Cardiovascular physiology II 🫀📊 Flashcards
what are the 3 components of the cardiac cycle?
- Generation of electrical events that are recorded on an EKG
- Mechanical activity: systole + diastole
- blood flow through the heart
what is being made during the electrical activity of the heart?
small electrical currents
the small electrical currents made during the electrical activity is due to the?
depolarization and repolarization of the heart
the small electrical currents move through?
bodily fluids
the potential difference that happens as a result of the small electrical current is measured where on the body using what?
- surface of the body using electrode pairs
one electrode pair is called a?
lead
the voltage or the potential difference in the electrical activity of the cardiac cycle is visualized as?
waves
the waves seen on the EKG are the result of?
sum of the electrical activity of all the myocardial fibres cells of the heart
name the 3 distinguishable waves seen on an EKG
- P wave
- QRS wave
- T wave
what are the 3 segments/intervals seen on an EKG
- P-Q interval
- S-T segment
- T-P intervals
the P wave on an EKG represents?
atrial depolarization
how does the P wave on an EKG leads to contraction of both atrium
depolarization from the SA node spreads thru the contractile fibres in both atrium -> leading to atrial contraction
the QRS wave on an EKG represents what?
ventricular depolarization =contraction
how does the QRS wave lead to the contraction of both ventricles?
action potential spreads through contractile fibres in the two ventricles -> leads to ventricular contraction
when do the atria REPOLARIZED? Explain why this is not seen on the EKG
atrial repolarization occurs during the QRS wave this is not seen due to the large muscle mass of the ventricles
the T wave on an EKG represents what?
ventricular repolarization
when does the T wave begin?
happens as the ventricles begin relaxation
what is the P-Q interval seen on an EKG
- the interval between the start of the P wave and the start of the Q wave during where the Atrium contract
and action potentials are spreading from SA node to AV node
The segment between the end of the S wave to the start of the T wave is called the?
S-T segment
what happens during the S-T segment on an EKG
the ventricles are contracted and depolarized & the atria is relaxed
- blood is ejected from the ventricles into the large arteries
what segment/intervals on an EKG represents when both the atria and the ventricles are at rest
T-P interval
what are some examples of abnormal heart rhythms
Tachycardia
Bradycardia
What is Tachycardia
abnormal FAST heart beat
Resting HR higher than 100 bpm
what is Bradycardia
abnormal SLOW heart beat
resting HR is lower than 60 BPM
what happens when the conduction through the AV node is slowed? what does this indicate?
the P-Q interval will increase in length
Indicates a heart block
what happens to the ventricles during a heart block
the ventricles may not contract after each atrial contraction
what happens during a 3rd-degree heart block
- No conduction happening through the AV node so there’s a complete loss of communication between the atrium and the ventricles. So all pacemaker cells end up firing independently at their own rates:
- SA node= 75 bpm
- AV node = 50 bpm
- BUNDLE OF HIS/Purkinje fibre= 30 bpm
what are the 2 main events that are found within the mechanical activity of the cardiac cycle
systole and diastole
define systole
contraction and emptying of blood
define diastole
relaxation and filling of blood
both systole and diastole are initiated by what?
electrical activity -> require an AP before contraction can be made
what occurs during one complete heartbeat
Systole+Diastole of the atrium
Systole + Diastole of the ventricles
- this doesn’t happen at the same time (they alternate)
what is an average heart rate
75 beats per minute
60secs/minute = 0.8 s/beat
during the 0.8 seconds/beat of the mechanical activity of the heart, when do the atria become systole?
0s = the atria are contracting (systole)
how long do the atria stay contracted (systole) during the 0.8 seconds/beat
atria will stay in systole for 0.1s
how long do the atria stay contracted (systole) during the 0.8 seconds/beat
atria will stay in systole for 0.1s
for the remaining 0.7 seconds of the 0.8 seconds of the mechanical event of the heart, what happens to the atria
it will be in diastole for the remaining 0.7 seconds
during the 0.8s of the heartbeat, when will the ventricles start contracting
at 0.1 ventricles will start systole
how long do the ventricles stay in systole during the 0.8seconds rhythm
0.3s
explain how long and when the ventricles will be in diastole during the 0.8seconds rhythm
diastole of the ventricles will start at 0.4s until 0.1s of the next cycle and will last for 0.5s
the movement of blood through the heart is due to:
- pressure changes (high-low)
- valves (prevents backflow)
- myocardial contraction (raises the pressure)
during diastole of the heart, ventricles have what? in terms of pressure changes
lowest pressure
during diastole of the ventricles, blood flows from?
