Flashcards in Lecture Notes Deck (114):
What is systolic BP?
Pressure when heart contracts
What is diastolic BP?
Pressure when heart relaxes
Which portion of the cardiac cycle is longer and by how much?
Diastolic is 2x as long as the systolic
Formulas for MAP?
MAP= 2xdiastolic pressure + systolic pressure/3
Forumla for CO?
What is the cardiac output?
Volume pumped by each ventricle per minute
What is stroke volume?
Volume pumped by each ventricle per heart beat
When is the 1st korotkoff sound heard?
At peak systolic pressure
What sound signifies diastolic pressure?
5th korotkoff sound
What is the total peripheral resistance?
Sum of resistance of all peripheral vasculature
Where are the baroreceptors?
Aortic arch and carotid sinus
What are the major resistance vessels?
What responds to acute changes in blood pressure?
What nerves transmit signals from the baroreceptors?
Carotid IXth CN
Aortic Xth CN
What do baroreceptors do when you stand up and MAP decreases?
Rate of firing decreases
What effect does a decrease in the rate of firing of baroreceptors have on the heart?
Vagal tone decreases
Sympathetic tone increases
What changes do the baroreceptors bring about to increase MAP?
increase HR, increase SV, increase TPR
Which 3 hormone systems regulate ECF fluid volume?
Atrial natriuretic Peptide
Anti diuretic hormone
Where is angiotensinogen released from?
Where is rennin relaxed from?
What does rennin convert?
Angiotensinogen to angiotensin 1
What converts to angiotensin 1 to 2?
Angiotensin converting enzyme (ACE)
What does angiotensin II act on and what does this cause?
Adrenal cortex which releases aldosterone
What effect does aldosterone have?
Increase sodium and water reabsorption
Increased Blood pressure
What effect foes angiotensin II have?
Increase ADH release
What is the rate limiting step in the RAAS?
What is ANP released in response to?
What does ANP cause?
Causes excretion of salt and water in the kidneys
What effect does ANP have on blood volume and BP?
What effect does ANP have on rennin release?
Where is ADH synthesised?
What stimulates the secretion of ADH?
Decreased ECF volume
Increased ECF osmolarity
What effect does AHD have?
Increases reabsorption of water
Increases ECF and Plasma Volume
Increases CO and BP
What is it called when the heat if able to beat in the absence of external stimuli?
Where does excitation of the heart originate?
In the sino atrial node
Where is the SA node located?
In the upper right atrium
How is the action potential generated in the SA cells?
Pace maker potential take the membrane potential to a threshold
What causes the pacemaker potential?
Reduction in K efflux
Slow Na influx
What causes the rising phase of the action potential?
Activation of voltage gated Ca channels
Resulting in Ca influx
What causes the falling phase of the action potential?
Activation of K channels
How is excitation spread in atrium and ventricular muscle?
Via gap junctions
How does excitation in the heart spread?
SA node - AV node - Bundle of His - Left and right branches - Purkinje fibres
Where is the AV node located?
Base of right atrium
What is the only point of electrical contact between atrium and ventricles?
Where is conduction delayed?
What causes the rising phase of the ventricular muscle potential?
What causes the plateau phase of the ventricular muscle potential?
What causes the falling phase of the ventricular muscle potential?
What effect does sympathetic stimulation have on HR?
What is the nerve supply to SA and AV nodes?
When is atropine used?
What effect does vagal stimulation have on the slope of the pacemaker potential?
What effect does parasympathetic stimulation have on HR?
What is the parasympathetic transmitter?
What is the sympathetic transmitter?
What are the 5 phases of the cardiac cycle?
1 - Passive filling
2- Atrial contraction
3 - Isovolumetric ventricular contraction
4 - Ventricular ejection
5- Isovolumetric ventricular relaxation
What % of ventricles fill by passive filling?
What does P wave in ECG signal?
When does atria contact in relation to ECG?
Between the P wave and the QRS complex
When does ventricular contraction start in relation to the ECG?
