Midterm 1 - Blood Vessels and Blood Pressure Flashcards
important factors of blood pressure in blood vessels
diameter
elasticity
contractility
what blood vessel is the target to regulate pressure
arteriole
how does an edema occur
no venous return, blood sits in capillaries and fluid builds
flow
volume of fluid transported per time unit
what is flow between 2 points dependent on
pressure difference between the 2 points and resistance to fluid
how to calculate flow (Q)
pressure difference/resistance
is pressure higher in arteries or veins
arteries
what are arterioles
the “bottlenecks” of the circulation
why are arterioles the main site of pressure/flow regulation
they have the most smooth muscle
what does initial pressure result from
heart contraction
does pressure progressively increase or decrease
decrease
what does resistance depend on
length of vessel
radius of vessel
blood viscosity
what is constant in an individual
the length of vessel
what is the most important factor for resistance
radius of vessel
why is radius so important for resistance
resistance decreases by the 4th power of the radius: if the radius increased 2 times, resistance decreases 16 times
what does viscosity of blood vary with
cells and proteins amount
what occurs during ventricular contraction when aortic valves open
rapid flow of blood
increased arterial pressure
some pressure is absorbed by aorta elasticity
what does aorta elasticity do with pressure
temporarily stores energy like a rubber plastic
what occurs during diastole when the aortic valve closes
no blood flowing from ventricle
stored energy is released
allows blood flow to continue in vessels
gradual decrease in arterial pressure
what are compliant
arteries
what does the elasticity and large diameter of arteries supply
low resistance
high flow
what does the recoil of wall of artery limit
the drop in pressure after systole
how can a difference in arterial blood pressure be observed
between systole pressure and diastole pressure
pulse pressure
difference between systolic and diastolic pressure
what occurs to the mean blood pressure during rest
MBP closer to diastolic pressure (diastolic lasts longer than systole)
what occurs to the mean blood pressure during exercise
MBP closer to systolic pressure (heart rate increased = diastole shortened)
what is pulse pressure the measure of
measure of pressure on artery wall during systole
factors influencing arterial pressure
elasticity of artery
cardiac output
respiration
resistance to blood flow
blood volume
what is the main factor influencing arterial pressure
resistance to blood flow
what influence does aging have with elasticity of artery
low elasticity = high pressure
what influence does more blood from systole have on pressure
more blood = increased pressure
what occurs during inspiration
low pressure in thoracic cavity, high pressure in abdominal cavity
what does the pressure occurring during inspiration promote
venous return
what does total peripheral resistance depend on
vasoconstriction of arterioles. increase in TPR = increase pressure
what does blood volume influence
cardiac output
why does blood volume have minimal effect on cardiac output
vein absorb the major effect
what is unique about arteriole walls
they have fewer elastic fibers but larger number of smooth muscle fibers
what is the basal level of constriction
myogenic (basal) tone
what does the myogenic tone make possible
to decrease and increase vessels contraction thus diameter
what happens too resistance when diameter decreases
resistance increases
what are the 2 levels of control of arteriolar resistance
autoregulation (local mechanisms)
extrinsic control factor (neuro-hormonal)
what does auto regulation do within organ or tissue
overrides extrinsic regulation
what does autoregulation control
flow to critical organs = protective mechanism
types of autoregulation
metabolic regulation
myogenic (pressure) regulation
what does metabolic regulation respond to
changes in metabolism, thus blood requirement
what does metabolic regulation increase in
diameter (decrease in pH, increase in CO2, K+, NO)
what does the relative importance of factors in metabolic regulation depend on
the organ
what does myogenic auto regulation entail
vessels respond to changes in tone or stretch
what does myogenic autoregutalion maintain
the blood supply is virtually unchanged even when pressure changes
how does autoregulation adapt
locally with specific organs to maintain function
when is extrinsic regulation activated
when there is a problem
what does extrinsic regulation regulate
the peripheral pressure as a whole
what are the vasoconstrictive influences of extrinsic regulation
sympathetic stimulation on a-adrenergic receptors
angiotensin II
arginin vasopressin
what is a vasodilatory influence of extrinsic regulation
parasympathetic stimulation (vagus nerve, mainly penis and clitoris)
how low can pressure be when blood enters venous system
10 mm Hg
what does the heart act as
a pump
what kind of muscles do veins possess
smooth
what occurs when pressure in veins is too high
flow is reduced and fluid leaks out and accumulates in tissue - edema
how can skeletal muscle activity help with veins and venous pressure
it can help squeeze blood upward
what side of the heart has higher pressure
right
what happens to pressure during inspiration
P in thoracic cavity decreases
P in abdonominal cavity increases
main variables of controlling blood pressure
heart rate
stroke volume
TPR
what contribute to blood pressure reflex
baroreceptors
sensory fibers
integration center
motor fibers
effectors
what are baroreceptors
stretch receptors
what do baroreceptors sense
stretching of arterial wall
where are baroreceptors located
sensitive areas:
aortic arch
carotid sinus
what do baroreceptors have
free nerve endings
where do sensory fibers ascend
via vagus nerve
what happens due to sensory fibers when stretch increases
increase in APs frequency
what happens due to sensory fibers when stretch decreases
decrease in AP frequency
what is the integration center
cardiovascular (vasomotor) center in the medulla oblongata
what does the integration center do
compares info to reference value
what are the effectors involved with controlling blood pressure
heart
arterioles and vein
example of baroreceptors in action
postural hypotension
what is postural hypotension
change from lying to standing position
what does the atrial volume receptor reflex
stretch receptors in wall of atria and regulate blood volume
how does the atrial volume receptor reflex regulate blood volume
via autonomic nervous system activity
neural input that controls this and the secretion of hormones that alter renal handling of sodium and water
what are the stretch receptors in wall of atria
volume receptors
what is atrial natriuretic peptide (ANP)
hormone synthesized in atrial wall
what does ANP increase
sodium excretion
what is renin
hormone synthesized in kidney which increases synthesis of angiotensin II to create aldosterone
what are hormones involved in BP regulation
atrial natriuretic peptide
renin
antidiuretic hormone = vasopressin (post. pituitary)
what does antidiuretic hormone vasopressin do
decrease water excretion in kidney - decrease water loss in urine
what does angiotensin II do `
vasoconstriction
what does aldosterone do
decrease sodium excretion
what is vasoconstriction
when there is a drop in blood volume, decreases arterial going into kidney
