Biological Measurement

Question 1

State ways to ensure good electrical contact between the electrodes and a person in an ECG.

Answer 1

• Electrodes that aren’t made from a material which does not become polarised.
• Electrodes coated with a conducting gel.
• Hair and dead skin cells removed.

Question 2

State properties of the amplifier needed to amplify the signal from the electrodes.

Answer 2

• High gain
• High input impedance
• Low noise

Question 3

Describe the processed involved in the production of an action potential when a nerve is stimulated.

Answer 3

• Sodium ions move into the cell
• PD rises from -70 to 0 (depolarisation)
• When stimulated by an electrical signal potassium ions move out of of cell through gate.
• ## PD falls to -70 (reverse polarisation)

Question 4

Describe the response of the heart to an action potential originating in the sino-atrial node.

Answer 4

• Electrical impulse causes atria muscles to contract
• Blood is pumped into ventricles
• Pulse is then delayed before ventricular node is fired
• Ventricles contract
• Pumps blood out of heart to lungs and body

Question 5

Describe the ion movement that produces depolarisation.

Answer 5

Sodium moves into the cell.

Question 6

Describe the ion movement that produces repolarisation.

Answer 6

Potassium moves out of the cell.