Physiological Measurements 1

Which mechanisms determine the resting membrane potential? (multiple choice)

• The size of the cell
• Na+ and K+ concentration gradients
• Na+ permeabiilty through the membrane
• K+ permeability through the membrane
• Na+/K+ pump

Sudden opening of voltage-gated Na+ channels causes

• Nothing
• Action potential repolarization
• Influx of Na+ into the cell and fast depolarization
• Na+ ions move from inside the cell to the extracellular space along a concentration gradient, which triggers an action potential

Reorder the 5 phases of a cardiac action potential (where 1 = phase 0 and 5=phase 4 )

• Ca++ channels close & slow K+ open

• Ca++ channels open & K+ channels close

• Fast Na+ channels close

• Resting potential

• Fast Na+ channels open

Connect ECG waves/components with corresponding phenomenon

• Ventricular depolarization

• ST-segment

• Ventricular myocytes at plateau

• QRS complex

• Atrial depolarization

• P-wave

• Ventricular repolarization

• T-wave

How many electrodes do you need to record a 12-lead ECG?

• 12

• 24

• 6

• 10

The Einthoven's triangle is:

• A beautiful painting by the famous painter Mark Einthoven

• The main square of Einthoven, a pretty Dutch town

• The spatial representation of limb leads, representing electrical potential at the right arm, left arms, and left foot

• The average of all chest leads

The Wilson Central Terminal is:

• A virtual reference point for unipolar precordial leads, measured as the average of 3 limb leads

• A virtual reference point for unipolar precordial leads, measured as the average of chest leads

• A virtual reference point for bipolar electrodes

• The largest terminal of Wilson's airport

In an ECG showing right-axis deviation lead I may be negative because:

• Stranger things have happened

• The main vector representing ventricular depolarization is pointing towards a direction which is opposite to lead I

• The main vector representing ventricular depolarization is pointing towards lead I

Reorder the following type of noise that may affect the ECG

• Bizarre ECG pattern (see rhythm strip)

• Power Line Noise

• High frequency interferences (50 Hz)

• electromyographic noise

• ECG amplitudes too small or large

• Poor electrode contact

• High frequency, spiky, interferences

• Over/Under-calibration

Match a type of noise with its possible solution

• Recalibrate ECG machine

• Power Line Noise

• Improve isolation, use notch filter

• Over/Under-calibration

• Ask patient to relax, band-pass filer

• electromyographic noise

• Improve contact and/or use gel

• Poor electrode contact