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Homs > Homs Practical > Flashcards

Homs Practical Flashcards

1
Q

High pass

A

Allows higher frequencies and low pass is vice versa

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2
Q

Occluding both arteries

A

Brachial pulse

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3
Q

Nernst equation

A

Ek = 58log10 ([outside]ref/[inside]test)

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4
Q

Membrane circuit representation

A

Resistor, capacitor and voltage source in parallel

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5
Q

Membrane time constant

A

T = Rm x Cm

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6
Q

Voltage capacitance relationship

A

V= QC

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7
Q

Adding capacitor

A

Drops current to 0 then allows it to rise again as charged- reaches Vmax when fully charged

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8
Q

Time constant percentage charged

A

At time t, voltage is 63% of final voltage

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9
Q

Frequency of UK mains

A

50Hz

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10
Q

How is a partial short circuit formed

A

If tissue between two electrodes has low electric resistance- smaller potential difference than expected will be recorded

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11
Q

Stimulus artefact

A

Stimulating current directly to recording electrodes through body or liquid on surface

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12
Q

Earth electrode

A

Channels some unwanted stimulating current

AP unaffected

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13
Q

Swapping around recording electrodes

A

Upside down APs

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14
Q

Intracellular recording convention

A

Ext electrode= reference

Internal is test (therefore test relative to ext = negative)

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15
Q

Normal electrode set up

A

Reference electrode closer to stimulating cathode

Stim anode; stim cathode, earth, recording ref (external); recording test (internal)

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16
Q

Anode block

A

Having stim anode after stim cathode - leads to hyperpolarisation preventing impulse passing onwards

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17
Q

Recruitment

A

Adding lateral fibres- respond to stimulus- lateral fibre has higher frequency and longer latency than medial fibre

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18
Q

Direction of AP in medial and lateral fibres

A

Cranial- caudal in MGF, caudal-cranial in LGF

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19
Q

Temperature effect on APs

A

Affects kinetic properties of channel gating mechanisms- cooling slows rate of sodium channels opening therefore slower conduction velocity
Repolarisation slower and sodium channels inactivate slower and potassium channels open slower

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20
Q

Compound AP

A

Many muscle fibres response

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21
Q

Latency

A

Time between first stimulus and first sign of a response

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22
Q

Short PR interval

A

Wolff Parkinson white syndrome- extra rapid path for signals to pass from atria to ventricles

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23
Q

Long PR value

A

First degree AV block

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24
Q

Long QRS interval

A

Bundle branch block

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25
Q

Long QT interval

A

Long QT syndrome- genetic mutation

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26
Q

Electric systole

A

Time between Q wave to end of T wave (rest is diastole)

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27
Q

Exercise effect on systole and diastole pressures

A

Systole pressures increase, diastole pressures fall

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28
Q

Heart rate increase effects

A

Increases slope of pacemaker potential
Adrenergic stimulation B1 increases current through VGKC= more rapid repolarisation of cell after plateau = shorter cardiac AP
B1 stimulation = calcium pumps in SR work harder quicker removal of Ca2+ from cytosol= rapid relaxation

29
Q

Respiratory sins arrhythmia

A

Increase in HR on inspiration, decrease in HR in expiration

Normal

30
Q

Mean arterial pressure

A

D + 1/3(S-D)

31
Q

Active hyperaemia

A

From of metabolic auto regulation

Demand outpaces supply changing metabolic levels leading to vasodilatation

32
Q

Increasing exercise intensity on breathing rate

A

Increases proportionallly then disproportional as exercise becomes anaerobic (low pH)

33
Q

Exercise effect on Pulse rate

A

Increases over first minute then stabilises at steady state

34
Q

Exercise effect on %SpO2

A

No change - body not reliant on negative feedback for gas levels

35
Q

Alveolar ventilation equation

A

VA= (VECO2/PACO2) xK

36
Q

Cardiac output- fick

A

CO= rate of CO2 production/ (venous-arterial CO2)

