fundamentals of circulation: Physiology and pathology of O2 Delivery and Perfusion Flashcards
what is hemodynamics
how blood flows through the cardiovascular system
what is heterogenous
from different origins
what are factors used to describe blood flow
- continual changing of the dimensions of blood vessels
- different physical and chemical stimuli to the heart muscle
- blood is not a uniform fluid but a heterogenous mixture of cells and proteins
what is velolcity
Velocity- the linear displacement of fluid per unit of time
what is cross-sectional area
Cross-sectional area (A)- the area the fluid moves through in any given section of the blood vessel by pi^2
what is flow
flow (q)- the volume of fluid that passes through vessel per unit of time
how do you calculate blood flow
blood flow Q=VA
what is laminar flow
- streamlined flow
- flow that occurs in concentric layer as the layers slide past each other at different velocities
what happens to fluid in laminar flow
fluid at the center will flow at the highest velocity but fluids in periphery will flow much slower due to higher frictional resistance
what is a turbulent flow
- involves rapid mixing which can disrupt normal laminar flow
- much higher pressure is necessary to maintain a constant flow
- less efficient
- if theres prolonged turbulence it may lead to hypertension
How does blood flow
- blood flows down a pressure gradient
- flow is pulsatile in the aorta and large arteries and becomes laminar in the capillaries and veins
what is pulmonary circulation
where is the mitral valve
left atrium and left ventricle
where is the aortic valve
between left ventricle and aorta
where is the tricuspid valve
between right atrium and right ventricle
where is the pulmonary valve
between right ventricle and pulmonary artery
what side of the heart has a lower pressure
right
what happens if there is an issue with the aortic valve
Left ventricle and aorta systolic pressures will be different
what happens if there is an issue with the pulmonary valve
the right ventricles and pulmonary artery systolic pressures will be different
what happens if there is an issue with the mitral valve
difference in left atrium and left ventricle diastolic pressure
what happens if there is an issue with the tricuspid valve
difference in the right atrium and right ventricle diastolic pressure
which has a higher arterial mean pressure: arteries in the systemic or pulmonary system
systemic
what are the arterial walls like in systemic circulation
thick
elastic
what are the arterial walls like in pulmonary circulation
thin
distensible
what are lumens of arterioles in systemic circulation like
small
what are lumens of arterioles in pulmonary circulation like
large
what is the resistance of the arterioles in systemic circulation like
high
what is the resistance of the arterioles in pulmonary circulation like
low
what are arterioles response to hypoxia in systemic circulation
vasodilation
what are arterioles response to hypoxia in pulmonary circulation
vasoconstriction
what is the wall thickness like for capillaries in systemic circulation
thin
what is the wall thickness like for capillaries in pulmonary circulation
thin
what is the flow like for capillaries in systemic circulation
continuous
what is the flow like for capillaries in pulmonary circulation
pulsatile
which has a higher venous mean pressure: veins in the systemic or pulmonary system
pulmonary
which has a higher venous capacity : veins in the systemic or pulmonary system
systemic
what is autoregulation
Maintains relatively constant flow over a wide range of blood pressures
what are the blood flow control mechanisms
- metabolic demand
- myogenic (originating from muscle) response
- local vasoactive mediators
- autonomic nervous system
- hormones
how does metabolic demand control blood flow
low O2, high CO2 and low pH cause vasodilation
how does myogenic response control blood flow
arteriolar smooth muscle contraction in response to stretch- to maintain a certain pressure
how does local vasoactive mediators control blood flow
- vasodilators: e.g. adenosine, NO
- vasoconstrictors: eg endothelin
how does the autonomic nervous system control blood flow
- external control
- basal sympathetic tone and responses
how do hormones control blood flow
external control
what is a portal system
2 sets of capillaries in series
what are the steps of renal circulation
liver secrets angiotensinogen
angiotensinogen binds with renin –> angiotensin I
angiotensin I binds with Lung/renal endothelial ACE (more lung compared to renal)–> angiotensin II
what happens overall when renal arterioles are constricted
increases overall resistance & reduces renal flow
what happens when renal afferent arterioles are constricted
decreases GFR- glomelular filtrate rate
what happens when renal efferent arterioles are constricted
increased GFR
what is blood flow controlled by in renal
- Autoregulation
- Renin-angiotensin-aldosterone system
- Tubulo-glomerular feedback
how is cerebral blood flow autoregulated
maintains constant flow for mean arterial pressures
Low pH and high CO2 levels increase flow to wash out H+ and excess CO2
Oxygen is a weaker controller
Flow only increases when PaO2 is very low
how is skin blood flow autoregulated
Arteriolar constriction
Arteriovenous anastomoses that bypass capillary beds
what are the control mechanisms for autoregulation of the skins blood flow
Sympathetic nervous system
Skin ambient temperature receptors
NO local metabolic control
how is skeletal muscle blood flow autoregulated
vasodilation due to tissue hypoxia (low PaO2)
High CO2, low pH (lactic acid), high K+
Local mediators, eg adenosine, NO
Sympathetic nervous system (b2 vasodilation)
what happens to blood flow during fight or flight response
To skeletal muscles and the heart (b2 – mediated vasodilation)
Away from skin, kidneys, GI system (a1 – mediated vasocontriction)
But…
Blood flow to the brain is preserved (autoregulation)
what is ischemia
Blood flow to a part of the body is inadequate to meet the metabolic demands of the tissue
Oxygen
Nutrients
Removal of waste products (eg CO2)
