Definitions Flashcards
1
Q
What is one second?
A
The base SI unit of time
Defined as the duration of 9.2x109 oscillations of the caesium-133 atom
2
Q
What is a metre?
A
The base SI unit of distance
Defined as the length of the path travelled by light in a vacuum during a given fraction of a second (1/3 x108)
3
Q
What is a mole?
A
The base SI unit of the amount of a substance
Defined as the amount of a substance that contains as many elementary particles as there are atoms in 0.012kg of carbon-12.
This corresponds to Avogadro’s number - 6.02 x 1023
4
Q
What is an ampere?
A
The base SI unit of current
Defined as the current which, if maintained in 2 parallel conductors of infinite length and negligible cross-sectional area, placed 1 metre apart in a vacuum, would produce between those conductors a force of 2 x 10-7 N per metre of length
5
Q
What is a candela?
A
The base SI unit of luminous intensity.
Defined as the luminous intensity in a given direction of a source that emits monochromatic light at a specific frequency and radiant intensity.
6
Q
What is a kilogram?
A
The base SI unit of mass.
Defined as the mass of the international prototype of the kilgram held in Sevres, France.
7
Q
What is a Kelvin?
A
The base SI unit of temperature.
Defined as 1/273.16 times the thermodynamic temperature of the triple point of water.
8
Q
What is force?
A
An influence that changes the state of motion of an object.
Force (N) = Mass (kg) x Acceleration (m/s2)
9
Q
What is a Newton?
A
The derived SI unit of force.
The force at which gives an object of 1 kg mass an acceleration of 1m/s per second (1 N = 1 kg/ms-2)
10
Q
What is a Pascal?
A
The derived SI unit of pressure, defined as the pressure created when a foce of one Newton is applied over an area of 1 m2
(1 Pa = 1Nm-2)
11
Q
What is work?
A
Work is done when a force acts upon an object and causes motion in the direction that the force is applied.
Work (J) = Force (N) x Distance (m)
12
Q
What is energy?
A
The potential to do work
13
Q
What is a joule?
A
The derived SI unit of work and energy, defined as the work done when a force of 1 N is exerted through a distance of 1m, in the direction which the force is applied
(1 J = 1 Nm)
14
Q
What is Power?
A
The rate at which work is done.
Power (W) = Work (J) x Time (s)
15
Q
What is a Watt?
A
The derived SI unit of power, defined as the power when 1 J of work is done every second, or 1 J of energy is expended every second (J/s).
16
Q
What is a volt?
A
The derived SI unit of potential difference, defined as the potential difference across a conductor when a current of 1 A dissipates 1 W of power
Power (W) = Current (A) x Voltage (V)
or P = IV
17
Q
What is a coulomb?
A
The derived SI unit of electrical charge, defined as the charge transported through a conductor by a current of 1A in 1 s.
Charge (C) = Current (A) x time (s)
Q = It
18
Q
What is a capacitor?
A
An electrical component that stores electrical charge. Used in circuits as a low frequency filter.
19
Q
What is capacitance?
A
A measure of a capacitor to store electrical charge.
20
Q
What is a farad?
A
The derived SI unit of capacitance, defined as the capacitance of a capacitor which has a potential which holds 1 C of charge when a potential difference of 1V is applied across it.
Charge (C) = Capacitance (F) x Voltage (V)
Q = CV
21
Q
What is resistance?
A
Opposition to flow, either flow of direct electrical current or fluid flow
22
Q
What is reactance?
A
Opposition to flow of alternating electrical current
23
Q
What is impedance?
A
The total of resistive and reactive components of opposition to electrical current.
**when describing resistance in an AC circuit use the term impedance as reactance never exists alone**
24
Q
What is an Ohm?
A
The derived SI unit of resistance.
Defined as the resistance present when a potential difference of 1 V across a conductor produces a current of 1A.
The same unit is used for reactance and impedance.
Voltage (V) = Current (A) x Resistance (Ω)
V = IR
25
What is Ohm's Law?
The strength of an electrical current is directly proportional to the potential difference and inversely proportional to resistance/impedance.
26
What is an inductor?
An electrical component that opposes changes in current flow by generation of back electromotive force.
Used in circuits as a high frequency filter.
27
What is inductance?
A measure of the ability of an inductor to generate a resistive electromotive force under the influence of changing current.
28
What is a Henry?
The derived SI unit of inductance, defined as the inductance of an inductor when a current 1A flowing in the inductor generates a magentic field strength of 1 weber.
29
What is absolute pressure?
