BP regulation Flashcards
What is the equation for the mean arterial pressure?
CO x TPR
What is the definition of BP?
Force exerted by the blood against any unit area of the vessel wall
Pressure is directly related to the product of what two variables?
Flow and resistance
True or false: CO is usually kept constant
True
What is the variable that is usually regulated to control BP?
Resistance
What is the cause of the dicrotic notch (incisura) in the arterial pressure waveform?
Due to closure of the aortic valve
“separation of the heart from the peripheral circulation”
What is the diastolic run off?
The drop in BP d/t blood flowing downstream after the aortic valve has closed
Increasing peripheral resistance (vasoconstriction), will change the slope of the diastolic run off curve how?
Decrease the slope d/t lowered flow
Decreasing peripheral resistance (vasodilation), what will happen to the slope of the diastolic run off curve?
Increases the slope (increases flow)
What is the equation for the estimated MAP?
1/3(SBP-DBP) + DBP
Why is the DBP weighted more in the equation for the estimated?
Stays longer in diastole
What is the equation for the pulse pressure?
SBP - DBP
How do you measure BP?
Cuff, listening for Korotkoff sounds
What are the limitations of measuring BP with a cuff?
Less accurate
Appropriate cuff size
The pulse pressure generates what? (What enables feeling the pulse in the radial artery prior to blood actually arriving)
A wave that travels faster than the blood
What are the two conditions that can lower the stroke volume output?
Persistent Ductus Arteriosus
Aortic regurg
What are the two factors that can change the compliance of vessels?
Arteriosclerosis
Aortic stenosis
The pressure wave is faster or slower with aortic distensibility?
Slower speed the more distensible
What are the four factors that affect the wave propagation of the pressure pulse wave?
Velocity
Stroke volume
Aortic compliance
Distance to reflection pts
What happens to the amplitude of the pressure pulse wave as you move downstream from the heart?
Increases since it is close to the point of reflection
What happens to the reflected pressure pulse wave if the aortic compliance is reduced?
Increases speed, and thus a higher reflected wave
What happens to the pressure pulse wave as we age?
Amplification d/t increased summation of the forward and reflected waves
Why does the amplitude of the pressure pulse wave increase in decreased aortic compliance?
increased summation of the forward and reflected waves
What happens to the incisura as you go distally?
Moves farther down the curve (felt later)
What happens to the wave oscillations as the pressure pulse wave hits the arterioles? What is the consequence of this on the capillaries?
Decreases to protect the delicate capillaries
Where is the resistance change the greatest in the blood circulation?
Arterioles
What happens to capillary pressure if the arteriole is constricted (increased resistance)? Why do you want to do this in skeletal muscle?
Decreases, to allow more time for the tissues to extract oxygen and nutrients
What happens to capillary pressure if the arteriole is dilated (lowered resistance)?
Increases
What are the acute changes in tone that can control blood flow control in tissues?
Vasoconstriction/dilation
What are the long term changes that can control the blood flow?
Change in size/number of capillaries in a tissue
Increasing metabolism in tissue (blanks) blood flow to those tissues
Increases
Decreasing oxygen saturation changes blood flow how?
Increases it
What is the myogenic theory of autoregulation of blood flow?
Stretching vessels will elicit contraction
What is the chemical that dilates arterioles, and is released from the endothelial cells of vessels?
NO (=EDRF)
What is the MOA of NTG?
“Donates” NO
What is the MOA of NO, bradykinin, and histamine?
Inhibit MLCK (myosin long chain kinase) and activates MLCP myosin long chain phosphatase)
What is the MOA of Endothelin, Norepi, angiotensin II, and vasopressin?
Inhibits MLCP (myosin long chain phosphatase)
Acute regulation of BP is mediated through change in what variable? Why part of the nervous system is responsible for this effect?
Resistance (acting on actin and myosin)
ANS
Long term changes in BP is mediated through what? What is the organ responsible for this?
Changes in salt and water reabsorption (changes volume)
Kidney effects this change
What is the SNS receptors on blood vessels? What is the effect they produce when stimulated?
Alpha 1
Vasoconstriction (thus increase in resistance)
What is the SNS receptors on the heart? What is the effect that these produce?
