Cardiac cycle

Question 1

Conduction of AP through the heart

Answer 1

SAN generates the pacemaker activity therefore creates the AP
conducts out through the atrial muscle to the AV node
from AV node to the bundle of HIS
branches to the purkinje fibres
eventually leading to the ventricles

Question 2

describe the contraction of ventricles?

where does it begin? where does it end? motion of conduction?

Answer 2

Contraction of ventricles begins at apex and works towards base
apex of the heart recieves electrical activity + contracts first
THEN, electrical activity spreads through the ventricles up till the base therefore causes a corkscrew motion which moves the blood out of the heart to the lungs and heart

Question 3

what is the cardiac cycle? (3 things)

what is it?
what does it describe?
wnat does it explain?

Answer 3

Describes the movement of blood through the heart during one heartbeat, so comprises both

the relaxation phase of the ventricles (diastole) AND the contraction phase of the ventricles (systole)

Helps explains how the heart produces the driving force required for convection transport of blood flow
to the lungs and the systemic circulation

Question 4

what is the electrical conduction activity of the heart?

Answer 4

Sino-atria (SA) node into atria. Slows down at atria-ventricular node (AV) to allow correct ventricular filling.
Enters ventricles leading to a coordinated contractions, chamber pressure changes, and ejection of blood

Question 5

principle of blood flow in the heart (3)

why flows?
valves?
simlairty and difference of rhs and lhs?

Answer 5

Areas of high pressure to low pressure, unless flow is blocked by a valve

Valves open/close depending on pressure changes in chambers

Events on the right and left sides of the heart are the same, but pressures are lower on the right

Question 6

route of blood flow through the heart

movement of blood from one side to next via valves?

Answer 6

Venous return great veins (SVC, IVC) - Right atrium
(return in low pressure but pressure increases if atria contract)
Tricuspid valve

Right ventricle

Pulmonary semilunar valve

Pulmonary arteries

LUNG CIRCULATION

Pulmonary veins

Left atrium

Bicuspid (Mitral) valve

Left ventricle

Aortic semilunar valve

Aorta

SYSTEMIC CIRCULATION

Question 7

what do we measure when we measure blood pressure?

why maintain high enough bp?

Answer 7

measure systolic circulation which is usally 120/80
120 is ejecting phase and 80 is resting phase
hence maintain bp high enough to perfuse to end organs

Question 8

ventricle filling/atria contraction phase

why movement? what happens? extra filling?

Answer 8

Higher pressure in atria > ventricles
tri/bi valves open - blood enters ventricles
Atrial contraction – extra filling into ventricles

Question 9

isovolumetric contraction phase
why? what happens/how?
importance?

Answer 9

Higher pressure in ventricles > atria so tri/bi valves close

Closed ventricle chamber means you can greatly increase pressure to open pulomonary and aortic valves

Question 10

Ejection phase

why movement? what happens?

Answer 10

Higher pressure in ventricles > aorta/pulmonary artery Valves open
Blood flows out of heart
Blood enters atria

Question 11

isovolumetric relaxation phase

why? what happens?
importance of this stage? (2)

Answer 11

Higher pressure in aorta/pulmonary artery > ventricles
Valves close
Closed ventricle
Relaxes, expands, ready to receive

once ejected all blood, pressure in the ventricles will decrease therefore the valves will close. Now, we have a closed chamber again but need to expand to recieve blood. This is what is meant by isovolumetric relaxation and this causes pressure to drop drastically, eventually being lower than atria pressure. AND as atria fills up with blood, BP will rise and the valve will open (repeating the cycle).

Question 12

Left ventricular pressure changes during atrial systole

importance?

Answer 12

Ventricle BP doesnt raise too much with atrial contraction but once it rasies enough, it will be greater than atria therefore the atrial and mitral valves close

Question 13

Left ventricular pressure changes during isovolumetric contraction

Answer 13

closed LV chamber leads to isovolumetric contraction

Drastic increase in BP which bypasses the aorta pressure

Question 14

Left ventricular pressure changes when aortic valve opens

initially? how and why does it change? what happens?

Answer 14

aortic valve opens which leads to ejection. The LV is still contracting therefore during intial stage, LV pressure is greater than aorta as its a full chamber and LV contracts firmly on full chamber.
HOWEVER, as we eject more blood, pressure drops as less blood is in the chamber and the pressure drops enough for the aortic valve to close.