Atmospheric pressure plus gauge pressure
30
What is gauge pressure?
The pressure measured in a system relative to the surrounding atmospheric pressure.
31
What is light?
Electromagnetic radiation of a wavelength that is visible to the human eye, usually around 400 nm to 700 nm, which, like all electromagnetic radiation, travels at a speed of approx 300,000 km/s in a vacuum.
32
What is sound?
Waves of pressure oscillations which are transmitted through a medium (which can be solid, liquid or gas) at a frequency detectable by the human auditory apparatus, usually 20 Hz to 20 kHz
33
What is the Doppler Effect?
The phenomenon by which the frequency of reflected sound changes if the source and observer are in motion relative to each other.
34
What is the ideal gas?
A theoretical gas which completely obeys all 3 gas laws on account of it containing molecules of infinitely small size, which therefore occupy no volume themselves, and have no forces of attraction between them.
35
What is Boyle's Law?
The first gas law.
Which states that for a given amount of an ideal gas at a constant temperature, pressure is inversely proportional to volume.
P ∝ 1/V
36
What is Charles' Law?
The second gas law, which states that for a given amount of a ideal gas at a constant pressure, volume is directly
proportional to absolute temperature
(V∝ T)
37
What is Guy-Lussac's Law?
The third gas law, which states that for a given amount of a ideal gas at a constant volume, pressure is directly proportional to absolute temperature
(P ∝ T)
38
What is Avogadro's hypothesis?
For an ideal gas at a constant pressure and temperature, volume is directly proportional to the amount i.e. the number of moles of gas.
(V ∝ n).
This means that equal volumes of ideal gases at the same temperature and pressure contain an equal number of elementary particles.
39
What is Molar volume?
The volume of 1 mole of gas at STP which is 22.4L
40
What is the Universal Gas Equation?
A combination of the 3 gas laws and Avogadro’s hypothesis, which states that
PV=nRT
where P =pressure, V =volume,
n =number of moles, R = the universal gas constant and T=absolute temp.
41
What is Isothermal change?
When a gas is compressed or decompressed, it's heat energy changes. If the pressure change occurs slowly then there is time for equilibration to occur with the surroundings, so the temp of the gas will remain constant.
42
What is Adiabatic Change?
When a gas is compressed/decompressed, it's heat energy changes. If the pressure change occurs rapidly then equilibration with surroundings cannot occur and there will be a temperature change.
43
What is partial pressure?
The partial pressure of an individual gas in a gas mixture is the pressure which that gas would exert if it alone occupied the same volume as the mixture.
44
What is Henry's Law?
The amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas in equilibrium with the liquid
45
What is Dalton's Law of Partial Pressures?
The total pressure exerted by a gas mixture is equal to the sum of the partial pressures of the individual gases in the mixture.
46
What is an osmole?
The amount of solute that exerts an osmotic pressure of 1 atm when placed in 22.4 L of solution at STP.
47
What is osmolaRity?
The number of osmoles per litre of solution (mOsm/L)
It is dependent on temperature and pressure, therefore prone to inaccuracy, and difficult to measure.
48
What is osmolaLity?
The number of osmoles per kg of solvent (mOsm/kg), independent of temperature and pressure. Measured in the lab using colligative properties or estimated using bedside formula.
49
What are colligative properties?
Properties of a solution which vary according to the osmolaLity of the solution which are:
* decrease of freezing point (1.86 K per Osm/kg)
* decrease of vapour pressure = Raoult's Law
* increasing in boiling point
* increase in osmotic pressure
50
What is Raoult's Law?
The reduction of vapour pressure of a solution is proportional to the molar concentration of the solute.
51
What is osmotic pressure?
The pressure which needs to be applied to a solution to prevent inward flow of pure solvent (water) across a semi-permeable membrane
52
What is oncotic pressure?
Also known as colloid osmotic pressure.
It's the osmotic pressure exerted by plasma proteins.
Most of the osmotic pressure of fluids in the body is due to electrolytes, however as these can freely diffuse in and out of blood vessels, they don't influence passage of water between intravascular and interstitial fluid.
53
What is oil:gas partition coefficient?
The ratio of amount of a vapour or gas present in equal volume phases of gas and oil at equilibrium, at a given temperature 37C)
54
What is the blood:gas partition coefficient?
Ratio of the amount of vapour or gas present in equal volume phases of blood and gas, at equilibrium, at a given temperature
55
What is the Fick principle?
The total uptake or release of a substance by an organ is equal to the product of the blood flow to the organ and the arterio-venous concentration difference of the substance.
