control.
* **Low-pressure**: found in heart chambers and large veins; regulate slower changes in blood volume (e.g., ANP).
94
Where do signals from **carotid body** and **aortic arch** baroreceptors converge?
**Nucleus tractus solitarius** in the medulla
From here, the vasomotor and cardio-inhibitory centers modulate autonomic outflow.
## Footnote
This response is fast because it is neurally mediated.
95
What compensatory changes occur with a **rapid drop in circulating volume** (e.g., hemorrhage)?
* **Baroreceptor reflex**
* Redistribution of cardiac output (from skin, muscle, and viscera)
* **ADH** secretion
* **Adrenaline** secretion
* **RAS** activation
* Starling forces favor movement into vessels
96
What are the five phases of the **cardiac cycle**?
* **Phase 1**: atrial contraction
* **Phase 2**: ventricular isovolumetric contraction
* **Phase 3**: ventricular ejection
* **Phase 4**: ventricular isovolumetric relaxation
* **Phase 5**: passive ventricular filling.
97
Over what range can the heart regulate **coronary perfusion pressure**?
60-180 mm Hg
## Footnote
NOTE: Normal coronary blood flow is 250 mL/min; oxygen extraction is around 70%.
98
What mechanisms enable **autoregulation of blood flow**?
* Metabolic (e.g. H+, K+, adenosine)
* Myogenic
* Endothelial (e.g. NO)
* Autonomic
* Hormonal (e.g. ANP)
99
What factors affect **myocardial oxygen consumption**?
* HR
* Contractility
* Afterload
* Tissue mass
* Temperature
100
What **cardiovascular changes** take place during exercise?
* Increased CO (HR and contractility)
* Increased muscle blood flow
* Increased oxygen extraction in muscle
* ODC shifted right due to lactate + increased temperature
101
What is the **anaerobic threshold**?
The point during exercise where aerobic metabolism **cannot meet energy demands**, leading to significant **lactate production**.
## Footnote
This threshold is typically observed at around 60% of VO₂ max, with values above 11 mL/kg/min considered good.
102
How are **body compartment volumes** measured?
* **Dilutional techniques**: dye distributes in specific compartments.
* Measure dye concentration; known amount given.
## Footnote
**TBW**: deuterium oxide
**ECF**: inulin
**Plasma**: radiolabelled albumin, Evan's blue dye
**Red Cell Volume**: radiolabelled red cells
103
What is a **low flow time** corrected suggestive of?
Low Preload; High Afterload
## Footnote
i.e. the blood is spending more time moving forward
104
What is the **electrical potential** of the **myocardium** and at the skin?
* **Myocardium**: 90 mV
* **Skin**: 1-2 mV (attenuated by tissues)
105
What is the **CM5** electrode configuration?
Best for myocardial ischaemia:
* R Arm: manubrium
* L Arm: 5th ICS anterior axillary line
* L Leg: left shoulder
106
What factors influence **arteriolar tone**?
* **Local**: myogenic autoregulation, metabolites (CO₂, acidosis)
* **Humoral**: adrenaline, angiotensin, vasopressin, NO, histamine, kinins
* **Neural**: SNS via alpha-1 receptors; beta-2 causes dilation
107
How does the **arterial waveform** change distally in the arterial system?
* Upstroke becomes steeper (higher systolic)
* DBP decreases
* MAP remains fairly constant
* Dicrotic notch shifts further down
## Footnote
**Note:** Higher systolic due to distal arteries being less elastic, reducing ejection wave buffering, leading to lower diastolic blood pressure.
108
What is the **Windkessel effect**?
Maintenance of forward flow during diastole due to **elastic recoil of the aortic wall**, converting potential energy to **kinetic energy**.
109
What is the **diameter** of a capillary?
5-10 µm
110
What are the three main types of **capillaries**?
* **Continuous**: muscle, brain, connective tissue; tight junctions, continuous basement membrane.
* **Fenestrated**: renal glomeruli, intestinal mucosa, choroid plexus; more permeable.
* **Sinusoidal**: bone marrow, lymph nodes, liver; large enough for whole cells.
111
What are the normal values for **capillary** and **interstitial** hydrostatic and oncotic pressures?
* **Capillary**:
* Hydrostatic: 36 mm Hg (a) → 10 mm Hg (v)
* Oncotic: 24 mm Hg
* **Interstitial**:
* Hydrostatic: 2 mm Hg
* Oncotic: 3 mm Hg
112
What are the functions of the **endothelium**?
