Circulatory System

arteries

main vessel, pressure reservoir

arterioles

branches into organs

capillaries

branches into capillary beds (half artery/half vein)

what are capillaries used for

nutrient and oxygen/carbon dioxide exchange

veins

blood reservoirs

venules

branch from organs

what is the external blood vessel made from

connective tissue

what is the middle blood vessel made from

smooth muscle

what is the internal blood vessel made from

endothelium

are arteries thick or thin smooth muscle layers

thick

what do arteries contain

elastin fibers

what do veins contain

venous pumps

do veins have a thick or thin smooth muscle layer

thin

what layers do capillaries have

only inner layer

do capillaries vasodilate/vasoconstrict?

no - they don’t have a middle layer of muscle

blood pressure definition

force exerted on blood by walls of blood vessels

compliance

ability of vessel walls to stretch

are arteries high/low compliance and high/low resistance

low-compliance, high resistance

are arterioles high/low compliance and high/low resistance

low compliance and high resistance

do veins/venules and capillaries have high/low compliance and high/low resistance

high compliance and low resistance

mean arterial pressure

average measurement of blood pressure

flow rate

volume of blood pumped at a given time

what defines adequate flow rate

pressure gradient and vascular resistance

pressure gradient

the pressure differences from the beginning to the end of a blood vessel

what is the main driving force for pressure

heart

ranking from high to low pressure

heart, aorta, arteries, arterioles, capillaries, veins

resistance

opposition to flow rate in a vessel; friction of blood against vessel walls

how does the circulatory system counter resistance

increasing pressure

what are the influences to resistance

viscosity, vessel length, vessel diameter

viscosity

molecules within a fluid causing friction to one another

is viscosity a big issue for blood?

no not normally

vessel length

surface area of a vessel

does more or less length increase resistance

more length (more surface area, more chance of resistance)

vessel diameter

circumference of an opening

does a smaller or larger diameter give greater resistance

smaller

what are the main pressure reservoirs

arteries/aorta

during which phase does the heart not provide pressure

diastole

what happens to the arteries when the when the heart relaxes

they gradually deflate

what does the deflation of arteries when the heart relaxes cause

a continual pressure gradient independent of the heart

vasoconstriction

narrow vessel diameter, increasing resistance and decreasing flow

vasodilation

widening vessel diameter, decreasing resistance and increasing flow

total peripheral resistance (TPR)

combined resistance of all systemic circuit peripheral vessels

afterload

the opposing force on the ventricles after contraction

does high afterload reduce or improve stroke volume

reduces stroke volume

mean arterial pressure (MAP)

average pressure driving blood forward during a cardiac cycle

MAP equation

MAP = Cardiac Output x TPR

does vasoconstriction lead to higher or lower TPR

higher TPR

TPR

arteriolar diameter

what does increased activity of the sympathetic nervous system cause

vasoconstriction

what does decreased activity of the sympathetic nervous system cause

vasodilation

what happens if MAP raises above normal

sympathetic activity decreases, promotes vasodilation, lowers blood pressure

changing TPR or MAP triggers what

baroreceptors

constant information for blood pressure is provided by

carotid sinus and aortic arch baroreceptors

carotid sinus

blood vessels for the brain

aortic arch baroreceptors

major arterial trunks/vessels

where is the cardiovascular control center

brainstem

what does the cardiovascular control center do

alters ratio of sympathetic and parasympathetic activity

venous capacity

volume of blood stored by the veins

what influences venous capacity

blood volume and factors that move blood

what does decreased venous capacity lead to

increased venous return

factors that move blood

atrial pressure, sympathetic activity, skeletal muscle and venous valves, respiratory activity

is there pressure inside the atrium when the atrium contracts

no

sympathetic neurons will trigger vasoconstriction, which drives blood where

right atrium (vena cava)

where are veins located

between muscles

what do venous valves do after contraction

they stop reverse flow

breathing involves movement of what

diaphragm