cardiac cycle/dynamics and the conduction system Flashcards
what is stoke volume(SV)
The volume of blood ejected from the left ventricle per beat (ml)
what is heart rate(HR)
The number of times the heart beats per minute (bpm)
what is the average HR
72
what is cardiac output (Q)
The volume of blood ejected (pumped) from the heart per minute (l/min)
What is bradycardia
when your HR is under 60 bpm
how do you calculate max HR
220-age
what cause anticipatory rise
adrenaline
what happens to HR during exercise
HR rises proportionately to exercise intensity
At submaximal levels HR will plateau when a steady state is reached and O2 demand is met.
what happens to HR post exercise
nitial rapid drop in HR due to less oxygen demand
Then gradual drop to repay oxygen debt
what is the resting SV
72ML
if you are an elite performer how does SV change
it decreases
what is starlings law
More blood to heart, leads to greater end diastolic volume
Greater stretch of atria walls lead to more forceful contraction
what happens to stroke volume at maximal exercise
it decreases slightly due to reduced time to fill heart
what is sub maximal exercise
exercise working between 40-60% of max HR
what are the 2 reasons stroke volume increases
increased venous return
starlings law
how to calculate stroke volume
SV=EDV-ESV
What is Ejection Fraction
An ejection fraction of 60 % means that 60 % of the total amount of blood in the left ventricle is pushed out with each heartbeat.
what SV percentage is right and what is too high
right=50-70%
too high=75%
how to calculate cardiac output(Q)
HR x SV = Q
what is the average Q at rest
5L
What happens to Q during exercise
Cardiac output increases in line with exercise intensity
Plateaus during maximal exercise, due to inefficient diastolic filling time
what happens to Q after exercise
In recovery there is a rapid decrease followed by a slower decrease to resting levels
what is diastole
Diastole is the phase of the cardiac cycle that sees the heart relax and fill with blood.
what is systole
The Systole phase is when the atria contracts, forcing blood into the ventricles
how long in total does systole and diastole take
0.8s
what happens in diastole
Oxygenated blood enters LA from pulmonary veins
Rising pressure is Atria against AV valves forces blood into ventricles passively
- right = tricuspid valve
- left = bicuspid valve
Volume of blood after filling stage is called END DIASTOLIC VOLUME (EDV)
how long is diastole
0.4s
how long is atrial systole
0.1s
what happens in atrial systole
the atria contracts, forcing blood into the ventricles.
how long is ventricular systole
0.3s
what happens on the left side of ventricular systole
-The ventricles contract, increasing pressure closing the AV valves to prevent backflow into the atria
-Increased blood pressure through ventricular contraction forces blood out of both ventricles (STROKE VOLUME)
-Left ventricle forces blood through aortic valve into aorta (to body)
-the valves remain shut and the aortic valves shut to prevent back flow
what happens on the right side of ventricular systole
-The ventricles contract, increasing pressure closing the AV valves to prevent backflow into the atria
-Increased blood pressure through ventricular contraction forces blood out of both ventricles (STROKE VOLUME)
-right ventricle forces blood through pulmonary valve into pulmonary artery (to lungs)
-the valves remain shut and the pulmonary valve close to prevent back flow
what does myogenic mean
this means it generates its own impulse.
what does cardiac impulse mean
The electrical impulse responsible for stimulating the heart
what is the route of the conduction system
1.The Sino-atrial Node (SA node) located in the right atrium wall, emits an impulse and fires it through the atria walls, causing an impulse.
2.The impulse spreads to the adjacent interconnecting fibres of the left atrium
3.It moves to the specialised cells called atria-ventricular nodes (AV nodes)
4.AV Node acts as a distributor and passes the action potential (impulse) to the Bundle of His
5. It moves down the bundle of his to the apex of the heart
6.The impulse then spreads up the Purkinje Fibres (in the ventricle walls), causing excitation and ventricular systole (contraction)
what is depolarisation
At every beat, the heart is depolarized to trigger its contraction
What is the stroke volume of an untrained person at rest
60-90ml per beat
What is the stroke volume of an trained person at rest
90-110ml per beat
What is the stroke volume of an untrained person during sub-maximal exercise
120-140ml per beat
What is the stroke volume of an trained person during sub-maximal exercise
160-200ml per beat
what is venous return
the term used for the volume of blood that returns to the RIGHT side of the heart via the venules and veins.
why is venous return needed
to assist the distribution of blood round the body
what happens to Q and SV when venous decrease
they decrease
what happens to Q and SV when venous increases
they increase
How does an increase in Venous Return affect ventricular contraction?
Increase in blood to right atrium
So, it stretches the (right atrium) chamber
This increase the SA node firing rate
…. So, HR increases
what happens to venous return at rest
VR is sufficient to maintain SV and Q to meet demand for O2
what happens to venous return during exercise
Blood pressure (BP) in the veins is too low to maintain VR, so SV and Q decrease
what are the 5 mechanisms aiding venous return
Pocket Valves
Muscle Pump
Respiratory Pump
Smooth Muscle
Gravity
what do pocket valves do
Pocket Valves prevent backflow of blood and direct it towards the heart.
what do muscle pumps do
Veins are situated between skeletal muscles.
When the muscles contract, this helps to push or squeeze blood back to the heart.
what do respiratory pumps do
During exercise, breathing becomes deeper and faster.
This causes pressure changes in the thorax and abdomen, squeezing large veins and thus blood back to the heart.
what do smooth muscles do
Contraction and relaxation of smooth muscle in the middle layer of the vein walls helps push the blood towards the heart.
what does gravity do
Blood from the upper body is aided by gravity
what is blood pooling
VR requires a force to push the blood back towards the heart
If there isn’t enough pressure, the blood will sit in the pocket valves of the veins.
what are the impacts of vr on performance
more oxygen to working muscles
less fatigue
quick recovery