For oxygen:
VO2 = CO x (CaO2 –CvO2)
56
What is flow?
The quantity of a fluid (which can be gas or liquid) that passes a given point per unit time. Flow can be laminar or turbulent.
57
What is laminar flow?
Efficient flow of a fluid in which the particles move in parallel layers, each of which has a constant velocity but is in motion relative to its neighbouring layers. The fastest velocity is found in the centre of the flow (twice the average velocity of the fluid), and the slowest velocity is found at the outsides of the flow. Particles adjacent to the containing vessel walls have, in theory, no motion at all.
58
What is turbulent flow?
Inefficient flow of a fluid in which the particles move in errative directions, creating swirls and eddies.
59
What is the Bernoulli principle?
Derived from the principle of conservation of energy, and states that in a fluid flow, an increase in velocity will be accompanied by a reduction in pressure.
60
What is the venturi effect?
An application of the Bernoulli principle.
Where a fluid flows within a tube, a constriction in the tube causes an increase in velocity and consequently a reduction in pressure.
The reduction in pressure can be used to entrain other liquids/gases, which allows for applications such as the Venturi mask and nebulizers.
61
What is the Coanda effect?
The tendency of fluid flowing in proximity to a convex surface to follow the line of the surface rather than it's original course.
62
What is temperature?
A measure of the average kinetic energy of all the particles within an object or system.
63
What is heat?
Energy which is transferred between objects or systems at different temperatures.
64
What is latent heat?
Energy required for a substance to undergo a phase change.
65
What is latent heat of vaporisation?
The energy required, at a specified temperature, to transform a substance from it's liquid to gaseous phase, without temperature change (for 1 kg of substance).
66
What is heat capacity?
The energy required to raise the temperature of an object by one degree (for 1kg of substance)
67
What is a gas?
A substance in it's gaseous phase above it's critical temperature
68
What is a vapour?
A substance in it's gaseous phase below it's critical temperature
69
What is critical temperature?
The temperature above which the gaseous phase of the substance cannot be liquefied regardless of how much pressure is applied to it.
70
What is critical pressure?
The pressure required to liquefy the gaseous phase of a substance at it's critical temperature.
71
What is the Poynting effect?
The dissolution of gaseous oxygen when bubbled through liquid nitrous oxide, with vaporization of the liquid to form a gaseous oxygen/nitrous oxygen mix.
The critical temperature of the nitrous oxide is lowered to a pseudocritical temperature, at which the nitrous oxide gas will condense out of the mix.
72
What is pseudocritical temperature?
The temperature at which a gas mixture such as entonox will separate into it's component parts.
It varies with pressure.
The pseudocritical temperature of entonox is highest at 117 bar when -5.5 °C
73
What is SVP?
The pressure of vapour in thermodynamic equilibrium with it's liquid phase in a closed system. This is therefore the max pressure of the vapour at a given temperature.
74
What is boiling point?
The temp at which the SVP of a substance in it's liquid phase is equal to the surrounding atmospheric pressure, and therefore all of the substance is changed into the gaseous phase.
75
What is the triple point?
The specific temperature and pressure at which all 3 phases of a substance (gas, liquid, solid) exist in equalibrium.
The triple point of water is at 273K and 611.7 Pa.
76
What is STP?
273.15 K and 101.3 kPa (1 atm)
77
What is humidity?
Amount of water vapour pressure in air or another gas mixture which can be absolute/relative
78
What is absolute humidity?
The mass of water vapour present in a gas mixture per unit volume (g/m3)
79
What is relative humidity?
The ratio of the vapour pressure of water vapour in a gas mix compared with the saturated vapour pressure of water at the same temperature.
80
What is Dew Point?
When a sample of air is cooled (and it's absolute humidity unchanged) the dew point is the temperature at which the relative humidity reaches 100% and water condenses out of the vapour phase to form liquid.
81
What is a supramaximal stimulus?
An electrical stimulus of sufficient current magnitude to depolarize all fibres within a given nerve bundle.
Usually \>60mA for a transcutaneous stimulation of a peripheral nerve.
82
What is train of four?
A pattern of peripheral nerve stimulation, where 4 square waves of supramaximal current, each 0.2 ms in duration are delivered at a frequency of 2 Hz every 500ms
83
What is double burst?
A pattern of peripheral nerve stimulation, where 2 bursts of supramaximal current delivered 750ms apart.
Each burst consists of 3 square waves of supramaximal current, each 0.2ms in duration, delivered at a freq of 50Hz.
84
What is tetanic stimulus?
