Control of CO and system responses

Question 1

What determines arterial and venous pressure

Answer 1

Arterial: CO X TPR
Venous: rate blood enters/leaves veins, blood volume

Question 2

Relationship between TPR and arterial/venous pressure?

Answer 2

Proportional to arterial pressure, inversely proportional to venous pressure

Question 3

When does Cardiac output increase?

Answer 3

1. Starling’s law: increased end diastolic volume/venous blood = increases SV
2. Decreased afterload/arterial pressure - increases sympathetic activity: HR and FOC increase = increases SV

Question 4

What defines the stroke volume

Answer 4

end diastolic volume - end systolic volume

the upstroke

Question 5

What is the ventricular compliance curve?

Answer 5

Relationship between ventricle volume and venous pressure

Question 6

What is proportional to the energy in a contraction?

Answer 6

Muscle fibre length

Question 7

Name 2 things that assist starling’s law

Answer 7

1. Increased CVP (venoconstriction)

2. Lower BP (activates sympathetic system)

Question 8

Define end-systolic volume, What two things determine the end-systolic volume

Answer 8

How much ventricles emptied

1. Contraction strength: FOC - sympathetic, end-diastolic volume
2. Aortic input impedence - TPR,

Question 9

Explain the Bainbridge reflex

Answer 9

Increased venous pressure sensed in R atria by atrial receptors

BB reflex: reduces PS activity and increases HR

Question 10

Explain how the CVS is restabilized after a meal

Answer 10

Gut releases vasodilatory metabolites -> lower TPR and arterial pressure -> venous pressure rises

• Hypotension -> Baroreceptors (carotid sinus/aortic arch) -> medullary oblongata -> increase HR
• BB reflex increases HR (due to high venous pressure)

HR increases -> arterial pressure re-raised -> venous pressure falls back to normal

Question 11

What happens to the system if HR is the only thing to increase

Answer 11

Initially CO rises (TPR stays same) -> reduces venous pressure -> starling’s law -> CO falls back

*HR driven by circulation (not the other way around)

Question 12

What does exercise do to arterial pressure?

Answer 12

Vasodilatory metabolites + pushing blood back to heart decreases arterial pressure BUT TPR lowers to compensate = keeps arterial pressure raised

Question 13

What is a pulmonary consequence of having venous pressure that is too high?

Answer 13

Pulmonary edema (backs up in the lungs)

Question 14

What does the brain do at the beginning of exercise to ensure that venous pressure doesn’t become too high?

Answer 14

Increases HR

Question 15

Explain the difference between static and dynamic exercise

Answer 15

Static: Weights raise BP
*discourage static exercise in patients with ischemic heart disease

Dynamic: Cardio increases the HR but not mean BP

Question 16

What happens to venous pressure in postural hypotension and hemorrhage?

Answer 16

Postural hypotension: Gravity -> blood pools in superficial veins ->
Hemorrhage: lower blood volume

CVP falls -> CO falls (starling’s) -> BP falls - baroreceptors increase HR -> lowers venous pressure further (more blood in systemic circulation, brings TPR and Arterial BP back up)

Question 17

What can you can do to increase the venous pressure (2)

Answer 17

Venoconstriction, auto-transfusion

Question 18

What is the most important long term regulator of blood pressure, and which organ is responsible for controlling it?

Answer 18

Blood volume, kidney

Question 19

Name 4 roles of starling’s law

Answer 19

1. Increases SV during upright exercise
2. Lowers CO during: orthostasis (standing, and hemorrhage and shock
3. Balances outputs of RV and LV
4. Restores CO in response to IV infusions

Question 20

Name 3 things you can do to help a fall in CVP

Answer 20

Bed rest (no gravity), Warmth (vasodilation), alpha-adrenoceptor antagonist (inhibits vasoconstriction)

Question 21

How does digoxin help with heart failure?

Answer 21

Cardiac glycoside: slows HR (improves ventricular filling)

Question 22

Name 2 symptoms of a fall in CVP

Answer 22

Dizziness and vision problems (cerebral underperfusion)

Question 23

What is the ejection fracture (EF)?

Answer 23

SV/Total volume in L ventricle

Question 24

Describe the kind of murmur that occurs in an aortic valve stenosis

Answer 24

Systolic: crescendo - decrescendo

Question 25

Describe the kind of murmur that occurs in an aortic valve incompetence

Answer 25

early diastolic decrescendo

Question 26

What kind of murmur is a mitral valve stenosis, what is it often a late (and highly specific) sequela of?

Answer 26

Diastolic, follows opening snap

Rheumatic fever

Question 27

What is an ‘opening snap’?

Answer 27

Stenosed valve finally opens (pre murmur)

Question 28

What does it indicate if there’s a decrescendo murmur?

Answer 28

A very stenosed valve having difficulty opening

Question 29

What often occurs as a result of a mitral valve stenosis and what can be heard as a result of this?

Answer 29

Atria contracts harder (enlarged) - increases turbulence and gives murmur a boost

Question 30

What kind of noise is generated by a systolic regurgitation

Answer 30

Pancystolic (no crescendo, decrescendo)

*mitral/tricuspid regurg

Question 31

Where do the following radiate?

a) aortic stenosis
b) mitral regurg

Answer 31

a) Carotid arteries

b) Axilla

Question 32

When is an ejection systole heard?

Answer 32

Aortic and pulmonary stenosis

Question 33

What produces an early and mid-diastolic murmur

Answer 33

Early: aortic and pulmonary regurg
Mid: mitral and tricuspid stenosis

Question 34

Explain the meaning of RILE

Answer 34

Expanding thoracic cavity crushes vena cava -> venoconstriction -> R heart louder on inspiration

Expiration -> increased pulmonary venous return -> L heart louder

Question 35

Why is it important to have a long diastole?

Answer 35

More time for perfusion to reach tissues