high pressure - low pressure
during systole, ventricles have what kind of pressure?
highest pressure
during systole, what happens to the blood in the ventricles
it flows out from high pressure - low pressure
what is the pressure in the vena cava + pulmonary veins
4.6mmHg
what is the pressure gradient in which blood flows in the heart?
high pressure - low pressure
describe how blood in the heart moves from high - low pressure (venous return)
blood moves from high - low pressure
- vena cava + pulomanary vein = 4.6 mmHg
- pressure from atria = 4.0mmHg
- venous returns (blood coming back to atrium thru vena cava) flows from high pressure - to low pressure
what is the pressure in the atrium?
<4 mmHg
during venous return, how much percentage of blood goes into the ventricles? describe
80% of blood passively flows to the ventricles (high-low)
t or f: contraction of the atria is needed to move 80% of the blood to the ventricles
false - no contraction of the atrium is needed to get the 80% of blood into the ventricles
describe what happens to the remaining 20% of blood left in the atria
during atria systole (contraction) this blood will be pushed to the ventricles
explain why atrial contraction is not necessary in order to get the blood going into the ventricles
because 80 per cent of blood will passively flow into the ventricles down its pressure gradient (high-low)
why is the atrial contraction needed to get the 20% of the blood into the ventricles
because as the ventricles starts to fill the pressure in them starts to build up and the flow will start to slow down or stop that’s why we need the atria to contract to push the remaining 20% of the blood into the ventricles
what happens to the ventricles and its pressure during diastole?
ventricles fill
pressure is nearly 0- veyr low
what happens to the ventricles and the atria during ventricular contraction (systole)
during systole:
- ventricles contract and the pressure increases to max value
- atria relaxes ( diastole)
the higher pressure in the ventricles than in the right and left atrium forces the closing of what valves?
AV VALVES
tricuspid and bicuspid valves
the first heart sound is called?
LUB (S1)
what events causes LUB (S1)
caused by the turbulence of blood flow by the closure of the AV valves
when is LUB (S1) heard?
after the QRS waves begin (heard after ventricular systole)
increased pressure in the ventricles than in the aorta/pulmonary trunk causes what valves to open?
semilunar valves
aortic and pulmonary valves
when the the semilunar valves becomes open, what happens to the blood in the ventricles
blood enters the aorta and the pulmonary trunk and is pushed out into systemic and pulmonary circulation
when the ventricles relax during diastole, what happens to its pressure
it reduces to a minimum
when the ventricles pressure drops to a minimum what happens to the aorta/pulmonary trunk
there is a higher pressure in the aorta and pulmonary trunk
the higher pressure in the aorta and pulmonary valves causes what valves to close
semilunar valves close
the turbulence that is made by the closing of the semilunar valves such as the aortic and pulmonary valves gives rise to a second heart sound called?
DUB (s2)
when is DUB (s2) heard
in the middle of the t wave (ventricular repolarization)
when does the av valves open?
when the pressure in the ventricles drops below atrial pressure
heart sounds are made from
the turbulent blood flow made the closing of valves
what is laminar flow
no sound is made
what is turbulent flow
it produces noise
what are sounds of korotkoff
the sound heard due to the turbulence in the brachial artery during blood pressure measurements
during blood pressure measurements, the first korotkoff sounds represent what?
what is being heard at this moment
it represents systolic pressure
- soft tapping sounds can be heard
at the end of the blood pressure measurements, what happens to the sounds of korotkoff? what does this represents
at the end, the sound can no longer be heard
and this represents diastolic pressure
t or f: at the end of the blood pressure measurements, the sounds of korotkoff is no longer heard and this is a sign of laminar flow
true
t or f: at the start of the blood pressure measurements the sounds of korotkoff is heard as tapping sounds and this can be a sign of turbulent flow
true