A pattern of peripheral nerve stimulation, where square waves of supramax current, each 0.2ms in duration, are delivered at a frequency of 50Hz for 5s
85
What is natural frequency?
The frequency a system will adopt when freely set in motion
86
What is resonance?
The tendency of a system to oscillate with greater amplitude when driven by a force with a frequency close to it's natural frequency
87
What is damping?
A decrease in the amplitude of oscillations in a system as a result of energy loss due to frictional or other resistive forces
88
What is decontamination?
The process of removing contaminants such that they are unable to reach a site in sufficient quantities to initiate an infection or other harmful reaction. This always begins with cleaning and is followed by either disinfection or sterilization
89
What is cleaning?
Process of physically removing foreign material from an object without necessarily destroying any infective material.
Methods include washing with detergent, ultrasonic bath and low temperature steam.
90
What is disinfection?
The process of rending an object free from all pathogenic organisms except bacterial spores.
Methods include:
* pasteurization
* alcohol
* chlorhexidine
Hydrogen peroxide and gluteraldehyde 2% (for \>20mins) are high level disinfectants that have some sporicidal activity.
91
What is sterilization?
The process of rendering an object completely free from all viable infections including bacterial spores.
Methods include:
* autoclaving
* ethylene oxide
* gluteraldelyde 2% (for \>10hrs)
* gas plasma
92
What is an exponential?
A function where the rate of change of a variable at any point in time is proportional to the value of the variable at that time.
93
What is a first order reaction?
Exponential process, where reaction rate is dependent on the concentration of substrate
94
What is a zero order reaction?
A linear process, where reaction rate is constant and independent of the concentration of substrates.
A small increase in the dosing or plasma concentration will results in a large increase in the availability of the drug eg alcohol, phenytoin, thiopentone, aspirin, theophylline.
95
What is summation?
The actions of 2 drugs are additive but each has an independent action
96
What is synergism?
The combined effect of 2 drugs is greater than can be explained by a purely additive effect.
97
What is potentiation?
The action of one drug is amplified by the addition of another, which has no independent action of it's own.
98
What is antagonism?
The action of one drug is inhibited by the addition of another
99
What is a ligand?
A molecule that binds to a receptor
100
What is the dissociation constant?
The dissociation constant is the molar concentration of a drug at which 50% of receptors are occupied at equilibrium.
This provides a
measure of affinity.
KD=([D].[R])/[DR]
101
What is affinity?
A measure of how avidly a drug binds to a receptor
102
What is efficacy?
Intrinsic activity, a measure of the magnitude of the effect once the drug is bound.
103
What is potency?
A measure of the quantity of drug needed to produce maximal effect.
Quantified using the median effective concentration or median effective dose.
104
What is the median effective concentration? (EC50)
The concentration of a drug that induces a response of a magnitude exactly half way between baseline and the maximal response possible,
105
What is the median effective dose? (ED50)
The does of a drug that induces a specified response in 50% of subjects in a population.
106
What is the median lethal dose? (LD50)
The does of a drug that is lethal in 50% of subjects in a population
107
What is a therapeutic index?
Quantifies the balance between a drug's useful effects and it's toxic effects, often defined as LD50/ED50
108
What is an interaction?
The effect of a drug is modified by another drug.
Can be physicochemical (outside or inside body), pharmacokinetic (ADME) or pharmacodynamic (summation, synergism, potentiation, antagonism).
109
What is an agonist?
A drug with receptor affinity and intrinsic activity. Full, partial or inverse.
110
What is a full agonist?
A drug with receptor affinity and full intrinsic activity, meaning once bound it can produce a maximal response (eg noradrenaline).
111
What is a partial agonist?
A drug with receptor affinity and partial intrinsic activity, meaning once bound it can only produce a sub-maximal response (eg buprenorphine).
Will behave as antagonists in the presence of sufficient doses of full agonist.
112
What is an inverse agonist?
Drug with receptor affinity and negative intrinsic activity that produces an effect opposite to that seen in the agonist (eg flumazenil, atropine).
113
What is an antagonist?
A drug that inhibits the agonist from producing a response.
Competitive, non-competitive or irreversible.
114
What is a competitive antagonist?
Drug with receptor affinity and no intrinsic activity, which blocks the agonist binding site, it's inhibitory effects can be overcome by increasing the concentration of the agonist (eg atracurium).
115
What is a non-competitive antagonist?
A drug that binds at a different site to the agonist and causes a conformational change in the receptor that prevents it's activation despite agonist binding.