37
Q

RQ

A

Amount of CO2 produced/ amount of O2 taken in

38
Q

how to avoid aliasing

A

set sampling rate at more than twixe frequency of origimal signal

39
Q

potential of membrane recorded as…

A

potential always reported as test relative to ref

40
Q

capacitive current

A

flow of electrons onto left plate and off of right plate- looks like current flowing through capacitor

41
Q

how to increase capacitance

A

larger surface area of plates, plates closer together (thinner insulating layer)

42
Q

capacitance key points

A

stores charge
capacitor takes time to charge and discharge- slows change in voltage
capacitance of excitable cell membrane affects velocity of AP conduction

43
Q

how does myelination increase conduction velocity

A

not through T=RC as myelination increases R but also decrease C- not much change
but increased R increases length constant (lambda)

44
Q

colours of electrodes

A

cathode (black)
anode (red)
earth (green)

45
Q

latent period

A

time taken for AP to travel from stim cathode to 1st recording electrode

46
Q

conduction velocity through absolute method and reeason why its not great

A

use single distance (D) and latent period (LP)
v=D/LP
delay with initiating AP in first place and AP peak measuring to occurs after first sign of electrical activity- gives v slighlty lower than true conduction v
if use strong stim current, AP generated further from cathode therfore v too high

47
Q

accurate conduction v

A

compare equivalent APs on two traces, obtained when recording at 2 diff distances -difference method
v= (D2-D1)/(LP2-LP1)

48
Q

ST segment

A

ventricular muscle all depolarised

49
Q

what does a bio amp do

A

electrically isolated device for increasing size of v small voltage (safe)

50
Q

aorta bp compared to pulm artery bp

A

5-6 x greater

51
Q

how to increase systolic p

A 
more blood pushed out
arteries stiffer (less compliant)
52
Q

misdiagnose hypertension using pressure cuff if…

A

if cuff v narrow relative to arm- gives falsely high bp (misdiagnose hypertension)- ie obese subject with larger arms

53
Q

misdiagnose hypotension if..

A

cuff wide relative to arm- falsely low bp

54
Q

recommended width of cuff

A

40% circumference of midpoint of arm

55
Q

bp slighlty higher in which arm

A

right- use this as standard

56
Q

cause of functional and reactive hyperaemia

A

hypoxia

accumulation of vasodilator metabolites (ie increase in PCO2, lactic acid, adenosine, K+ and temp, fall in pH)

57
Q

how do pulse oximeters work

A

measures colour of blood to determine percentage saturation of arterial blood (more saturated = brighter red)
gives peripheral oxygen saturation (%SpO2)

58
Q

end expiratory sample

A

first gas similar to atmospheric air (dead space)

terminal stages=exhalation from alveoli(arterial blood)

59
Q

resp gas analyser measures

A

Dried O2 and CO2 percentages

60
Q

measurements made in douglas bag(CO) exp

A 
arterial blood gas concs
amount of gas exhaled in 5 mins
no. of breaths in 5 mins
conc of O2 nad CO2 in exhaled gas 
last 3 measuremtns = tidal vol, rate of CO2 and O2 consumption
61
Q

why shouldnt you hyperventilate in douglas bag exp

A

blows off a lot of stored CO2- gives abnormally high values for CO

62
Q

haemorrhage events

A

BV falls -> decrease in VR -> decrease MSP -> decrease atrial P -> decrease CO -> HR increases to try to restoore MAP -> increase in TPR -> decrease in splanchnic flow

63
Q

normal glucose levels

A

4-7mmol/l

64
Q

cephalic phase of digestion

A

parasympathetic stimulation of beta cells via vagal ACh = anticipatory insulin release

65
Q

what potentiates insulin release in response to oral glucose

A

incretins- GIP and GLP-1

66
Q

How is insulin release inhibited in exercise

A

sympathetic stimulation of alpha-2 receptors - increases blood glucose

67
Q

most common source of error in RQ

A

hyperventilation- increases amount of CO2 unloaded from blood (should be aiming for an expired %O2 od 14-17%

68
Q

how much heat does each gram of sweat take

A

2.45kJ

Homs (3 decks)

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