Beta 1
Increase in contractility, HR
What are the SNS receptors on the kidney? Effects (2)?
Beta 2
Decreased GFR
Releases renin
What is the effect of angiotensin II, that is produced from Renin release by activation of the SNS?
Vasoconstriction
What is the effect of SNS stimulation of the adrenal glands?
(Nor)epi release
What is the effect of the PNS on the heat?
Decreased HR
M2 receptors!!
How do you pharmacologically decrease BP?
Decrease SNS (alpha 1) of the vessels
Is there PNS innervation of the blood vessels?
No
Stimulating SNS (increases/decreases) cutaneous capillary resistance? Through what receptors?
Increases through alpha 1
Nor epi acts on which receptors in the blood vessel to effect vasoconstriction?
Alpha 1
What is the effect of the SNS activation of arterioles? What is the effect this produces on blood flow through tissues?
Constricts Arterioles, increasing resistance, and leading to decrease blood flow through tissues, so that more oxygen can be extracted
What is the effect of the SNS activation of veins? What is the effect this produces on blood flow back to the heart?
Increasing venous return to the heart
Increases heart pumping to the periphery
What is the NTS?
The place in the CNS that receives all of the sensory information from the PNS relating to BP
This then sends projections to the cardioinhibitory center
What are the two bilateral structures in the NTS?
RVLM
CVLM
Excitation of the RVLM produces what? Excitation of the CVLM?
RVLM = constrict CVLM = dilate
What are the two main mechanisms through which BP is maintained?
(1) a system of rapidly acting vascular reflexes, and
(2) a group of slower mechanisms that adjust fluid volume and indirectly affect arterial pressure.
What happens to capillary pressure if the vessels upstream are constricted?
Decreased
What happens to capillary pressure if the vessels upstream are dilated?
Increased
What is endothelin? What cells release it, and what is its effect?
Released from endothelium of the vessels, and causes vasoconstriction
Lowered SNS to the blood vessels causes what?
Vasodilation
What happens to the outlet pressure of an arteriole when it is constricted?
Decreases
What is the function of the CVLM?
Inhibits the RVLM, thus effecting vasodilation
What is the RVLM?
The vasoconstrictor center
What is the CVLM?
The vasodilatory center
What are the two cardiac centers in the medulla?
Cardioinhibitor centers
Cardioexcitatory centers
What are the two inhibitory areas of the cardioinhibitor center?
Nucleus ambiguous
Dorsal motor nucleus of the vagus
What happens when the cardioinhibitory center is stimulated?
Increase in vagal tone to the heart
What happens when the cardioexcitatory center is activated?
these cells cause an increase in the activity of the sympathetic nervous system to the heart
Where are all of the baroreceptors synapses located? Where do the go from here?
At the NTS in the medulla
Then go to either CVLM or RVLM and/or the cardiogenic centers
What are the 5 steps of the parasympathetic pathway of BP regulation, starting with sensory input?
- Sensory input
- NTS
- DMNV and NA
- Vagus
- Heart
What are the 7 steps of the sympathetic pathway of BP regulation, starting with sensory input?
- Sensory input
- NTS
- CVLM
- EVLM
- IML
- Symp chain
- Effector
Where are the chemoreceptors located?
Carotid sinus
Aortic bodies
Where are baroreceptor located?
In the aortic arch and in arteries
What are the three main reflexes that control arterial pressure?
Arterial baroreflex
Cardiopulmonary baroreflex
Chemoreflex
What is the arterial baroreflex activated by? Where are the receptors located? Is this a short term or long term response?
High pressure
Carotid sinus and aortic arch
Short term
What is the cardiopulmonary baroreflex activated by? Where are the sensors located?
Activated by low pressure (volume)
Sensors in the atria, pulmonary vessels
What is the chemoreflex activated by? What is the effect they produce?
Changes in [O2, CO2, pH]
Peripheral activation of chemoreceptors leads to what?
Changes in symp tone, and vasoconstriction
Central activation of chemoreceptors leads to what?
local dilation and change in symp tone in periphery to vasoconstrict
What are the five steps of activation of the arterial baroreflex, starting with stretch on vessel walls?
