Nordgren: Arterial Pressure Regulation Flashcards
What are the four pathways that control the baroreceptor reflex?
- Efferent
- Afferent
- Central Integration
- Operation
What does the baroreceptor reflex do?
Helps to maintain blood pressure at constant levels
Describe the path of the efferent pathway in the baroreceptor reflex?
SNS and PNS POSTgang fibers terminate on the HEART and VESSELS.
What does the efferent pathway influence?
- SV
- Heart Rate
- TPR
What are arterial baroreceptors?
sensory receptors located in the walls of the AORTA and CAROTID ARTERIES
What are the two types of arterial baroreceptors?
- aortic baroreceptor
2. carotid sinus baroreceptor
How does the afferent pathway play a role in the baroreceptor reflex?
Arterial baroreceptors sense arterial pressure via STRETCH of the elastic arterial walls.
Increased stretch leads to increased AP generation by the baroreceptors.
What pathway is active at normal pressures and supplies a TONIC signal?
Afferent baroreceptors
Are baroreceptors better for short term or long term pressure regulation?
SHORT TERM
Baroreceptors can ADAPT. Continually elevated pressure over several days leads to a gradual decrease in the firing rate.
Where does central integration of the baroreceptor reflex occur?
In the medulla oblongata (medullary cardiovascular center)
What is carotid massage?
A clinical technique for ACTIVATING THE PNS
Interrupts atrial trachyarrhythmias.
How does carotid massage work?
It causes physical deformation of carotid sinuses and ‘tricks’ them into sending a HIGH PRESSURE alarm to the medullary control centers.
Where are cardiopulmonary baroreceptors located?
- atria
- ventricles
- coronary vessels
- lungs
What do cardiopulmonary baroreceptors do?
Sense pressure (or volume)
What has a tonic inhibitory influence on SNS activity?
Cardiopulmonary baroreceptors
Low PO2 and high PCO2 in arterial blood will cause what reflex?
Increases in RR and MAP d/t:
- Increased activity in the arterial chemoreceptors
- Increased activity of central chemoreceptors
Where are arterial chemoreceptors?
carotid arteries and arch of the aorta
Where are central chemoreceptors?
Somewhere in the CNS
What is Cushing reflex?
Reduced cerebral circulation/ishemia –>
An INCREASE in intracranial pressure leads to an INCREASE in arterial pressure.
This:
- prevents collapse of cranial vessels
- preserves blood flow to the brain
What happens in exercising skeletal muscle?
Chemoreceptors responding to muscle ischemia stimulate afferent fibers in the skeletal muscle and lead to:
- Reflex tachycardia
- Increased atrial pressure
What is the dive reflex?
Diving animals will experience BRADYCARDIA and intense VASOCONSTRICTION in all the systemic organs except the brain and heart.
This PROLONGS SUBMERSION by limiting the rate of oxygen use and directing flow to essential organs.
Why is the dive reflex unique?
It’s the only circumstance in which both the PNS (bradycardia) and SNS (vasoconstriction) are stimulated.
What is the dive reflex used for clinically?
Activate cardiac PNS in order to interrupt atrial tachyarrhythmias.
How does emotion effect arterial pressure?
Response in cerebral cortex –>
Medullary CVC–>
corticohypthalamic pathways
What causes blushing?
Loss of sympathetic vasoconstrictor activity to PARTICULAR cutaneous vessels–>
engorgement of cutaneous venous sinuses
What causes excitement?
ALERTING RXN
Increase in SNS and decreased PNS–> Increase in bp
What causes fainting?
VASOVAGAL SYNCOPE
Sudden loss of sympathetic tone and large INCREASE in PNS–> sudden loss of arterial bp–> decreased cerebral blood flow
What type of pain causes a RISE in blood pressure?
superficial or cutaneous
What type of pain causes a severe decrease in blood pressure?
Deep pain
Caused by decreased sympathetic tone and increased parasympathetic tone (similar to vasovagal syncope)
What promotes heat loss?
Dilation of cutaneous vessels
What controls heat loss?
Hypothalamus > regulates SNS activity > regulates vasoconstriction of cutaneous vessels (VERY sensitive to hypothalamic temperature)
What are the two components that regulate cutaneous vessels?
Arterial pressure and temperature
What normally and continuously supplies the major input to the medullary centers?
Arterial baroreceptor input
What raises the set point in the medullary center?
- Response to exercise
- Sense of danger
- Cerebral ischemic response
- Intracranial pressure (cushing reflex)
- Decreased O2, Increased CO2
- Decreased central venous pressure
- Cutaneous pain
What lowers the set point of the medullary center?
- Vasovagal syncope
- deep pain
- increased central venous pressure
How does circulating blood volume influence arterial pressure?
Decreased BV> Decrease in peripheral venous pressure> left shift of venous fxn curve> decrease in central venous pressure> decreased CO> decrease in arterial pressure
How does arterial pressure affect urinary output rate?
Increased AP> Increased urinary output rate> decreased fluid volume> decreased BV> decreased CO> decreased arterial prssure
What is glomerular filtration?
Plasma fluid that flows into kidneys is filtered across the glomerular capillaries and then enters the renal tubules (forms the glomerular filtrate)
What is glomerular filtration dependent on?
Hydrostatic and Oncotic pressures
*GF decreased by factors that decrease glomerular capillary pressure
What happens to fluid once it’s in the renal tubules?
It’s either reabsorbed into the CV system or passed along and excreted as urine
How do kidneys play a major role in homeostasis?
Regulate the electrolyte (mainly Na) composition of plasma
What is the equation for urinary output rate?
UOR= GFR- Renal fluid resorption rate
What increases the renal fluid resorption rate?
Anything that promotes renal tubular Na resorption (Na pumped out and water leaves with it)
What is RAAs?
Renin, Angiotensin, Aldosterone system
What does renin do?
Converts Angiotensinogen to angiotensinogen I
Where is renin produced?
kidneys
What is angiotensinogen?
Precursor protein produced in the liver
What is angiotensin I?
Inactive protein
What converts Antiotensin I to it’s activeform angiotensin II?
ACE (on the surface of endotehlial cells)
What controls the release of aldosterone?
Angio II
What is aldosterone?
The primary regulator of rate of Na resabsorption by renal tubular cells
What produces aldosterone?
Adrenal glands
What influences the rate renin is released from the kidneys?
- Increase in SNS activity
- Lowered GFR
- Activation of sympathetic vasoconstrictor nerves to renal arterioles (lowers glomerular capillary hydrostatic pressure and filtration rate)
How does renin release affect urinary output?
it DECREASES urinary output rate b/c of increased Na reabsorption from renal tubules
What is primary function of vasopressin (ADH)?
It INCREASES water permeability by acting on the renal collecting ducts (V2 receptors) and DECREASES urine formation.
How does vasopressin affect the CVS?
Increases:
blood volume
CO
arterial pressure
What is the secondary function of vasopressin?
Vasoconstriction
(binds to V1 on VSM > IP3 signal transduction pathway and Rho-kinase pathway) > Vasoconstriction > increase in arterial pressure