* Semipermeable membrane for gas, nutrient, and metabolite movement
* **Haemostasis**
* Releases vasoactive substances (e.g., **NO**)
* Involved in inflammation (adhesion molecules)
113
What is the name of the **shunting vessels** that enable bypass of capillary beds?
Metarterioles
## Footnote
NOTE: pre-capillary sphincters will regular flow into the capillary beds based on local demand
114
How long does each **phase** of the **cardiac action potential** last?
* Phases 0 and 1: **1-2 msec**
* Phase 2: **200 msec**
* Phase 3: **50 msec**
115
What is the **absolute refractory period** in cardiomyocytes?
After membrane depolarization, voltage-gated Na⁺ channels are **inactivated**. They can't return to resting state until **membrane repolarization** occurs, lasting about 200 msec.
116
What's the **resting membrane potential** of a nerve cell, skeletal muscle cell, cardiac myocyte, and pacemaker cell?
* **Pacemaker Cell**: -60 mV
* **Cardiac Myocyte**: -90 mV
* **Nerve Cell**: -70 mV
* **Skeletal Muscle Cell**: -90 mV
## Footnote
NOTE: Non-excitable cells have an RMP of -30 mV.
117
Describe the **pacemaker potential**.
* **Phase 4**: Funny sodium current gradually increases membrane potential from -60 mV to -50 mV.
* **Phase 0**: At -40 mV, L-type calcium channels open, causing depolarization.
* **Phase 3**: At +20 mV, Ca²⁺ channels close, and voltage-gated K⁺ channels open, repolarizing the pacemaker cell.
118
How much of ventricular filling is due to the **atrial kick**?
* 10% under normal conditions
* 40% during exercise (due to reduced diastolic time)
119
What are important considerations for anaesthesia in **aortic stenosis**?
* Maintain sinus rhythm (AF impairs LV filling)
* Low/normal heart rate (allows time for coronary perfusion and slow ejection)
* Avoid drops in SVR (can impair coronary perfusion)
120
What are important considerations for anaesthesia in **aortic regurgitation**?
* High/normal heart rate (shorter diastolic time increases regurgitant fraction)
* Low SVR (maintains forward blood flow)
121
State **Frank-Starling Law**.
Ventricular contraction strength depends on resting fiber length (determined by preload).
122
What are two important compensatory mechanisms in **heart failure**?
* **Sympathetic stimulation**: increases myocardial contractility and heart rate.
* **Blood volume expansion**: occurs via the RAS.
123
What is **coronary blood flow** at rest?
250 mL/min
## Footnote
NOTE: Right coronary flow is maintained throughout the cardiac cycle; left coronary flow is briefly halted during ventricular contraction.
124
What is **reperfusion injury**?
Injury occurring when blood flow resumes after ischaemia, causing reactive oxygen species (ROS) production, leading to microvascular endothelial damage and thrombosis.
## Footnote
This can result in arrhythmias and contractile dysfunction.
125
What is **ischaemic preconditioning**?
Protective mechanism against ischaemic insults; largely experimental. Isoflurane may provide protective effects in **CABG**.
126
What are the surrogate markers for **RV** and **LV** preload?
* **RV**: CVP
* **LV**: PCWP
127
# Define:
afterload
Stress in the left ventricular wall during ejection (force opposing myocyte shortening).
MAP and SVR indicate afterload.
128
What does the **oesophageal Doppler waveform** depict?
* **Peak velocity**: contractility
* **Flow time corrected**: preload
* **Stroke volume**: area under the velocity-time graph (velocity-time integral) multiplied by the cross-sectional area of the **LVOT** to give volume.
129
What is the **cardiac index**?
CI = CO/BSA
Resting CI = 3-3.5 L/m²
130
How do increasing contractility, preload, and afterload affect the **left ventricular pressure-volume loop**?
Increasing contractility **raises the pressure during systole**, preload increases the volume at the end of diastole, and afterload raises the pressure required to eject blood.
## Footnote
These changes can shift the pressure-volume loop, indicating alterations in cardiac function and efficiency.
131
How does the **left ventricular (LV)** pressure-volume curve change in **systolic** and **diastolic heart failure**?
In **systolic heart failure**, the curve shifts downward and right, indicating reduced contractility and stroke volume. In **diastolic heart failure**, the curve shifts upward, reflecting increased filling pressures and decreased compliance.
