Cardiology Lectures 1-3 : The Cardiac Cycle

Question 1

What electrically couples the cardiac mycocytes?

Answer 1

Gap junctions

Question 2

What provides the mechanical adhesion between the adjacent cardiac cells?

Answer 2

Desmosomes

Question 3

What is the thin filament in the heart myofibrils calles?

Answer 3

Actin

Question 4

What is the thick filament of the heart myofibrils called?

Answer 4

Myocin

Question 5

How are actin and myocin arranges in myfibrils

Answer 5

As sacromeres

Question 6

How is muscle tension in the heart produced?

Answer 6

Sliding of actin and myosin filaments

Question 7

What two things are required for muscle contraction in the heart?

Answer 7

ATP and calcium

Question 8

True or False: ATP is required for muscle relaxation.

Answer 8

True

Question 9

Why is calcium required?

Answer 9

Switches on the cross bridge formation

Question 10

What is the importance of having a long refractory period?

Answer 10

Prevents tetanic contraction

Question 11

What is a refractory peroid?

Answer 11

Peroid following an action potential in which it is not possible to produce another action potential

Question 12

What is stroke volume?

Answer 12

The volume of blood ejected by each ventricle per heart beat

Question 13

What is the end diastolic volume?

Answer 13

The volume of blood withn each ventricle at the end of diastole

Question 14

What determines the end diastolic volume?

Answer 14

the venous return to the heart

Question 15

What is afterload?

Answer 15

The resistance the heart is pumping into

Question 16

What is the preload?

Answer 16

How much blood is loaded in the heart before contraction

Question 17

What is the consequence to the heart of chronically increased afterload?

Answer 17

Ventricular hypertrophy

Question 18

What effect on the heart in cAMP mediated?

Answer 18

The increased inotropic affect of sympathetic stimulation to the heart

Question 19

What effect do parasympathetic nerves have on heart contractility?

Answer 19

LIttle effect- little innervation by the vagus

Vagus stimulates rate not force

Question 20

What is the cardiac output?

Answer 20

The volume of blood pumped by each ventricle of the heart per minute

Question 21

What is the resting CO in a healthy adult typically?

Answer 21

5 litres ( 70 x 70ml= 4900ml)

Question 22

What is meant by autorhythmicity of the heart?

Answer 22

The electrical signals which control the heart are generated within the hear itself

Question 23

Where does excitiation originate?

Answer 23

Sino-atrial node

Question 24

What happens during the funny current?

Answer 24

Decrease in efflux of K

Slow Na influx

Question 25

What happens during the rising phase of the pacemaker AP?

Answer 25

Calcium influx

Question 26

What happens during the falling phase of the pacemaker action potential?

Answer 26

K efflux

Question 27

What is resting membrane potential?

Answer 27

-90

Question 28

What happens during phase 0 of the ventricular muscle AP?

Answer 28

Fast influx of Na

Question 29

What happens during phase 1?

Answer 29

Slow K efflux | Closure of Na channels

Question 30

What happens during phase 2

Answer 30

Ca influx

Question 31

What happens during phase 3

Answer 31

K efflux | closure of Ca channels

Question 32

What is phase 4

Answer 32

resting membrane

Question 33

Which phase is known as the plateau phase?

Answer 33

Phase 2

Question 34

Which nerve dominates the rhythmic control of the heart under resting conditions?

Answer 34

Vagus | parasympathetic

Question 35

What effect does the vagal tone have on the heart

Answer 35

slows its intrinsic rate

Question 36

How does vagal stimulation slow the heart

Answer 36

Increases AV nodal delay

Question 37

What is receptor does the parasympathetic stimulation act on?

Answer 37

M2

Question 38

What is the affect of atropine?

Answer 38

Speeds up the heart

Question 39

Define the cardiac cycle.

Answer 39

All the events that occur from the beginning of one heart beat to the beginning of the next.

Question 40

Name the stages of the cardiac cycle

Answer 40

``` Passive filling Atrial contraction Isovolumetric contraction Ventricular ejection Isovolumetric relaxation ```

Question 41

What is the pressure in the atria and ventricles during passive filling

Answer 41

Close to zero

Question 42

Are the AV valves open or closed in passive filling?

Answer 42

Open

Question 43

When do the AV valves shut?

Answer 43

When the ventricular pressure exceed atrial pressure ie ventricles begin to contract

Question 44

What is isovolumetric contraction

Answer 44

Contraction of the ventricles when both the Av valves and pulmonary/aortic valves are shut - thus there is no change in volume

Question 45

When do the aortic/pulmonary valves open?

Answer 45

When the ventricular pressure exceeds aortic/pulmonary pressure

Question 46

When do the aortic/pulmonary valves shut?

Answer 46

When the ventricular pressure falls below the aortic/pulmonary pressure

Question 47

What does the valve vibrtion when the aortic valve shuts produce?

Answer 47

Dicrotic notch in the aortic pressure wave

Question 48

What is isovolumentric relaxation?

Answer 48

The ventricles are relaxing but both sets of valves are shut so there is no change in volume

Question 49

When do the Av valves open again?

Answer 49

When ventricular pressure is lower than atrial pressure

Question 50

What is S1?

Answer 50

The closure of the AV valves

Question 51

What is S2?

Answer 51

The closure of the aortic and pulmonary valves

Question 52

What does S1 mean?

Answer 52

The beginning of systole

Question 53

What does S2 mean?

Answer 53

The beginning of diastole