After the QRS complex
What does T wave signal in ECG?
What causes the first heart sound?
The closure of the mitral and tricuspid valves
What does S1 herald?
Beginning of systole
What causes the 2nd heart sound?
Closure of the aortic and pulmonary valves
What does S2 herald?
End of systole and beginning of diastole
What type of muscle is cardiac muscle?
How is muscle tension produced?
Sliding of actin filaments on myocin
What is the refractory period?
A period following an AP in which is it not possible to produce another AP
What does SV =?
What is a positive inotropic effect?
Increase in force of contraction
What determines end diastolic volume?
What is a positive chronotropic effect?
Increase in HR
What does the starling law state?
The more the ventricle is filled with blood the greater the volume of ejected blood will be during systolic contraction
Will increase sympathetic discharge cause vasoconstriction or vasodilation?
What are the capacitance vessels?
Veins - hold most volume during rest
Does angiotensin II cause vasoconstriction or vasodilation?
How does sympathetics stimulation increase the HR?
Increases rate of firing by the SA node
Decreasing AV nodal delay
Increases force of contraction
4 chronic responses to exercise?
Decrease in sympathetic tone
Increase in parasympathetic tone
Decreased aterial stiffness
3 effects of nitrates on the vasculature?
Venorelaxation, arteriolar dilatation, increased coronary blood flow
Two examples of organic nitrates?
Glyceryltrinitrate and isosorbide mononitrate
2 unwanted effects of nitrates?
Repeated administration may cause diminished effect
How do ACE inhibitors work?
Block the conversion of angiotensin 1 to angiotensin II
How do AT1 receptor antagonists work?
Block the agonist action of angiotensin II at AT1 receptors in a competitive manner
What effect does an ACE inhibitor have?
Causes venous and arterial dilatation - Decreasing TPR and so BP
2 adverse effects of ACE inhibitors?
May initially cause hypotension
What type of drugs would you prescribe if patient cannot tolerate cough of ACE inhibitor?
AT1 receptor antagonist
Contraindications of ACE inhibitors and AT1 receptor antagonists?
Pregnancy and bilateral renal artery stenosis
3 indications for ACE inhibitors and AT1 receptor antagonists?
Hypertension, cardiac failure, post MI
What does stimulation of beta 1 receptors cause?
Increase HR, Force and AV node condition velocity
What does stimulation of beta 2 receptors cause?
Bronchiole and blood vessel relaxation
How do Beta blockers treat angina?
Decrease myocardial O2 requirement
How do Beta blockers treat hypertension?
Reduce cardiac output, reducing rennin release from kidney
How do calcium antagonists work?
Prevents opening of L type channels and so limit calcium influx
Name 3 calcium antagonists?
Verapamil, amlodipine, diltiazem
Calcium antagonist in atrial fibrillation?
Uses of thiazide diuretics?
Mild heart failure, hypertension,
Uses of loop diuretics?
Acute pulmonary oedema
1 Example of thiazide diuretic?
1 example of a loop diuretic?
1 example of an ACE inhibitor?
1 example of an AT1 receptor antagonist?
Losartan - 'sartans'
2 examples of Beta blockers?
How does Ivabradine work?
Selective blocker of HCN channels, used to slow heart rate
Effect of beta adrenoreceptor agonists on the heart?
Increase force, rate, CO and O2 consumption
Decrease cardiac efficiency
Name 2 beta adrenoreceptor agonists?
Adrenaline and dobutamine
Is propanolol a selective beta blocker or not?
Name 2 selective Beta 1 blockers?
Metoprolol and atenolol
6 adverse effects of Beta blockers?
Bronchospasm, Aggravation of cardiac failure, bradycardia, hypoglycaemia, fatigue, cold extremities
Name one non selective muscarinic receptor antagonist?
Clinical uses of atropine?
To reverse bradycardia following an MI,
Is digoxin positively or negatively inotropic?
What type of drug is digoxin?
What effects does digoxin have on the heart?
Slows SA node discharge, Slow AV node conduction, increases refractory period