## Footnote
These changes in the pressure-volume loop indicate the heart's impaired ability to pump effectively.
132
What are clinical applications of the **Valsalva manoeuvre**?
* Termination of **SVT**
* Diagnosis of murmurs
* Temporary increase in venous pressure for haemostasis (e.g., tonsillectomy)
133
What mediates the increase in **cardiac output** during exercise?
* **Increased preload**: due to venoconstriction and skeletal muscle pump
* **Reduced afterload**: due to vasodilation in skeletal muscle
* **Increased heart rate**: from sympathetic activation
* **Increased contractility**: due to SNS and Bowditch effect
## Footnote
**Note**: CO increases from 5 L/min to 25 L/min.
134
Describe the effects of **exercise** on the **cardiovascular system**.
* **VO₂**: 250 → 5000 mL/min
* **CO**: 5 → 25 L/min
* **Skeletal Blood Flow**: 1 → 20 L/min
* **Coronary Blood Flow**: 250 → 1250 mL/min
135
What are the **physiological changes** after exercise?
Oxygen consumption remains elevated to repay oxygen debt.
**ALACTACID PHASE** (rapid): Replenishes phosphocreatine, ATP, myoglobin O₂, and glycogen in muscle and liver.
**LACTACID PHASE** (slow): Converts lactate to pyruvate in the liver; supports muscle hypertrophy and repair.
136
What does the CVP waveform represent?
* A: Right atrial contraction
* C: Right ventricular contraction causing tricuspid valve bulging into the right atrium
* X: Atrial relaxation and downward movement of the right atrium during ventricular contraction
* V: Right atrial filling against a closed tricuspid valve
* Y: Decrease in central venous pressure as the tricuspid valve reopens
## Footnote
The CVP waveform provides insights into the cardiac cycle and right heart function.
137
What are the main **differences** between skeletal and cardiac muscle?
* Skeletal muscle is under voluntary control, while cardiac muscle is involuntary.
* Skeletal muscle fibers are multinucleated, whereas cardiac muscle cells have a single nucleus.
* Cardiac muscle has intercalated discs that facilitate synchronized contractions, unlike skeletal muscle.
## Footnote
These differences are crucial for their respective functions in the body.
138
What are the two types of **smooth muscle**?
* **Single-unit**: found in viscera and blood vessels; syncytial units innervated by the autonomic nervous system, allowing rapid action potential propagation for synchronous contraction.
* **Multi-unit**: located in large elastic arteries, trachea, and iris; not connected by gap junctions, with single autonomic nerves branching to several smooth muscle cells for finer motor control.
139
What triggers **depolarization** of smooth muscle?
* **Neuronal**: SNS and PNS
* **Hormones**: O₂, CO₂, NO, adrenaline, histamine, prostaglandins
* **Stretch**
* **Pacemaker**: interstitial cells of Cajal in the GI tract
## Footnote
Multi-unit smooth muscle can only be stimulated by nerve impulses.
140
How does **smooth muscle contraction** occur?
* Depolarization opens L-type calcium channels.
* Ca²⁺ influx binds to **Calmodulin**.
* Calmodulin activates **MLCK**.
* MLCK phosphorylates **myosin**.
* Myosin binds to **actin**.
**MLCP** dephosphorylates myosin, allowing relaxation.
141
How does the rate of **smooth muscle contraction** compare to **skeletal muscle**?
* **10 times slower**
* Lasts **30 times longer** (due to slower Ca²⁺ removal from sarcoplasm)
142
Describe **foetal circulation**.
* **Umbilical Vein**: 4-5 kPa, 80-90%
* **Aortic Arch**: 3.5 kPa, 65%
* **Umbilical Artery**: 3 kPa, 50%
* **SVC**: 2.5 kPa, 40%
## Footnote
Ductus arteriosus closes due to rise in PaO₂ and decrease in prostaglandin E₂ and prostacyclin.
143
What is the pO₂ in the **intervillous spaces** compared to the **umbilical artery**?
* **Intervillous Spaces**: 6.7 kPa
* **Umbilical Artery**: 2.7 kPa
144
Why does **hyperkalaemia** cause **ventricular fibrillation**?
Raised extracellular K⁺ makes the membrane potential **less negative**, bringing the RMP closer to threshold, increasing spontaneous action potential generation, **leading to VF**.
145
How can an **arrhythmia** be described?