Cannot be overcome by increasing the concentration of the agonist, but will eventually dissociate with time (eg ketamine).
116
What is an irreversible antagonist?
A drug that either binds at the agonist binding site or at a distant site, which permanently prevents receptor activation.
Cannot be overcome by increasing the concentration of agonist, and will not dissociate with time (eg phenoxybenzamine).
117
What is an allosteric modulator?
Drug that binds at a different site to the agonist and either increases or decreases the affinity of the receptor for the agonist (eg benzodiazepines).
118
What is dose ratio?
The factor by which the agonist concentration must be increase when in the presence of a competitive antagonist to produce an equivalent response,
119
What is bioavailability?
The fraction of drug that reaches the circulation compared with the same does given intravenously.
Calculated by using the AUC of the given concentration-time curve to the AUC of the IV concentration-time curve.
120
What is hepatic extraction ratio?
The fraction of total drug removed from the blood by the liver with each pass through it.
Dependent on rate of uptake of the drug by hepatocytes and the capacity of the enzyme system to metabolise the drug.
The rate of metabolism of drugs with a high ER is most dependent on hepatic blood flow. The rate of metabolism of drugs with a low ER and high PB is most dependent on level of PB. The rate of metabolism of drugs with a low ER and low PB varies little with changes in either hepatic blood flow or PB.
121
What is volume of distribution?
Theoretical volume into which a drug distributes following it's administration
(VD = dose/CO = Cl.τ = Cl/k)
122
What is clearance?
The volume of plasma from which a drug is completely removed per unit time (ml/min)
123
What is elimination?
Removal of drug from plasma, which may occur due to metabolism or excretion.
Relim = Ct.Cl
124
What is excretion?
Removal of drug from the body (either directly or it's metabolites)
125
What is first order elimination?
An exponential process where the rate of elimination at any time depends on the drug concentration at that time.
A constant proportion of drug is eliminated per unit time,
126
What is zero order elimination?
A linear process where the rate of elimination at any time is constant and independent of the drug concentration.
A constant *amount* of drug is eliminated per unit time.
This can occur when enzyme systems become saturated.
127
What is elimination half life?
1. The time taken for the plasma concentration to drop to 50% of it's original value.
2. Time constant multiplied by natural logarithm of 2.
128
What is the time constant?
1. The time it would taken for all the drug to be eliminated if elimination continued at the initial rate.
2. Time taken for plasma concentration to drop to 37% of it's original value.
3. Reciprocal of the rate constant.
4. Half life divided by the natural logarithm of 2.
129
What is context sensitive half time?
The time taken for plasma concentration of a drug to fall to 50% of it's value on cessation of an infusion designed to maintain a steady state plasma concentration.
130
What is a compartmental model?
Pharmacokinetic models which help us predict how the body will handle a given dose of drug.
These assist with calculation of doses and are the basis of target-controlled infusions.
131
What is tachyphylaxis?
Rapid decrease in magnitude of response to the same dose of a drug, eg ephedrine due to exhausted NA stores
132
What is desensitization?
Slower decrease in magnitude of response to the same dose of a drug.
Thought to be due to decrease in receptor or G-protein numbers, or reduced receptor affinity (eg opioids, nitrates, adrenaline).
133
What is tolerance?
The need to give larger doses to obtain the same magnitude of response with desensitization.
134
What are isomers?
Molecules with the same molecular formula (therefore same number of individual atoms) but different atomic arrangements.
135
What are structural isomers?
Molecules with the same molecular formula but a different order of atomic bonds.
Subdivided into static (chain, position or functional group) and dynamic (tautomers).
136
What are stereoisomers?
Molecules with the same molecular formula and same order of atomic bonds, but different spatial atomic arrangement.
Subdivided into enantiomers (also known as optical steroisomers) and diasteroisomers (geometric or multichiral).
137
What are enantiomers?
Isomers with one chiral centre which form non-superimposable mirror images of each other. Also called optical steroisomers because each isomer rotates plane polarized light in a different direction.
138
What is a chiral centre?
An atom with 4 dissimilar groups attached to it, which can be a carbon atom or quaternary nitrogen atom.
139
What are diasteroisomers?
Complex stereoisomers which to not form mirror images of each other.
Either have multiple chiral centres or are geometric steroisomers with variation occuring around a rigid molecular structure, usually a double bond or ring.
140
What is a racemic mixture?
Preparation of two enantiomers of a compound in equal proportions
141
What is the Seebeck effect?
In a circuit composed of 2 dissimilar metals, a potential difference is produced between the junctions of these metals when the junctions are at different temperatures.
