Excitable Tissues and Biological Potentials

Question 1

Regarding the ECG (true or false):

It is always measured using gel electrodes on the skin

Answer 1

False. It may be measured using other sensors, e.g. oesophageal or epicardial electrodes, as well.

Question 2

Regarding the ECG (true or false):

Cardiac cells have a resting membrane potential of -90 mV

Answer 2

True

Question 3

Regarding the ECG (true or false):

The potential commonly measured at the surface is 10-20 mV

Answer 3

False. The measured potential is usually 1-2 mV because of attenuation by the chest wall.

Question 4

Regarding the ECG (true or false):

The QRS component is larger than the P wave because the ventricles are larger than the atria

Answer 4

True

Question 5

Regarding the ECG (true or false):

The pacemaker is the sinoatrial node

Answer 5

True

Question 6

Regarding the EEG (true or false):

It may be measured using scalp or intracranial electrodes

Answer 6

True

Question 7

Regarding the EEG (true or false):

Measured potentials from scalp electrodes are usually in mV

Answer 7

False. They are heavily attenuated by meninges and the skull so they are in microvolts.

Question 8

Regarding the EEG (true or false):

Morphologically, it broadly resembles an ECG

Answer 8

False. An EEG is much more complex and difficult to interpret than an ECG.

Question 9

Regarding the EEG (true or false):

Higher frequency activity is seen when patients are awake than when asleep

Answer 9

True

Question 10

Regarding the EEG (true or false):

Evoked potentials only provide information about the integrity of the cortex

Answer 10

False. Evoked potentials provide information about the stimulated pathway.

Question 11

Regarding the recording systems of biological potentials (true or false):

Anaesthetic practice commonly uses surface electrodes

Answer 11

True

Question 12

Regarding the recording systems of biological potentials (true or false):

Polarization refers to placing the sensing electrode in the wrong location

Answer 12

False. Polarization refers to chemical changes in the electrode caused by the biological potential.

Question 13

Regarding the recording systems of biological potentials (true or false):

The recording electrode may cause a battery effect

Answer 13

True

Question 14

Regarding the recording systems of biological potentials (true or false):

Common-mode rejection of an amplifier refers to the range of frequencies across which the device functions

Answer 14

False. This is bandwidth, not common-mode rejection.

Question 15

Regarding the recording systems of biological potentials (true or false):

The gain of an amplifier is the ratio of the output to the input amplitude

Answer 15

True

Question 16

Regarding biological potentials (true or false):

Fourier analysis refers to the breaking down of complex waves into simpler components

Answer 16

True

Question 17

Regarding biological potentials (true or false):

A peripheral nerve stimulator used for neuromuscular blockade uses the same current as one used for regional anaesthesia

Answer 17

False. The one used for regional anaesthesia uses much lower current.

Question 18

Regarding biological potentials (true or false):

All evoked potentials involve stimulation of a sensory nerve

Answer 18

False. Motor evoked potentials may be used.

Question 19

Regarding biological potentials (true or false):

All artificial cardiac stimulators require insertion of wires into the heart

Answer 19

False. Transcutaneous pacing may be employed.

Question 20

Regarding biological potentials (true or false):

Cells maintain a resting membrane potential actively

Answer 20

True