* **Origin**: e.g., sinus
* **Discharge pattern**: e.g., tachycardia
* **Conduction sequence**: e.g., AV block
146
Which adrenoceptor mediates **coronary vasodilation**?
Beta-2 receptors.
147
What are the roles of **capillaries**?
* Deliver nutrients
* Remove waste
* Distribute body water
148
What are the mechanisms for exchange at the **capillary-tissue interface**?
* **Simple diffusion**
* **Bulk flow** (solute drag)
* **Pinocytosis** (vesicular transport)
149
What is the **threshold potential** for cardiomyocytes?
Approximately -65 mV.
Resting: -90 mV; Peak: +20 mV.
150
Describe the activity of **hyperpolarisation-activated cyclic nucleotide-gated channels**.
Also known as **funny sodium channels**. When membrane potential reaches **-60 mV**, they allow Na⁺ and K⁺ to diffuse down their electrochemical gradients, resulting in a slight Na⁺ influx that leads to **slow depolarisation**.
151
Describe the mechanism behind the following abnormal heart sounds:
* Split S1
* Split S2
* S3
* S4
* **Split S1:** mitral before tricuspid (RBBB)
* **Split S2**: aortic before pulmonary (sinus arrhythmia)
* **S3**: rapid ventricular filling (e.g. mitral regurgitation)
* **S4**: atria contracting against stiff ventricles
152
What is the oxygen extraction ratio for the **heart**, **kidneys**, **liver**, and **skeletal muscle**?
* **Heart**: 60%
* **Liver**: 50%
* **Kidney**: 15%
* **Skeletal Muscle**: 10% to 100% (varies with exercise)
153
What are the effects of **low pressure baroreceptors**?
* Regulate fluid balance via kidneys
* Modulate ADH release
* Promote ANP secretion
* Reduce sympathetic activity
154
What is the relationship of **oxygen deficit** and **oxygen debt** during exercise?
**Oxygen Deficit**: difference between oxygen needed for exercise and actual oxygen consumption at the start. Caused by initial reliance on anaerobic metabolism.
**Oxygen Debt**: extra oxygen consumed post-exercise above resting levels to “repay” the oxygen deficit.
155
What is **stroke index**?
Stroke volume/body surface area
156
What is the **difference** between **SVR** and **SVRI**?
**SVR**: MAP - CVP divided by cardiac output.
**SVRI**: MAP - CVP divided by cardiac index (accounts for body surface area).
157
What is the normal range for **pulmonary capillary wedge pressure**?
4-12 mm Hg
158
What are indications for a **pacemaker**?
* **Sick sinus syndrome**
* **Complete heart block**
* **Symptomatic second-degree heart block**
* **Chronic AF**
159
List causes of **ST segment changes** in an ECG?
* Ischaemia
* Infarction
* Hypothermia
* Electrode malposition
* Hyperkalaemia (elevation)
* Hypokalaemia (depression)
* Benign early repolarisation
160
Outline the **ECG changes** associated with **left ventricular hypertrophy**.
* Increased QRS voltage; Sokolow–Lyon index: **S in V1 + R in V5 or V6 > 35 mm**
* Left axis deviation
* Left atrial enlargement (P mitrale)
* ST depression and T-wave inversion in lateral leads (strain pattern)
161
What are indications for an **implantable cardiac defibrillator**?
* Previous cardiac arrest due to **VF** or unstable **VT**
* **VT** with structural heart disease
* Non-ischaemic dilated cardiomyopathy
* Severely impaired ejection fraction (< 35%) despite 3 months of optimal medical management
162
Which nerve roots are responsible for **sympathetic innervation to the heart**?
T1-T4
163
How is adrenaline synthesized in the body?
Adrenaline is synthesized from the amino acid **L-tyrosine** through a series of enzymatic reactions: it is first converted to **L-Dopa**, then to **Dopamine**, followed by **Noradrenaline**, and finally to **Adrenaline** via the enzyme **PNMT** (phenylethanolamine N-methyltransferase).
## Footnote
This process primarily occurs in the adrenal medulla and is crucial for the body's fight-or-flight response.
164
What are the five types of **muscarinic receptors**?
* **M1**: brain
* **M2**: heart
* **M3**: smooth muscle (bronchioles, arterioles, bladder), glandular secretion (saliva, sweat, pancreatic), gastric parietal cells
* **M4**: CNS
* **M5**: CNS
165
State the **normal oxygen saturation** in the foetal circulation at the following points:
* Umbilical Vein
* Umbilical Artery
* Aorta
* Umbilical vein: **80-90%**
* Aorta: **65-70%**
* Umbilical artery: **40%**
166
What are complications associated with **intra-aortic balloon pumps**?
