Cardio Lec 8 Flashcards
Factors affecting resistance
tube length (fixed) & viscosity (thickness)
An increase in tube length or viscosity __ flow
decrease
Can blood viscosity change?
yes; (in polycythemia & anemia)
Most important regulator of blood flow
diameter & MAP
Small changes in vessel radius have large effects on resistance & flow
t
As vessel length or blood viscosity go up -> resistance will go
up
As vessel radius goes up -> resistance will go
down
By doubling radius, you DECREASES resistance by
a factor of 16 -> INCREASE flow by a factor of 16
Flow is the __ of resistance
inverse
as pressure gradient goes up blood flow goes
up
as the radius is increased blood flow goes
up
as vessel length increases blood flow goes
down
as viscosity increases blood flow goes
down
Blood viscosity doesn’t change in healthy individuals
t
Velocity measured by
distance per time
Flow measured by
volume per time
Which vessels have the largest cross sectional area & therefore slowest velocity of blood movement
capillaries
Which vessel has the smallest cross sectional area & therefore the greatest velocity
aorta
Arterioles aka
resistance vessels
Arterioles act like a
clamp
Total peripheral resistance =
sum of all vascular resistances w/in systemic circulation
Stress causes tpr to go
up
Tpr main determinant of
afterload
Bp resistance greatest in
arterioles
Pressure & flow reduced most in
capillaries (have smallest diameter)
BP =
CO x TPR
What organ control blood vol
kidneys
Baroreceptors detect
stretch/pressure
Baroreceptor reflex
maintain relatively constant pressure on a min by min basis
How do baroreceptors respond to bp elevation
fire more to inhibit SNS -> lower bp
How do baroreceptors respond to bp drop
fire less -> SNS more active -> bp rises
Valsalva maneuver used to break
SVT
Pulse pressure refers to
diff between systolic & diastolic (ex: 120/180=40)
Myoglobin
binds 02 when 02 levels are high but doesn’t release its 02 until levels are dangerously low
Aortic compliance decreases greatly w/ age, systolic press gets higher & diastolic gets lower & pulse pressure gets bigger w/ age
t
MAP =
diastolic press + 1/3 (pulse pressure) -> Ex: 120/90 -> 90 + 1/3 (30) = 90+10= 100 mmHg
TPR due to
alpha receptor stimulation
myogenic mechanism: When bp goes up -> increased flow to brain -> to oppose..
cerebral vessels constrict (keeps flow the same)
myogenic mechanism: When bp goes down -> decrease flow to brain -> to oppose..
vessels dilate (keeps flow the same)
Myogenic control refers to
vessels regulate their own flow
Reactive hyperemia
accumulated end products BC FLOW WAS DIMINISHED to an area
Active hyperemia
BC TISSUES ARE MORE ACTIVE
In both reactive & active hyperemia you get an increase in flow due to
accumulation of end products
Cerebral flow remains constant due to the
myogenic mechanism
Heart must use __ respiration
aerobic
Alpha receptors
constriction & bind NE
Beta receptors
dilate & bind Epi
During exercise, as heart exceeds 180 bpm, CO will
fall due to reduction of filling time
EDV decreases during exercise
f; increases
Hypoventilation
co2 levels rise -> vessels dilate
Hyperventilation
co2 levels fall -> vessels constrict
Most active areas of brain receive most blood
t
Most people have 2ndary htn
f; most have primary/essential htn
We try to keep bp under
120/80
