Lecture 13 - Cardiac Cycle

Question 1

What chamber of the heart pumps deoxygenated blood to the lungs?

Answer 1

Right Ventricle

blood moves through the pulmonary artery away from heart to the lungs

Question 2

What chamber of the heart should have thicker walls in a healthy patient?

Answer 2

The left ventricle

It needs to be more muscular to push blood through the body

Question 3

How to calculate mean ABP?

Answer 3

Mean = diastolic pressure + (1/3) pulse pressure

Question 4

How to calculate pulse pressure?

Answer 4

Systolic pressure - diastolic pressure

Question 5

What is the pathway for conduction starting at the SA node?

Answer 5

SA node —> AV Node —> Bundle of His —> Right and Left Bundle Br.

Question 6

Contractile cells do what in the heart and are the (most or least) numerous?

Answer 6

Are responsible for contraction and are the most numerous (~99% of heart cells)

Question 7

What are conducting cells?

Answer 7

Cells responsible for electrical conduction in the heart.

e.g. SA node, AV node, bundle of His, bundle branches, purkinje fibres

Question 8

PEA

Answer 8

Pulseless electrical activity
ECG shows signals but heart rate is 0

Question 9

Asytole

What does this look like on the ECG? What else might we call it?

Answer 9

Flat line

Question 10

Ventricular fibrilation look like what on an ECG?

Answer 10

Squiggles on the ECG screen

Question 11

How much do atria contribute to cardiac output?

Answer 11

20%

Question 12

AV block

What does it look like on an ECG?

Answer 12

Arrhythmia between the atria and the ventricle.
Will show a p wave without the presence of a QRS complex following

Question 13

Ectopic pacemaker

Answer 13

When another area of the heart becomes the pacemaker

Question 14

Chronotropy

autonomic effects on:

Answer 14

Influencing heart rate

Question 15

Dromotropy

autonomic effects on:

Answer 15

Cardiac conduction

speed of beats

Apparently doesn’t always lead to an increase in heart rate if the effect is minute

Question 16

Inotropy

Autonomic effects on:

Answer 16

Cardiac contractility

How hard it’s squeezing

Question 17

Standardized lead placement

3 leads

Answer 17

White on the right front
Black on the left front
Red on the left hind

Smoke over fire to remember black and red

Question 18

P wave

what action in the heart does this wave portray?

Answer 18

Atrial depolarization

Question 19

QRS complex

what action in the heart causes this complex?

Answer 19

Ventricular depolarization

Question 20

T wave

what action in the heart does this wave portray?

Answer 20

Ventricular repolarization

Question 21

QT interval

What events would the mark the start and end of this interval?

Answer 21

time from start of ventricular depolarization to the end of ventricular repolarization

Question 22

Heart rate calculation from ECG

hint: two variations exist depending on what strip you are reading

Answer 22

if 25mm/s strip 1500/R wave
if 50mm/s strip 3000/R wave

R waves (count the number of squares between R’s on the 2 different QRS complexes

Question 23

Stroke volume

Answer 23

Blood volume ejected with one ventricular contraction
End diastolic volume - end systolic volume

Question 24

Cardiac output

Answer 24

Total volume of blood ejected over time (expressed as ml or L/min)
SV x HR

Question 25

What would happen if the mitral valve is leaky?

Answer 25

Blood backs up into the atria. Stroke volume will be decreased. | (Mitral valve is between left atrium and ventricle)

Question 26

Frank Starling relationship

Answer 26

As the amount of blood that enters the heart increases, the heart naturally pumps harder to push out that extra blood. ## Footnote Cardiac output correlates with end diastolic volume As venous return increases cardiac output increases Curvilinear relationship

Question 27

4 Auscultation areas in dog

Answer 27

1. Mitral valve (left AV) - left 5th intercostal space (beneath elbow) 2. Aortic valve - left 4th intercostal space (level with shoulder) For hearing S2 3. Pulmonic valve - Left 3rd intercostal space at sternal border (axilla) 4. Tricuspid valve (right AV) - Right 3rd to 4th intercostal space at costal chondral junction

Question 28

Causes of heart murmurs:

Answer 28

Leaky valves, stenosis valves, septal defects, decreased blood viscosity (e.g. anemia)

Question 29

4 Descriptors of heart murmurs

Answer 29

Timing, intensity, location, quality

Question 30

Baroreceptor reflex

Answer 30

Keeps blood pressure stable by adjusting heart rate based on sensing stretch in the carotid sinus

Question 31

Patent ductus arteriosus

Answer 31

The patent ductus is a shunt needed for fetal hearts since they do not use their lungs. This shunt should close shortly after birth, when it does not it causes leakage of blood.

Question 32

4 Auscultation areas in horses

Answer 32

1. Mitral valve - left 5th intercostal space (1/3 distance from point of elbow to point of shoulder, caudal edge of triceps) 2. Pulmonic valve - Left 3rd intercostal space (rostral dorsal to mitral valve) 3. Aortic valve - left 4th intercostal space (under triceps) 4. Tricuspid valve - Right 4th intercostal space (halfway between elbow and point of shoulder)

Question 33

What happens to blood pressure when PDA is clamped?

Answer 33

Sharply increases

Question 34

S1 heart sound | what sound does it make, where does it come from

Answer 34

Lub - AV valves close

Question 35

S2 heart sound | What sound does it make and where does it come from

Answer 35

Dub - Aortic/Pulmonic valves close

Question 36

Which type of adrenergic receptors lead to vasoconstriction?

Answer 36

Alpha adrenergic receptors | found on vascular smooth muscle multiple vascular beds

Question 37

What would happen to blood pressure if a neurotransmitter bound to an alpha adrenergic receptor?

Answer 37

Increase | A-1 causes vasoconstriction

Question 38

What type of adrenergic receptor causes vasodilation?

Answer 38

Beta adrenergic receptors | Found in skeletal muscle

Question 39

What would happen to blood pressure if a neurotransmitter bound to a beta adrenergic receptor?

Answer 39

Decrease | Beta receptors lead to vasodilation thus decreasing blood pressure

Question 40

What type of muscles are found in arterioles?

Answer 40

Smooth

Question 41

What would happen if the SA node is knocked out?

Answer 41

The next most excitable group of cells takes over

Question 42

Where do normal conduction pathways begin in the heart?

Answer 42

SA node

Question 43

Starting at the left ventricle, what is the movement of blood -also naming the major arteries which take blood from and send blood to the heart?

Answer 43

Left ventricle -->aorta --> body --> vena cava --> right atrium --> right ventricle --> lungs --> left atrium --> left ventricle