Flashcards in Blood Flow (5) Deck (44):
What is blood flow?
Continuous movement of blood through the circulatory system
What is the average overall blood flow in an adult (CO)?
What are the main functions of circulatory system?
Deliver blood to organs
Delivery of O2 and nutrients
Removal of CO2
Maintenance of ion concentrations
Delivery of hormones around the body
What makes up the circulatory system?
A series of collecting tubes
Extensive system thin vessels, exchange of nutrients, fluids across walls
What are the 3 components of the vasculature?
1. Arterial system
2. Venous system
3. Microcircualtion (nutrients/exchange waste)
What makes up hemodynamics?
Dimensions of components of systemic circulation
What is the role of arterial blood pressure?
Development and maintenance adequate to perfuse tissues
How do you determine blood pressure?
MABP (Mean arterial blood pressure)= CO (cardiac output)x TPR (total peripheral resistance)
CO=HR (heart rate) x SV (stroke volume)
What other factors will affect blood pressure?
Change flow and change in resistance
What is flow?
A measure of volume per unit of time
What is a measure of flow?
Q (flow)= V (velocity)A (cross-sectional area)
What is pressure differential?
Difference in blood pressure at the beginning and end of a tube at any one time
What happens in terms of areas as vessels get smaller?
Cross-sectional areas get larger
Where is resistance greatest in the body?
Where is velocity at it's lowest and why?
In the capillaries to promote exchange
What is velocity?
Measurement of the movement of an objected divided by the time it took to travel to a location (speed)
What is sheer stress?
As blood flows through a blood vessel it exerts a force on the vessel wall parallel to the wall
What is sheer stress dependent on?
Area and location of vessels
What is sheer stress directly proportional to?
Flow rate and viscosity
What is Poiseuille's Law?
Q= (pie x Pr4)/ 8nl
Q- flow rate
n- fluid viscosity
l- length of tubing
What is resistance to blood flow directly proportional to?
Length of the vessels and viscosity of blood
What is the equation for resistance?
L- length of vessel
N- viscosity of blood
R-radius of vessel
What is total peripheral resistance (TPR)?
Sum of all vascular resistance within systemic circulation
What alters resistance?
Contraction of the smooth muscle in the vessel wall-
Local tissue factors
Local wall stress
What is functional hyperaemia?
Increase in organ blood flow (hyperaemia) associated with increased metabolic activity of an organ or tissue
What are the by-products vasodilators of metabolism?
CO2, H+, K+, lactate, adenosine
What is reactive hyperaemia?
Occurs after cessation of blood flow e.g. after myocardial infarction or stroke
Why does reactive hyperaemia occur?
Due to tissue hypoxia and a build up of vasodilator metabolites to dilate arterioles and decrease vascular resistance
What is sympathetic innervation?
Vasoconstriction (alpha-adrenergic stimulation) of vascular smooth muscle
What happens when skeletal muscle (sympathetic) vasodilates?
beta-adrenergic and cholinergic sympathetic stimulation releasing acetylcholine
What increases Mean Arterial Pressure (MAP) in sympathetic innervation?
TPR and CO
What is involved in parasympathetic innervation?
Vasodilation of vascular smooth muscle (few organs)
Slows heart rate (deceleration of SA node, decreased atrial contractility- muscarinic receptors
What can signal innervation?
Baroreceptors or chemoreceptors
What is innervation?
Where are baroreceptors found?
Carotid sinus and aortic arch
What do baroreceptors do?
Respond to vascular stretch
How do you lower blood pressure?
Decrease in sympathetic innervation and increase in parasympathetic innervation
What happens when parasympathetic stimulation increases?
Decrease in heart rate and stroke volume which decreases cardiac output
What happens when sympathetic stimulation increases?
Increase in heart rate and stroke volume which increases cardiac output
What hormones are involved in vasoconstriction?
Adrenalin, angiotensin II, vasopressin
What hormones are involved in vasodilation?
Atrial natriuetic factor, kallikrein-kinin system
What are paracrine agents?
chemical messengers involved in cell-cell communication
What does Nitric Oxide do as a paracrine agent?
Released from endothelium, vasodilator which is also anti-proliferative and anti-thrombotic