The bases of a thermocouple.
142
What is general anaesthesia?
Reversible loss of consciousness, awareness and response to pain.
143
What is MAC?
A measure of the potency of inhaled anaesthetic agents, defined as the minimum alveolar concentration of the agent at steady state required to prevent reaction to a standard surgical stimulus, usually a skin incision, in 50% of subjects at 1 atm.
144
What is the Meyer-overton hypothesis?
The potency of an anaesthetic agent is directly proportional to it's lipid solubility. Therefore, it is proposed that the mechanism of action of these agents is at a lipid site.
This was further developed to the critical volume hypothesis.
Examples of problems are isoflurane & enflurane, and extreme outliers (eg ketamine).
Superseeded by the protein site-of-action hypothesis.
145
What is tidal volume?
The volume of gas inhaled or exhaled during the course of a normal resting breath.
146
What is residual volume?
The volume of gas remaining in the lungs after a maximal forced expiration.
147
What is the inspiratory reserve volume?
The volume of gas that can be further inhaled at the end of a normal tidal inspiration.
148
What is expiratory reserve volume?
The volume of gas that can be further exhaled at the end of normal tidal expiration.
149
What is capacity?
The sum of 2 or more lung volumes
150
What is total lung capacity?
The total volume of gas in the lungs at the end of a maximal inspiration
151
What is vital capacity?
The total volume of gas inhaled when a maximal expiration is followed immediately by a maximal inspiration.
The sum of ERV, VT and IRV.
152
What is functional residual capacity?
The total volume of gas that remains in the lungs at the end of a normal tidal expiration.
The sum of ER & RV.
This is the point where the inward elastic recoil forces of the lung are balanced by the outward, springlike forces of the chest wall.
Modified by factors in 3 categories:
lung size, lung pathology, diaphragmatic displacement
153
What is closing volume?
The volume of gas exhaled between the beginning of small airway collapse and the end point of maximal expiration.
154
What is closing capacity?
Total volume of gas that remains in the lungs when dynamic small airway collapse begins on expiration.
The sum of CV and RV.
Reaches supine FRC by age 44 and standing FRC by age 66.
155
What is FEV1?
Following a maximal inspiration, the volume of gas which can be forcibly exhaled in 1 second.
Used to calculate FEV1/FVC ratio in health is \>75%.
156
What is a shunt?
Areas of the lung that are PERFUSED but not VENTILATED (blood passes through without being involved in gas exchange)
157
What is dead space?
Areas of the lung that are VENTILATED but not PERFUSED.
Gas is inhaled then exhaled without being involved in gas exchange. Can be anatomical or alveolar, combined to give physiological dead space.
Physiological dead space can be calculated from Bohr equation.
158
What is anatomical dead space?
The volume of the conducting airways that does not contain any respiratory epithelium, which stretches from the nostrils to the 16th generation terminal bronchioles.
Measured using Fowler's method.
159
What is alveolar dead space?
The volume of those alveoli that are ventilated but not perfused.
160
What is the Bohr effect?
The reduction in Hb's affinity for O2 and therefore rightward shift of the oxyHb dissociation curve when there is a reduction in blood pH.
161
What is the haldane effect?
The phenomenon where deoxy-Hb can carry more CO2 than oxyHb
162
What is the Hamburger effect?
Bicarbonate ions diffuse out of erythrocytes and to maintain electroneutrality chloride ions diffuse in.
163
What is compliance?
The change in volume per unit change of pressure.
164
What is static compliance?
The compliance of the lung measured when all gas flow has ceased.
Higher than dynamic compliance.
165
What is dynamic compliance?
The compliance of the lung measured during the respiratory cycle when gas flow is ongoing
166
What is lung resistance?
The change in pressure per unit change of volume
167
What is cardiac output?
The volume of blood ejected by the left ventricle into the systemic circulation every minute
168
What is preload?
The length of the cardiac muscle fibres immediately prior to contraction which is dependent on the end-diastolic volume. Clinically equated to the end-diastolic pressure which is estimated using CVP for the RV and PCWP for the LV.
169
What is afterload?
The tension developed in the cardiac muscle fibres during contraction which is dependent on the mechanical resistance to shortening of the muscle fibres.
Often clinically equated to SVR although this is a poor surrogate as afterload is also depdent on wall thickness and aortic valve.
170
What is contractility?
The intrinsic ability of cardiac muscle fibres to contract given a particular preload and afterload.
171
What is the Frank-Starling mechanism?
