CV VI Flashcards
How can we tell difference between capillaries and venules
Capillaries begin to converge
What is the volume reservoir
Veins
Very distensable, can add significant volume without adding pressure
Angiogenesis
Formation of new blood vessels
When is microcirculation not constant
Wound healing, endurance training, inflammation, tumour growth, endometrium during menstrual cycle
What drives angiogenesis
Angiogenic growth factors (pro-mitotic) activate receptors on endothelial cells
How does angiogenesis work after endothelial cells are activated
- Acted cells produces proteases that degrade basal lamina so it moves from parent vessel
- Cells proliferate into surrounding matrix and grow sprouts toward stimulus
- Sprouts form loops to become full-fledged vessel lumen
How is angiogenesis a part of progression of cancer
Progresses from small, localized neoplasms to larger, growing and potentially metastatic tumours
How is angiogenesis a possible treatment option for CV diseases
Instead of artificial vessel, speed up growth of natural ones to bypass damage
What is blood pressure
Ventricles creating enough force to propel blood through the CV system
What does ventricular contraction cause
Semilunar valves open
Blood ejected
Aorta and arteries expand and store pressure in elastic walls
What does ventricular relaxation do
Semilunar valve shuts
Preventing flow back
Elastic recoil of arteries send blood forward into rest of circulatory system
Elastic recoil allows blood to continually move
What sustains driving pressure during ventricular diastole
Aorta and large arteries
Where is pressure the highest
Aorta and decreases throughout the circuit
When is aortic pressure the highest and lowest
Highest during ventricular contraction (systole)
Systolic pressure (120mmHg)
Lowest during ventricular relaxation (diastole)
Diastolic pressure (80mmHg)
What is pulse pressure
The difference between systolic and diastolic pressure
In aorta: 120mmHg - 80mmHg
= 40mmHg
Normally only exists on arterial side
Where is pressure measured
In a major artery (brachial) as reflection of ventricle (driving pressure)
Why do we look at a single value of arterial blood pressure
Mean arterial blood pressure as driving pressure
- because pressure is pulsatile
Why is mean arterial pressure not an average
Because equal amounts of time are not spent in systole and diastole
Cardiac cycle time
~ 800ms
250ms ventricular systole
550ms ventricular diastole
What is the MAP equation
Diastolic pressure + 1/3 (pulse pressure)
= 80mmHg + 1/3 (120 - 80mmHg)
= 93 mmHg
Hypotension
BP falls too low (<90/60)
Can cause driving force for blood flow to be inadequate to overcome opposition of gravity
Hypertension
BP is chronically elevated (>140/90)
High pressure on vessel walls can cause them to weaken or even rupture and leak
What can rupture or leak of vessel in brain do
Cerebral hemorrhage
Cause loss of neurological function, stroke
How is blood pressure estimated
Sphygmomanometry
Blood pressure cuff
Elevated BP
120-129/<80
High BP (hypertension) stage 1
130-139/80-89
High BP (hypertension) stage 2
140 or higher/ 90 or higher
Hypertensive crisis
Higher than 180/ higher than 120
Consult doctor
What is driving force for blood flow
Mean arterial blood pressure
Balance between blood flow into arteries and blood flow out
What is mean arterial pressure proportional to
Cardiac output x peripheral resistance
What happens if cardiac output increases and peripheral resistance does not change
Blood pumped into arteries faster than removed
Increase volume in arteries (blood will pool)= increase in arterial BP
If Cardiac output stays the same and peripheral resistance increases what happens
Blood will pool in large arteries
What are cases of hypertensions due to
Increased peripheral changes without changes in cardiac output
What are 2 most important factors influencing arterial BP
Cardiac output and peripheral resistance
What are two other factors influencing arterial BP
Blood volume and relative distribution of blood between arterial and venous blood vessels
How much of total blood volume do arteries contain
~11%
How much of circulating blood volume do veins contain
~60%
What do veins do if blood needs to shift to arterial side
Constrict
What are small changes in blood volume caused by
Ingestion or food or liquids
Primarily resolved by kidneys
What do decreases in blood volume require
Integrated response from kidney, CV system (increase sympathetic output), ingestion of fluid
What does changes in blood volume affect
Blood pressure
Where is resistance highest
Arterioles
Why do arterioles have highest resistance
Not only depends on radius of each vessel but also how vessels are arranged
Arterioles are in series and encounter resistance at each series
How much does resistance in arterioles contribute to total resistance in CV system
> 60%
What is arteriolar resistance influenced by
Local control and systemic control mechanisms that alter vascular smooth muscle changing radius of vessels
What is local control of arteriolar resistance
- matches tissue blood flow to the metabolic needs of tissue
- in heart and skeletal, local takes precedence over reflex control
What are sympathetic reflexes
Mediated by CNS maintain mean arterial pressure for homeostatic needs
How do hormones influence arteriolar resistance
Regulate salt and water excretion, influence BP by acting directly on arterioles
