CVS Flashcards
Functions of CVS you always forget?
Infrastructure for immune system
Thermoregulation
Feature of metabolically active tissues that aid diffusion?
High capillary density leading to greater perfusion and SA
What molecules diffuse easiest?
Small, uncharged polar molecules
Nature of barrier?
Number of pores and size
Maintenance of conc gradient t?
constant high perfusion flow
What is in blood?
RBCs,
WBCs
Platelets
What is blood flow?
5L/min
Constant flow to which organs?
Brain & kidneys
What type of verses have faster flow?
Low cross-sectional area, like veins
Feature of capillaries affecting flow?
Many branches, increasing cross-sectional area of vascular bed > slows down flow for exchange
What are arteries?
resistance vessels regulating flow to direct perfusion
What are end arteries?
terminal arteries supplying blood to a body part without significant collateral circulation
Examples of end arteries?
Splenic, coronary and renal
What are elastic arteries?
large & conducting
What are the layers of arteries?
Tunica intima - endothelium
Tunica media - smooth muscle & collagen
Tunica adventitia - CT, vasa vasorum and nerves
Describe elastic arteries?
TI - elastic lamina
TM - fenestrated elastic membranes
TA - thin fibroelastic connective tissue with nerves & vast vasorum
What are muscular arteries?
Medium sized & distributing
Describe muscular arteries?
circularly arranged smooth muscle. Contain nerve endings for sympathetic stimulation of vasoconstriction
What are arterioles?
Narrowest arteries with thin CT, single smooth muscle layer and thin layer of fibroblasts
Able to constrict and dilate
What are Metarterioles?
Arteries supplying blood to a capillary bed with non-continuous regions of smooth muscles = pre-capillary sphincters
What do pre-capillary sphincters do?
regulate flow to capillary beds
CONTRACTED = REDUCED CAPILLARY FLOW
Features of capillaries?
Mono-layer of endothelium and basement membrane
RBC fills entire lumen
Low blood velocity
Types of capillaries?
Continuous - tight cell junctions (muscle, exocrine, lungs)
Fenestrated - interruptions of endothelium with thin diaphragms (endocrine, glomerulus and gut)
Sinusoidal/ discontinuous - gaps in wall for whole cells to more (liver, spleen and bone marrow)
Features of post-capillary venuoles?
More permeable than capillaries with lower pressure:
Tissue fluid drains back into vessels.
Site of emigration of leukocytes from blood
What are veins?
Capacitance vessels - distend to cope with changes to CO
Features of veins?
Thin and distend able walls = reservoir
Low pressure with thin smooth muscle
Valves to prevent retrograde flow. Work with muscles in legs to propel blood to heart
Large diameters
What are venue comitantes?
2 paired deep veins accompanying smaller arteries wrapped in a vascular sheath.
The pulsing artery helps venous return.
What is ventricular systole pressure?
120mmHg
What is ventricular diastole pressure?
80mmHg
What happens to BP as you go further from the heart?
Decreases with distance
Fluctuating in sync with ventricular systole & diastole > drops are capillaries > constant low at veins
Describe cardiac muscle?
Discrete cells connected electrically with intercalated discs.
Involuntary, striated and myogenic branching muscle
1/2 central nuclei per cell
Diad (t-tubules) occurs at Z-line
How long is systole?
280 ms
How long is diastole?
700ms
What is pulse pressure?
Systolic = Diastolic pressure = 40mmHg
What is Mean Arterial Blood Pressure?
Diastole + 1/3 systolic pressure
What are the names of heart valves?
Atrioventricular:
Tricuspid (RH)
Bicuspid (LH)
Outflow:
Pulmonary
Aortic
What is the SAN?
Sino-atrial node in the RA
How long is the delay at the AVN?
120ms
What is the AVN?
Atrio-ventricular node
What direction do the ventricles contract?
Endocardium to epicardium, from the apex up
What is the tissue in the septum?
Bundle of His
How doe the ventricular muscles contract?
figure of 8 contraction movement for most effective ejection
What are the important stages of cardiac contraction?
Rapid filling phase
Isovolumetric contraction
Rapid ejection phase
Isovolumetric relaxation
What is the 1st heart sound - S1?
Atrioventricular valves closing (beginning of systole)
What is the 2nd heart sound - S2?
Outflow valves closing (end of systole)
What creates murmurs?
Turbulent flow through valves:
narrowed valve or back flow through incompetent valve
What is the most common congenital heart defect?
Ventricular septal defect
VSD
Which Congenital Heart defects are acyanotic?
Atrial septal defect Patent Foramen Ovale Ventricular septal defect Patent Ductus Arteriosus Coarctation of Aorta
Which Congenital heart defects are cyanotic?
