Drugs and the Cardiovascular System – The Heart Flashcards Preview

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Flashcards in Drugs and the Cardiovascular System – The Heart Deck (57)
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1

What is the major store of calcium within the cardiomyocyte?

Sarcoplasmic reticulum

2

Channels associated with initiating a heart rate

If
ICa Transient
ICa Long lasting
Ik

3

Role of If channels

Associated with cAMP
Are hyperpolarisation activated cyclic nucleotide gated channels which tend to let in sodium during hyperpolarised times

4

Role of 2 calcium channels

Main drivers behind depolarisation

5

Role of Ik

Initiate repolarisation

6

The heart has two signalling pathways that are involved in elevating the level of two intracellular second messengers. What are these second messengers?

Ca2+ and cAMP

7

Which plasma membrane proteins allow calcium to enter the cell in response to depolarisation?

Dihydropyridine receptors

8

What happens to the calcium once it has passes into the cell viathis channel?

It binds to ryanodine receptors on the sarcoplasmic reticulum and cause calcium release from the SR

9

How does the calcium stimulate contraction?

It binds to troponin on the thin filament

10

What are the different ways in which calcium is removed from the myoplasm after it has stimulated contraction? Which method is responsible for the majority of calcium removal?

Plasma membrane calcium ATPase
Na+/Ca2+ exchanger
SERCA2a (sarcoendoplasmic reticulum calcium ATPase) –responsible for >70% of calcium removal

11

What features of contraction is SERCA2a responsible for and why?

Rate of calcium removal and so it’s responsible for the rate of cardiac muscle relaxation
Size of calcium store, which affects the contractility of the subsequent beat

12

What are beta adrenoceptors coupled with?

Adenylate cyclase – it increases cAMP, which is important in the opening of the If channel to begin depolarisation

13

How does the parasympathetic nervous system affect heart rate and contractility?

It is negatively coupled with adenylate cyclase

14

What are the determinants of myocardial oxygen supply?

Arterial oxygen content
Coronary blood flow

15

What are the determinents of myocardial oxygen demand?

Heart rate
Contractility
Preload
Afterload

16

What effect do beta-blockers and calcium channel blockers have on the channels responsible for the SA node action potential?

Beta-blockers decrease If and calcium channel activity
Calcium channel blockers only decrease calcium channel activity
These 2 affect both HR and contractility

17

Name a drug that decreases If activity.

Ivabradine (blocks the If channel)

18

What effect does Ivabradine have on contractility?

It has no effect on contractility because it doesn’t affect the calcium channels

19

What are the two types of calcium channel blocker?

Rate slowing - cardiac and smooth muscle effects
Non-rate slowing - only really potent in smooth muscle

20

What is a consequence of non-rate slowing calcium channel blockers?

Reflex tachycardia (baroreceptor reflex)

21

How do organic nitrates cause vasodilation in coronary vasculature?

Organic nitrates are substrates for nitric oxide production
The NO then diffuses into the smooth muscle and causes smooth muscle relaxation by activating guanylate cyclase
They are often given in angina patients before they exercise

22

How do potassium channel openers work?

They open the potassium channels and hyperpolarise the vascular smooth muscle so that it is less likely to contract

23

How do vasodilation and venodilation of nitrates and potassium channel openers reduce myocardial oxygen demand?

They reduce the pressure against which the heart is pumping (reduce afterload) and it also causes reduce venous return to the heart (reduced preload) meaning that contractility is decreased

24

As these drugs reduce the myocardial oxygen demand, what condition can they all be used to treat?

Angina pectoris

25

State some unwanted effects of beta-blockers.

Bradycardia
Hypotension
Hypoglycaemia in diabetics on insulin
Cold extremities (because of beta-2 blockade)
Bronchoconstriction
Fatigue
Impotence
Depression
CNS effects
Last 4 not examined

26

Under what circumstance must caution be taken when giving beta-blockers?

Cardiac failure – because they reduce heart rate and contractility it can have catastrophic consequences in cardiac failure patients
Reduced CO and increased vascular resistance

27

What are the side effects of verapamil?

Bradycardia and AV block
Constipation

28

What are the side effects of dihydropyridines?

Ankle oedema - due to vasodilation
Headaches/flushing - due to vasodilation in brain
Palpitations- reflex tachycardia

29

What is a simple classification of arrhythmias?

Based on its point of origin
Supraventricular, Ventricular and Complex

30

What is the main classification of anti-arrhythmic drugs and how are the drugs ordered?

Vaughan-Williams classification
I – sodium channel blockers
II – beta-blockers
III – prolongation of repolarisation (mainly due to potassium channelblockade)
IV – calcium channel blockers