The strength of cardiac muscle fibre contraction is dependent on the initial fibre length.
EDV reflects initial fibre length, but as this cannot be measured we used EDP instead (although this assumes normal compliance) .
Strength of the fibre contraction can be equated to SV (although this assumes afterload and inotropy are constant).
172
What is end-diastolic pressure volume relationship?
If multiple pressure-volume loops for one ventricle are recorded, and the multiple end diastolic points taken, a line drawn through these points is the EDPVR.
Within normal parameters the relationship is a linear increase, but becomes curved upwards at higher volumes.
The line is moved up and left by decreases in compliance.
173
What is the end-systolic pressure volume relationship?
If multiple pressure-volume loops for one ventricle are recorded, and the end-systolic points taken, a line drawn through them is the ESPVR.
The relationship is a linear increase.
The line is moved up and left by increases in contractility, and down and right by decreases in contractility.
174
What is the anrep effect?
The phenomenon by which an increase in afterload causes an increase in myocardial contractility. The mechanism for which is unknown.
175
What is the Bowditch Effect?
The phenomenon by which an increase in HR causes an increase in myocardial contractility
176
What is the neuromuscular junction?
The chemical bridge between the motor neurone (usually an A alpha fibre) and the skeletal muscle fibre.
ACh is the neurotransmitter released from pre-synaptic membrane.
The post synaptic membrane is folded, the shoulders being covered with nicotinic ACh receptors and the clefts covered with AChEsterase enzyme.
177
What is an acid?
A proton donor (HA)
178
What is a base?
Proton acceptor (A)
179
What is a weak acid/base?
Not completely dissociated in solution
180
What is a strong acid/base?
Completely dissociated in solution
181
What is a buffer?
A solution which resists changes to pH when an acid or base is added to it. Normally composed of a weak acid and it's conjugate base.
182
What is base excess?
The amount of strong acid which must be added to 1 litre of blood at 37C and with PaCO2 corrected to 5.3 kPa in order to restore its pH to 7.4
When the value is negative, this is the base deficit and is therefore the amount of strong base which must be added.
(standard BE is corrected to Hb 5 g/dL which is supposed to better reflect ECF acid-base)
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What is pKa?
The pKa of a weak acid/base is the negative logarith to the base 10 of the dissociation constant.
This is also the pH at which the weak acid or base is 50% dissociated in solution.
For a bugger system the pKa is the pH around which the buffer has it's greatest buffering capability.
184
What is the Henderson-Hasselbach equation?
Relates pH to the pKa and concentrations of proton donor and acceptor
185
What is the Gibbs Donnan equalibrium?
The equilbrium reached by a charged ion on either side of a semi permeable membrane, which reflects a balance of the concentration and electrochemical gradients acting on it.
186
What is pain?
An unpleasant sensory or emotional experience associated with actual or potential tissue damage
187
What is chronic pain?
Pain persisting for \>12 weeks
188
What is neuropathic pain?
Pain caused by a primary lesion or dysfunction of the peripheral or CNS
189
What is BMR?
The amount of energy liberated by catabolism per unit time, under standardised conditions, these being a relaxed subject at a comfortable temperature, over 12 hrs after eating
190
What is Hb?
A haemoprotein composed of 4 globin chains
Each associated with it's own haem moeity, which is a porphyrin ring with an iron ion at it's centre.
Each Hb molecule therefore has 4 haem groups within it, allowing it to carry 4 O2 molecules.
191
What is cytochrome P450?
A family of haemoproteins which are enzymes contained within the smooth ER of hepatocytes in zone 3 of the hepatic acinus.
Responsible for many phase 1 oxidative reactions of hepatic drug metabolism.
192
What is a phase 1 reaction?
Hydrolysis, oxidation and reduction (HOR)
193
What is a phase 2 reaction?
Glucuronidation, acetlyation, sulphation and methlyation (GASM)
Phase 1 + 2 = (HOR) (GASM)
194
What is the portal circulation?
A circulation which drains the capillary bed of one organ structyre to the capillary bed of another, usually through a vein or venule.
Eg hepatic portal circulation, hypothalamo-pituitary circulation and renal circulation
195
What is the mean?
Measure of central tendency, calculated by summing all the data points then dividing the total by n.
Used to describe parametric data
196
What is the median?
Middle data point of the sample, with equal numbers of data points lying above and below it
197
What is the mode?
Most frequently occuring variable
198
What is variance?
A measure of the spread of data around the mean
199
What is standard deviation?
Measure of the spread of data around the mean.
Defined as the square root of the variance.