Tetralogy of Fallot
Tricuspid atresia
Transposition of the great arteries
Hypoplastic left heart
Why are Patent Foramen Ovale not a true ASD?
Clinically silent as high LA pressure functionally closes flap valve
What is dangerous about PFOs?
Route for venous embolism to reach systemic circ. if RA pressure transiently > LA pressure
Most common site for VSD?
membranous portion of septum
What is the ductus arteriosus?
In foetuses, shunt from pulmonary art. to aorta due to underdeveloped lungs. Shunt closes after birth.
Patent DA leads to blood flowing from aorta –> pulmonary artery creating a mechanical murmer
What is the consequence of PDA?
Increase volume cause vascular remodelling of pulm. circa > increase in resistance > increase pressure > revere direction from pulm. to aorta = Eisenmenger Syndrome
What is coarctaction of the aorta?
narrowing of the lumen at the ligament arteriosum (former DA) increasing resistance leading to Left Ventricular Hypertrophy.
In CoA, why are some body regions under-perfused?
Coarctation occurs after B,C,S arteries branching, hence not compromised. But the rest of the flow is compromised - weak and delayed femoral pulses, upper limb hypertension.
What are the 4 lesions in Tetralogy of Fallot?
VSD
Overriding Aorta
Pulmonary stenosis
Right ventricular hypertrophy
Pulmonary stenosis > RVH due to resistance > increased RV pressure > blood shunt R–>L due to VSD & Overriding Aorta > mixture of deoxy & oxy blood in systemic circ > cyanosis
What is tricuspid atresia?
Lack of development hence X inlet into RV.
Need to have an ASD or PFO (shunting RA –> LA) and VSD (shunting LV –> RV for oxygenation)
What is Transposition of the Great Arteries?
Incompatible with life, unless there is a shunt - Ductus Arteriosus or ASD
What is Hypoplastic Left Heart?
Underdeveloped LV and Ascending aorta
Requires a PFO or ASD, and a PDA
Where is the Sympathetic Nervous System outflow?
Thoraco-lumbar
Sympathetic pre & post-ganglionic lengths?
Short pre
Long post
What type of neurones are sympathetic pre-gang?
Cholinergic releasing nicotinic Ach
What type of neurones are sympathetic post-gang?
Noradrenergic releasing NA to either Alpha 1/2 or Beta 1/3
Where is the parasympathetic Nervous System outflow?
Cranio-sacral
Parasympathetic pre & post-ganglionic lengths?
Long pre
Short post
What type of neurones are parasympathetic pre-gang?
Nicotinic cholinergic
What type of neurones are parasympathetic post-gang?
muscarinic cholinergic –> G-protein coupled receptors
What are the receptors of the heart?
Symp = B1
Parasym = M2
What are the receptors of the airways?
Symp = B2
Parasym = M3
What are the receptors of the pupils?
Symp = A1 –> dilation
Parasym = M3 –> constriction
What are the receptors of the sweat glands?
Symp:
Localised secretion = A1
General secretion = M3
No parasymp.
What signals go to beta-adrenoreceptors?
Adrenaline or Noradrenaline
What protein and effector occurs at Beta-adrenoceptors?
Gs –> stim. adenylyl cyclase
What signals go to Muscarinic receptors?
muscarinic Acetylecholine
What protein and effector occurs at M3 receptors?
Gq –> stim. phospolipase C > smooth muscle contraction
What protein and effector occurs at M2 receptors?
Gi –> inhibits adenylyl cyclase
Describe the relationship between sympathetic NS and blood vessels?
Innervates smooth muscle in the wall of vessels and cause vasoconstriction via A1 receptors.
Constant sympathetic stimulation = vasomotor tone. Less symp. stim = vasodilatation,
More symp. stim = vasoconstriction
What is the vasomotor tone of skin?
High
arterioles, pre-capillary sphincters and artery-venous anastomoses are shut
What is the vasomotor tone of skeletal muscle?
High at rest
Antagonised by vasodilator metabolites in exercise
How is distribution of blood in the CVS controlled?
Balance between sympathetic vasoconstriction tone and vasodilator metabolites
Where do the symp & parasymp. fibres innervate in the heart?
Both to SA and AV nodes
Symp also to ventricular myocytes to increase FoC –> increase CO
What controls the symp/parasym stimulation?
Baroreceptors in the arch of the aorta & carotid sinuses –> sending signals via hypoglossal nerve
What is HR without parasymp?
100BPM
How does the heart increase in rate?
1) reduce parasymp stim
2) increase symp. swim
What are all the signals that act of the heart?
