CV overeview Flashcards
1
Q
small arteries and arterioles
A
- relatively large proportion of vascular smooth muscle
- highly innervated
- major site of resistance
- regulate arterial blood pressure
- regulate flow to capillaries/tissue
2
Q
capillaries
A
- endothelial tubes
- no smooth muscle
- regulate permeability
- exchange fluid, nutrients, electrolytes, hormones, CO2, waste
3
Q
venules
A
- no smooth muscle
- no innervation
- function to collect blood from capillaries
- participate in blood-tissue exchange
4
Q
veins
A
- limited smooth muscle
- sometimes innervated
- low resistance to flow
- high capacitance
- conduct blood, reservoir, regulate blood volume distribution
- constriction increases return and CO while decreasing the volume in circulation
5
Q
pulse pressure
A
- systolic-diastolic
- decreases in smaller vessels due in part due to hydraulic filtering
- can increase with decreased compliance and increasing stroke volume
6
Q
arterial compliance
A
-change in volume over change in pressure
7
Q
Blood pressure equation
A
- change in pressure (input minus output)
- delta P=R (resistance to flow) xQ (flow)
- MABP=TPR x CO
8
Q
vascular resistance
A
- changes can be due to smooth muscle contraction or changes in hematocrit
- changes are due to vessel diameter changes or viscosity changes
9
Q
influence of vessel internal radius on resistance
A
- inversely proportional to r^4
- small changes in radius, have large impact on resistance
- regulated mostly by VSM
- thickening of the walls because of remodeling, atherosclerosis and inflammation can increase resistance
10
Q
influence of blood viscosity on vascular resistance
A
-polycythemia (increased hematocrit) would have an increase in vascular resistance
11
Q
laminar versus turbulent flow
A
- normal resting conditions provide laminar flow
- turbulent flow is most often seen in aorta and arterial branch points
- in laminar, highest velocity is in the middle, lowest is on the sides of the tube
- eddy currents can occur at branch points
12
Q
Reynold’s number and turbulence
A
- flow become turbulent at higher reynolds numbers
- takes into account fluid density, vessel diameter, mean flow velocity, fluid velocity
- turbulent flow predicted when vessel is large, blood velocity is high, and blood viscosity is low
- can be seen in exercise, cardiac valve stenosis, occlusion
- causes heart murmurs and vascular bruits
13
Q
regulation of vascular resistance
A
- sympathetic nervous system
- hormones
- VSM tone
14
Q
neural control of vascular resistance
A
- SNS
- NE released from varicosities
- binds to adrenergic receptors to elicit VSM contraction
- withdrawal of sympathetic tone leads to relaxation
15
Q
hormonal control of vascular resistance
A
- catecholamines, angiotensins, arginine vasopression
- can be a stress response, can be present in disease states
- can bind to endothelial cell membrane or directly to VSM membranes
- can cause release of vasoactive factors from the endothelium
16
Q
enothelial control of vascular resistance
A
- vasoactive factors that provide regulation mechanisms
- both dilatory and constrictive factors
- gap junctions between VSM and endothelial cells for electric and chemical messages to pass
17
Q
autoregulation on vascular resistance
A
- change to keep constant blood flow when there are changes in arterial pressure
- dilation when pressure decreases, constriction when pressure increases
- explained by myogenic response
18
Q
myogenic mechanism
A
- arterial constriction in response to distending force exerted by increasing transmural pressure
- fall in transmural pressure elicits dilation
- helps maintain basal vascular tone
19
Q
metabolic regulation of vascular resistance
A
- increases blood flow to delivery oxygen to hypoxic tissue
- can result from increased metabolic activity or decreased oxygen availability
20
Q
flow (CO)
A
- product of stroke volume and heart rate
- both are regulated by sympathetic and parasympathetic
- SV can be altered by changes in myocardial performance through an intrinsic mechanism (Starling)
