pharmacology Flashcards
sympathetic stimulation on cardiac rate and force
through Gs, B1-adrenoceptors > increase SA node action potential frequency ad heart rate
- cardiac muscle hypertrophy
parasympathetic stimulation
acetylcholine activate M2 cholinoceptors in nodal cells
Gi protein
may cause arrhythmias
valsalva manoeuvre
activates aortic baroreceptors
used in supraventricular tachycardia or aortic stenosis
massage of bifurcation of carotid artery
stimulates baroreceptors in the carotid sinus
pacemaker potential
modulated by the funny current
- hyperpolarization
- cAMP
block of HCN channels
decreases the slope of the pacemaker potential and reduces heart rate
Ivabradine
selective blocker of HCN (funny) channels
used to slow heart rate in angina
does not work in AF
acts on SA node
b-adrenoceptor agonists
dobutamine, adrenaline and noradrenaline
increase force, rate and cardiac output and O2 consumption
b-adrenoceptor antagonists
non-selective (b1 or b2) or cardioselective (b1) propranolol- non-selective atenolol, bisoprolol, metoprolol- selective - arrhythmias - angina - HF - Hypertension side effects: asthma, fatigue, HF
non-selective muscarinic ACh antagonist - on the heart
atropine- increase HR, no change in BP, used in severe bradycardia
digoxin- HF
Organic nitrates in angina
GTN or ISMN
side effects: headaches, hypotension
Calcium channel blockers
block the opening of L-type channels > limiting calcium concentration
reduce conduction through AV node
reduce force of contraction
selective for smooth muscle preferred for hypertension
ACE inhibitors
Blocks angiotensin I becoming angiotension II
used in hypertension and heartfailure
lisinopril
good for kidneys in diabetes
bad for kidneys in renal artery stenosis
side effects: cough, angioneurotic oedema
two types of CCB
Dihydroperidines- amlodipine
rate limiting calcium antagonists- verapamil, diltiazem
ARBs
angiotensin II receptor blockers eg losartan used in hypertension and heart failure good for kidneys no cough
Angiotensin II hormone
constricts blood vessels = increase in BP
stimulates salt and water retension in the body = increase BP
Alpha blockers
block alpha adrenoceptors to cause vasodilatation
used in hypertension and prostatic hypertrophy
eg doxazosin
side effect: postural hypotension
Mineralocotoid antagonist
block aldosterone receptor
used in heart failure and resistant hypertension
eg spironolactone
side effects: hyperkalaemia, renal impairment
anti anginal vasodilators
Nitrates (isosorbide), nicorandil (K ATP channel opener), calcium antagonists (amlodipine)
anti anginal slow heart rate drug
beta blockers calcium antagonists (diltiazem, verapamil), Ivabradine
anti anginal drugs- metabolic modulator
ranolazine
What is the role of calcium in a normal cardiac action potential
slow influx causes a plateau in the myocardial action potential- prolongs contraction of cardiac myocytes
prolong QT segment on ECG
hypocalcaemia
what is the role of rapid influx of sodium ions in normal cardiac action potential
depolarisation of the cardiomyocytes
triggered by pacemaker cells within the sinoatrial node
what is the role of an efflux of potassium ions in normal cardiac action potential
repolarisation of cardiomyocytes
occurs in two steps:
Directly after depolarisation, there is a transient period of repolarisation followed by the plateau
After this plateau, complete repolarisation occurs as more potassium channels are opened
ECG changes due to hypokalemia
U waves- a deflection immediately following T wave
small or absent T waves (occasionally inversion)
prolong PR interval
ST depression
long QT
Bifid P waves
the p-wave has 2 peaks, found in left atrial enlargement
Inverted T-waves
found in myocardial ischaemia
Delta waves
slurred upstrokes of the QRS complex, found in Wolff-Parkinson-White syndrome
Pathological q-waves
large q-waves, found in current or prior myocardial infarction
