Week 4 Flashcards
What artery begins systemic circulation and where does it exit from?
The aorta begins systemic circulation and exits from the left ventricle.
Why do the arterial walls have to be thick and elastic?
Elastic - to hold large quantities of blood and thick to withstand the high pressure from all the blood.
Why is it beneficial that arterioles are surrounded by rings of smooth muscle?
To contract and restrict blood flow to certain areas while prioritising others. Ex) want more blood to muscles during exercise and less to the GI tract.
What are the 2 main roles of the arterioles?
- Determine the relative blood flow to organs.
2. Major factor in determining mean arterial pressure.
What controls arterioles?
Hormones and neural control from the SNS and PNS.
Why is it good that capillaries are only one blood cell thick?
Decreases gas exchange distance and slows blood flow down to increase transit time. More time for gas and nutrient exchange.
How much of the total blood volume is in the veins?
61%
Why is it vital that we have valves and skeletal muscle pumps.
When blood gets to the capillaries, it is moving very slowly and skeletal muscle pumps squeeze the blood back to the heart and valves prevent backwards flow.
Why do you get varicouse veins?
Occurs when the valves do not work anymore that the muscles are squeezing but the blood does not move up but rather pools.
What is the Ejection Fraction? What is it rest?
EF is the proportion of blood pumped out of the left ventricle per beat. At resting its about 60%.
Why does a larger after-load cause a smaller stroke volume?
IN you have a lot of pressure in your vascular system already, your body will be fighting against the pressure produced by the LV when it pumps resulting in a smaller SV.
What does Frank Starling Mechanism represent?
Ventricles contract more forcefully during systole when greater filling occurs during diastole.
Why is our max possible heart rate top out at 200 beats per minute.
With increasing heart rate, there is less diastolic filling and therefore decreased stroke volume that cannot be maintained.
How do we decrease blood flow to non-active tissue?
Increased SNS activation leads to vasoconstriction.
How do we increase flow to active tissue?
Active hyperemia- local control during exercise.
Opening of dormant capillaries.
