CVS 3,4,8,9,10,12,14 Flashcards
What are the 7 phases of the cardiac cycle?
- Atrial contraction
- Isovolumetric contraction
- Rapid ejection
- Reduced ejection
- Isovolumetric relaxation
- Rapid filling
- Reduced filling
In which side of the heart are valve pathologies most common and why?
Left side
Higher pressure
Give 3 causes of Aortic valve stenosis.
- Degeneration (old age-senile calcification/fibrosis)
- Congenital eg bicuspid aortic valve
- Chronic rheumatic fever- inflammation
What happens as a result of aortic valve stenosis?
- Less blood getting through
- Increased left ventricular pressure
- LV hypertrophy
- Left sided heart failure
- Syncope (fainting)
- Angina (not enough blood to coronary arteries)
- Increased left ventricular pressure
Give 2 causes of aortic valve regurgitation.
- Valve damage- endocarditis
- Aortic root dilation
What happens as a result of aortic valve regurgitation?
Blood flows back into LV during diastole- RBCs lyse (Microangiopathic haemolytic anaemia)
Increase Stroke Volume
Increased systolic pressure
- Bounding pulse
- Heading bobbing
- Quinke’s sign- nail beds flush w./ heart beat
LV hypertrophy
Name some causes of mitral valve regurgitation.
- Myxomatous degeneration (CT disorder)
- Weak chordae tendinae
- Weak papillary muscle
- Causing prolapse
- Damge to papillary muscles after heart attack
- Left sided heart failure- LV dilation
- Rheumatic fever
What causes mitral valve stenosis in 99.9% of cases?
Rheumatic fever
Commissural fusion of valve leaflets
What happens as a result of mitral valve stenosis?
- Increase LA pressure
- Pulmonary oedema
- Difficulty breathing
- Pulmonary hypertension
- RV hypertrophy
- LA dilation
- Artial fibrillation
- Thrombus
- Oesaophagus compression
- Dysphagia (difficulty swallowing)
- Artial fibrillation
- Pulmonary oedema
Complete the equations:
CO= SV x …..
…..= EDV - ESV
CO= SV x HR
SV = EDV - ESV
What is the typical stroke volume of a 70kg man?
70ml (=about 67% of normal EDV)
What does the ventricular compliance curve show?
Relationship between how much ventricles fill and LV pressure
What is the Frank-Starling law of the heart?
More the heart fills, harder it contracts
What are cardiac muscle cells increasingly sensitive to as the muscles are stretched?
Ca2+ ions
What type of stimulation affects the contractility of the heart?
Sympathetic/adrenaline
What is aortic impedence?
LV afterload
Why is the jugular venous pulse used clinically?
Direct colum of blood into right atrium
What conditions will increase the Jugular venous pulse?
- Right side of heart- not pumping blood out properly
- Vol overload with IV infusion
- Something impairing heart filling eg stap wound
Label the follwing waves and describe what produces them:
- A
- C
- X-descent
- V
- Dicrotic notch
- Y-descent
- A: Atrial systole
- C: Closing mitral valve
- X-descent: Atrial pressure initially decreases
- V: Atrial pressure rising- venous return from lungs
- Dicrotic notch: Aortic valve closing
- Y-descent: Opening of mitral valve- ventricular filling
In what unit is BP measured?
mmHg (milimetres of mercury)
What is the normal/ideal BP?
90/60 mmHg and 120/80mmHg
What are the values of Blood pressure for:
- Stage 1 hypertension
- Stage 2 hypertension
- Severe hypertension
What’s the difference between primary and secondary hypertension?
- Primary= cause unknown (95% cases)
- Secondary= cause defined
Give some examples of secondary causes of hypertension
- Renovascular disease
- Chronic renal disease
- Hyperaldosteronism
- Cushing’s syndrome
What can hypertension lead to? (5)
- Heart failure
- MI
- Stroke
- Renal failure
- Retinopathy
What are the 4 neurohumoral pathways controlling circulating volume and BP?
- RAAS
- Sympathetic nervous system
- ADH
- ANP (Atrial natriuretic peptide)
What are the actions of angiotensin II?
Give an example of an ACE inhibitor.