Question 15

Left ventricular pressure changes when aortic valve closes

what happens? why and what does it lead to?

Answer 15

once the valve is closed, closed LV chamber AND it is in relaxtion phase so pressure drops a lot (also less blood in chamber)
Once pressure drops below pressure in LA, mitral valve opens

Question 16

Left ventricular volume changes and stroke volume

how is Sv calculated?

Answer 16

Mitral valve closes End diastolic volume (EDV) = 120 ml
Aortic valve closes End systole volume (ESV) = 40 ml
SV = EDV – ESV = 80 ml

Question 17

what is the ejection fraction?
equation?
what is the normal value?

Answer 17

Ejection fraction = SV / EDV

Normal value 2/3rd or more; lower values in heart failure

Question 18

describe Ventricular pressure-volume loop diagram

what gives it the loop shape? describe the different stages and the correspondence on the graph?

Answer 18

Low pressure in LV means mitral valve opens
Filling phase of LV means increased volume therfore pressure till eventually mitral valve closes
drastic increase in pressure due to isovolumetric contraction
aortic valves open therfore decrease in volume and decrease in pressure
aortic valve closes and isovolumetric relaxtion therefore decrease in pressure

Question 19

what is Ventricular pressure-volume loop - what does it relate to?

work equation?
area inside of loop meaning?

Answer 19

Work (mechanical energy into increase in pressure and movement of blood) =
change in ventricle pressure x change in volume

Area inside loop = amount of stroke work done

Relates to the amount of energy consumption during cardiac cycle

Question 20

right atria/great vein pressures - A wave

describe the shape and why?

Answer 20

pressure increase as blood returns from S/I Vena cava
peak increase as atrial contracts
decrease in pressure as blood moves into RV

Question 21

right atrai/great vein pressure - X descent

describe shape and why?

Answer 21

as the tricuspid valve is open, blood moves into the RV

therefore a peak decrease in pressure as volume decreases and the atria is relaxing when valve closed

Question 22

right atria/great vein pressure - V wave

describe shape and why?

Answer 22

gradually pressure increases as blood fills up in atria from great veins and the valve is closed

Question 23

right atria/great vein pressure - y descent

describe shape and why?

Answer 23

tricuspid valve open, the pressure slightly decreases known as the Y descent
atrial will contract therefore peak pressure for A wave and the cycle repeats

Question 24

what does x descent look like in the body?

what happens when pressure increase? decrease?

Answer 24

drop in pressure seen as collpasing neck vein
looks pulsatile
as pressure increases, they expand and as pressure decrease, they collapse

Question 25

Clinical relevance of right atria and jugular venous pressures changes

what happens if pressure is RA is raised?
describe rs heart failure?
effect of this and relevance?

Answer 25

If pressures in right atria is raised, Then height of venous pulsatile distension is increased

Right sided heart failure, Less blood is ejected from right ventricle, more blood volume and pressure present in right atria, Hence raised jugular venous pressure observed

Increased pressure + volume in RV but not pulmonary artery for lungs which means increased pressure backed up into RA and into great veins hence the jugular pressure of collpasing and distension is going to rise which causes a reolcation of vein (4-5 cm)

Question 26

why do we hear heart sounds? ( 2)

Answer 26

Vibrations induced by closure of cardiac valves

Vibrations in ventricular chambers caused by turbulent blood flow through valves

Question 27

S1 heart sound

what sound and why? what stage?

Answer 27

Lubb

Closure of tricuspid/mitral values at beginning of ventricular systole

Question 28

S2 heart sound

what sound? why? what stage?

Answer 28

Dupp

Closure of aortic/pulmonary valves at beginning of ventricular diastole

Question 29

s3 - occasional heart sound

why? common in who?

Answer 29

Turbulent blood flow into ventricles, detected near end of first 1/3 diastole – common in young

Question 30

s4 - pathological sound in adults

why?

Answer 30

Forceful atrial contraction against a stiff ventricle – potentially abnormal

Question 31

cardiac cycle - whole picture

Answer 31

Atrial contraction 
Isovolumetric ventricular contraction  
Rapid ventricular  ejection 
Reduced ventricular ejection 
Isovolumetric ventricular relaxation
Rapid ventricular filling 
Reduced  ventricular filling