CVS

Question 1

What is the rate of diffusion limited by?

Answer 1

Area available for exchange Diffusion resistance - nature of barrier and molecules, path length Concentration gradient

Question 2

What is capacitance?

Answer 2

Ability to cope with changes in cardiac output - a store of blood

Question 3

Define flow

Answer 3

Volume of fluid passing a particular point per unit time Flow = volume/time (L/min-1)

Question 4

Define velocity

Answer 4

The rate of movement of fluid particles along the tube Velocity = distance/time (m/min-1)

Question 5

What is laminar flow?

Answer 5

Gradient of velocity from the middle to the edge of a vessel. Velocity is highest in the centre, fluid is stationary at edge

Question 6

What is turbulent flow?

Answer 6

Velocity gradient breaks down due to increased mean velocity. Fluid tumbles over, increasing flow resistance

Question 7

What is viscosity?

Answer 7

Extent to which fluid layers resist sliding over one another

Question 8

What is the equation for resistance?

Answer 8

Resistance = Pressure/Flow

Question 9

If flow is fixed, how does pressure change if resistance is increased?

Answer 9

Increase in pressure

Question 10

If pressure is fixed, how does flow change if resistance is increased?

Answer 10

Decrease in flow

Question 11

What is systolic pressure?

Answer 11

Maximum arterial pressure

Question 12

What is systolic pressure affected by?

Answer 12

Heart contractility Total peripheral resistance Compliance of arteries

Question 13

What is diastolic pressure?

Answer 13

Minimum arterial pressure

Question 14

What is diastolic pressure affected by?

Answer 14

Systolic pressure Total peripheral resistance

Question 15

What is pulse pressure?

Answer 15

Difference between systolic and diastolic pressure

Question 16

What is equation to work our average arterial pressure?

Answer 16

= 2/3 diastolic pressure + 1/3 systolic pressure

Question 17

Define total peripheral resistance

Answer 17

Sum of the resistance of all the peripheral vasculature in systemic circulation

Question 18

What is the dicrotic notch?

Answer 18

Occurs when left ventricular pressure falls below aortic pressure and there is a subsequent backflow of blood closing aortic value

Question 19

What is the dicrotic wave?

Answer 19

Occurs as the aortic valve closes causing a slight increase in pressure and blood recoils off valve

Question 20

How do arteries act to reduce arterial pressure flucuations in systole and diastole?

Answer 20

They have distensible walls allowing them to stretch in systole so pressure does not change that much

Question 21

How do arterioles act as resistance vessels?

Answer 21

Walls contain smooth muscle and state of contraction determines lumen diameter

Question 22

What is vasomotor tone?

Answer 22

Smooth muscle does not actively relax so even under maximum flow there is always some vasoconstriction. This continuous contraction is vasomotor tone. Vasodilation is actually a reduction in vasconstriction

Question 23

How do vasodilator metabolites modify vasomotor activity?

Answer 23

Metabolically active tissues produce vasodilator metabolites which cause relaxation of local smooth muscle.

Question 24

State the vasodilator metabolites

Answer 24

H+ K+ Adenosine

Question 25

What occurs in reactive hyperaemia?

Answer 25

When circulation is cut off from a organ or limb for a short period, the organ/limb continues metabolising so when blood flow is restored the local arterioles dilate maximally and flow is very high.

Question 26

What is auto-regulation in relation to blood flow?

Answer 26

At most levels of metabolic activity most organs can automatically take the blood flow that they need, as long as arterial pressure is kept within certain range

Question 27

Define central venous pressure

Answer 27

The pressure in the great veins supplying the heart

Question 28

Define venous return

Answer 28

The rate of flow of blood back to the heart - limits cardiac output

Question 29

Define pre-load

Answer 29

End diastolic stretch of myocardium. Determined by venous pressure

Question 30

Define after-load

Answer 30

Force necessary to expel blood into arteries. Determined by systemic vascular resistance and ventricular wall tension

Question 31

Define contractility

Answer 31

The stroke volume for a given venous pressure. Slope of the Starling Curve

Question 32

What happens to cardiac output if venous pressure rises?

Answer 32

Cardiac output rises Increased pre-load

Question 33

What happens to cardiac output when venous pressure falls?

Answer 33

Cardiac output falls Decreased pre-load

Question 34

What happens to cardiac output when arterial pressure rises?

Answer 34

Cardiac output falls Increased afterload

Question 35

What happens to cardiac output when arterial pressure falls?

Answer 35

Cardiac output increases Decreased afterload

Question 36

Describe what happens to CVS system after eating a meal

Answer 36

1. Increased activity of gut leads to release of metabolites = local vasodilation 2. Causes decrease in TPR = * Fall in arterial pressure = baroreceptors = increased HR via sympathetic activation = increased cardiac output * Rise of venous pressure = increased pre-load = increased contractility = increased cardiac output 3. Increased cardiac output decreases venous pressure and increases arterial pressure

Question 37

What is the difference between NSTEMI and STEMI

Answer 37

* NSTEMI - Infarct is not full thickness of myocardium * STEMI - full thickness of myocardium

Question 38

What is acute coronary syndrome?

Answer 38

* Group of symptoms attributed to the obstruction of coronary arteries * Includes STEMI, NSTEMI, unstable angina

Question 39

What is a pathological Q wave?

Answer 39

* Deepened Q wave * Indicated previous MI

Question 40

Define heart failure

Answer 40

Heart failure is a state in which the heart fails to maintain cardiac output to meet metabolic need of the body despite an adequate filling pressure. * Heart can no longer produce same amount of force for given level of filling

Question 41

List some causes of heart failure

Answer 41

* Ischaemic heart disease * Hypertension * Dilated cardiomyopathy - infections, drugs, pregnancy * Valvular heart disease * Arrhythmia

Question 42

List compensary mechanisms activated in heart failure

Answer 42

1. Sympathetic nervous system - baroreceptors detecting low pressure * Increases HR, contractility * Vasoconstriction 2. RAAS - decreased renal perfusion * ATII causes vasoconstriction * Aldosterone and ADH increases Na/H₂O reabsorption 3. Myocardial hypertrophy and remodelling

Question 43

What are the types of shock? Give an cause for that type of shock

Answer 43

1. Cardiogenic shock - inability of heart to eject enough blood (ischaemic cardiac damage, heart failure, arrhythmias) 2. Mechanical shock - restriction on heart of the filling of the heart (cardiac tamponade) or obstruction to flow through lungs (PE) 3. Hypovolaemic shock - loss of circulating volume (haemorrhage, burns) 4. Norovolaemic (distributive) shock - fall in peripheral resistance (sepsis, anaphylaxis)

Question 44

What are the acyanotic heart defects?

Answer 44

All those where left side pressure \> right side pressure 1. Atrial septal defect 2. Patent foramen ovale 3. Ventricular septal defect 4. Patent ductus arteriosus 5. Coarctation of aorta

Question 45

What are the cyanotic heart defects?

Answer 45

1. Tetralogy of Fallot - placing outflow portion of interventricular spetum too far in anterior and cephalad direction 2. Tricuspid atresia - no development of tricuspid valve 3. Transposition of great arteries - results in two unconnected parallel circulations

Question 46

What is tetralogy of fallot?

Answer 46

Placing outflow portion of interventricular septum too far in anterior and cephalad direction 1. Pulmonary stenosis 2. Right ventricular hypertrophy 3. Overriding aorta 4. Ventricular septum defect