lecture 17: blood pressure and cardiac output Flashcards
pressure reservoir
maintain blood flow during ventricular relaxation
aorta and arteries
expandable tissue/very elastic
elastic recoil
blood flow continues forward
ensures pressure gradient
resistance vessels
arterioles
vasoconstriction and vasodilation
changing blood flow
distributing blood by changing resistance
capillaries
where exchange between blood and cells takes place
O2, CO2, metabolites, etc.
diffusion happens effectively
BP too low
sympathetic nervous system causes vasoconstriction to increase BP in veins
cannot hold as much blood, can only go towards the heart
increase venous return
larger EDV
increase in pumping more forcefully, increase speed of contraction
near pressure reservoir
volume reservoir
veins and venules
some elastin, some smooth muscle
walls thinner, more superficial, more compliant than arterioles
help with venous return
60% of blood flow
blood pressure decrease
- ventricle contracts (systole)
- SL valve opens
—-threshold reached
—-blood ejected from ventricles flows into the arteries - aorta and arteries expand and store pressure/energy in elastic walls
blood pressure increase
- isovolumic ventricular relaxation (lower pressure)
- SL valve shuts
—-ventricle in diastole
—- prevents flow back into ventricle - elastic recoil of arteries sends blood forward towards tissues
systole
contraction
diastole
relaxation
systolic blood pressure
max aortic pressure
caused by L. ventricle contracting and pushing blood into aorta
total peripheral resistance
no blood being pushed into aorta and causing pressure change
diastolic blood pressure as best indicator
ventricle relaxes
pulse pressure
systolic P - diastolic P
larger difference means more contraction
diastolic pressure
baseline
best indicator of heart contractility or inotropy
minimum pressure in aorta
ventricle relaxes, spend more time here
arterial circulation
highest BP
vena cavae
pulsations decrease after aorta
pressure is almost 0
resistant to flow
raise low BP in vena cava
- vasoconstriction (sympathetic NS)
—-helps with venous return - continuous blood flow by capillaries
- respiratory pump and skeletal pump
venous valves
valves in the veins that prevent backflow of blood
skeletal muscle pump there as well to compress veins and force blood to go to heart
mean arterial pressure
described the average arterial blood pressure during one cardiac cycle, in the aorta
pulsatile/oscillations of pressure from contraction then relaxation
diastolic P + 1/3(systolic P - diastolic P)
or = 2/3(diastolic P) + 1/3(systolic P)
MAP = CO x TPR
high MAP
hypertension
can cause rupture/bleeding
worse than low
start to damage walls of blood vessels
can cause stroke
low MAP
not enough force to cause blood flow
hypotension
cant overcome gravity
cant take blood to tissues
decrease BV, decreased stretch
cardiac output
CO = SV x HR
CO = Q or flow rate
change in pressure
= Pressure in aorta - pressure in vena cavae
BP in vena cavae is 0
= MAP - 0 mmHg —-> MAP
higher CO but same VPR
increase in MAP
increase in BV
same CO but increase in VPR
increase in MAP
increase in BV
less being let out so BP increases
factors that affect BP
distribution of blood in systemic circulation
total blood volume
arteriolar resistance
influenced by both local and systemic control mechanisms
local control
affects arteriolar resistance
matches tissue blood flow to the metabolic needs of the tissue
change in blood vessels to allow for change in contraction and relaxation
change in resistance
systemic control
affects arteriolar resistance
sympathetic reflexes and hormones
sympathetic reflexes
part of systemic control
autonomic nervous system
mediated by CNS (alpha 1 and beta 2 receptors) to maintain MAP and affect blood distribution for homeostatic needs
ex: temperature regulation
innervates blood vessels
ex: vasoconstriction —> increases BP, contraction, venous return
hormones
part of systemic control
act directly on arterioles and alter autonomic reflex control
ex: angiotensin II (vasoconstriction)
ex: atrial natriuretic peptide (vasodilation)
control of vascular smooth muscle
GO OVER DIAGRAM IN NOTES
baroreceptors
mechanoreceptors
nerve endings in outer layer of the blood vessel
stimuli as stretch of blood vessels
blood pressure regulation
constant monitoring —> tonic receptors
ex: increase CO = expand aortic walls, baroreceptors pick up on this
location of baroreceptors
carry sensory/afferent information about stretch
aortic arch
carotid sinus
aortic arch
soon as it comes out of L. ventricle
innervated by a branch of the Vagus nerve
aortic depressor nerve
carotid sinus
bifurcation
external and internal
going into brain, bringing oxygenated blood to head
innervated by a branch of the Glossopharyngeal nerve
carotid sinus nerve
example of baroreceptor action
- increase in BV and BP
- elevates vascular wall tension
- PIEZO channels activated
—-allow Na and Ca to go in, depolarizes the cell
—-generates AP, gets carried through nerves to medulla
—-information is integrated
low BP
baroreceptors fire less
less frequent AP
efferent signal needs to be produced
high BP
baroreceptors increase firing of AP
activated by stretch
send information of stretch to medulla
send efferent signal to ANS
parasympathetic innervation
SA node and AV node
sympathetic innervation
SA node and AV node
contractile cells
blood vessels
baroreceptor reflex to low BP
increase sympathetic output
1. increase HR (SA node), + chronotropic effect
2. increase conduction velocity (decrease delay in AV node), + dromotropic effect
3. increase If and LTCC activation
—–increase Ca from ECF
4. increase Ca concentration, + inotropic effect, increase force of contraction
5. increase SV, decrease flow rate
6. increase CO
—-vasoconstriction of blood vessels, decrease radius, increase resistance
7. decrease Ohm’s law
decrease parasympathetic output
baroreceptor reflex to high BP
increase parasympathetic output
decrease sympathetic output
1. decrease HR, - chronotropic effect
2. decrease conduction velocity, - dromotropic effect
3. SV stays the same but CO decreases
—-less blood going into aorta
—-decrease amt of signals getting to blood vessels
4. vasodilation —-> increase radius, decrease resistance, increase blood flow
—–lots leaving aorta but not much coming in
5. decrease BV and BP
6. decrease MAP
