Lec 22 Flashcards
During ventricular ejection, blood presuure
will cause arteries to stretch and expand and store pressure in elastic walls
During isovolumc ventricular relaxation, how blood goes forward
the pressure that was stored in elastic walls, will recoil to maintain pressure
blood presuure measured in
arteries
pulse pressure
systolic pressure - diastolic pressure
mean arterial pressure formula
Diastolic pressure + 1/3 (pulse pressure)
why MAP formula is like that
as bloood spend less time in systolic than diastolic
MAP calculation in 120/80 BP
80 +1/3(120-80)=80+13.3=93.3
MAP illustrates
Mass balance
what do we mean by mass balance
what comes in, should go out
MAP minimum
60
two main ways bp is regulated
1- fluid loss/retention of kidneys
2- arterial tone -> vasodilation/vasoconstriction
four elements acting on MAP
1- Blood vloume
2- CArdiac output
3- resistance of system
4- relative distribution of blood (mass balance)
if MAP increase what have happened to four major elements
1- blood vol. increase (higher intake/lower loss)
2- cardiac output increases
3- resistance increase
4- diameter of veins decrease
cardiac output increase by (2 factors)
1- higher HR – dual input sym/parasym
2- Higher SV – contractility only by sympathetic
higher resistance is due to
lower diameter of arterioles
lower diameter of veins is leads to (4step in order)
1- higher venous constriction
2- higher venous return
3- higher sv
4- higher MAp
two systems acting in response of increase in BV/Bp
1- cardiovascular
2- renal system
response to high BV is —- feedback
negative
high BV triggers two different response
1- fast response (sec-min)
2- slow response (hour-days)
slow response to BP
compensation by kidneys (excretion of fluid in urine
fast response to high bp
compensation by cardiovascular system
1- vasodilation
2- lower CO
arteriole resistance formula
Ln/r^4 (n is viscosity)
in resistance formula — and — is not changing
length and viscosity
radius can be changed by changes in
vascular smooth muscle
changes in vascular muscle is due to
*local factors:
1- Myogenic response
2- paracrine
*3-Sympathetic nervous system
Myogenic autoregulation
constriction blood flow in response to increase pressure
myogenic is
wall of muscle from within
myogenic autoregulation pathway
1-pressure high
2- stretch in arteriole
3- open mechanically gated channels on smooth muscles
4- cell depolarize
5- opens voltage gated Ca channels
6- CA in smooth muscle (4 output)
Ca in smooth muscle will lead to
1- high contraction
2- higher arteriolar resistance
3- lower blood flow
4- lower pressure through vessel
myogenic response will hepl an organ to
maintain a constant blood flow as changes in perfusion pressure
Paracrine release
1- Active hyperemia
2- reactive hypermia
Active hyperemia
matching flow to metabolic demand
muscles working harder
active hypermia patheway
1- higher tissue metabolism
2- metabolites released from local cells act on arterile smooth muscle
3- smooth muscle decrease cross-bridge cycling
4- vasodilation
5- lower resistance
6- higher blood flow
some paracrine cause relaxation of muscle cells
O2/CO2/H+/NO/ADP
Reactive hypermia
1- lower blood flow due to blockage
2- build up metabolites (vasodilators in ECF)
3- arteriole dilate but flow still blocked
4- faster pace will wash blockage
5- short period of increased blood flow as low resistance
6- metabolites wash out
7- arterioles regain normal tone
SNS exert tonic control on
MOST arteriole resistance
SNS tonic control via
1- NPH
2- ephinephrine
Norepinephrine pathway
1- NPH release from postganglionic sympathetic neurons
2- bind alpha 1- adrenergic receptor on smooth muscles
3- alpha 1 coupled to Gq proteins (activate PLC)
4- increase in IP3
5- increase Ca release from SR– IP3
6- smooth muscle cell contraction (vasoconstriction)
Contraction increases during –
exercise and stress
higher expression of alpha 1 adrenergic receptors in
skin and visceral organs (GI tract)
to have more blood for muscles
Epinephrine pathway
1- release from adrenal medulla
2- during fight/flight- or exercise
3- act on betta 2 adrenergic receptors on smooth muscles, heart ,liver
4- Betta 2 coupled to Gs
5- cAMP activation
6- cause smooth muscle relaxation
7- contraction decrease during exercise
higher expression of betta 2 receptors on
vascular smooth muscle supplying heart, lungs, liver
more blood supply during fight/flight
central control of MAP
Baroreceptor reflex
Baroreceptors are – sensors
pressure
baroreceptors are located in
wall of carotid sinus and aortic arch
baroreceptors are
nerve endings with stretch-activated channels
baroreceptor reflex is —-
tonically active
always active more or less
baroreceptor stimulus
high pressure
baroreceptor effect on
1- open more channels
2- more depolarization
3- higher AP frequency
baroreceptor reflex ensures
adequate blood flow to heart and brain
baroreceptor sensor
carotid and aortic baroreceptor
baroreceptor integrating center
medullary cardiovascular control center
baroreceptor integrating center will effect on
1- parasympathetic neurons
2- sympathetic neurons
always one active one inactive
Parasympathetic neuron will
release more ACh on muscarinic receptor in SA node
-lower HR
–lower CO
—lower BP
—-lower MAP
sympathetic neuron will
release less NE on
1- alpha receptor (arteriolar smooth muscle)
2- betta 1 receptors (ventricular myocardium and SA node)
alpha receptor (arteriolar smooth muscle) when less NE release
vasodilation
-lower periheral resistance
–lower BP
—lower MAP
betta 1 receptors (ventricular myocardium) when less NE release
lower force of contraction
-lower SV
–lower CO
—lower BP
—-lower MAP
betta 1 receptors (SA node) when less NE release
lower HR
-lower CO
–lower BP
—lower MAP
lowering MAP will have —- feedback directly on —-
negative
on baroreceptors in arteries and aorta
