Lecture 21: Regulation of Arterial Pressure

Question 1

What are the equations for calculating Mean Arterial Pressure?

Answer 1

• 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)

Question 2

What regulates mean arterial pressure?

Answer 2

• Baroreceptor Reflex
• RAAS System
• ADH
• ANP

Question 3

Where are baroreceptors located?

Answer 3

• Carotid sinus
• Aortic sinus

Question 4

What nerves are involved in the carotid sinus?

Where do they send their information?

Answer 4

• CN IX
• Sinus nerve of Hering

Question 5

What nerves are involved in the aortic sinus?

Answer 5

• CN X
• Aortic Nerve

Question 6

Describe the Baroreceptor Reflex Arc

Answer 6

Detector > Afferent > brain stem (coordination center) .> efferent > effectors (correct pressure)

Question 7

Where do nerves from the aortic and carotid sinus send their information?

Answer 7

Nucleus Tractus Solitatrius

Question 8

What neurotransmitter do afferent signals from baroreceptors use when sending information to the nucleus tractus soliatrius?

Answer 8

Glutamate

Question 9

What do chemoreceptors respond to?

Answer 9

• PO₂
• PCO₂
• pH

Question 10

What do mechanoreceptors respond to?

Answer 10

• Changes in arterial pressure

Question 11

What causes increased firing in a baroreceptor?

Answer 11

Increased pressure/stretch

Question 12

What causes decreased firing in a baroreceptor?

Answer 12

Decreases in pressure/stretch

Question 13

Where do baroreceptors send their signals to?

Answer 13

Medulla: Vasomotor center

Question 14

What area of the brainstem is involved in parasympathetic activity in cardiovascular function?

Answer 14

• Dorsal motor nucleus of the vagus
• Nucleus ambiguus

Question 15

What area of the brainstem is involved in sympathetic activity in cardiovascular function?

Answer 15

Rostral ventrolateral medulla

Question 16

From the SNS/PNS centers in the medulla, where is info about BP sent to next?

Answer 16

Cerebral cortex and hypothalamus (which will regulate BP by controlling the endocrine system)

Question 17

What is stroke volume is dependent on?

Answer 17

• Sympathetic stimulation of the heart
• Preload (EDV)

Question 18

Heart rate is dependent on?

Answer 18

• Sympathetic stimulation
• Parasympathetic stimulation

Question 19

Total peripheral resistance (TPR) is dependent on?

Answer 19

Sympathetic stimulation of arterioles

Question 20

What is the difference between aortic and carotid baroreceptors?

Answer 20

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

Question 21

What are the effects of the sympathetic nervous system on HR, contractility, vein and arteriolar radius, fluid retention?

Answer 21

• Constriction of arterioles and veins (alpha receptors)
• Increases HR and contractility (beta 1)
• Renin secretion and increased fluid retention

Question 22

Sympathetic nervous system responds to _ baroreceptor firing rate

Parasympathetic nervous system responds _ baroreceptor firing rate

Answer 22

Decreased

Increased

Question 23

What are the effects of the parasympathetic NS on arterial pressure?

Answer 23

• We want to decrease MAP
• Decrease HR
  
  • Vagus nerve signal to SA node
  • Muscarinic receptors
• Also indirect vasodilation on blood vessels via NO

Question 24

How does hypertension saffect baroreceptors?

Answer 24

Changes “normal” set point to something higher, which becomes the new “normal”

Question 25

What enzyme is secreted by the kidney in response to drops in BP? What type of cell secretes this?

Answer 25

Juxtaglomerular cells produces _renin._

Question 26

What stimulates the release of renin?

Answer 26

* Sympathetic Nervous System * \*Specifically beta 1 adrenergic receptor activation\*

Question 27

What does renin do as an enzyme?

Answer 27

Converts _angiotensinogen to angiotensin I_

Question 28

Angiotensin I is converted to Angiotensin II via which enzyme? Where is this occurring?

Answer 28

Converted by ACE in lungs

Question 29

What does angiotensin II do in its active form?

Answer 29

* Causes secretion of aldosterone from the adrenal cortex * Stimulates secretion of ADH/Vasopressin * Causes global constriction of arterioles by binding to AT1 receptors

Question 30

What does aldosterone do?

Answer 30

* Increases Na⁺ and H₂O retention * Increases blood volume, preload, SV, CO, and MAP

Question 31

What does ADH/Vasopressin do? It is not only secreted in response to angiotensin II, but what other factors?

Answer 31

* 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

Question 32

What are the three natriuretic peptides that affect arterial pressure? When are they secreted? What are their effects?

Answer 32

* 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

Question 33

What happens when you have a hemorrhage?

Answer 33

* 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

Question 34

What happens when you have too much blood?

Answer 34

* 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?)\*

Question 35

What happens during exercise?

Answer 35

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

Question 36

What happens to MAP, HR, TPR, CO and venous pressure during orthostatic hypotension? What happens in response?

Answer 36

* 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