microcirculation Flashcards
what is Blood flow rate
– Volume of blood passing through a vessel per unit time
flow circuit equation
Q(flow rate) = pressure gradient/resistane
what does vasodialation do
Vasodilation is a mechanism to enhance blood flow to areas of the body that are lacking oxygen and/or nutrients. The vasodilation causes a decrease in systemic vascular resistance (SVR) and an increase in blood flow, resulting in a reduction of blood pressure.
Resistance
Hindrance to blood flow due to friction between moving fluid and stationary vascular walls’
when would the viscoisity of gas matter
Altitude
Scuba diving- go down 50m, you would want to reduce o2 and nitrogen, so you would helium
Space flight- fluid ventilation, fill the lung with a fluid that can carry out gas exchange
how to increase pressure gradinet
increase blood pressure
how to increase blood flow
increase blood pressure
how to increase resistance
arteiolar vasoconstriction
how to decrease blood flow
arteiolar vasoconstriction
can blood flow without pressure difference
: Without this pressure difference blood would not reach tissue capillary beds
blood flow equation
F(ORGAN)=change in P (MAP)/R(ORGAN)
what is vascular tone
arteriolar smooth muscle are always partially constricted- this is called vascular tone
Radii of arterioles are adjusted independently to accomplish two functions
which are
Function 1: Match blood flow to the metabolic needs of specific tissues (depending on body’s momentary needs)
Function 2: Help regulate systemic arterial blood pressure
how is blood flow regulation of arterioles regulated
Regulated by local (intrinsic) controls and independent of nervous or endocrine stimulation
what regulates arterioles regulation of blood pressure
Regulated by extrinsic controls which travel via nerves or blood and are usually centrally coordinated
what is active hyperaemia
Increase in blood in response to local need like exercise hat
is associated with increased metabolic activity of an organ or tissue
what causes active hypereamia
Vasodilation of arterioles
more metabolites
more O2 usage
what is myogenic autoregulation
Myogenic mechanisms are intrinsic to the smooth muscle blood vessels, particularly in small arteries and arterioles. If the pressure within a vessel is suddenly increased, the vessel responds by constricting.
Vasoconstriction of arterioles
what can cause myogenic autoregulation
low blood temp
more strecth/distention due to high bp
skeletal muscle arteioles are more prone to
Active hyperaemia
and small intestine arterioles
Myogenic
vasoconstriction
Q: Generate an equation for flow across the whole circulation and rearrange to generate a BP equation.
blood pressure= cardiac output x total peripheral resistance
what are the 2 methods to regulate arterial blood pressure
nervous and hormonal
neural control
vasoconstriction by cardiovascular control centre in the medulla
hormonal
vesopressin
angiotensin II
adrelaline and noradrelaline
what does ang ii do
increases amount of blood volume
pressor/vasoconstriction
aldesterone
increase blood pressure
function of the cappiliries
The purpose of capillary exchange is the delivery of metabolic substrates to the cells of the organism [which is the ultimate function of the CVS]
Q: Why is capillary density important?
enhance diffusion- fick’s law
maximise surface area
minimise diffusion distance
what force forces fluid out of cappaliries
hydrostatic
what pulls it in
albumin
oncotic pressure generated by plasma protien
why should you measure blood pressure in the heart
One reason for not doing upper arm is so you don’t apply pressure to upper arm lymph nodes if the axillary lymph node has been taken out in breast cancer
So do It on forearm
what causes oedema
If rate of production > rate of drainage
then OEDEMA ensues
what is one cause of Elephantiasis
parasitic blockage of lymph nodes
Elephantiasis
what intrinsic factors affect arterioles
Affected by intrinsic factors (chemical & physical; e.g. metabolic activity & stretch) to match blood flow to needs
what extrinsic factors
Affected by extrinsic factors (neural & hormonal; e.g. SNS activity & adrenaline) to regulate arterial blood pressure
what are the capiliry strcutures and their permability
continuous vs. fenestrated vs. discontinuous
