A3 Anti-arrhythmic drugs

Question 1

Define Arrhythmia….. (as a result of…)

Answer 1

Group of conditions where heart beats: irregularly, too fast, or too slowly as a result of abnormal electrical activity.

Question 2

how may arrhythmia arise

Answer 2

ischaemia, infarction, fibrosis or drugs

due to altered formation of impulses/ conduction of impulses through heart

Question 3

Cardiac arrhythmias-symptoms

Answer 3

Palpitations
Heart failure symptoms (e.g. edema)
Fatigue
Dyspnea (breathing difficulties)
Dizziness
Angina
Syncope (fainting)
No symptoms at all

Question 4

Explain

1. Ectopic beats
2. Heart block
3. Re-entry phenomenon

Answer 4

1. beats arising from fibres/group of fibres outside normal pacemaker region (SA node))
2. obstruction in electrical conduction system
3. Return of same impulse into a zone of heart muscle that it has recently activated

Question 5

Define

1. Excitability
2. Refractory period
3. Membrane responsiveness

Answer 5

1. ability to respond to stimuli by producing and conducting action potentials
2. Time following excitation during which a second action potential can not be elicited and conducted
3. relationship between membrane activation voltage and the maximal rate of rise of the action potential

Question 6

What affect do Antiarrhythmic drugs result in

- how do they achieve their effect

Answer 6

increase the refractory period or slow upstroke of action potentials or both
- control electrical signals by altering action potential generation or propagation.

Question 7

name and describe the 2 important features of ion channels

Answer 7

1. Gating: opening/ closing to give membrane potential

2. Ion selectivity - only certain ions are allowed to pass through

Question 8

which ions are high conc
1. inside
2. outside
how does membrane potential generate

Answer 8

1. K high inside
2. Na and Ca high outside
   one side must gain charge at the expense of the other

Question 9

describe mechanism of death by lethal injection

Answer 9

IV - anesthetic administered to cause unconsciousness

Potassium chloride given = cardiac arrest/ death

Question 10

1. depolarization due to which ion influx…

2. hyperpolarization due to

Answer 10

1. depolarization = Na influx
   - -> +ve feedback
2. hyperpolarization = K Efflux