Week 9 - Study Guide Flashcards
Definition of Cardiac Output
blood pumped by the ventricle in one minute (minute volume)
Formula for Cardiac Output
CO = (SV)(HR)
(ml/min) = (ml/beat)(bpm)
Average heart rate
75 bpm
Stroke Volume is
amount of blood pumped by each ventricle with each heart beat
Stroke Volume =
average 70 ml/beats
what is the AVG CO =
5.35 L/min
for every minute = is nearly the entire blood volume of the body
Total Blood volume =
5.5 L
Each ventricle pumps equivalent of total blood volume/minute at rest
Cardiac Reserve =
difference between CO at rest and all-out work
which is allowing us to understand that there is a normal resting cardiacoutput
AND
a large reserve capacity allowing us to increase our activity quite a bit
Exercise CO =
14-20 L/min
Hemorrhage CO =
1.5 L/min
Elite Athletes CO =
30 L/min
Contraction phase
Systole
pumped volume
Relaxation phase
Diastole
filled volume
Formula for Stroke Volume (SV) =
SV = EDV - ESV
when ventricles are full = EDV
when ventricles pump = ESV
SV is the difference
Dicrotic Notch
closure of the aortic semilunar valve causes temporary increase pressure
blood briefly backflow against the valve.
Which contraction is the biggest pressure change?
Left ventricular contraction
which alters Left atria and aortic pressure
Frank-Starling Law
Better fill = Better pumping
Amount of stretching in ventricle prior to contraction
Factors affecting stroke volume
- Frank-Starling Law
- Sympathetic nerve activity
- Venous return (determines and influences the EDV)
What do you want in cardiac muscle in regards to sarcomere length?
Want the most stretching, the greatest filling that you can - in order to create the greatest pumping efficiency
The more you stretch - the better the contractile strength.
Preload
filling or stretching of the ventricles - creating the strength of their contractions
for heart to be effective, preload has to be greater than afterload
Afterload
Pressure in the artery that the heart has to contract against.
is pressure in vessels applied to backside of semilunar valve,
Has to pump against back pressure of semilunar valves for things like hardening of the arteries, etc.
Increasing afterload =
decreased SV
increased ESV
Sympathetic enhances contractility and relaxation by
enhancing Ca2+ movements
When you are stressed you need more blood which means
Stroke volume rises
Norepinephrine does what
speeds things up
Norepinephrine Release has 3 main effects
- Makes pacemaker speed up (SA node)
- Heart beats faster, pause is shorter – decreases conduction time through AV node
- heart more reactive - effective pump - gap junctions. increases excitability of entire heart
ACH release does what?
- Vagus nerve stimulates the heart
- Decreases heart rate
Vagus nerve input is going to slow down the heart - because that is the parasympathetic signal.
Preload > Afterload
your ventricles will be able to pump blood effectively out to the pulmonary circuit and the systemic circuit.
Pumping blood out of the heart
Preload = Afterload
your ventricle does not have sufficient pressure to overcome the afterload
so- the semilunar valves are not open
Preload < Afterload
Not able to open the semilunar valve.
Probably be pushing blood backward.
Making sure that any blood that is trying to enter the ventricles is actually backing up
How do you calculate Cardiac Output?
What are the average adult values?
CO = (HR)(SV)
5.25 L/min = (70 mL/beat)(75 bpm)
EDV
End Diastolic Value
(Volume of blood in ventricle, right before it contracts, i.e. how full it is)
ESV
End Systolic Value
(volume of blood in ventricle left over right after it contracts. i.e. indicates how much blood was pumped
Another way to describe preload and afterload
preload is stretch
afterload is the opposition the heart works against
Syncope
pass out
Venous return
summary of all the things that help to assure wherever the blood is in the body’s system - that it will make it back to the heart to keep the cycle going.
Heart cannot pump what it does not receive
Return of blood to the heart influences –
stroke volume
Influencing factors of stroke volume
- Total Blood volume
- Venous pressure
- Breathing
EDV dependent on Venous retrun. Did the blood from the veins get back to the heart.
Factors that influence this?
BLOOD VOLUME (BV)
- BV goes up when you pee more. that fluid is no longer in the bloodstream (an inverse relationship)
As urine volume goes up - blood volume goes down
meaning - if you BV is down - Venous return will. be down.
TISSUE FLUID VOLUME
1. Edema (build-up of fluids in the tissues) would cause a blood volume decrease
2. which would then cause a venous return decrease.
Venous return is inversely related to
- urine output
- tissue fluid volume
more urine volume = less BV
more tissue fluid = less BV
What keeps the blood clean and creates urine? (filter)
Kidneys
20% of heart beat foes to kidneys to filter
Build-up of fluid in the tissues
Edema
What happens to the pressure the farther you get away from the heart?
the more the pressure drops
Venoconstriction
The SNS can constrict the muscle in the vein to increase a little bit of pressure to push blood from the vein back to the heart.
Skeletal Muscle Pump
About you voluntarily moving and pushing blood back to your heart.
One of the reasons it is important to move around to keep your blood from being stuck in your periphery.
Negative interthoracic pressure - Breathing
- Ribs will be pushed out
- Diaphragm contracts and pushes downward
- Causing a pressure gradient
meaning - the pressure in the thoracic cage - actually falls because your diaphragm contracts and pushes down on the abdomen.
Meaning - the abdomen has a higher pressure than the thoracic activity.
pressure gradient
If there is HIGH pressure in the abdomen and LOW pressure in the thoracic cage - BLOOD wants to go from the abdomen back to the heart.
REMEMBER
1. Blood wants to go from High pressure to Low pressure
How does this impact venous return?
Breathing
Good for Venous return
Blood wants to for from high pressure to low pressure
How does this impact venous return?
Urine volume
urine volume up
venous pressure low
How does this impact venous return?
Skeletal muscle activity
skeletal muscle activity up
Venous goes up
How does this impact venous return?
Edema
Edema goes up
Venous pressure goes down
Blood volume goes down
How does this impact venous return?
Sympathetic Activity
Sympathetic Activity goes up
Everything goes up
