Cardiac Physiology Pt. II Flashcards
Cardiac output
• How to ensure the right amount of blood is pumped
• Determined by total tissue blood flow
• How to ensure the right amount of blood is pumped
CO=____
• Brain - \_\_\_\_% • Heart - \_\_\_\_% • Spleen a lot, kidneys muscles, skin use a lot • CO = HR x SV ○ Amount of blood that leaves heart with each cycle, times number of cycles per minute
HR x SV
14
4
Cardiac output = O2 need
- Cardiac output increases with body’s consumption of ____
- Sum of total body factors to control blood flow
- Tight curve – very well ____• O2 consumption in blue; cardiac output (L/min per L2, area) in red
○ Relationship between both
§ Drives the amount of blood that’s needed
oxygen
regulated
Cardiac output – decreases with ____
• Declining activity and declining ____
• Cardiac Index – ____
• Peaks at age \_\_\_\_ > declines with age (muscle mass, activity, etc.)
age
muscle mass
CO/area
10
Measuring heart rate
• EKG ____ interval
• Pulse
– ____
– phone – gym
R-R
manually
Heart rate
• Normalheartrateatrest ________ bpm
• Maximum =____ bpm-age
60
60
100
200
Compare max heart rate with refractory periods
Can drugs you give as dentists change this RRP?
• How does HR compare to refractory periods? ○ ERP > minimum duration of \_\_\_\_; won't be able to initiate another AP in that amount of time
ventricular contraction
Stroke volume
Stroke Volume=
____ – End Systole Volume
In typical male, =120 ml-50 ml=70 ml
SV = EDV – ESV EF = SV / EDV
* End diastolic volume - end systolic volume * How do you measure this?
end diastole volume
Measuring stroke volume
• Estimate ventricle volumes from ____
– Subtract volume of the blood ESV from EDV
• Fick’s principal O2 consumption
• Can measure using an echocardiogram ○ Measure volume in chambers, and do the subtraction • Can use Ficks - \_\_\_\_ is a close measure of your cardiac output ○ Can measure changes in \_\_\_\_
echocardiogram
O2 consumption
SV
Calculating cardiac output CO=HRxSV
- Volume of blood being pumped by the heart per unit time
- CO(L/min)=HR(beat/min) x SV (L/beat)
- 70 beats/m x 70 ml/beat = 4900 ml/min ~ ____ L/min
5
Cardiac output
Cardiac factors:
____
____
Coupling factors:
____
____
heart rate
myocardial contractility
preload
afterload
The P-V Loop
• A > mitral valve \_\_\_\_ (end diastolic volume) • B > isometric \_\_\_\_ (aortic valve \_\_\_\_) • C > end systolic (aortic valve \_\_\_\_) • D > isovolumetric \_\_\_\_ ○ One loop of this curve = one heart beat • If stop the heart from contracting at all > removing the Ca++ (add EGTA to remove any excess Ca++) and inject solution > takes more to get it contracting (during diastolic) • Systolic pressure curve is much \_\_\_\_ slope > add Ca++ to keep the LV contracted all the time > constant \_\_\_\_ ○ Properties are different then when relaxed; much smaller volume to get base line pressure, and increase the volume > pressure fills up much more \_\_\_\_ than in the relaxed in the state (diastolic)
closes contraction opens closes relaxation
steeper
contraction
rapidly
The P-V Loop
Ejection fraction = ____/Peak Vol
50ml/100 ml = 50%
• Curve allows you to get the SV, and the ejection fraction (how efficient the pumping heart is)
stroke volume
Modeling stroke volume with pressure-volume curve
- Opening and closing of valves
- Isovolumetric relaxation and contraction
- Tan area = ____
- Stroke volume =EDV-ESV
i.e. when to valves open and close
• Tan area = external work output; energy that your heart is using ○ Isovolumetric relaxation > \_\_\_\_ isn't changing; same with the isovolumetric contraction > no change in \_\_\_\_
external work output
volume
volume
Factors affecting HR and SV – the simple version
HR: autonomic innervation \_\_\_\_ fitness levels \_\_\_\_
SV: heart size \_\_\_\_ gender \_\_\_\_ duration of contraction \_\_\_\_ afterload(resistance)
hormones
age
fitness levels
contractility
preload (EDV)
Cardiac output affected by intrinsic and extrinsic factors
• Intrinsic factors
– Preload: amount ventricles are ____ by contained blood, EDV
– Afterload: ____ exerted by blood in the large arteries leaving the heart
• Extrinsic factors – Neural – Hormonal – Ionic – Temperature
• Preload ○ Amount by which ventricles are stretched by blood they contain ○ Larger end \_\_\_\_ volume > the more stretched • Afterload ○ What does the heart have to pump against • Important in normal \_\_\_\_ (making CO matches needs of body), and the factors that can influence CO
stretched
back pressure
diastolic
regulation
Effect of increasing muscle length on force & velocity
• Relationship bt force and velocity ○ Speed at which you can contract is increased by \_\_\_\_ to a certain point § Increasing the \_\_\_\_ of muscle > allows you to alter load-velocity relationship
load
length
Degree of sarcomere overlap underlies Frank-Starling law
Greater ____ increases amount of tension that can be developed, up to a point
• Sarcomere overlap (higher degree, A) > signal to contract > you're not going to get a lot of movement because you're almost completely overlapped • As you increase the \_\_\_\_ between sarcomeres > gain more when you trigger a contraction > overly stretched and cannot engage the contact • Length of sarcomere is \_\_\_\_ to the tension you will develop ○ Reasoning behind the Frank-starling law
stretch
distance
proportional