- Stretch on vessel walls (via carotid sinus and aortic arch)
- Increased in BR firing
- Signal to CNS (NTS)
- Inhibition of vasoconstrictor center (via CVLM) and activation of the cardioinhibitory center
- Vasodilation of vessels and decrease in HR/contractility
Which two nerves are used in the afferent nerves from the carotid sinus and aortic arch in the arterial baroreflex pathway?
CN X or XII
What are the two effector organs that the arterial baroreflex activate (via symp and parasymp)?
Symp = Heart, bloow vessels, kidnery, adrenal Parasymp = heart
What is the net effect produced from the arterial baroreflex pathway? (start with the stimulus)
Increased BP leads to decreased HR, vasoconstriction, and increase in di/natriuresis
Increases in BP will increase or decrease afferent traffic? How about for efferent traffic?
Increases afferent traffic
Decreases Efferent traffic (think inhibiting RVLM)
Baroreceptors are most reactive to what?
CHANGES in BP
The baroreflex is good for the short term or the long term?
Short term
How do the baroreceptors lower heart rate through the vagus nerve?
- Send afferent nerves to the NTS
- NTS stimulates the DMNVNA
- Vagus signals heart to slow
True or false: the baroreflex can change, leading to HTN
True
What are the 4 steps of the chemoreflex, starting with decreased arterial BP?
- Increased firing of chemoreceptors in response to low pH, O2 or increased CO2 (which is brought about from BP change)
- increased firing to the CNS
- Activation of the vasoconstriction center
- Vasoconstriction
When does the chemoreflex take effect?
around 80 mmHg
What are the cells that are in chemoreflex receptors?
Glomus cells
The CNS also has a chemoreflex of its own. What are the 2 effects of this reflex?
- Same as peripheral (increase SNA to increase BP)
2. Vasodilation of local blood vessels
What does the cardiopulmonary reflex react to?
Changes in blood volume produced by changes in the stretch of the atria
What two major things happen in the cardiopulmonary reflex when there is less atrial stretching (from decreased volume)?
- Receptors fire to CNS to the RSNA. This causes vasoconstriction and increased ADH
- ANP is not released, causing a decrease in naturesis
What is the effect of ADH that is released in response to the cardiopulmonary reflex?
Increase water reuptake
What is natuirusis?
Loss of Na through urination
Which nerve does the cardiopulmonary reflex travel through?
Vagus
What are the two hormones that are regulated via the cardiopulmonary reflex?
ANP
ADH
What is the bainbridge reflex?
the reflex in the cardiopulmonary pathway that sends afferent signals through the Vagus to stimulate cardioexcitatory center
What are the effects of respiratory oscillation in blood pressure?
- Signals from the respiratory center spill over into the vasomotor center
- Inspiration decreases pressure in thoracic blood vessels, momentarily decreasing CO and AP
What is the mechanism for the long term regulation of BP?
Kidneys reduce volume through the enhanced excretion of salts and water
True or false: direct increased pressure to the kidney can affect BP
True
What are the two major mechanisms through which the kidneys effect long term BP changes?
Naturiesis
Diuresis
What is the three horomne system that the kidneys have that regulate BP?
Renin-angiotensin- aldosterone
Increasing BP has what effect on urinary output?
Increases
True or false: the kidneys have a set point around which BP and urine output are maintained
true
How is HTN reflected in the BP/renal output curve?
Shift of the curve to the right
Is the long term BP/renal output curve more elastic or inelastic?
Inelastic
What are the two scenarios in which Renal water and salt output increase?
Increased NaCl intake
HTN
Activation of the Renin-angiotensin system leads to what overall effect? What activates this?
Vasoconstriction/increased BP
Lower BP to kidney activates this
What are the two ways in which angiotensin II affects BP?
- Regulates renal Na and H2O retention (volume)
2. Systemic vasoconstriction (resistance)
What is the enzyme that is needed to convert ANGI to II?
ACE 1
Why will renal artery stenosis lead to increased BP?
Increased Renin-angiotensin system
What are the three short term modulator systems of BP?
baroreceptors
Chemoreceptors
CNS ischemic response
What are the three mid-term modulator systems of BP?
Renin-angiotensin system
Stress-relaxation
Capillary fluid shift
What are the two long term regulatory mechanisms of BP?
Renal fluid mechanism
Renal interactions with the Nervous system
