Lecture 21: Regulation of Arterial Pressure Flashcards
What are the equations for calculating Mean Arterial Pressure?
- Mean Arterial Pressure = Cardiac Output x Total Peripheral Resistance
- Mean Arterial Pressure = Heart Rate x Stroke Volume x Total Peripheral Resistance
- Mean Arterial Pressure = 2/3 (Diastolic BP) + 1/3 (Systolic BP)
What regulates mean arterial pressure?
- Baroreceptor Reflex
- RAAS System
- ADH
- ANP
Where are baroreceptors located?
- Carotid sinus
- Aortic sinus
What nerves are involved in the carotid sinus?
Where do they send their information?
- CN IX
- Sinus nerve of Hering
What nerves are involved in the aortic sinus?
- CN X
- Aortic Nerve
Describe the Baroreceptor Reflex Arc
Detector > Afferent > brain stem (coordination center) .> efferent > effectors (correct pressure)
Where do nerves from the aortic and carotid sinus send their information?
Nucleus Tractus Solitatrius
What neurotransmitter do afferent signals from baroreceptors use when sending information to the nucleus tractus soliatrius?
Glutamate
What do chemoreceptors respond to?
- PO2
- PCO2
- pH
What do mechanoreceptors respond to?
- Changes in arterial pressure
What causes increased firing in a baroreceptor?
Increased pressure/stretch
What causes decreased firing in a baroreceptor?
Decreases in pressure/stretch
Where do baroreceptors send their signals to?
Medulla: Vasomotor center
What area of the brainstem is involved in parasympathetic activity in cardiovascular function?
- Dorsal motor nucleus of the vagus
- Nucleus ambiguus
What area of the brainstem is involved in sympathetic activity in cardiovascular function?
Rostral ventrolateral medulla
From the SNS/PNS centers in the medulla, where is info about BP sent to next?
Cerebral cortex and hypothalamus (which will regulate BP by controlling the endocrine system)
What is stroke volume is dependent on?
- Sympathetic stimulation of the heart
- Preload (EDV)
Heart rate is dependent on?
- Sympathetic stimulation
- Parasympathetic stimulation
Total peripheral resistance (TPR) is dependent on?
Sympathetic stimulation of arterioles
What is the difference between aortic and carotid baroreceptors?
Carotid sinus is more sensitive to firing rate, but also stops firing after limits are reached (high at 200 mmHg, low at 40 mmHg)
Aortic sinus continues firing even after reaching the saturation point
What are the effects of the sympathetic nervous system on HR, contractility, vein and arteriolar radius, fluid retention?
- Constriction of arterioles and veins (alpha receptors)
- Increases HR and contractility (beta 1)
- Renin secretion and increased fluid retention
Sympathetic nervous system responds to _ baroreceptor firing rate
Parasympathetic nervous system responds _ baroreceptor firing rate
Decreased
Increased
What are the effects of the parasympathetic NS on arterial pressure?
- We want to decrease MAP
- Decrease HR
- Vagus nerve signal to SA node
- Muscarinic receptors
- Also indirect vasodilation on blood vessels via NO
How does hypertension saffect baroreceptors?
Changes “normal” set point to something higher, which becomes the new “normal”
What enzyme is secreted by the kidney in response to drops in BP? What type of cell secretes this?
Juxtaglomerular cells produces renin.
What stimulates the release of renin?
- Sympathetic Nervous System
- *Specifically beta 1 adrenergic receptor activation*
What does renin do as an enzyme?
Converts angiotensinogen to angiotensin I
Angiotensin I is converted to Angiotensin II via which enzyme?
Where is this occurring?
Converted by ACE in lungs
What does angiotensin II do in its active form?
- Causes secretion of aldosterone from the adrenal cortex
- Stimulates secretion of ADH/Vasopressin
- Causes global constriction of arterioles by binding to AT1 receptors
What does aldosterone do?
- Increases Na+ and H2O retention
- Increases blood volume, preload, SV, CO, and MAP
What does ADH/Vasopressin do?
It is not only secreted in response to angiotensin II, but what other factors?
- Acts on V1 and V2 receptors of smooth muscle, and collecting ducts, respectively and increases TPR and water retention (also leading to decreased urination)
- Atrial receptors during low preload, increased osmolarity of blood or when SNS is activated
What are the three natriuretic peptides that affect arterial pressure?
When are they secreted?
What are their effects?
- ANP, BNP, CNP
- Excessive preload of atria and ventricles
- Effects
- Arteriolar dilation: decrease TPR
- Increases fluid loss: decreases preload
- Inhibits renin: decreases TPR and preload
What happens when you have a hemorrhage?
- Decrease in blood volume and MAP
- Decreased firing of mechanoreceptors
- Increase sympathetic activation to bring MAP back up
- Sympathetics will:
- Increase HR, CO and contractility via alpha ine adrenergic receptors
- Constrict arterioles to increase TPR
- Constrict the veins to decrease unstressed volume and increase venous return
- Increased RAAS activation
What happens when you have too much blood?
- Increase in blood volume and increase in MAP
- Activate parasympathetics to bring MAP back down
- Increased ANP secretion
- Decreased ADH secretion
- Renal vasodilation
- Increased HR? (d/t increased preload?)*
What happens during exercise?
increased sympathetic output (B1 receptors), decrease PNS
increase HR and contractility
increase venous return
increase vasoconstriction via (a1 receptors)
Basically you wnna pump more blood out since your body needs a lot of blood since it’s exerting itself
What happens to MAP, HR, TPR, CO and venous pressure during orthostatic hypotension?
What happens in response?
- Decreased MAP; no change in HR and TPR, CO goes down from decreased venous return, central venous pressure decreases d/t pooling of blood in lower extremities
- Increase sympathetic activation
- Increase HR, contractility and CO via beta 1 adrenergic receptors
- Want to increase TPR via constriction of arterioles
- Want to decrease unstressed volume and increase venous return so we constrict the veins
