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342 > cardiovascular current treatments 2 > Flashcards

cardiovascular current treatments 2 Flashcards

1
Q

cardiac action potential

A

change in membrane potential/ voltage across cell membrane of myocardial cells

not initiated by nervous activity unlike skeletal muscle fibres, instead heart has pacemaker cells that automatically generate action potentials

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2
Q

where are pacemaker cells found

A

in sinoatrial SA node in the right atrium

dysregulation can cause arrhythmia

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3
Q

cardiac action potential differs from neuronal action potential due to

A

differences in ion flux

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4
Q

neuronal action potential stages - 5

A

stimulus

depolarisation (sodium ion influx)

repolarisation (potassium ion efflux)

hyperpolarisation

resting potential

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5
Q

cardiac action potential stages phase 0 -4

A

phase 0 - depolarisation due to sodium ion influx

phase 1 - initial repolarisation due to sodium ion channels closing, potassium ion channels opening and closing rapidly

phase 2 - plateu due to calcium ion influx balanced by potassium ion efflux

phase 3 - rapid repolarisation due to calcium ion channels closing and rapid potassium ion efflux

phase 4 - resting potential due to sodium potassium ion pump stabilising membrane potential

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6
Q

cardiac cells have ___ refractory periods where they reset the membrane potential before a second stimulus

A

2

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7
Q

cardiac cells have 2 refractory periods where they reset the membrane potential before a second stimulus. when are these

A

phase 0 - part way through phase 3

impossible to produce another action potential during this - absolute refractory period

immediately after is the relative refractory period until end of phase 3

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8
Q

how is cardiac action potential activity recorded

A

electrocardiogram ecg

arrhythmias can be seen here if looks irregular

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9
Q

what are antiarrythmic drugs used to treat

A

abnormallyfast heart rhythms aka tachycardia

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10
Q

tachycardia examples

A

atrial fibrillation

supraventricular tachycardia

ventricular tachycardia

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11
Q

atrial fibrillation

A

rapid irregular beating on the atria

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12
Q

supraventricular tachycardia

A

fast heart rhythms from the top of the heart

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13
Q

ventricular tachycardia

A

rapid beating of ventricles

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14
Q

amiodarone used when

A

antiarrythmic drug - cardiac dysrhythmias

target SA node

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15
Q

amiodarone has ___ mechanisms of action

A

several

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16
Q

amiodarone mechanisms of action

A

inhibit potassium ion channels reducing efflux in phase 3

inhibits sodium ion channels in phase 0, thus depolarisation and repolarisation slowed down

blocks calcium channels so longer plateu

overall reduces cardiac action potential, slows heart rate down, prevent rapid heart beating

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17
Q

digoxin used when

A

treatment of atrial fibrillation, atrial flutter, heart failure

reduces heart rate, increases myocardial contractility - strength at which heart can push blood out of chambers

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18
Q

digoxin mechanism of action

A

inhibits alpha subunits of sodium-potassium ATPase ion channels

mainly but not exclusively inhibits these pumps in myocardium

also reverses sodium calcium exchange pump, increasing intracellular cacium

inc binding of calcium to troponin C

promotes stronger contraction between two filaments thus muscular force during heart contraction but without increasing energy expenditure

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19
Q

sodium potassium ion pump

A

exports 3 sodium ions
imports 2 potassium ions

needs ATP

net export of 1 charge per pump cycle, so membrane potential of cells is negative - net loss of positive charge

20
Q

sodium calcium ion pump

A

imports 3 sodium ions

exports 1 calcium ion

is reversible, so can export 3 sodium ions for every calcium ion imported after digoxin treatment

increases intracellular calcium

21
Q

troponin C

A

protein that forms part of thin filaments alongside actin

calcium binding causes conformational change of troponin C allowing better interaction of actin and myosin

promotes stronger contraction between two filaments thus muscular force during heart contraction but without increasing energy expenditure

22
Q

hypertension

A

high blood pressure in arteries

long term or acute

23
Q

long term hypertension is a risk factor for

A

stroke, heart attack, coronary artery disease

24
Q

high blood pressure is considered

A

above 140/90mmHg

25
Q

normal blood pressure is considered

A

less than 120/80 mmHg, dec if more active

26
Q

what is used to treat hypertension

A

verapamil

used for angina and supraventricular tachycardia also

27
Q

verapamil mechanism of action

A

L-type calcium channel blocker

inhibits calcium ions into cell

dec impulse conduction in SA and AV node

for hypertension specifically, relax smooth muscle lining blood vessels so dec blood pressure by inhibiting calcium ions in smooth muscle cells, reduction in actin myosin interaction

28
Q

where are L-type calcium channels found

A

SA node and AV atrioventricular nodes

also in smooth muscle lining blood vessels

29
Q

what is blood pressure the result of

A

balance of vasoconstriction and vasodilation

also hormones

30
Q

what is vasoconstriction endogenously controlled by

A

epinephrine and norepinephrine

31
Q

epinephrine and norepinephrine signalling

A

via alpha 1 adrenergic receptor

(Gq coupled receptor)

raises intracellular caclium

activates myosin light chain kinase

32
Q

what hormones control blood pressure

A

angiotensin

33
Q

what is angiotensin

A

peptide hormone

34
Q

where is angiotensin produced

A

liver

35
Q

what precursor is angiotensin produced in the liver as

A

angiotensinogen

36
Q

angiotensinogen pathway

A

activated by renin

to angiotensin 1

converted by angiotensin-converting enzyme ACE

to angiotensin II

angiotensin II can interact with angiotensin II receptor 1 or 2 ATR1 or ATR2

Gq signalling

inc intracellular calcium

inc smooth muscle contractility, raises blood pressure

37
Q

what is renin

A

enzyme secreted by kidneys

38
Q

how many angiotensin II receptors are there

A

two

angiotensin II receptor 1 or 2 ATR1 or ATR2

39
Q

what are angiotensin II receptors

A

GPCRs

Gq-coupled

inc intracellular calcium ions

40
Q

IP3 can interact with the IP3 receptor on the _____ to release calcium ions

A

sarcoplasmic reticulum, inc caclium ions intracellularly

41
Q

what do hypertension drugs target - 2

A

block angiotensin II receptors directly, thus intracellular calcium ions

stop production of angiotensin II/ binding of agonist via angiotensin II receptor antagonists

(can also use ACE inhibitors to prevent conversion of angiotensin 1 to 2)

42
Q

examples of angiotensin II receptor antagonists - 4

A

competitive:

losartan

valsartan

irbesartan

non competitive:
candesartan

43
Q

drugs ending in sartan

A

ART antagonists

44
Q

candesartan mechanism of action

A

candesartan cilexitil undergoes rapid conversion to candesartan

metabolism in liver and GI tract prior to liver - hydrolytic reaction in intestinal wall

candesartan can interact with ATR receptors

45
Q

candesartan is a prodrug administered as

A

candesartan cilexitil

46
Q

angiotensin converting enzyme inhibitor examples - 4

A

enalapril

lisinopril

ramipril

captopril

47
Q

drugs ending in PRIL

A

ace inhibitor drugs

342 (21 decks)

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