* Limb ischaemia (thromboembolism or mechanical obstruction)
* Bleeding
* Infection
* Balloon rupture
## Footnote
Contraindications include severe aortic regurgitation, aortic dissection, and sepsis.
167
Which ECG leads are best for:
* Ischaemia
* Arrhythmias
* **Ischaemia**: V5
* **Arrhythmias**: II (P wave)
168
What type of receptors are **muscarinic receptors**?
**M1, 3 and 5**: Gq coupled
**M2 and 4**: Gi coupled
169
What causes the closure of the **foramen ovale** after birth?
**First breath**: Negative intrathoracic pressure reduces PVR, increasing blood flow to the left atrium and causing mechanical closure.
**Cord clamping**: Removal of low-pressure placental circulation reduces venous return and increases SVR.
170
What is the purpose of the **sinus of Valsalva**?
Facilitates aortic valve closure (prevents cusps from sticking to the wall).
Aids coronary perfusion by directing blood into the coronary ostia during diastole.
171
What is the function of **chordae tendineae**?
Anchor AV valve leaflets to papillary muscles, **preventing prolapse** during ventricular systole.
## Footnote
This ensures unidirectional flow.
172
What are the **directly measured** and **derived variables** in cardiopulmonary exercise testing?
**DIRECTLY MEASURED**
* VE (minute ventilation)
* FEO₂, FECO₂, FiO₂
* Breath-by-breath flow, tidal volume, RR
* HR (ECG), BP, SpO₂
**DERIVED**
* VO₂
* VCO₂
* Anaerobic threshold
* VE/VCO₂ slope (ventilatory efficiency)
* O₂ pulse (= VO₂/HR, surrogate SV)
* VO₂ peak / VO₂ max
173
What is the **P50** of foetal haemoglobin?
2.5 kPa
174
What percentage of blood flow goes through the **foramen ovale** compared to the **right ventricle**?
60% to foramen ovale
40% to right ventricle.
From the right ventricle, 90% goes via the **ductus arteriosus** and 10% to the lungs.
175
What occurs in **foetal circulation** during the inspiratory gasp?
Negative intrathoracic pressure alters Starling forces, reducing interstitial fluid. This **decreases PVR**, allowing more blood to flow through the lungs into the left atrium. Increased left atrial pressure leads to mechanical **closure of the foramen ovale**.
176
What happens to **foetal circulation** when the **cord is clamped**?
Removal of low-pressure placental circulation **increases SVR**. This reduces venous return to the right heart, lowering right atrial pressure (LA pressure > RA pressure → closure of foramen ovale).
177
What physiological states keep the **ductus arteriosus** open after birth?
* **PGE1** (e.g., alprostadil)
* Conditions that increase **PVR** (e.g., cold, acidosis, hypoxia)
178
What changes lead to **over- or under-estimation** of left ventricular end diastolic pressure using pulmonary capillary wedge pressure?
* **OVERESTIMATE**: mitral stenosis, PEEP, pulmonary hypertension
* **UNDERESTIMATE**: poorly compliant left ventricle
179
What is **coronary steal**?
**Vasodilation** of normal coronary vessels causes blood flow to be re-routed away from regions of myocardium that are already supplied by stenotic or collateral vessels (which are already maximally dilated), thereby reducing perfusion to those ischaemic zones.
Primary FRCA
flashcards
Decks in class (17)
# Cards
-
Anatomy for Anaesthesia223
-
Physiology: Respiratory303
-
Physiology: Cardiovascular179
-
Physiology: Renal, Hepatic & GI63
-
Physiology: Neuro, Endo, & Haem237
-
Pharmacokinetics and Pharmacodynamics213
-
Pharmacology: Inhalational & Intravenous Agents232
-
Pharmacology: Analgesics & Muscle Relaxants160
-
Pharmacology: Emergency & Miscellaneous Drugs251
-
Part 1: Physics & Equipment242
-
Part 2: Physics & Equipment227
-
Part 3: Physics & Equipment232
-
Part 4: Physics & Equipment217
-
Statistics & Evidence-Based Practice36
-
Part 1: Applied Clinical Anaesthesia165
-
Part 2: Applied Clinical Anaesthesia169
-
Part 3: Applied Clinical Anaesthesia157