Increase rate & FoC = Noradrenaline from post-gang sympathetic fibres & Adrenaline from Adrenal Glands acting on B1 receptors
Decrease HR & FoC = mAch from parasym. fibres acting on M2 receptors
Define FLOW
volume of fluid passing a given point per unit of time
Flow = Volume/Time
Define VELOCITY
rate of movement of fluid particles along a tube
Velocity = Distance/Time
What is LAMINAR FLOW?
Gradient of velocity, highest in the centre and stationary at the edge.
Most blood vessels have laminar flow
What is TURBULENT FLOW?
Increased mean velocity > gradient breaks down ? layers of fluid move over each other > tumble over each other > increased flow resistance
What is VISCOSITY?
The extent that fluid layers slide over each other.
High viscosity = more overlap and slow central layer flow
Low viscosity = less overlap, fast central layer flow
Relationship between diameter and flow?
The wider the tube, the faster the central layers flow. Mean velocity = proportional to cross sectional area of tube
What is resistance and it’s relationship to flow?
Pressure = Flow X Resistance
R increases with viscosity (thicker blood)
R decreases with greater diameter - harder to flow in small vessels
Vessels in series affect on resistance?
Add together
Vessels in parallel affect on resistance?
Decreased, as more that 1 path for flow
If the heart pumps more blood, but resistance is the same, what happens to pressure?
PRESSURE RISES
Describe how the distensibility of blood vessels affect flow and pressure?
vessel pressure exerts a transmural pressure causing the vessel to stretch.
Stretch > increased diameter > reduced resistance > increases flow.
Hence with increased pressure > stretch > increased flow
Low pressure > walls collapse > no flow
What affects systolic pressure?
FoC
TPR
Compliance of arteries
What affects diastolic pressure?
Systolic pressure
TPR
What is TPR?
Total Peripheral Resistance is the sum of the resistance of all the peripheral vasculature in the systemic circ.
What is the pulse wave?
The contraction of the ventricles propagated along the arteries
List vasodilator metabolites:
H+, adenosine and K+
What doe vasodilator metabolites do?
Relax the local smooth muscle > decrease resistance > increase flow
Whats reactive hyperaemia?
Cut off circ. to limb > cells continue metabolising > produce vasodilators which are not removed > circulation restored > dilated arterioles > max. blood flow
What s auto-regulation?
Organs automatically take the blood flow supply they require matching their demand, as long as arterial pressure is within a certain range
What is venous return?
Venous return = rate of flow back to the heart - determines CO
What is Central Venous Pressure?
Central Venous Pressure = pressure of the great veins supplying heart
what is stroke volume?
The differences between end diastolic & end systolic volume
Describe the relationship between venous pressure and ventricle filling?
The amount ventricles fill is determined by the venous pressure. Ventricle walls stretch to equal the venous pressure.
Higher VP = more heart filling in diastole = increased end diastolic volume.
End diastolic stretch of myocardium = Pre-load - determined by venous pressure
What is after load?
the pressure needed to expel blood through arteries
What is the Starling’s curve?
The more the heart stretched, the harder it contracts giving a bigger stroke volume - shown by starling’s curve.
If the heart is over-filled, the myocardium is overstretched.
Gradient = contractility of the heart, not FoC.
What is postural hypotension?
Failure of baroreceptor reflex.
Standing - blood pools in legs > reduced VP > reduced CO > reduced AP = both low VP & AP –> solved by increased HR (detected by baroreceptors) and increased TPR
When do coronary arteries fill with blood?
During diastole, via the left & right coronary sinuses.
Cardiac muscle = high capillary density for O2 delivery & constant NO production for keep basal flow high
What is angina?
Narrowest coronary artery.
Stress & cold causes sympathetic coronary vasocontriction, as well as extra O2 demand, as well as shorter diastole so reduced blood delivery
What is syncope?
Loss of consciousness
what is the cushion’s reflex?
impaired blood flow to vasomotor control regions of brainstem (due to haemorrhage or tumour) leads to increased peripheral vasomotor activity increased art. BP > maintaining cerebral blood flow
How is blood supply to brain controlled/maintained?
Many anastomoses, myogenic auto-regulation (vasoconstriction with increased BP, vice versa), metabolic regulation - panic hyper vent > hypercapnia > cerebral vasoconstriction > dizziness & fainting
Areas with increased neural activity have increased blood flow as adenosine is a powerful vasodilator
Temperature regulation in skin?
Blood flows via atria-venous anastomoses to remove heat
What are non-modifiable risk factors for coronary atheroma?
Age, male and family history
Modifiable risk factors for coronary atheroma?
Hyperlipideamia, smoking, hypertension and diabetes
What is Ischeamic Chest Pain?
central, retrosternal/left-sided pain, radiating down left shoulder, arm, neck or jaw
What is ischeamic chest pain described as?
heavy, crushing, tightening pain
Describe stable angina?
