18 16 and a little 17

Question 1

Order of the impulses passing through the heart?

Answer 1

SA node –> AV node –> AV bundle –> R/L bundle branches –> Purkinje fibers

Question 2

P wave

Answer 2

(Patrial depolarization) Lasts 0.08s, results from movement of the depolarization wave from the SA node through the atria. Appx. 0.1s after P wave begins, the atria contract.

Question 3

QRS wave

Answer 3

(Ventricular depolarization) Lasts 0.08s, results from ventricular depolarization and precedes ventricular contraction.

Question 4

T wave

Answer 4

(Ventricular repolarization) Lasts 0.16s, caused by ventricular repolarization

Question 5

Heart sounds are the?

Answer 5

Valves closing.

First the AV valves (when ventricular pressure rises above atrial pressure, ventricle systole) lub or S1 - soft, low pitched.

Then the SL valves (snap shut at the beginning of ventricular diastole) Dup or S2 - sharper, louder, higher-pit

Question 6

Cardiac cycle

Answer 6

All the events associated with the flow of blood through the heart during a single complete heartbeat.

Question 7

Duration of a heartbeat?

Answer 7

0.8s - 0.5s in diastole, 0.3s in systole

Question 8

Cardiac cycle - ventricular filling

Answer 8

1

ECG: Includes P (atria contract) and part of QRS (ventricular depolarization starts)

VALVES: AV open, SL closed.

PRESSURE: Atrial higher than ventricle, both rise with atrial contraction/P
Atria - max pressure here, also lowest, P
Vent - lowest, 0 to about 20
Aorta - 110 falling to 80

VOLUME: Ventricular filling.
Starts at about 50 - end of phase 1, ventricles are on the last part of their diastole and contain maximum blood volume (EDV) around 120.

mid-late diastole - 80%
(20% of ventricle filling is from atrial contraction.)

Question 9

Cardiac cycle - Isovolumetric contraction

Answer 9

2a

ECG: RS

HEART SOUNDS: AV close

VALVES: AV closes at start (pressure surpassed by ventricle), SL closed

PRESSURE: Ventricle higher than atria as ventricle contraction starts
Atria - rises
Ventricle - Spikes up to about 75
Aorta - still falling

VOLUME: EDV (valves closed, pressure constant)

Occurs at the beginning of systole.
Ventricles contract, AV valves close, and for a moment SL valves are still closed (vent press not high enough to open).

Question 10

Cardiac cycle - Ventricular ejection

Answer 10

2b

ECG: Time before T and start of T (vent repolarization)

VALVES: AV closed, SL opens (ventricle pressure surpasses aortic pressure)

PRESSURE: High arch of vent/aorta (75-120-100)
Atria - drop then rise
Ventricle - highest pressure here
Aorta - highest pressure here, and lowest!

VOLUME: Falls as blood is ejected

Occurs when the pressure in the ventricles exceeds the pressure in the large arteries and the SL open.

Question 11

Cardiac cycle - Isovolumetric relaxation

Answer 11

3

ECG: Second half of T (vent depolarization wave)

HEART SOUNDS: SL closing

VALVES: AV closed (but open at the end of 3 because atrial pressure surpasses ventricle), SL closes at beginning because aortic pressure surpasses ventricular.

PRESSURE: Vent pressure continues to fall back to almost zero. Aortic pressure spikes briefly because of the closing of the SL valve (dicrotic notch).

VOLUME: ESV, about 50, minimum value. Remains in ESV/constant because all valves are closed.

Occurs when the ventricles enter early diastole. Remaining blood in ventricles is no longer compressed - ventricular pressure is too low to keep the SL valves open and too high to allow the AV valves to open.

Question 12

Cardiac output

Answer 12

Amount of blood pumped out by one ventricle in 1 minute. HRxSV

Question 13

Stroke volume

Answer 13

Volume of blood pumped out by one ventricle with each beat. EDV - ESV = stroke volume (end diastolic volume/end systolic volume)

Question 14

Ejection Fraction

Answer 14

ESV/EDV (i.e. 70/120, 58%)

Question 15

Cardiac cycle phases

Answer 15

1. ventricular filling (ventricular filling and atrial contraction)
2. ventricular systole (2a - Isovolumetric contraction, 2b Ventricular ejection phase)
3. early diastole (Isovolumetric relaxation)

Question 16

ESV

Answer 16

End systolic volume (lowest in ventricle, just pumped, about 50)

Question 17

EDV

Answer 17

End diastolic volume (Highest in ventricle, just finished filling, about 120)

Question 18

Pressure ranges for Aorta, ventricle, atria (mmHg)

Answer 18

MAP = 93 for aorta, 80-120

Vent = 0-120

Atria = 0-24

Question 19

Dicrotic notch

Answer 19

A temporary drop then spike in BP in the aorta that occurs when the semilunar valve closes

Question 20

Compliance

Answer 20

Measure of the ability of a hollow structure to stretch

Question 21

What happens when only the HR is increased but not the contractility?

Answer 21

A decrease in SV.

The heart beats faster which means less fill time. Less preload means a decrease in contractility.

Question 22

atrial (Bainbridge) reflex

Answer 22

An autonomic reflex initiated by increased venous return and increased atrial filling. Stretching the atrial walls increases heart rate by stimulating the SA node and the atrial stretch receptors. Stretch receptor activation triggers reflexive adjustments of autonomic output to the SA node ↑ HR.