Captopril
Is bradykinin a vasodilator or vasoconstrictor?
Vasodilator
Bradykinin= inflammatory mediator
Releases nitric oxide + others to cause vasodilation
What effects does hyperkalaemia have on myocytes and their ability to fire APs?
- Slows upstroke
- Inactivates some Na+ channels as Ek is now more negative
What can happen to the heart as a result of hyperkalaemia?
Asystole (heart stops)
may initially get some increased excitiability
What is the normal plasma concentration of K+?
3.5-5.5 mmol/L
How is hyperkalaemia treated?
- Calcium gluconate
- Insulin and glucose- enhance potassium uptake
(won’t work if heart already stopped)
How can hypokalaemia cause ventricular fibrillation?
- Longer action potential
- Delays repolarisation
- Causes early after depolarisations
- Oscillations in membrane potential
- Ventricular fibrillation
How does an action potential in the cardiac myocyte result in contraction?
- L-type Ca2+ channels= open
- Ca2+ opens CICRs
- Ca2+ binds to troponin C
- Tropomyosin reveals myosin binding site for actin filament
What is MLCK?
Myosin light chain kinase
Phosphorylates myosin light chains
Phosphorylated to allow binding to actin
What enzyme inhibits contraction by inhibiting MLCK
PKA (protein kinase A)
Phosphorylates myosin itself
How does vascular smooth muscle contract?
- alpha-adrenoceptors depolarised/activated
- Increased intracellular Ca2+
- Ca2+ binding to calmodulin
- Activation of MLCK
- Phosphorylates myosin light chain
What is the affect of sympathetic stimulation of β1 receptor in the heart?
Increase rate and force of contraction
What is the effect of parasympathetic stimulation of the M2 muscarinic receptors in the heart?
Decreased rate
(Released ACh)
The parasympthetic nervous system influences the heart via which nerve?
Vagus nerve
(10th cranial nerve)
Innervates SA node and AV node
How does the sympathetic nervous system influence the heart?
- Post ganglionic fibres from sympathetic trunk
- Innervates SA node, AV node, myocardium
- Releases noradrenaline–> β1 receptors
What is the If funny current?
Slow Na+ conductance- slow depolarisation of pacemaker potential
Arteries and veins can receive sympathetic stimulation via α1 adrenoreceptors.
Coronary and skeletal muscle blood vessels also have what other type of receptor?
β2 adrenoreceptors
If sympathetic output to α1 adrenoreceptors is increased- what will occur in the blood vessels?
Increased output= vasoconstriction
What is caused by the activation of β2 adrenoreceptors?
Vasodilation
What effect do local metabolites have on vasodilation in active tissue?
Active tissue- increases metabolites
Increase vasodilation
How do baroreceptors work?
In carotid sinus and aortic arch
- Increase in arterial pressure- stretches receptors
- Vagus nerve- to medulla
- Parasympathetic stimulation
- Bradycardia and vasoldilation to counteract increased mean arterial pressure
What drug may be given for cardiogenic shock? (pump failure)
Dobutamine β1 agonist
How does Salbutamol work?
β2 agonist
What is the muscarinic agonist Pilocarpine used to treat?
Gluacoma
(Optic nerve damaged- due to pressure of fluid inside eye)
How does sympathetic stimualtion cause renin release?
Renal blood flow decreases
Sympathetic stimulation of cells in afferent arteriole to release renin
(Renin release increase Angiotensin II levels)
What effect do prostaglandins have on BP?
Lower BP
= vasodilators
= enhance glomerular filtration rate
= reduce Na+ reabsorption
Locally acting
What effect does dopamine have of blood pressure?
Lower BP
Formed locally in kidney
Dopamine receptors in renal blood vessels
Reduce reabsorption of NaCl
Explain how renovascualr disease can cause high BP.
- Occlusion of renal artery
- Fall in perfusion pressure- kidney
- Activation of RAAS
- Vasoconstriction and Na+ retention in other kidney
Explain how renal parenchymal disease causes high BP?
(Chronic kidney disease)
Initially less vasodilator substances
Later Na+ retention
What is Conn’s syndrome?
Aldosterone secreting adenoma
Hypertension and hypokalaemia
