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Flashcards in Pharmacology Deck (320)
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1

what 2 endogenous substance act on the B1-adrenoceptors in the heart?

noradrenaline (sympathetic transmitter)
adrenaline (hormone)

2

what G protein do B1-adrenoceptors in the heart couple to?

Gs proteins

3

when a B1-adrenoceptor is stimulated, what does the Gs coupled protein do?

acitvates adenylyl cyclase to increase intracellular cAMP concentration
stimulates pKA (within myocytes)

4

what does increasing intracellular cAMP concentration within the pacemaker cells do?

increases slope of pacemaker potential and so increases heart rate
(positive chronotrophic effect)

5

what endogenous substance acts on M2 muscarinic cholinoreceptors in the heart?

ACh

6

What G protein do M2-adrenoceptors in the heart couple to?

Gi

7

when a M2 muscarinic receptor is stimulated, what does the Gi coupled protein do?

1. decreases activity of adenylyl cyclase to decrease intracellular concentrations of cAMP
2. opens potassium channels to cause hyperpolarisation of SA node

8

what does decreasing intracellular concentrations of cAMP and opening potassium channels within pacemaker cells do?

decreases slope of pacemaker potential and so decreases heart rate
(negative chronotropic effect)

9

what are the 3 internodal pathways between the SA node and the AV node? (contained within the right atrium)

anterior internodal pathway
middle internodal pathway
poterior internodal pathway

10

what is pathway goes to the left atrium from the SA node?
(apart from cell-cell spread of excitation through gap junctions)

anterior interatrial myocardial band
(Bachmann's Bundle)

11

what does the bundle of his split up into?

right bundle branch
left bundle branch (which splits into anterior division and posterior division)

12

what is the hierarchy of pacemakers?

SA > AV > other cells within the heart

13

why is it necessary that the AV node can produce an AP?

in case the SA node fails

14

why is it necessary that other cells within the heart can produce an AP? (ie like within the conducting fibres)

in case both the SA and AV nodes fail

15

what is the inwards current of the pacemaker potential also known as?

I(f)
funny current

16

what stimulates the inwards current of the pacemaker potential? (funny current)

1. hyperpolarisation
(ie turning resting potential negative)
2. cAMP

17

what does blocking HCN (hyperpolarisation-activated cycline neucleotide gated) channels do to the pacemaker potential slope?

decreases the slope
(negative chronotrophic effect)

18

what does ivabradine do?

a selective blocker of HCN channels so slows the heart rate down

19

what medical condition is ivabradine used in and why?

angina
because slower rate reduces O2 consumption and so reduces coronary artery supply requirement

20

what does isoprenaline do?

a agonist of B-adrenoceptors and so increases intracellular cAMP concentration and so increases heart rate

21

what do thyroid hormones do to heart rate?

increase heart rate
(positive chronotrophic effect)

22

what does adenosine do to the heart rate?

decreases heart rate
(negative chronotropic effect)

23

what does nitric oxide do to the heart rate?

increases heart rate
(positive chronotrophic effect)

24

what are the 6 effects of the sympathetic system on the heart?

1. increases heart rate
2. increases contractility
3. increases conduction velocity in AV node (decreases delay)
4. increases automacity (tendancy for non-nodal regions to acquire spontaneous activity)
5. decreases duration of systole
6. decreases cardiac efficiency (with respect to O2 consumption)

25

what are the 4 effects of the parasympathetic system on the heart?

1. decreased heart rate
2. decreased contractibility
3. decreased conduction in AV node (increased delay)
4. overaction may cause dysrhythmias in the atria (not fatal)

26

what is the Frank-Starling mechanism?

the more the myocardium is stretched, the greater force it exerts upon contraction
(despite of autonomic control)
[ie the greater the venous return, the greater the stroke volume]

27

what autonomic control can tweak the frank-starling curve?

sympathetic

28

what happens to the frank-starling curve in cardiac failure?

curve fails as force is not able to match the venous return (stretch)

29

what 3 factors contribute to increased venous return? (and therefore increased stretch)

1. increased skeletal muscle activity
2. adrenergic effects on blood vessels (increased venous tone)
3. respiratory pump (increased depth and freq)

30

what does increased intracellular calcium cause?

contraction