How the heart functions Flashcards
Systole
Contraction of the heart chambers
Diastole
Relaxation of the heart chambers
Name for when the atria are conteracted
artial systole
Sequence of blood being pumped through the heart (systole and diastole)
Atrial systole (semi lunar valves closed)
Atrial diastole and ventricular systole ( atrioventicular valves close)
Ventricular diastole
Effect of atrial diastole
Decreases vol of atria
Increases pressure above that of ventricles
Remaining blood in the atria pushed throught he already open valves
Effect of ventricular systole
Vol of ventricles decreased
Pressure increases
Blood moves out into the artery down the pressure grad
What stops blood flowing backwards into the atria from ventricles down the pressure grad
Blood flows collects at pockets in the valves pinching the valves closed in attempt to pass backwards.
Based on what gradients do valves prevent back flow of blood
Pressure gradients
Atrioventricular valves?
Prevent back flow of blood from ventricles to atria: Tricuspid and bicuspid
Semi lunar valves?
Prevents back flow of blood from the arteries to the ventricles: Aortic and pulmonary
When do valves open
When the pressure above is greater than that in the chamber beneath
When do valves close
When the pressure in the chamber beneath the valve is greater than in front of it
What produces the lub- dum sound perceived as a heart beat
The closing of the atrioventricular valves followed by that of the semi lunar valves
Function of coronary artery
Supplies O2/ blood to the heart muscle
Location of coronary arteries
2: left and right on the surface of the heart
Why do valves on the left of the heart more often become defective
Exposed to a higher pressure as left side pumps O2 blood to the whole body
Symptoms of failing valves (leaky)
Breathlessness
Fatigue
rapid or irregular heart beat
Location of pacemaker
Right atrium
Name for peace maker
Sino-atrial node
Characteristics of pacemaker 2
Myogenic
Causes heart to beat 55-70 bpm
myogenic?
Heartbeat is initiated from within the muscles and is not dependent on nervous of hormonal stimulation
Sequence of electrical impulse by SAN
SAN initiates a wave of excitation
Wave spreads over walls of atria causing atrial systole
Excitation is prevented from spreading to ventricles by thin layer of insulating, connective tissue
Sequence of electrical impulse from AVN onwards
The wave of excitation reaches the AVN and is delayed through this node before it it RELAYED
The wave then travels down the bundle of His
As it reaches the apex of the heart and moves up purkyne fibres, causing ventricular systole
Heart then experiences diastole as the electrical impulse is terminated
What causes the termination of the electrical signal following to produce diastole of the heart
There is no more conductive tissue after the purkyne fibres
Apex of the heart?
Pointed bit: bottom of ventricles
Bundle of His?
Highly conductive tissue in the septum
What doe AVE stand for and what is it
Atrioventricular node, patch of muscle fibres at the top of the inter ventricular septum
Why is the delay of the impulse to the His necessary
To allow the atria to have fully contracted and the ventricles filled before they begin systole
Where does the impulse travel after reaching the apex of the heart
Through the purkinje fibres up the sides of the ventricles
why does ventricular systole begin from the apex of the heart upwards
to direct blood upwards into the arteries most efficiently
Heart rate?
Beats per minute
Stroke volume
Vol of blood in cm3 pumped by heart in one beat
Cardiac output
Vol of blood pumped by the heart in 1 minute (Stroke vol× heart rate)
ECG?
ElectricoCardioGram: measures electrical activity of the heart to detect heart problems
What structures ensure the heart valves only open in one direction- are not blown open by pressure
Chordae tendineae
What does the P wave correlate to
Atrial systole
what does the QRS complex correlate to
Depolarisation of the ventricles followed by Ventricular systole
what does the T wave correlate to
repolarisation of the ventricles, ventricular diastole
Depolarisation meaning
Electrical process that causes systole
Fibrillation meaning
Irregular contractions of the cardiac muscles
how many times thicker is the left ventricle than the right
3 times
What does the diameter of the pressure-volume loop represent
Stroke volume
What does volume describe on the pressure- volume graph
Volume of BLOOD in the left ventricle
What are the three important graphs
Pressure-time graph
Pressure-volume graph (LV)
Blood pressure-flow graph
Key things to remember when reading graph of pressures in heart
Atrioventricular valves open when pressure in atria is greater than in ventricle and close in the opposite situation
Semi lunar valves open when pressure in ventricle is greater than in aorta/pulmonary artery
Diasotolic filling?
Passive filling of the atria/ ventricles between T wave and P wave via venous return
Why do the atria have less muscular tissue and weaker systole than the ventricles
They pump blood into the ventricles which is a far shorter distance than around the when body as the LV does
PR interval?
Time between start of P wave and start of QRS complex, time taken for excitation to spread from atria to ventricles through AVN
ST segment on ECG
End of S wave to beginning of T wave
What is the name for the line between the T and P wave of the next cycle and what is it
The isoelectric line, it is the baseline of the ECG trace
Heartbeat
complete contraction and relaxation of the whole heart
Function of the chordae tendinae
Prevent inversion of valves during high pressure created by systole
