Cardivascular System - Lec 4 Flashcards
Explain what’s the ejection fraction
The ventricle doesn’t empty completely each time it contracts
The end diastolic volume is relevant to the volume of blood in the ventricle after it has been filled before contraction, so the proportion of this end diastolic volume that is pumped out is known as the ejection fraction
EF = SV/end diastolic volume
Around 50%-60% is normal
This shows how well the heart is functioning, a bad heart will suggest a lowered ejection fracture
What’re blood vessels in the conduction system
It’s more so relevant to the just-beginning and just-end of systemic circulation in which blood vessels allow for the distribution and return of blood
There are many types of vessels with specific function determined by its structure
Explain the basic structure of a blood vessel
Tunica intima = endo(in)thelial layer and underlying connective tissue. Make sure the blood doesn’t clot
Tunica media = concentric layers of smooth muscle (non-existent in veins and capillaries). Relaxation of contraction basically changes the diameter of the vessel
Tunica externa = connective tissue sheath
Explain the function of the arteries. First blood vessels
Receive blood under High pressure directly from heart. HIGHEST PRESSURE FOUND HERE AS ITS THE BEGINNING
Blood flow from heart is pulsatile,but blood flow to tissues needs to continuous
Arterial pressure dependent on vessel diameter (THEY HAVE ELASTIC WALLS - SMOOTH MUSCLE TUNICA MEDIA)
- expansion occurs due to increase blood flow from heart, therefore, pressure Rise limited
- this gives us the systolic pressure of artery
- they contract back once the wave of blood has passed, and return back to normal good pressure (diastolic pressure of artery)
IF ARTERIS CLUKDNT EXPAND, THIS WILL CAUSE THE PRESSURE RO BE HIGH ALL THE TIME AND ALLOW DOR BACKFLOW
Explain the function of arterioles. Second vessel
Function = control distribution of blood flow around body. Have smooth muscle to allow for dilation and constriction
Diameter decreases = resistance of blood flow
Diameter increases = resistance decreases
This diameter is controlled by:
- SNS = vasoconstriction of vessels (sectioning of how much blood should be delivered to specific regions of body at point time, ie. when confronted with flight response, blood flow increases to lower extremetis and decreases for the upper region)
- local factors (ie. increase temp, decreased pH…shit that happens in muscle where you want more blood)= vasodilation of vessels
The areterioles are site of major resistance to blood flow, and SO THEY ARE IMPORTANT in determining blood pressure
Explain the function of capillaries. Third vessels
Function = allow exchange between blood and tissues. DELIVERING OXYGEN FROM BLOOD AND INTO THE CELLS OF THE TISSUE, AND TAKE BACK THE CO2
Most abundant vessels in body
In peripheral tissues, oxygen leaves the blood and CO2 enters into the capillaries
In order for this to occur, the capillaries must have:
- very thin walls (allow easy diffusion of gas)
- very low blood pressure (allows for walls to be thin)
- very slow blood flow (plenty of time to allow gas exchange to occur)
Explain the function of the venules and veins. 4th vessels
Function = return blood to heart
SNS activated causing venoconstriction
Blood pressure is low in these vessels and SO the walls tend to be thin, and this low Blood pressure is insuffiecnt to maintain blood flow
- if blood pressure is too high in vessels, pressure in capillaries would also have to go up to allow blood to actually move from capillaries and to the veins (and so blood flow might stop)
- if oressure is too low = flow can stop and can lead to clotting (deep vein thrombosis).
During respiration, the pressure changes in the thorax which directly transmit to the veins (the stage in the respiratory cycle effects their appearance on radiographs), so this change in thoracic pressure, compress the veins due to the contraction of muscles involved in respiration
THEREFORE, helping maintain blood flow in veins
Veins have valves (work like semilunar)to prevent back flow due to gravity
- pressure isn’t enough to counteract effect of gravity will clause valves to stay open
Explain the impact of respiratory cycle on the blood pressure in the venules and veins diameter and the effect on image
Inspiration = pressure is higher in thorax = veins appear narrower
Expiration = low thoracic oressure = suck on the veins and make them bigger
MAKE OEOPLE BREATHE IN AND OUT TO INCREASE PRESSURE IN VEINS AND ALLOW BLOOD FLOW
WEARING LIKE THOSE BANDS CAN MAKE VEINS NARROWER AND ALLOW FOR INCREASE IN ORESSURE AND THEREFORE ALLOW INCREASE BLOOD FLOW
Why is deep vein thrombosis of high concern
The thrombus which is a clot can break up and fragments (emboli) can enter the circulation
Leg vein - IVC - right atrium and ventricle - pulmonary vessels
This little emboli can get into a vessel that’s too small for it and this can block off the blood vessel. So this can get in the lungs (pulmonary circuit) and lead to pulmonary embolism
This can be prevented by compression stockings, thus, helping maintain blood flow within veins with no clots
Explain whata blood pressure and how it’s calculated
Blood pressure is the force which allows blood flow through ARTERIES
THEREFORE, BLOOD PRESSURE IS DETERMINED BY RESISTANCE TO BLOOD FLOW IN VESSELS. Blood is very sticky (viscosity)
BloP= Q x TPR
Q = cardiac output - amount of blood flowing in TPR = total peripheral resistance (amount of blood flowing out), resistance to blood flow in arterioles (ie. diameter). Increase TPR means increase in peripheral vasoconstriction
Increase SNS activity = decreases blood pressure (homeostasis) by vasoconstriction
What factors determine and have a direct impact on the blood pressure
The amount of blood in vessels
The cardiac output (CONT BY SNS)
The blood volume
The downstream resistance to blood flow (CONT by SNS)
- more SNS = MORE resistance of arterioles. TPR
Discuss the activation of the SNS in relevance to blood pressure
Increase in SNS activity causes
- increase in heart rate and SV, thus, increase cardiac output (hence blood pressure increases)
- constricts the downstream resistance vessels (the arterioles) ie. decreases blood flow in tissues
Adrenaline can be used to treat low blood pressure as it is increased for SNS activity presence
Explain the homeostatic regulation of blood pressure
This is SHORT TERM CONTROL OF BLOOD PRESSURE CHANGE
Blood pressure can fall ( shock, or standing up too quickly and gravity takes place where less blood going to head) really quickly but this can be quickly retracted
Therefore, SNS activity increases which causes increase cardiac output and vasoconstriction which restores the blood pressure
SNS is activated during shock which causes
- increase heart rate
- cold, pale skin
What are the risks of the activity of SNS
Drugs used to treat high blood pressure
- beta blockers. Blocking receptors of adrenaline therefore SNS can’t exert its effects As efferent pathway is blocked
Explain the long term control of blood pressure
We can’t have the SNS become activated for extended preiods of time as this causes significant strain on the heart
So instead, we control it by changing the blood volume (amount of blood in vessels). INCREASE CROWDING OF BLOOD = INCREASE PRESSURE
There’s a homeostatic system using a expample, the kidney
1. Decreased Renal perfusion = minimal blood flow to the kidneys, blood pressure drops, so kidney function drops and kidneys Ray to retract this by
- Renin release = it acts with another protein and creates angiotensin
- Angiotensin release= causing vasoconstriction (thus, increase blood pressure), and sodium retention in kidneys (which increases blood volume)
- this tells us why people with high blood pressure, you should cut out sodium in your diet