Atheromatous plaques with thin necrotic centre & thick fibrous cap that occlude coronary lumen
Isheamic chest pain on exertion - physically / emotionally
At what level of occlusion does angina occur?
> 70%
Stable angina Tx?
Acute: Sub-lingual nitrate spray
Preventative: B-blockers, Ca channel blockers, oral nitrates, aspirin, statins, ACE inhibitors
What is unstable angina?
Progression of the formation of atheromatous plaque with increase occlusion. Thin fibrotic cap and thick necrotic centre.
Main characteristic of unstable angina?
ICP at rest - severe pain
What is a MI?
Myocardial Infarction - complete occlusion of coronary artery > ischeamic death of myocardium.
Cause of MI?
- The thin fibrous cap has ruptured leading exposure of blood to thombogenic necrotic core causing a platelets blot that has occluded the vessel.
- embolism broken off
Presentation of MI?
very severe pain, not relived by rest or nitrate spray, breathless, fainting (loss of LV function), feeling of impending doom, sweating, pallor, N/V
What is a NSTEMI?
Non-ST elevating MI, infarct not full thickness of myocardium
What is a STEMI?
ST elevated MI, infarct = full thickness of myocardium
What are the investigations for angina?
Risk factors - corneal Arcus, elevated BP
LV dystfunction
Normal resting ECG (pathological Q wave)
Exercise stress test
What is a pathological Q wave indicative of?
Previous MI
What is the exercise stress test?
Graded exercise connected to ECG. Increase speed until target HR reached/ chest pain / ECG changes
+ve test = ST depression greater than 1mm
What is Acute Coronary Syndrome?
Group of symptoms connected to obstruction of coronary arteries - caused by unstable angina, NSTEMI & STEMI
What are the biomarkers in MIs?
Troponin I & T,
Creatine kinase can also be used after 24hours
Do you know which ECG lead corresponds to an MI in which coronary artery?
Yes - great!
No - better go learn it!
MI Tx?
Anti-thrombotics: aspirin, heparin
Surgery:
Percutaneous Coronary Intervention PCI = angioplasty & stunting
Coronary Artery Bypass Graft (CABG) from radial art or saphenous vein
What are causes of acute pericarditis?
Infection - viral, TB
Post-MI
Autoimmune
Ureamia
Symptoms of acute pericarditis?
Central/left-sided chest pain
Sharp pain,
worse with inspiration
What is Heart Failure?
Heart fails to maintain adequate circulation needed for the body, despite adequate filling pressure
Cause of HF?
Hypertension
Dilated cardiomyopathy - alcohol, pre, drugs
Congenital heart defect
Arrhythmia
Describe the classes of HF?
1 - asymptomatic
2 - slight limitations in activity, asymptomatic at rest
3 - marked limitations, asymptomatic at rest
4 - inability to do physical activity and symptoms at rest
What is congestive heart failure?
Heart failure of both ventricles
Left heart failure > increased pulmonary pressure > right heart failure
Signs of Left HF?
Fatigue, SOB, pulmonary oedema
Sign of Right HF?
Raised JVP Peripheral oedema Ascites pitting oedema Fatigue, SOB Hepatospenomegaly
Causes of RHF?
Often 2ndary to LHF
Pulmonary embolism
Pulmonary hypertension
Left–> right shunt
HF Tx?
B-blockers,
ACE inhibitors
Nitrates > veno-dilators > reduced BP
Cardiac Glycosides > increase CO & FoC
What is shock?
Inadequate distribution of blood to tissues resulting in generalised lack of oxygen to cells.
Either affecting CO or TPR
What is cardiogenic shock?
Inability of heart to eject enough blood.
Caused by arrhythmias or ischeamic cardiac damage
What is mechanical shock?
Restriction on filling of heart due to cardiac tamponade - pressure on outside of heart, or obstructed blood through lungs - PE
What is hypovolameic shock?
Loss of circulating blood volume due to burns / haemorrhage - falling venous pressure = falling CO = falling AP
Tx = IV fluids
What is distributive shock?
Uncontrolled fall in TPR due to dramatic fall in AP, Sepsis (circulating bacteria > endotoxin triggering vasodilation) - tachy, red and warm skin- or anaphylaxis (mast cells release histamine causing vasodilation. Tx = adrenaline to trigger A1 receptors –> vasoconstriction) which is associated with bronchoconstriction
What types of shock reduce CO?
Hypovoleamic, mechanical or cardiogenic shock
What type of shock leads to reduced TPR?
Septic or anaphylactic shock
What are the effects of HF in the body?
- Activation of RAAS due to underperfusion of kidneys > reduced GFR> activates cells to release renin > Angiotensin 2 > vasoconstriction & Aldosterone > Na & Water retention > increased blood volume
- ADH release > increased water uptake
