Cardio Physiology 7-9 Flashcards
What type of pressure is in the arteries?
Pulsatile pressure
This is a critically important determinant of blood flow.
Mean arterial blood pressure
High pressure in systemic arteries are due to? (2 things)
Ventricular contraction and ejection of blood
How does ejection of blood maintain blood flow?
The balance between blood flow in and out determines blood flow.
Blood flow in - arteries are occupied = arterial pressure increases = arterial blood volume increases
Blood flow out - arteries are being emptied = arterial pressure is decreasing = arterial blood volume is decreasing as well
What is the nature of the blood pressure of veins and why?
Veins have a very low pressure, and it has a low pressure so that it can get pumped back to the right atrium.
What creates a driving force for blood flow?
The difference in pressure between the artery and veins (artery = high pressure, veins = low pressure)
This describes how blood flows in a single vessel.
Haemodynamics
What is the equation for blood flow? Explain.
Blood flow = Change in pressure over Resistance
Blood flow is dependent on changes in pressure, and inversely proportional to changes in resistance (eg: when blood flow increases - resistance decreases because that means blood vessel diameter is increasing)
What are the 2 determinants of blood pressure?
Cardiac output and arterial resistance/TPR
just think of equation
What are the 2 determinants of cardiac output?
Stroke volume and heartrate
This is the volume of blood released in each heartbeat. (which also refers to the strength of the contraction, because the stronger the contraction, the higher the volume)
Stroke volume
________ is variable due to changes in heart rate and/or stroke volume.
Cardiac output
Where is the mean arterial blood pressure coordinated in the brain?
The medulla oblongata/brainstem
Where are the 2 locations where we would usually find baroreceptors in the heart?
Carotid sinus and aortic arch
This activates the parasympathetic inputs in the SA and AV node to decrease blood pressure when it’s increased,
Vagus nerve (parasympathetic = rest and digest)
These increase the heart rate and force of contraction to increase blood pressure.
Sympathetic nerves
What afferent signal do baroreceptors send to the brain?
Changes in blood pressure (because baroreceptors detect changes in blood pressure)
How does signaling through the vagus nerve affect the heart?
The heart will relax. Slows heart rate.
Cardiac output and stroke volume would decrease therefore blood pressure would decrease.
The cardiomyocytes would relax because more Ca2+ being pumped back into SR
How does signaling through the sympathetic trunk ganglion affect the heart?
The heart will be active. Speeds up heart rate.
Cardiac output and stroke volume will increase so blood pressure will also increase.
There will be more contractions because of the pressure so more Ca2+ would be released from SR
Cardiac blood is distributed to:
all organs
The branching of the arterial network within the systemic circulation establishes what kind of flow?
Regional flow - so flow is divided among regional circulations
What is the distribution of cardiac output to organs during exercise?
Increased blood flow to muscle, skin and heart
Decreased blood flow to GI tract and kidneys
Constant blood flow to brain
This circulation has an increased cardiac output, constant mean arterial pressure, and decreased total peripheral resistance during exercise.
Systemic circulation
These are the resistance vessels of the vascular system. They are lined with smooth muscle and determine blood pressure.
Arterioles
Blood flow to an organ or region is controlled by adjusting the ___________ and _____.
arteriolar tone and radius (resistance)
The bigger the radius, the larger the blood flow (because less resistance)
The smaller the radius, the smaller the blood flow (because more resistance)
What is the rule of 16?
R (resistance) = 1/r^4
Small changes to the lumen of the arteriole will decrease or increase the blood flow/resistance by a factor of 16
Fine vascular control depends on:
High arterial pressure
- high pressure means better control of flow/vascular flow
Most blood is found where?
Systemic veins
What kind of system allows for blood to be redistributed depending on the needs of the body?
Parallel redistribution system
- basically what amount goes in is the same amount that will go out. So keeps volume of blood in those organs constant.
This is the extent to which a vessel allows deformation in response to an applied force.
Compliance
What is the equation for compliance?
Compliance = change in volume / change in pressure
This is a neurologically induced contraction of the smooth muscle in veins to push blood onto arteries that have been punctured to ensure blood pressure keeps going.
Venoconstriction
In the upright position, venous volume below the heart _________ and venous volume above the heart _________.
increases; decreases
These counteract venous pooling and allow a more even distribution of weight in the veins.
Venous valves
This acts to stiffen veins, and makes them less compliant and prone to pooling.
Muscle tone
- so a low muscle tone = less blood flow to certain areas of the body and excessive amounts in some = usually leads to fainting
What increases venous return to the heart when you’re standing upright?
Skeletal muscle contractions. Basically just engaging your muscles more helps the veins to pump the blood back into the heart
This states that the more stretched muscle fibres are before a contraction, the stronger the contraction will be.
Starling’s Law of the Heart
Increased venous return means increased:
stroke volume (heart beats stronger because the muscles are engaged before the contraction, so the contraction of the heart will be stronger)
These are thin-walled vessels that have high compliance compared to arteries.
Veins
What are the mechanisms that counter venous pooling in the legs? (2)
Venous valves and changing the muscle tone of the legs
This tells us that the more the walls of the heart contract before contraction, the stronger the contraction and greater stroke volume we’ll have.
Starling’s Law of the Heart
What generates pressure for the systemic circulation?
Left ventricle
