CVS self study 3 cardiac cycle

Question 1

what is the relationship between CVP and EDV?

Answer 1

as CVP inc, EDV inc

CVP is the pressure in large veins draining into heart.

Question 2

what is CVP value dependent on?

Answer 2

total blood in circulation and distribution of the blood

Question 3

what causes INC in CVP?

Answer 3

venoconstriction
transfusion (inc blood vol)

Question 4

what causes DEC in CVP?

Answer 4

haemorrhage/dehydration (dec blood vol)

postural hypotension

Question 5

what is the relevance of The Frank Starling mechanism?

Answer 5

matches venous return to cardiac output > ensures R and L side pump the same amount of blood per minute

if CO in one ventricle increases, venous return to the other ventricle will increase

Question 6

what is the relationship relationship between stroke volume (SV) and end diastolic volume (EDV)

Answer 6

Stroke volume and end diastolic volume are proportional. one inc, other also inc.

Question 7

how does the sympathetic nervous system increase the slope of the pacemaker potential?

Answer 7

The sympathetic nervous system increases the slope of the pacemaker potential in the SA node by increasing cAMP in the cells. >activates PKA, which phosphorylates Ca2+ channels, increasing the Ca2+ entry into the cells. This increases Ca2+ uptake into the SR which causes a positive inotropic effect.

Basically: cAMP increases -> PKA phosphorylates Ca2+ channels -> more Ca2+ into cell -> more Ca2+ into SR -> increased heart rate.

Question 8

what does Post-gangionic fibres in the PARASYMPATHETIC nervous system release?

what does it act on?

its effect on the heart?

Answer 8

acetylcholine

M2 receptors on the epicardial surface, or within the heart walls at the sino-atrial and atrioventricular node

negative chronotropic effect on the heart

Question 9

Which neurotransmitter is released from post-ganglionic SYMPATHETIC neurones in cardiac tissue?

Answer 9

noradrenaline

Question 10

How is HR controlled?

Answer 10

ANS

Parasympathetic-
slow HR via Vagus nerve,
and postganglionic fibres release Acetylcholine
>act on M2 receptors.

Sympathetic
increase HR
through noradrenaline release from postgangionics
>act on the Beta-1 receptors.

Question 11

describe the action of adrenaline in coronary muscle, skeletal muscle and in the liver’s vasculature?

which receptors?

Answer 11

At physiological (normal body) levels = vasodilation (β2 receptors)/
At pharmacological levels = vasoconstriction (α1 receptors)'

Question 12

How is vasomotor tone maintained?

Answer 12

ANS Release of noradrenaline causing vasoconstriction

Question 13

what are the 7 phases of the cardiac cycle?

Answer 13

atrial contraction
isovolumetric contraction
rapid ejection
reduced ejection
isovolumetric relaxation
rapid filling
reduced filling

Question 14

where do you feel for femoral pulse?

Answer 14

inferior to the mid-inguinal point (this is halfway between the ASIS and the pubis).

Question 15

what are the 6 stages of the cardiac cycle shown on Wiggers diagram?

Answer 15

isovolumetric contraction
ejection
isovolumetric relaxation
rapid inflow
diastole 
atrial systole

Question 16

what parts of the cardiac cycle are systole?

Answer 16

isovolumetric contraction (ventricles contract with no volume changes)
ejection (rapid and reduced)

Question 17

what parts of the cardiac cycle are diastole?

Answer 17

isovolumetric relaxation
rapid filling
reduced filling
atrial contraction

Question 18

what are the valves doing in atrial contraction

Answer 18

mitral/tricuspid open

aortic/pulmonary closed

Question 19

what are the valves doing in isovolumetric contraction?

Answer 19

ALL valves closed
ventricles contract with no volume changes

closure of the mitral and tricuspid valve results in first heart sound (S1)

Question 20

what is the importance of atrial contraction?

Answer 20

accounts for final 10% of ventricular filling

>atrial kick

Question 21

what are the valves doing in rapid ejection?

Answer 21

mitral/tricuspid closed
aortic/pulmonary open

ejection begins when the intraventricular pressure exceeds the pressure in the aorta> aortic valve open

Question 22

what are the valves doing in reduced ejection?

why does the rate of ejection fall?

Answer 22

mitral/tricuspid closed
aortic/pulmonary open

as repolarisation of ventricle leads to a decline in tension/ pressure

Question 23

what are the valves doing in isovolumetric relaxation?

Answer 23

ALL valves closed
volume doesn’t change.

closure of aortic and pulmonary valves result in the second heart sound (S2)

Question 24

what causes the aortic valve to close during isovolumetric relaxation?

Answer 24

intraventricular pressure falls below aortic pressure.

brief back flow of blood which causes the valve to close.

Question 25

what are the valves doing in rapid filling?

Answer 25

mitral/tricuspid open

aortic/pulmonary closed

Question 26

describe heart noises in ventricular filling

Answer 26

ventricular filling normal silent

BUT S3 sound is normal in children, sign of pathology in adults.

Question 27

what are the valves doing in reduced filling?

why does diastasis occur?

Answer 27

mitral/tricuspid open
aortic/pulmonary closed

but filling slows down (diastasis) as ventricle reaches its inherent relaxed volume.
this is the passive filling.

Question 28

In which phase of the cardiac cycle can the QRS complex be seen on an ECG?

Answer 28

isovolumetric contraction.
>contraction of the ventricles, by ventricular depolarisation t
(seen on the ECG trace as the QRS complex. )