Easier to understand because it's in the same units as data being described,
68% of data points lie within 1 SD of either side of the mean, 96% within 2, 99% within 3.
200
What is the standard error of the mean?
Used to determine whether the sample mean reflects the mean of the true population.
Calculated by dividing the SD by the square root of n.
Used to determine confidence limits.
201
What is parametric data?
Data which there is an assumption of an underlying distribution. Commonly the normal distribution.
202
What is non-parametric data?
Data in which we cannot make an assumption of an underlying distribution.
Eg skewed data
203
What is quantitative data?
Data represent points on a numerical measurement scale
204
What is qualitative data?
Data are placed into descriptive categories. Nominal vs ordinal.
205
What is continous data?
Quantitative data which can take any numerical value (eg height)
206
What is discrete data?
Quantitative data which can only take certain numerical values (eg number of children)
207
What is ratio data?
Any data series that has zero as a baseline (eg Kelvin temp scale)
208
What is interval data?
Any data series that includes zero as a point on a larger scale (eg celcius temp scale)
209
What is nominal data?
Qualitative data in which categories have an implicit order of magnitude (eg ASA grade)
210
What is ordinal data?
Qualitative data in which categories have no implicit order or magnitude (eg ABO blood group)
211
What is the freezing point?
Temperature at which liquid and solid phases of a substance of specified composition are in equilibrium at a given pressure. Liquid turns to a solid when it's temp is below freezing.
212
What is a calorie?
Amount of energy required to increase the temperature of 1g of water by 1C.
1 cal = 4.16 J
213
What is the specific heat capacity?
Amount of energy required to raise the temperature of 1 kg of a substance by 1C
SHC water = 4.16J/kg
SHC human body = 3.5J/kg
214
1 atm = 1 bar = 101kPa = 14.7 psi = 760mmHg
What is atmospheric pressure?
215
What is the concentration effect?
Rise in alveolar partial pressure of N2O is disproportionately rapid when administered in high concentrations
216
What is the second gas effect?
The phenomenon by which the speed of onset of inhalational anaesthetic agents is increased when they are administered with N2O as the carrier gas,
217
What is kinetic energy?
The energy a body possesses because of it's motion. It's the energy needed to accelerate the object from a state of rest to it's given velocity.
This energy = work it would do when decelerating to return to rest.
218
What is potential energy?
The energy of a body or system as a result of its position in an electric, magnetic or gravitational field.
It is the potential of that body to do work.
219
What is the latent heat of fusion?
Melting.
The amount of heat required to convert a unit mass of solid at it's melting point into a liquid without an increase in temperature.
220
What is pH the log of?
pH = -log10[H+]
the negative log to the base 10 of the H+ ion conc in solution
221
What is pKa the log of?
pKa = -log10 (Ka)
the negative log of the dissociation constant = the pH at which 50% of the drug is ionised and 50% is unionised.
222
What is an enzyme?
A biological catalyst that increases the speed of a chemical reaction without being consumed in the reaction
223
What is Graham's law?
The rate of diffusion of a gas is inversely proportional to the square root of it's molecular weight
224
What is Beer's Law?
The absorption of radiation increases (transmission decreases) as the concentration of a substance increases
225
What is Lambert's Law?
The intensity of transmitted light decreases exponentially as the distance travelled through the substance increases.
226
What is the isobestic point?
The point at which 2 substances absorb a certain wavelength of light to the same extent (ie reference point where absorption of light is indepedent of degree of saturation).
For oxy/deoxyHb = 590nm in red spectrum and 805 infrared spectrum
227
What does laser stand for?
Light amplification by stimulated emission of radiation
228
What is the piezoelectric effect?
A potential difference may be produced across crystalline substances when subject to a mechanical stress
229
What is somatic pain?
Localised pain due to activation of peripheral nociceptors
230
What is visceral pain?
Diffuse pain difficult to localise or referred to a specific structure distant to the source of pain
231
What is allodynia?
Painful response to a painless stimulus
232
What is hypovolaemic shock?
Loss of circulating volume - reduction in preload and cardiac output
233
What is cardiogenic shock?
Myocardial dysfunction - reduced systolic dysfunction and CO (MI/valve lesion)
234
What is obstructive shock?
Physical obstruction to cardiac filling - reduction in preload and CO (tamponade/PE)
235
What is distributive shock?
Reduction in SVR such that organ perfusion cannot be maintained (sepsis/neurogenic)
236
What is cytotoxic shock?
Uncoupling of O2 delivery and uptake (CO or cyanide poisoning)
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