Physiology of Circulation Flashcards
Circulation is primarily influenced by what?
tissue needs
3 characteristics of arteries?
1) transport blood under high pressure
2) strong vascular walls
3) rapid blood flow
4 characteristics of arterioles?
1) final small branches of arterial system
2) act as control conduits - blood released into capillaries
3) strong muscular walls that vasoconstrict/dilate
4) innervated by SNS only
4 characteristics of capillaries?
1) exchange site for nutrients, wastes, electrolytes, fluid
2) very thin walls
3) contain small capillary pores
4) permeable to small molecular substances, H2O
3 characteristics of venules?
1) gathers low oxygenated blood
2) collects blood from capillaries
3) gradually merge into larger veins
Major function of veins?
- serve as a blood reservoir (64% of total blood volume)
- transport blood from tissues to heart
Distribution of blood volume?
- veins = 64%
- arteries = 15%
- capillaries = 5%
- pulmonary = 9%
- heart = 7%
What is the volume of blood flowing through a vessel, an organ, or the entire, circulation in a given period (ml/min)?
blood flow
What is the force per unit area exerted on a vessel wall by the contained blood (mmHg)?
blood pressure
What is the opposition to flow; amount of friction blood meets when passes through the vessels?
resistance
Blood flow is affected by what 2 factors?
- pressure gradient
- vascular resistance
What is the calculation of flow through a vessel?
Ohm’s law:
blood flow = change in pressure between 2 ends of vessel/ resistance
What is the normal adult overall blood flow?
5,000 ml/min = cardiac output
What are the two descriptions of blood flow?
- laminar
- turbulent
What is known as the measure of blood flow through a vessel for a given pressure difference? Also known as the reciprocal of resistance?
conductance
What plays the greatest role in determining rate of blood flow?
diameter
What controls most of the blood flow through the vessels?
arterioles
An increase in viscosity does what to blood flow?
decreases blood flow
- inverse relationship
What is known as the percent of blood that consists of cells (RBC and WBC)?
% of blood that consists of cells
What tightly controls blood flow?
needs of tissue
What is controlled independently of local blood flow or cardiac output?
arterial pressure
What is known as the pressure that propels blood to tissues?
mean arterial pressure (MAP)
equation for MAP?
MAP = DBP + (pulse pressure/3)
What is pulse pressure?
difference between systolic and diastolic pressure
MAP and pulse pressure decrease with and increase in what?
increasing distance from the heart
2 effects of pressure on blood flow?
- increases force on blood flowing through vessels
- distends vessel (expands or stretches the vessel which increases blood flow)
Veins have a _______ distensibility than arteries?
greater
What is known as the total quantity of blood that can be stored in a given portion of the circulation for each mmHG pressure rise?
compliance (capacitance)
equation for compliance?
distensibility x volume
What is another name for right atrial pressure?
central venous pressure
What are the 5 blood reservoirs of the body?
- veins
- spleen
- liver
- heart
- lungs
Do different tissues have different metabolic needs over time?
YES (blood flow/100g of tissue)
What are the 2 phases of local blood control?
- acute
- long term
What is the effect on blood flow with decreased oxygen?
increased blood flow
What is stated by the vasodilator theory?
- vasodilator substance released from local tissue when there is low oxygen in that particular area
- causes more blood flow to that local tissue area
What is stated by the Oxygen Lack Theory?
- the precapillary and metarteriole sphincters constrict the vessels
- but once you start moving, oxygen reduces and now the sphincters open and allow for dilation to increase blood flow
What are the effects of nitric oxide?
vasodilator that allows for more blood flow which allows for more nutrients to get to the tissues
2 other methods affecting local blood flow?
- reactive hyperemia
- active hyperemia
Do tissues have the ability to autoregulate?
YES – after increase in BF to a tissue due to increase in arterial pressure, BF returns to near normal levels
4 vasoconstrictors?
2 vasodilators?
Vasoconstrictors: - norepinephrine/epinephrine - angiotensin II - vasopressin - endothelin Vasodilators: - bradykinin - histamine