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Flashcards in *Physiology 3 (lecture 3) Deck (58)
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1

What are the events during the cardiac cycle?

1. Passive Filling
2. Atrial Contraction
3. Isovolumetric ventricular Contraction
4. Ventricular Ejection
5. Isovolumetric ventricular relaxation

2

What happens during passive filling?

The pressure in the atria and ventricles is close to 0.
AV valves open so that venous return flows into the ventricles.

3

What causes the flow of blood during passive filling?

A small pressure gradient.

4

What is the pressure in the aorta during passive filling?
Is the aortic valve open?

80mmHg
No

5

How full, roughly, do the ventricles become during passive filling?

About 80% full.

6

What happens during atrial contraction?

The atrias contract completing the end diastolic volume

7

What does the P wave in the ECG signal?

Atrial depolarisation

8

What happens between the P wave and the QRS complex?

Atrial contraction

9

What is the end diastolic volume in a resting normal adult?

approx .130ml

10

When does ventricular contraction start?

After the QRS complex

11

When do the AV valves shut?
What does this produce

When ventricular pressure exceeds atrial pressure
S1

12

Why is phase 3 called isovolumetric ventricular contraction?

The tension rises around a closed volume

13

When does the aortic/ pulmonary valves open?

When the ventricular pressure exceeds the aortic/ pulmonary pressure

14

What is ejected during ventricular ejection?

Stroke volume

15

SV=? (equation + values)

SV = EDV - ESV = 135 - 65 = 70ml

16

T wave represents?

Ventricular repolarisation

17

When does the aortic/ pulmonary valves shut?
What does the produce?

When the ventricular pressure falls below aortic/ pulmonary pressure
S2

18

What signals the start of isovolumetric ventricular relaxation?

Closure of the aortic/ and pulmonary valves

19

Why is stage 5 called isovolumetric ventricular relaxation/

The tension falls around a closed box

20

When does the heart start a new cycle?

When the ventricular pressure falls below atrial pressure causing the AV valve to open

21

What does S1 signal?

The start of systole (closure of mitral and tricuspid valves)

22

What does S2 signal?

The end of systole and beginning of diastole (closure of aortic and pulmonary valves)

23

What is the JVP an indirect measure of?
How does this work?

The pressure in the right atrium
The jugular vein becomes the SVC which connects to the right atrium meaning any changes in the RA will be reflected in the JVP

24

What is the SA node made of?

Specialised pacemaker cells

25

Sinus rhythm?

Heart is controlled by the SA node

26

How is an action potential generated?

Cells in the SA node exhibit spontaneous pacemaker potential meaning the membrane potential gradually drifts until it reaches threshold which causes the cell to fire

27

Pacemaker potential?

Gradual drift of the membrane potential towards depolarisation

28

What is the ionic basis of the pacemaker potential?

There is a decrease in K efflux whilst there is slow Na influx

29

What causes depolarisation of the SA node cells?

At threshold, activation of voltage-gated Ca channels occur resulting in Ca influx

30

What is the ionic basis of repolarisation?

Activation of K channels results in K efflux